1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Generic ring buffer
4 *
5 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6 */
7 #include <linux/trace_recursion.h>
8 #include <linux/trace_events.h>
9 #include <linux/ring_buffer.h>
10 #include <linux/trace_clock.h>
11 #include <linux/sched/clock.h>
12 #include <linux/cacheflush.h>
13 #include <linux/trace_seq.h>
14 #include <linux/spinlock.h>
15 #include <linux/irq_work.h>
16 #include <linux/security.h>
17 #include <linux/uaccess.h>
18 #include <linux/hardirq.h>
19 #include <linux/kthread.h> /* for self test */
20 #include <linux/module.h>
21 #include <linux/percpu.h>
22 #include <linux/mutex.h>
23 #include <linux/delay.h>
24 #include <linux/slab.h>
25 #include <linux/init.h>
26 #include <linux/hash.h>
27 #include <linux/list.h>
28 #include <linux/cpu.h>
29 #include <linux/oom.h>
30 #include <linux/mm.h>
31
32 #include <asm/local64.h>
33 #include <asm/local.h>
34 #include <asm/setup.h>
35
36 #include "trace.h"
37
38 /*
39 * The "absolute" timestamp in the buffer is only 59 bits.
40 * If a clock has the 5 MSBs set, it needs to be saved and
41 * reinserted.
42 */
43 #define TS_MSB (0xf8ULL << 56)
44 #define ABS_TS_MASK (~TS_MSB)
45
46 static void update_pages_handler(struct work_struct *work);
47
48 #define RING_BUFFER_META_MAGIC 0xBADFEED
49
50 struct ring_buffer_meta {
51 int magic;
52 int struct_sizes;
53 unsigned long total_size;
54 unsigned long buffers_offset;
55 };
56
57 struct ring_buffer_cpu_meta {
58 unsigned long first_buffer;
59 unsigned long head_buffer;
60 unsigned long commit_buffer;
61 __u32 subbuf_size;
62 __u32 nr_subbufs;
63 int buffers[];
64 };
65
66 /*
67 * The ring buffer header is special. We must manually up keep it.
68 */
ring_buffer_print_entry_header(struct trace_seq * s)69 int ring_buffer_print_entry_header(struct trace_seq *s)
70 {
71 trace_seq_puts(s, "# compressed entry header\n");
72 trace_seq_puts(s, "\ttype_len : 5 bits\n");
73 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
74 trace_seq_puts(s, "\tarray : 32 bits\n");
75 trace_seq_putc(s, '\n');
76 trace_seq_printf(s, "\tpadding : type == %d\n",
77 RINGBUF_TYPE_PADDING);
78 trace_seq_printf(s, "\ttime_extend : type == %d\n",
79 RINGBUF_TYPE_TIME_EXTEND);
80 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
81 RINGBUF_TYPE_TIME_STAMP);
82 trace_seq_printf(s, "\tdata max type_len == %d\n",
83 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
84
85 return !trace_seq_has_overflowed(s);
86 }
87
88 /*
89 * The ring buffer is made up of a list of pages. A separate list of pages is
90 * allocated for each CPU. A writer may only write to a buffer that is
91 * associated with the CPU it is currently executing on. A reader may read
92 * from any per cpu buffer.
93 *
94 * The reader is special. For each per cpu buffer, the reader has its own
95 * reader page. When a reader has read the entire reader page, this reader
96 * page is swapped with another page in the ring buffer.
97 *
98 * Now, as long as the writer is off the reader page, the reader can do what
99 * ever it wants with that page. The writer will never write to that page
100 * again (as long as it is out of the ring buffer).
101 *
102 * Here's some silly ASCII art.
103 *
104 * +------+
105 * |reader| RING BUFFER
106 * |page |
107 * +------+ +---+ +---+ +---+
108 * | |-->| |-->| |
109 * +---+ +---+ +---+
110 * ^ |
111 * | |
112 * +---------------+
113 *
114 *
115 * +------+
116 * |reader| RING BUFFER
117 * |page |------------------v
118 * +------+ +---+ +---+ +---+
119 * | |-->| |-->| |
120 * +---+ +---+ +---+
121 * ^ |
122 * | |
123 * +---------------+
124 *
125 *
126 * +------+
127 * |reader| RING BUFFER
128 * |page |------------------v
129 * +------+ +---+ +---+ +---+
130 * ^ | |-->| |-->| |
131 * | +---+ +---+ +---+
132 * | |
133 * | |
134 * +------------------------------+
135 *
136 *
137 * +------+
138 * |buffer| RING BUFFER
139 * |page |------------------v
140 * +------+ +---+ +---+ +---+
141 * ^ | | | |-->| |
142 * | New +---+ +---+ +---+
143 * | Reader------^ |
144 * | page |
145 * +------------------------------+
146 *
147 *
148 * After we make this swap, the reader can hand this page off to the splice
149 * code and be done with it. It can even allocate a new page if it needs to
150 * and swap that into the ring buffer.
151 *
152 * We will be using cmpxchg soon to make all this lockless.
153 *
154 */
155
156 /* Used for individual buffers (after the counter) */
157 #define RB_BUFFER_OFF (1 << 20)
158
159 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
160
161 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
162 #define RB_ALIGNMENT 4U
163 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
164 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
165
166 #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
167 # define RB_FORCE_8BYTE_ALIGNMENT 0
168 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
169 #else
170 # define RB_FORCE_8BYTE_ALIGNMENT 1
171 # define RB_ARCH_ALIGNMENT 8U
172 #endif
173
174 #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
175
176 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
177 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
178
179 enum {
180 RB_LEN_TIME_EXTEND = 8,
181 RB_LEN_TIME_STAMP = 8,
182 };
183
184 #define skip_time_extend(event) \
185 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
186
187 #define extended_time(event) \
188 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
189
rb_null_event(struct ring_buffer_event * event)190 static inline bool rb_null_event(struct ring_buffer_event *event)
191 {
192 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
193 }
194
rb_event_set_padding(struct ring_buffer_event * event)195 static void rb_event_set_padding(struct ring_buffer_event *event)
196 {
197 /* padding has a NULL time_delta */
198 event->type_len = RINGBUF_TYPE_PADDING;
199 event->time_delta = 0;
200 }
201
202 static unsigned
rb_event_data_length(struct ring_buffer_event * event)203 rb_event_data_length(struct ring_buffer_event *event)
204 {
205 unsigned length;
206
207 if (event->type_len)
208 length = event->type_len * RB_ALIGNMENT;
209 else
210 length = event->array[0];
211 return length + RB_EVNT_HDR_SIZE;
212 }
213
214 /*
215 * Return the length of the given event. Will return
216 * the length of the time extend if the event is a
217 * time extend.
218 */
219 static inline unsigned
rb_event_length(struct ring_buffer_event * event)220 rb_event_length(struct ring_buffer_event *event)
221 {
222 switch (event->type_len) {
223 case RINGBUF_TYPE_PADDING:
224 if (rb_null_event(event))
225 /* undefined */
226 return -1;
227 return event->array[0] + RB_EVNT_HDR_SIZE;
228
229 case RINGBUF_TYPE_TIME_EXTEND:
230 return RB_LEN_TIME_EXTEND;
231
232 case RINGBUF_TYPE_TIME_STAMP:
233 return RB_LEN_TIME_STAMP;
234
235 case RINGBUF_TYPE_DATA:
236 return rb_event_data_length(event);
237 default:
238 WARN_ON_ONCE(1);
239 }
240 /* not hit */
241 return 0;
242 }
243
244 /*
245 * Return total length of time extend and data,
246 * or just the event length for all other events.
247 */
248 static inline unsigned
rb_event_ts_length(struct ring_buffer_event * event)249 rb_event_ts_length(struct ring_buffer_event *event)
250 {
251 unsigned len = 0;
252
253 if (extended_time(event)) {
254 /* time extends include the data event after it */
255 len = RB_LEN_TIME_EXTEND;
256 event = skip_time_extend(event);
257 }
258 return len + rb_event_length(event);
259 }
260
261 /**
262 * ring_buffer_event_length - return the length of the event
263 * @event: the event to get the length of
264 *
265 * Returns the size of the data load of a data event.
266 * If the event is something other than a data event, it
267 * returns the size of the event itself. With the exception
268 * of a TIME EXTEND, where it still returns the size of the
269 * data load of the data event after it.
270 */
ring_buffer_event_length(struct ring_buffer_event * event)271 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
272 {
273 unsigned length;
274
275 if (extended_time(event))
276 event = skip_time_extend(event);
277
278 length = rb_event_length(event);
279 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
280 return length;
281 length -= RB_EVNT_HDR_SIZE;
282 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
283 length -= sizeof(event->array[0]);
284 return length;
285 }
286 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
287
288 /* inline for ring buffer fast paths */
289 static __always_inline void *
rb_event_data(struct ring_buffer_event * event)290 rb_event_data(struct ring_buffer_event *event)
291 {
292 if (extended_time(event))
293 event = skip_time_extend(event);
294 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
295 /* If length is in len field, then array[0] has the data */
296 if (event->type_len)
297 return (void *)&event->array[0];
298 /* Otherwise length is in array[0] and array[1] has the data */
299 return (void *)&event->array[1];
300 }
301
302 /**
303 * ring_buffer_event_data - return the data of the event
304 * @event: the event to get the data from
305 */
ring_buffer_event_data(struct ring_buffer_event * event)306 void *ring_buffer_event_data(struct ring_buffer_event *event)
307 {
308 return rb_event_data(event);
309 }
310 EXPORT_SYMBOL_GPL(ring_buffer_event_data);
311
312 #define for_each_buffer_cpu(buffer, cpu) \
313 for_each_cpu(cpu, buffer->cpumask)
314
315 #define for_each_online_buffer_cpu(buffer, cpu) \
316 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
317
318 #define TS_SHIFT 27
319 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
320 #define TS_DELTA_TEST (~TS_MASK)
321
rb_event_time_stamp(struct ring_buffer_event * event)322 static u64 rb_event_time_stamp(struct ring_buffer_event *event)
323 {
324 u64 ts;
325
326 ts = event->array[0];
327 ts <<= TS_SHIFT;
328 ts += event->time_delta;
329
330 return ts;
331 }
332
333 /* Flag when events were overwritten */
334 #define RB_MISSED_EVENTS (1 << 31)
335 /* Missed count stored at end */
336 #define RB_MISSED_STORED (1 << 30)
337
338 #define RB_MISSED_MASK (3 << 30)
339
340 struct buffer_data_page {
341 u64 time_stamp; /* page time stamp */
342 local_t commit; /* write committed index */
343 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
344 };
345
346 struct buffer_data_read_page {
347 unsigned order; /* order of the page */
348 struct buffer_data_page *data; /* actual data, stored in this page */
349 };
350
351 /*
352 * Note, the buffer_page list must be first. The buffer pages
353 * are allocated in cache lines, which means that each buffer
354 * page will be at the beginning of a cache line, and thus
355 * the least significant bits will be zero. We use this to
356 * add flags in the list struct pointers, to make the ring buffer
357 * lockless.
358 */
359 struct buffer_page {
360 struct list_head list; /* list of buffer pages */
361 local_t write; /* index for next write */
362 unsigned read; /* index for next read */
363 local_t entries; /* entries on this page */
364 unsigned long real_end; /* real end of data */
365 unsigned order; /* order of the page */
366 u32 id:30; /* ID for external mapping */
367 u32 range:1; /* Mapped via a range */
368 struct buffer_data_page *page; /* Actual data page */
369 };
370
371 /*
372 * The buffer page counters, write and entries, must be reset
373 * atomically when crossing page boundaries. To synchronize this
374 * update, two counters are inserted into the number. One is
375 * the actual counter for the write position or count on the page.
376 *
377 * The other is a counter of updaters. Before an update happens
378 * the update partition of the counter is incremented. This will
379 * allow the updater to update the counter atomically.
380 *
381 * The counter is 20 bits, and the state data is 12.
382 */
383 #define RB_WRITE_MASK 0xfffff
384 #define RB_WRITE_INTCNT (1 << 20)
385
rb_init_page(struct buffer_data_page * bpage)386 static void rb_init_page(struct buffer_data_page *bpage)
387 {
388 local_set(&bpage->commit, 0);
389 }
390
rb_page_commit(struct buffer_page * bpage)391 static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage)
392 {
393 return local_read(&bpage->page->commit);
394 }
395
free_buffer_page(struct buffer_page * bpage)396 static void free_buffer_page(struct buffer_page *bpage)
397 {
398 /* Range pages are not to be freed */
399 if (!bpage->range)
400 free_pages((unsigned long)bpage->page, bpage->order);
401 kfree(bpage);
402 }
403
404 /*
405 * We need to fit the time_stamp delta into 27 bits.
406 */
test_time_stamp(u64 delta)407 static inline bool test_time_stamp(u64 delta)
408 {
409 return !!(delta & TS_DELTA_TEST);
410 }
411
412 struct rb_irq_work {
413 struct irq_work work;
414 wait_queue_head_t waiters;
415 wait_queue_head_t full_waiters;
416 atomic_t seq;
417 bool waiters_pending;
418 bool full_waiters_pending;
419 bool wakeup_full;
420 };
421
422 /*
423 * Structure to hold event state and handle nested events.
424 */
425 struct rb_event_info {
426 u64 ts;
427 u64 delta;
428 u64 before;
429 u64 after;
430 unsigned long length;
431 struct buffer_page *tail_page;
432 int add_timestamp;
433 };
434
435 /*
436 * Used for the add_timestamp
437 * NONE
438 * EXTEND - wants a time extend
439 * ABSOLUTE - the buffer requests all events to have absolute time stamps
440 * FORCE - force a full time stamp.
441 */
442 enum {
443 RB_ADD_STAMP_NONE = 0,
444 RB_ADD_STAMP_EXTEND = BIT(1),
445 RB_ADD_STAMP_ABSOLUTE = BIT(2),
446 RB_ADD_STAMP_FORCE = BIT(3)
447 };
448 /*
449 * Used for which event context the event is in.
450 * TRANSITION = 0
451 * NMI = 1
452 * IRQ = 2
453 * SOFTIRQ = 3
454 * NORMAL = 4
455 *
456 * See trace_recursive_lock() comment below for more details.
457 */
458 enum {
459 RB_CTX_TRANSITION,
460 RB_CTX_NMI,
461 RB_CTX_IRQ,
462 RB_CTX_SOFTIRQ,
463 RB_CTX_NORMAL,
464 RB_CTX_MAX
465 };
466
467 struct rb_time_struct {
468 local64_t time;
469 };
470 typedef struct rb_time_struct rb_time_t;
471
472 #define MAX_NEST 5
473
474 /*
475 * head_page == tail_page && head == tail then buffer is empty.
476 */
477 struct ring_buffer_per_cpu {
478 int cpu;
479 atomic_t record_disabled;
480 atomic_t resize_disabled;
481 struct trace_buffer *buffer;
482 raw_spinlock_t reader_lock; /* serialize readers */
483 arch_spinlock_t lock;
484 struct lock_class_key lock_key;
485 struct buffer_data_page *free_page;
486 unsigned long nr_pages;
487 unsigned int current_context;
488 struct list_head *pages;
489 /* pages generation counter, incremented when the list changes */
490 unsigned long cnt;
491 struct buffer_page *head_page; /* read from head */
492 struct buffer_page *tail_page; /* write to tail */
493 struct buffer_page *commit_page; /* committed pages */
494 struct buffer_page *reader_page;
495 unsigned long lost_events;
496 unsigned long last_overrun;
497 unsigned long nest;
498 local_t entries_bytes;
499 local_t entries;
500 local_t overrun;
501 local_t commit_overrun;
502 local_t dropped_events;
503 local_t committing;
504 local_t commits;
505 local_t pages_touched;
506 local_t pages_lost;
507 local_t pages_read;
508 long last_pages_touch;
509 size_t shortest_full;
510 unsigned long read;
511 unsigned long read_bytes;
512 rb_time_t write_stamp;
513 rb_time_t before_stamp;
514 u64 event_stamp[MAX_NEST];
515 u64 read_stamp;
516 /* pages removed since last reset */
517 unsigned long pages_removed;
518
519 unsigned int mapped;
520 unsigned int user_mapped; /* user space mapping */
521 struct mutex mapping_lock;
522 unsigned long *subbuf_ids; /* ID to subbuf VA */
523 struct trace_buffer_meta *meta_page;
524 struct ring_buffer_cpu_meta *ring_meta;
525
526 /* ring buffer pages to update, > 0 to add, < 0 to remove */
527 long nr_pages_to_update;
528 struct list_head new_pages; /* new pages to add */
529 struct work_struct update_pages_work;
530 struct completion update_done;
531
532 struct rb_irq_work irq_work;
533 };
534
535 struct trace_buffer {
536 unsigned flags;
537 int cpus;
538 atomic_t record_disabled;
539 atomic_t resizing;
540 cpumask_var_t cpumask;
541
542 struct lock_class_key *reader_lock_key;
543
544 struct mutex mutex;
545
546 struct ring_buffer_per_cpu **buffers;
547
548 struct hlist_node node;
549 u64 (*clock)(void);
550
551 struct rb_irq_work irq_work;
552 bool time_stamp_abs;
553
554 unsigned long range_addr_start;
555 unsigned long range_addr_end;
556
557 struct ring_buffer_meta *meta;
558
559 unsigned int subbuf_size;
560 unsigned int subbuf_order;
561 unsigned int max_data_size;
562 };
563
564 struct ring_buffer_iter {
565 struct ring_buffer_per_cpu *cpu_buffer;
566 unsigned long head;
567 unsigned long next_event;
568 struct buffer_page *head_page;
569 struct buffer_page *cache_reader_page;
570 unsigned long cache_read;
571 unsigned long cache_pages_removed;
572 u64 read_stamp;
573 u64 page_stamp;
574 struct ring_buffer_event *event;
575 size_t event_size;
576 int missed_events;
577 };
578
ring_buffer_print_page_header(struct trace_buffer * buffer,struct trace_seq * s)579 int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s)
580 {
581 struct buffer_data_page field;
582
583 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
584 "offset:0;\tsize:%u;\tsigned:%u;\n",
585 (unsigned int)sizeof(field.time_stamp),
586 (unsigned int)is_signed_type(u64));
587
588 trace_seq_printf(s, "\tfield: local_t commit;\t"
589 "offset:%u;\tsize:%u;\tsigned:%u;\n",
590 (unsigned int)offsetof(typeof(field), commit),
591 (unsigned int)sizeof(field.commit),
592 (unsigned int)is_signed_type(long));
593
594 trace_seq_printf(s, "\tfield: int overwrite;\t"
595 "offset:%u;\tsize:%u;\tsigned:%u;\n",
596 (unsigned int)offsetof(typeof(field), commit),
597 1,
598 (unsigned int)is_signed_type(long));
599
600 trace_seq_printf(s, "\tfield: char data;\t"
601 "offset:%u;\tsize:%u;\tsigned:%u;\n",
602 (unsigned int)offsetof(typeof(field), data),
603 (unsigned int)buffer->subbuf_size,
604 (unsigned int)is_signed_type(char));
605
606 return !trace_seq_has_overflowed(s);
607 }
608
rb_time_read(rb_time_t * t,u64 * ret)609 static inline void rb_time_read(rb_time_t *t, u64 *ret)
610 {
611 *ret = local64_read(&t->time);
612 }
rb_time_set(rb_time_t * t,u64 val)613 static void rb_time_set(rb_time_t *t, u64 val)
614 {
615 local64_set(&t->time, val);
616 }
617
618 /*
619 * Enable this to make sure that the event passed to
620 * ring_buffer_event_time_stamp() is not committed and also
621 * is on the buffer that it passed in.
622 */
623 //#define RB_VERIFY_EVENT
624 #ifdef RB_VERIFY_EVENT
625 static struct list_head *rb_list_head(struct list_head *list);
verify_event(struct ring_buffer_per_cpu * cpu_buffer,void * event)626 static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
627 void *event)
628 {
629 struct buffer_page *page = cpu_buffer->commit_page;
630 struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
631 struct list_head *next;
632 long commit, write;
633 unsigned long addr = (unsigned long)event;
634 bool done = false;
635 int stop = 0;
636
637 /* Make sure the event exists and is not committed yet */
638 do {
639 if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
640 done = true;
641 commit = local_read(&page->page->commit);
642 write = local_read(&page->write);
643 if (addr >= (unsigned long)&page->page->data[commit] &&
644 addr < (unsigned long)&page->page->data[write])
645 return;
646
647 next = rb_list_head(page->list.next);
648 page = list_entry(next, struct buffer_page, list);
649 } while (!done);
650 WARN_ON_ONCE(1);
651 }
652 #else
verify_event(struct ring_buffer_per_cpu * cpu_buffer,void * event)653 static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
654 void *event)
655 {
656 }
657 #endif
658
659 /*
660 * The absolute time stamp drops the 5 MSBs and some clocks may
661 * require them. The rb_fix_abs_ts() will take a previous full
662 * time stamp, and add the 5 MSB of that time stamp on to the
663 * saved absolute time stamp. Then they are compared in case of
664 * the unlikely event that the latest time stamp incremented
665 * the 5 MSB.
666 */
rb_fix_abs_ts(u64 abs,u64 save_ts)667 static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
668 {
669 if (save_ts & TS_MSB) {
670 abs |= save_ts & TS_MSB;
671 /* Check for overflow */
672 if (unlikely(abs < save_ts))
673 abs += 1ULL << 59;
674 }
675 return abs;
676 }
677
678 static inline u64 rb_time_stamp(struct trace_buffer *buffer);
679
680 /**
681 * ring_buffer_event_time_stamp - return the event's current time stamp
682 * @buffer: The buffer that the event is on
683 * @event: the event to get the time stamp of
684 *
685 * Note, this must be called after @event is reserved, and before it is
686 * committed to the ring buffer. And must be called from the same
687 * context where the event was reserved (normal, softirq, irq, etc).
688 *
689 * Returns the time stamp associated with the current event.
690 * If the event has an extended time stamp, then that is used as
691 * the time stamp to return.
692 * In the highly unlikely case that the event was nested more than
693 * the max nesting, then the write_stamp of the buffer is returned,
694 * otherwise current time is returned, but that really neither of
695 * the last two cases should ever happen.
696 */
ring_buffer_event_time_stamp(struct trace_buffer * buffer,struct ring_buffer_event * event)697 u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
698 struct ring_buffer_event *event)
699 {
700 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
701 unsigned int nest;
702 u64 ts;
703
704 /* If the event includes an absolute time, then just use that */
705 if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
706 ts = rb_event_time_stamp(event);
707 return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp);
708 }
709
710 nest = local_read(&cpu_buffer->committing);
711 verify_event(cpu_buffer, event);
712 if (WARN_ON_ONCE(!nest))
713 goto fail;
714
715 /* Read the current saved nesting level time stamp */
716 if (likely(--nest < MAX_NEST))
717 return cpu_buffer->event_stamp[nest];
718
719 /* Shouldn't happen, warn if it does */
720 WARN_ONCE(1, "nest (%d) greater than max", nest);
721
722 fail:
723 rb_time_read(&cpu_buffer->write_stamp, &ts);
724
725 return ts;
726 }
727
728 /**
729 * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
730 * @buffer: The ring_buffer to get the number of pages from
731 * @cpu: The cpu of the ring_buffer to get the number of pages from
732 *
733 * Returns the number of pages that have content in the ring buffer.
734 */
ring_buffer_nr_dirty_pages(struct trace_buffer * buffer,int cpu)735 size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
736 {
737 size_t read;
738 size_t lost;
739 size_t cnt;
740
741 read = local_read(&buffer->buffers[cpu]->pages_read);
742 lost = local_read(&buffer->buffers[cpu]->pages_lost);
743 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
744
745 if (WARN_ON_ONCE(cnt < lost))
746 return 0;
747
748 cnt -= lost;
749
750 /* The reader can read an empty page, but not more than that */
751 if (cnt < read) {
752 WARN_ON_ONCE(read > cnt + 1);
753 return 0;
754 }
755
756 return cnt - read;
757 }
758
full_hit(struct trace_buffer * buffer,int cpu,int full)759 static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
760 {
761 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
762 size_t nr_pages;
763 size_t dirty;
764
765 nr_pages = cpu_buffer->nr_pages;
766 if (!nr_pages || !full)
767 return true;
768
769 /*
770 * Add one as dirty will never equal nr_pages, as the sub-buffer
771 * that the writer is on is not counted as dirty.
772 * This is needed if "buffer_percent" is set to 100.
773 */
774 dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
775
776 return (dirty * 100) >= (full * nr_pages);
777 }
778
779 /*
780 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
781 *
782 * Schedules a delayed work to wake up any task that is blocked on the
783 * ring buffer waiters queue.
784 */
rb_wake_up_waiters(struct irq_work * work)785 static void rb_wake_up_waiters(struct irq_work *work)
786 {
787 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
788
789 /* For waiters waiting for the first wake up */
790 (void)atomic_fetch_inc_release(&rbwork->seq);
791
792 wake_up_all(&rbwork->waiters);
793 if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
794 /* Only cpu_buffer sets the above flags */
795 struct ring_buffer_per_cpu *cpu_buffer =
796 container_of(rbwork, struct ring_buffer_per_cpu, irq_work);
797
798 /* Called from interrupt context */
799 raw_spin_lock(&cpu_buffer->reader_lock);
800 rbwork->wakeup_full = false;
801 rbwork->full_waiters_pending = false;
802
803 /* Waking up all waiters, they will reset the shortest full */
804 cpu_buffer->shortest_full = 0;
805 raw_spin_unlock(&cpu_buffer->reader_lock);
806
807 wake_up_all(&rbwork->full_waiters);
808 }
809 }
810
811 /**
812 * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
813 * @buffer: The ring buffer to wake waiters on
814 * @cpu: The CPU buffer to wake waiters on
815 *
816 * In the case of a file that represents a ring buffer is closing,
817 * it is prudent to wake up any waiters that are on this.
818 */
ring_buffer_wake_waiters(struct trace_buffer * buffer,int cpu)819 void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
820 {
821 struct ring_buffer_per_cpu *cpu_buffer;
822 struct rb_irq_work *rbwork;
823
824 if (!buffer)
825 return;
826
827 if (cpu == RING_BUFFER_ALL_CPUS) {
828
829 /* Wake up individual ones too. One level recursion */
830 for_each_buffer_cpu(buffer, cpu)
831 ring_buffer_wake_waiters(buffer, cpu);
832
833 rbwork = &buffer->irq_work;
834 } else {
835 if (WARN_ON_ONCE(!buffer->buffers))
836 return;
837 if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
838 return;
839
840 cpu_buffer = buffer->buffers[cpu];
841 /* The CPU buffer may not have been initialized yet */
842 if (!cpu_buffer)
843 return;
844 rbwork = &cpu_buffer->irq_work;
845 }
846
847 /* This can be called in any context */
848 irq_work_queue(&rbwork->work);
849 }
850
rb_watermark_hit(struct trace_buffer * buffer,int cpu,int full)851 static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full)
852 {
853 struct ring_buffer_per_cpu *cpu_buffer;
854 bool ret = false;
855
856 /* Reads of all CPUs always waits for any data */
857 if (cpu == RING_BUFFER_ALL_CPUS)
858 return !ring_buffer_empty(buffer);
859
860 cpu_buffer = buffer->buffers[cpu];
861
862 if (!ring_buffer_empty_cpu(buffer, cpu)) {
863 unsigned long flags;
864 bool pagebusy;
865
866 if (!full)
867 return true;
868
869 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
870 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
871 ret = !pagebusy && full_hit(buffer, cpu, full);
872
873 if (!ret && (!cpu_buffer->shortest_full ||
874 cpu_buffer->shortest_full > full)) {
875 cpu_buffer->shortest_full = full;
876 }
877 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
878 }
879 return ret;
880 }
881
882 static inline bool
rb_wait_cond(struct rb_irq_work * rbwork,struct trace_buffer * buffer,int cpu,int full,ring_buffer_cond_fn cond,void * data)883 rb_wait_cond(struct rb_irq_work *rbwork, struct trace_buffer *buffer,
884 int cpu, int full, ring_buffer_cond_fn cond, void *data)
885 {
886 if (rb_watermark_hit(buffer, cpu, full))
887 return true;
888
889 if (cond(data))
890 return true;
891
892 /*
893 * The events can happen in critical sections where
894 * checking a work queue can cause deadlocks.
895 * After adding a task to the queue, this flag is set
896 * only to notify events to try to wake up the queue
897 * using irq_work.
898 *
899 * We don't clear it even if the buffer is no longer
900 * empty. The flag only causes the next event to run
901 * irq_work to do the work queue wake up. The worse
902 * that can happen if we race with !trace_empty() is that
903 * an event will cause an irq_work to try to wake up
904 * an empty queue.
905 *
906 * There's no reason to protect this flag either, as
907 * the work queue and irq_work logic will do the necessary
908 * synchronization for the wake ups. The only thing
909 * that is necessary is that the wake up happens after
910 * a task has been queued. It's OK for spurious wake ups.
911 */
912 if (full)
913 rbwork->full_waiters_pending = true;
914 else
915 rbwork->waiters_pending = true;
916
917 return false;
918 }
919
920 struct rb_wait_data {
921 struct rb_irq_work *irq_work;
922 int seq;
923 };
924
925 /*
926 * The default wait condition for ring_buffer_wait() is to just to exit the
927 * wait loop the first time it is woken up.
928 */
rb_wait_once(void * data)929 static bool rb_wait_once(void *data)
930 {
931 struct rb_wait_data *rdata = data;
932 struct rb_irq_work *rbwork = rdata->irq_work;
933
934 return atomic_read_acquire(&rbwork->seq) != rdata->seq;
935 }
936
937 /**
938 * ring_buffer_wait - wait for input to the ring buffer
939 * @buffer: buffer to wait on
940 * @cpu: the cpu buffer to wait on
941 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
942 * @cond: condition function to break out of wait (NULL to run once)
943 * @data: the data to pass to @cond.
944 *
945 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
946 * as data is added to any of the @buffer's cpu buffers. Otherwise
947 * it will wait for data to be added to a specific cpu buffer.
948 */
ring_buffer_wait(struct trace_buffer * buffer,int cpu,int full,ring_buffer_cond_fn cond,void * data)949 int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full,
950 ring_buffer_cond_fn cond, void *data)
951 {
952 struct ring_buffer_per_cpu *cpu_buffer;
953 struct wait_queue_head *waitq;
954 struct rb_irq_work *rbwork;
955 struct rb_wait_data rdata;
956 int ret = 0;
957
958 /*
959 * Depending on what the caller is waiting for, either any
960 * data in any cpu buffer, or a specific buffer, put the
961 * caller on the appropriate wait queue.
962 */
963 if (cpu == RING_BUFFER_ALL_CPUS) {
964 rbwork = &buffer->irq_work;
965 /* Full only makes sense on per cpu reads */
966 full = 0;
967 } else {
968 if (!cpumask_test_cpu(cpu, buffer->cpumask))
969 return -ENODEV;
970 cpu_buffer = buffer->buffers[cpu];
971 rbwork = &cpu_buffer->irq_work;
972 }
973
974 if (full)
975 waitq = &rbwork->full_waiters;
976 else
977 waitq = &rbwork->waiters;
978
979 /* Set up to exit loop as soon as it is woken */
980 if (!cond) {
981 cond = rb_wait_once;
982 rdata.irq_work = rbwork;
983 rdata.seq = atomic_read_acquire(&rbwork->seq);
984 data = &rdata;
985 }
986
987 ret = wait_event_interruptible((*waitq),
988 rb_wait_cond(rbwork, buffer, cpu, full, cond, data));
989
990 return ret;
991 }
992
993 /**
994 * ring_buffer_poll_wait - poll on buffer input
995 * @buffer: buffer to wait on
996 * @cpu: the cpu buffer to wait on
997 * @filp: the file descriptor
998 * @poll_table: The poll descriptor
999 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
1000 *
1001 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
1002 * as data is added to any of the @buffer's cpu buffers. Otherwise
1003 * it will wait for data to be added to a specific cpu buffer.
1004 *
1005 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
1006 * zero otherwise.
1007 */
ring_buffer_poll_wait(struct trace_buffer * buffer,int cpu,struct file * filp,poll_table * poll_table,int full)1008 __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
1009 struct file *filp, poll_table *poll_table, int full)
1010 {
1011 struct ring_buffer_per_cpu *cpu_buffer;
1012 struct rb_irq_work *rbwork;
1013
1014 if (cpu == RING_BUFFER_ALL_CPUS) {
1015 rbwork = &buffer->irq_work;
1016 full = 0;
1017 } else {
1018 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1019 return EPOLLERR;
1020
1021 cpu_buffer = buffer->buffers[cpu];
1022 rbwork = &cpu_buffer->irq_work;
1023 }
1024
1025 if (full) {
1026 poll_wait(filp, &rbwork->full_waiters, poll_table);
1027
1028 if (rb_watermark_hit(buffer, cpu, full))
1029 return EPOLLIN | EPOLLRDNORM;
1030 /*
1031 * Only allow full_waiters_pending update to be seen after
1032 * the shortest_full is set (in rb_watermark_hit). If the
1033 * writer sees the full_waiters_pending flag set, it will
1034 * compare the amount in the ring buffer to shortest_full.
1035 * If the amount in the ring buffer is greater than the
1036 * shortest_full percent, it will call the irq_work handler
1037 * to wake up this list. The irq_handler will reset shortest_full
1038 * back to zero. That's done under the reader_lock, but
1039 * the below smp_mb() makes sure that the update to
1040 * full_waiters_pending doesn't leak up into the above.
1041 */
1042 smp_mb();
1043 rbwork->full_waiters_pending = true;
1044 return 0;
1045 }
1046
1047 poll_wait(filp, &rbwork->waiters, poll_table);
1048 rbwork->waiters_pending = true;
1049
1050 /*
1051 * There's a tight race between setting the waiters_pending and
1052 * checking if the ring buffer is empty. Once the waiters_pending bit
1053 * is set, the next event will wake the task up, but we can get stuck
1054 * if there's only a single event in.
1055 *
1056 * FIXME: Ideally, we need a memory barrier on the writer side as well,
1057 * but adding a memory barrier to all events will cause too much of a
1058 * performance hit in the fast path. We only need a memory barrier when
1059 * the buffer goes from empty to having content. But as this race is
1060 * extremely small, and it's not a problem if another event comes in, we
1061 * will fix it later.
1062 */
1063 smp_mb();
1064
1065 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1066 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1067 return EPOLLIN | EPOLLRDNORM;
1068 return 0;
1069 }
1070
1071 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
1072 #define RB_WARN_ON(b, cond) \
1073 ({ \
1074 int _____ret = unlikely(cond); \
1075 if (_____ret) { \
1076 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1077 struct ring_buffer_per_cpu *__b = \
1078 (void *)b; \
1079 atomic_inc(&__b->buffer->record_disabled); \
1080 } else \
1081 atomic_inc(&b->record_disabled); \
1082 WARN_ON(1); \
1083 } \
1084 _____ret; \
1085 })
1086
1087 /* Up this if you want to test the TIME_EXTENTS and normalization */
1088 #define DEBUG_SHIFT 0
1089
rb_time_stamp(struct trace_buffer * buffer)1090 static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1091 {
1092 u64 ts;
1093
1094 /* Skip retpolines :-( */
1095 if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1096 ts = trace_clock_local();
1097 else
1098 ts = buffer->clock();
1099
1100 /* shift to debug/test normalization and TIME_EXTENTS */
1101 return ts << DEBUG_SHIFT;
1102 }
1103
ring_buffer_time_stamp(struct trace_buffer * buffer)1104 u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1105 {
1106 u64 time;
1107
1108 preempt_disable_notrace();
1109 time = rb_time_stamp(buffer);
1110 preempt_enable_notrace();
1111
1112 return time;
1113 }
1114 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1115
ring_buffer_normalize_time_stamp(struct trace_buffer * buffer,int cpu,u64 * ts)1116 void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1117 int cpu, u64 *ts)
1118 {
1119 /* Just stupid testing the normalize function and deltas */
1120 *ts >>= DEBUG_SHIFT;
1121 }
1122 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1123
1124 /*
1125 * Making the ring buffer lockless makes things tricky.
1126 * Although writes only happen on the CPU that they are on,
1127 * and they only need to worry about interrupts. Reads can
1128 * happen on any CPU.
1129 *
1130 * The reader page is always off the ring buffer, but when the
1131 * reader finishes with a page, it needs to swap its page with
1132 * a new one from the buffer. The reader needs to take from
1133 * the head (writes go to the tail). But if a writer is in overwrite
1134 * mode and wraps, it must push the head page forward.
1135 *
1136 * Here lies the problem.
1137 *
1138 * The reader must be careful to replace only the head page, and
1139 * not another one. As described at the top of the file in the
1140 * ASCII art, the reader sets its old page to point to the next
1141 * page after head. It then sets the page after head to point to
1142 * the old reader page. But if the writer moves the head page
1143 * during this operation, the reader could end up with the tail.
1144 *
1145 * We use cmpxchg to help prevent this race. We also do something
1146 * special with the page before head. We set the LSB to 1.
1147 *
1148 * When the writer must push the page forward, it will clear the
1149 * bit that points to the head page, move the head, and then set
1150 * the bit that points to the new head page.
1151 *
1152 * We also don't want an interrupt coming in and moving the head
1153 * page on another writer. Thus we use the second LSB to catch
1154 * that too. Thus:
1155 *
1156 * head->list->prev->next bit 1 bit 0
1157 * ------- -------
1158 * Normal page 0 0
1159 * Points to head page 0 1
1160 * New head page 1 0
1161 *
1162 * Note we can not trust the prev pointer of the head page, because:
1163 *
1164 * +----+ +-----+ +-----+
1165 * | |------>| T |---X--->| N |
1166 * | |<------| | | |
1167 * +----+ +-----+ +-----+
1168 * ^ ^ |
1169 * | +-----+ | |
1170 * +----------| R |----------+ |
1171 * | |<-----------+
1172 * +-----+
1173 *
1174 * Key: ---X--> HEAD flag set in pointer
1175 * T Tail page
1176 * R Reader page
1177 * N Next page
1178 *
1179 * (see __rb_reserve_next() to see where this happens)
1180 *
1181 * What the above shows is that the reader just swapped out
1182 * the reader page with a page in the buffer, but before it
1183 * could make the new header point back to the new page added
1184 * it was preempted by a writer. The writer moved forward onto
1185 * the new page added by the reader and is about to move forward
1186 * again.
1187 *
1188 * You can see, it is legitimate for the previous pointer of
1189 * the head (or any page) not to point back to itself. But only
1190 * temporarily.
1191 */
1192
1193 #define RB_PAGE_NORMAL 0UL
1194 #define RB_PAGE_HEAD 1UL
1195 #define RB_PAGE_UPDATE 2UL
1196
1197
1198 #define RB_FLAG_MASK 3UL
1199
1200 /* PAGE_MOVED is not part of the mask */
1201 #define RB_PAGE_MOVED 4UL
1202
1203 /*
1204 * rb_list_head - remove any bit
1205 */
rb_list_head(struct list_head * list)1206 static struct list_head *rb_list_head(struct list_head *list)
1207 {
1208 unsigned long val = (unsigned long)list;
1209
1210 return (struct list_head *)(val & ~RB_FLAG_MASK);
1211 }
1212
1213 /*
1214 * rb_is_head_page - test if the given page is the head page
1215 *
1216 * Because the reader may move the head_page pointer, we can
1217 * not trust what the head page is (it may be pointing to
1218 * the reader page). But if the next page is a header page,
1219 * its flags will be non zero.
1220 */
1221 static inline int
rb_is_head_page(struct buffer_page * page,struct list_head * list)1222 rb_is_head_page(struct buffer_page *page, struct list_head *list)
1223 {
1224 unsigned long val;
1225
1226 val = (unsigned long)list->next;
1227
1228 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1229 return RB_PAGE_MOVED;
1230
1231 return val & RB_FLAG_MASK;
1232 }
1233
1234 /*
1235 * rb_is_reader_page
1236 *
1237 * The unique thing about the reader page, is that, if the
1238 * writer is ever on it, the previous pointer never points
1239 * back to the reader page.
1240 */
rb_is_reader_page(struct buffer_page * page)1241 static bool rb_is_reader_page(struct buffer_page *page)
1242 {
1243 struct list_head *list = page->list.prev;
1244
1245 return rb_list_head(list->next) != &page->list;
1246 }
1247
1248 /*
1249 * rb_set_list_to_head - set a list_head to be pointing to head.
1250 */
rb_set_list_to_head(struct list_head * list)1251 static void rb_set_list_to_head(struct list_head *list)
1252 {
1253 unsigned long *ptr;
1254
1255 ptr = (unsigned long *)&list->next;
1256 *ptr |= RB_PAGE_HEAD;
1257 *ptr &= ~RB_PAGE_UPDATE;
1258 }
1259
1260 /*
1261 * rb_head_page_activate - sets up head page
1262 */
rb_head_page_activate(struct ring_buffer_per_cpu * cpu_buffer)1263 static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1264 {
1265 struct buffer_page *head;
1266
1267 head = cpu_buffer->head_page;
1268 if (!head)
1269 return;
1270
1271 /*
1272 * Set the previous list pointer to have the HEAD flag.
1273 */
1274 rb_set_list_to_head(head->list.prev);
1275
1276 if (cpu_buffer->ring_meta) {
1277 struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
1278 meta->head_buffer = (unsigned long)head->page;
1279 }
1280 }
1281
rb_list_head_clear(struct list_head * list)1282 static void rb_list_head_clear(struct list_head *list)
1283 {
1284 unsigned long *ptr = (unsigned long *)&list->next;
1285
1286 *ptr &= ~RB_FLAG_MASK;
1287 }
1288
1289 /*
1290 * rb_head_page_deactivate - clears head page ptr (for free list)
1291 */
1292 static void
rb_head_page_deactivate(struct ring_buffer_per_cpu * cpu_buffer)1293 rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1294 {
1295 struct list_head *hd;
1296
1297 /* Go through the whole list and clear any pointers found. */
1298 rb_list_head_clear(cpu_buffer->pages);
1299
1300 list_for_each(hd, cpu_buffer->pages)
1301 rb_list_head_clear(hd);
1302 }
1303
rb_head_page_set(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * head,struct buffer_page * prev,int old_flag,int new_flag)1304 static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1305 struct buffer_page *head,
1306 struct buffer_page *prev,
1307 int old_flag, int new_flag)
1308 {
1309 struct list_head *list;
1310 unsigned long val = (unsigned long)&head->list;
1311 unsigned long ret;
1312
1313 list = &prev->list;
1314
1315 val &= ~RB_FLAG_MASK;
1316
1317 ret = cmpxchg((unsigned long *)&list->next,
1318 val | old_flag, val | new_flag);
1319
1320 /* check if the reader took the page */
1321 if ((ret & ~RB_FLAG_MASK) != val)
1322 return RB_PAGE_MOVED;
1323
1324 return ret & RB_FLAG_MASK;
1325 }
1326
rb_head_page_set_update(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * head,struct buffer_page * prev,int old_flag)1327 static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1328 struct buffer_page *head,
1329 struct buffer_page *prev,
1330 int old_flag)
1331 {
1332 return rb_head_page_set(cpu_buffer, head, prev,
1333 old_flag, RB_PAGE_UPDATE);
1334 }
1335
rb_head_page_set_head(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * head,struct buffer_page * prev,int old_flag)1336 static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1337 struct buffer_page *head,
1338 struct buffer_page *prev,
1339 int old_flag)
1340 {
1341 return rb_head_page_set(cpu_buffer, head, prev,
1342 old_flag, RB_PAGE_HEAD);
1343 }
1344
rb_head_page_set_normal(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * head,struct buffer_page * prev,int old_flag)1345 static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1346 struct buffer_page *head,
1347 struct buffer_page *prev,
1348 int old_flag)
1349 {
1350 return rb_head_page_set(cpu_buffer, head, prev,
1351 old_flag, RB_PAGE_NORMAL);
1352 }
1353
rb_inc_page(struct buffer_page ** bpage)1354 static inline void rb_inc_page(struct buffer_page **bpage)
1355 {
1356 struct list_head *p = rb_list_head((*bpage)->list.next);
1357
1358 *bpage = list_entry(p, struct buffer_page, list);
1359 }
1360
1361 static struct buffer_page *
rb_set_head_page(struct ring_buffer_per_cpu * cpu_buffer)1362 rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1363 {
1364 struct buffer_page *head;
1365 struct buffer_page *page;
1366 struct list_head *list;
1367 int i;
1368
1369 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1370 return NULL;
1371
1372 /* sanity check */
1373 list = cpu_buffer->pages;
1374 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1375 return NULL;
1376
1377 page = head = cpu_buffer->head_page;
1378 /*
1379 * It is possible that the writer moves the header behind
1380 * where we started, and we miss in one loop.
1381 * A second loop should grab the header, but we'll do
1382 * three loops just because I'm paranoid.
1383 */
1384 for (i = 0; i < 3; i++) {
1385 do {
1386 if (rb_is_head_page(page, page->list.prev)) {
1387 cpu_buffer->head_page = page;
1388 return page;
1389 }
1390 rb_inc_page(&page);
1391 } while (page != head);
1392 }
1393
1394 RB_WARN_ON(cpu_buffer, 1);
1395
1396 return NULL;
1397 }
1398
rb_head_page_replace(struct buffer_page * old,struct buffer_page * new)1399 static bool rb_head_page_replace(struct buffer_page *old,
1400 struct buffer_page *new)
1401 {
1402 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1403 unsigned long val;
1404
1405 val = *ptr & ~RB_FLAG_MASK;
1406 val |= RB_PAGE_HEAD;
1407
1408 return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
1409 }
1410
1411 /*
1412 * rb_tail_page_update - move the tail page forward
1413 */
rb_tail_page_update(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * tail_page,struct buffer_page * next_page)1414 static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1415 struct buffer_page *tail_page,
1416 struct buffer_page *next_page)
1417 {
1418 unsigned long old_entries;
1419 unsigned long old_write;
1420
1421 /*
1422 * The tail page now needs to be moved forward.
1423 *
1424 * We need to reset the tail page, but without messing
1425 * with possible erasing of data brought in by interrupts
1426 * that have moved the tail page and are currently on it.
1427 *
1428 * We add a counter to the write field to denote this.
1429 */
1430 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1431 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1432
1433 /*
1434 * Just make sure we have seen our old_write and synchronize
1435 * with any interrupts that come in.
1436 */
1437 barrier();
1438
1439 /*
1440 * If the tail page is still the same as what we think
1441 * it is, then it is up to us to update the tail
1442 * pointer.
1443 */
1444 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1445 /* Zero the write counter */
1446 unsigned long val = old_write & ~RB_WRITE_MASK;
1447 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1448
1449 /*
1450 * This will only succeed if an interrupt did
1451 * not come in and change it. In which case, we
1452 * do not want to modify it.
1453 *
1454 * We add (void) to let the compiler know that we do not care
1455 * about the return value of these functions. We use the
1456 * cmpxchg to only update if an interrupt did not already
1457 * do it for us. If the cmpxchg fails, we don't care.
1458 */
1459 (void)local_cmpxchg(&next_page->write, old_write, val);
1460 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1461
1462 /*
1463 * No need to worry about races with clearing out the commit.
1464 * it only can increment when a commit takes place. But that
1465 * only happens in the outer most nested commit.
1466 */
1467 local_set(&next_page->page->commit, 0);
1468
1469 /* Either we update tail_page or an interrupt does */
1470 if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page))
1471 local_inc(&cpu_buffer->pages_touched);
1472 }
1473 }
1474
rb_check_bpage(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * bpage)1475 static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1476 struct buffer_page *bpage)
1477 {
1478 unsigned long val = (unsigned long)bpage;
1479
1480 RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK);
1481 }
1482
rb_check_links(struct ring_buffer_per_cpu * cpu_buffer,struct list_head * list)1483 static bool rb_check_links(struct ring_buffer_per_cpu *cpu_buffer,
1484 struct list_head *list)
1485 {
1486 if (RB_WARN_ON(cpu_buffer,
1487 rb_list_head(rb_list_head(list->next)->prev) != list))
1488 return false;
1489
1490 if (RB_WARN_ON(cpu_buffer,
1491 rb_list_head(rb_list_head(list->prev)->next) != list))
1492 return false;
1493
1494 return true;
1495 }
1496
1497 /**
1498 * rb_check_pages - integrity check of buffer pages
1499 * @cpu_buffer: CPU buffer with pages to test
1500 *
1501 * As a safety measure we check to make sure the data pages have not
1502 * been corrupted.
1503 */
rb_check_pages(struct ring_buffer_per_cpu * cpu_buffer)1504 static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1505 {
1506 struct list_head *head, *tmp;
1507 unsigned long buffer_cnt;
1508 unsigned long flags;
1509 int nr_loops = 0;
1510
1511 /*
1512 * Walk the linked list underpinning the ring buffer and validate all
1513 * its next and prev links.
1514 *
1515 * The check acquires the reader_lock to avoid concurrent processing
1516 * with code that could be modifying the list. However, the lock cannot
1517 * be held for the entire duration of the walk, as this would make the
1518 * time when interrupts are disabled non-deterministic, dependent on the
1519 * ring buffer size. Therefore, the code releases and re-acquires the
1520 * lock after checking each page. The ring_buffer_per_cpu.cnt variable
1521 * is then used to detect if the list was modified while the lock was
1522 * not held, in which case the check needs to be restarted.
1523 *
1524 * The code attempts to perform the check at most three times before
1525 * giving up. This is acceptable because this is only a self-validation
1526 * to detect problems early on. In practice, the list modification
1527 * operations are fairly spaced, and so this check typically succeeds at
1528 * most on the second try.
1529 */
1530 again:
1531 if (++nr_loops > 3)
1532 return;
1533
1534 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1535 head = rb_list_head(cpu_buffer->pages);
1536 if (!rb_check_links(cpu_buffer, head))
1537 goto out_locked;
1538 buffer_cnt = cpu_buffer->cnt;
1539 tmp = head;
1540 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1541
1542 while (true) {
1543 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1544
1545 if (buffer_cnt != cpu_buffer->cnt) {
1546 /* The list was updated, try again. */
1547 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1548 goto again;
1549 }
1550
1551 tmp = rb_list_head(tmp->next);
1552 if (tmp == head)
1553 /* The iteration circled back, all is done. */
1554 goto out_locked;
1555
1556 if (!rb_check_links(cpu_buffer, tmp))
1557 goto out_locked;
1558
1559 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1560 }
1561
1562 out_locked:
1563 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1564 }
1565
1566 /*
1567 * Take an address, add the meta data size as well as the array of
1568 * array subbuffer indexes, then align it to a subbuffer size.
1569 *
1570 * This is used to help find the next per cpu subbuffer within a mapped range.
1571 */
1572 static unsigned long
rb_range_align_subbuf(unsigned long addr,int subbuf_size,int nr_subbufs)1573 rb_range_align_subbuf(unsigned long addr, int subbuf_size, int nr_subbufs)
1574 {
1575 addr += sizeof(struct ring_buffer_cpu_meta) +
1576 sizeof(int) * nr_subbufs;
1577 return ALIGN(addr, subbuf_size);
1578 }
1579
1580 /*
1581 * Return the ring_buffer_meta for a given @cpu.
1582 */
rb_range_meta(struct trace_buffer * buffer,int nr_pages,int cpu)1583 static void *rb_range_meta(struct trace_buffer *buffer, int nr_pages, int cpu)
1584 {
1585 int subbuf_size = buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
1586 struct ring_buffer_cpu_meta *meta;
1587 struct ring_buffer_meta *bmeta;
1588 unsigned long ptr;
1589 int nr_subbufs;
1590
1591 bmeta = buffer->meta;
1592 if (!bmeta)
1593 return NULL;
1594
1595 ptr = (unsigned long)bmeta + bmeta->buffers_offset;
1596 meta = (struct ring_buffer_cpu_meta *)ptr;
1597
1598 /* When nr_pages passed in is zero, the first meta has already been initialized */
1599 if (!nr_pages) {
1600 nr_subbufs = meta->nr_subbufs;
1601 } else {
1602 /* Include the reader page */
1603 nr_subbufs = nr_pages + 1;
1604 }
1605
1606 /*
1607 * The first chunk may not be subbuffer aligned, where as
1608 * the rest of the chunks are.
1609 */
1610 if (cpu) {
1611 ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
1612 ptr += subbuf_size * nr_subbufs;
1613
1614 /* We can use multiplication to find chunks greater than 1 */
1615 if (cpu > 1) {
1616 unsigned long size;
1617 unsigned long p;
1618
1619 /* Save the beginning of this CPU chunk */
1620 p = ptr;
1621 ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
1622 ptr += subbuf_size * nr_subbufs;
1623
1624 /* Now all chunks after this are the same size */
1625 size = ptr - p;
1626 ptr += size * (cpu - 2);
1627 }
1628 }
1629 return (void *)ptr;
1630 }
1631
1632 /* Return the start of subbufs given the meta pointer */
rb_subbufs_from_meta(struct ring_buffer_cpu_meta * meta)1633 static void *rb_subbufs_from_meta(struct ring_buffer_cpu_meta *meta)
1634 {
1635 int subbuf_size = meta->subbuf_size;
1636 unsigned long ptr;
1637
1638 ptr = (unsigned long)meta;
1639 ptr = rb_range_align_subbuf(ptr, subbuf_size, meta->nr_subbufs);
1640
1641 return (void *)ptr;
1642 }
1643
1644 /*
1645 * Return a specific sub-buffer for a given @cpu defined by @idx.
1646 */
rb_range_buffer(struct ring_buffer_per_cpu * cpu_buffer,int idx)1647 static void *rb_range_buffer(struct ring_buffer_per_cpu *cpu_buffer, int idx)
1648 {
1649 struct ring_buffer_cpu_meta *meta;
1650 unsigned long ptr;
1651 int subbuf_size;
1652
1653 meta = rb_range_meta(cpu_buffer->buffer, 0, cpu_buffer->cpu);
1654 if (!meta)
1655 return NULL;
1656
1657 if (WARN_ON_ONCE(idx >= meta->nr_subbufs))
1658 return NULL;
1659
1660 subbuf_size = meta->subbuf_size;
1661
1662 /* Map this buffer to the order that's in meta->buffers[] */
1663 idx = meta->buffers[idx];
1664
1665 ptr = (unsigned long)rb_subbufs_from_meta(meta);
1666
1667 ptr += subbuf_size * idx;
1668 if (ptr + subbuf_size > cpu_buffer->buffer->range_addr_end)
1669 return NULL;
1670
1671 return (void *)ptr;
1672 }
1673
1674 /*
1675 * See if the existing memory contains a valid meta section.
1676 * if so, use that, otherwise initialize it.
1677 */
rb_meta_init(struct trace_buffer * buffer,int scratch_size)1678 static bool rb_meta_init(struct trace_buffer *buffer, int scratch_size)
1679 {
1680 unsigned long ptr = buffer->range_addr_start;
1681 struct ring_buffer_meta *bmeta;
1682 unsigned long total_size;
1683 int struct_sizes;
1684
1685 bmeta = (struct ring_buffer_meta *)ptr;
1686 buffer->meta = bmeta;
1687
1688 total_size = buffer->range_addr_end - buffer->range_addr_start;
1689
1690 struct_sizes = sizeof(struct ring_buffer_cpu_meta);
1691 struct_sizes |= sizeof(*bmeta) << 16;
1692
1693 /* The first buffer will start word size after the meta page */
1694 ptr += sizeof(*bmeta);
1695 ptr = ALIGN(ptr, sizeof(long));
1696 ptr += scratch_size;
1697
1698 if (bmeta->magic != RING_BUFFER_META_MAGIC) {
1699 pr_info("Ring buffer boot meta mismatch of magic\n");
1700 goto init;
1701 }
1702
1703 if (bmeta->struct_sizes != struct_sizes) {
1704 pr_info("Ring buffer boot meta mismatch of struct size\n");
1705 goto init;
1706 }
1707
1708 if (bmeta->total_size != total_size) {
1709 pr_info("Ring buffer boot meta mismatch of total size\n");
1710 goto init;
1711 }
1712
1713 if (bmeta->buffers_offset > bmeta->total_size) {
1714 pr_info("Ring buffer boot meta mismatch of offset outside of total size\n");
1715 goto init;
1716 }
1717
1718 if (bmeta->buffers_offset != (void *)ptr - (void *)bmeta) {
1719 pr_info("Ring buffer boot meta mismatch of first buffer offset\n");
1720 goto init;
1721 }
1722
1723 return true;
1724
1725 init:
1726 bmeta->magic = RING_BUFFER_META_MAGIC;
1727 bmeta->struct_sizes = struct_sizes;
1728 bmeta->total_size = total_size;
1729 bmeta->buffers_offset = (void *)ptr - (void *)bmeta;
1730
1731 /* Zero out the scatch pad */
1732 memset((void *)bmeta + sizeof(*bmeta), 0, bmeta->buffers_offset - sizeof(*bmeta));
1733
1734 return false;
1735 }
1736
1737 /*
1738 * See if the existing memory contains valid ring buffer data.
1739 * As the previous kernel must be the same as this kernel, all
1740 * the calculations (size of buffers and number of buffers)
1741 * must be the same.
1742 */
rb_cpu_meta_valid(struct ring_buffer_cpu_meta * meta,int cpu,struct trace_buffer * buffer,int nr_pages,unsigned long * subbuf_mask)1743 static bool rb_cpu_meta_valid(struct ring_buffer_cpu_meta *meta, int cpu,
1744 struct trace_buffer *buffer, int nr_pages,
1745 unsigned long *subbuf_mask)
1746 {
1747 int subbuf_size = PAGE_SIZE;
1748 struct buffer_data_page *subbuf;
1749 unsigned long buffers_start;
1750 unsigned long buffers_end;
1751 int i;
1752
1753 if (!subbuf_mask)
1754 return false;
1755
1756 buffers_start = meta->first_buffer;
1757 buffers_end = meta->first_buffer + (subbuf_size * meta->nr_subbufs);
1758
1759 /* Is the head and commit buffers within the range of buffers? */
1760 if (meta->head_buffer < buffers_start ||
1761 meta->head_buffer >= buffers_end) {
1762 pr_info("Ring buffer boot meta [%d] head buffer out of range\n", cpu);
1763 return false;
1764 }
1765
1766 if (meta->commit_buffer < buffers_start ||
1767 meta->commit_buffer >= buffers_end) {
1768 pr_info("Ring buffer boot meta [%d] commit buffer out of range\n", cpu);
1769 return false;
1770 }
1771
1772 subbuf = rb_subbufs_from_meta(meta);
1773
1774 bitmap_clear(subbuf_mask, 0, meta->nr_subbufs);
1775
1776 /* Is the meta buffers and the subbufs themselves have correct data? */
1777 for (i = 0; i < meta->nr_subbufs; i++) {
1778 if (meta->buffers[i] < 0 ||
1779 meta->buffers[i] >= meta->nr_subbufs) {
1780 pr_info("Ring buffer boot meta [%d] array out of range\n", cpu);
1781 return false;
1782 }
1783
1784 if ((unsigned)local_read(&subbuf->commit) > subbuf_size) {
1785 pr_info("Ring buffer boot meta [%d] buffer invalid commit\n", cpu);
1786 return false;
1787 }
1788
1789 if (test_bit(meta->buffers[i], subbuf_mask)) {
1790 pr_info("Ring buffer boot meta [%d] array has duplicates\n", cpu);
1791 return false;
1792 }
1793
1794 set_bit(meta->buffers[i], subbuf_mask);
1795 subbuf = (void *)subbuf + subbuf_size;
1796 }
1797
1798 return true;
1799 }
1800
1801 static int rb_meta_subbuf_idx(struct ring_buffer_cpu_meta *meta, void *subbuf);
1802
rb_read_data_buffer(struct buffer_data_page * dpage,int tail,int cpu,unsigned long long * timestamp,u64 * delta_ptr)1803 static int rb_read_data_buffer(struct buffer_data_page *dpage, int tail, int cpu,
1804 unsigned long long *timestamp, u64 *delta_ptr)
1805 {
1806 struct ring_buffer_event *event;
1807 u64 ts, delta;
1808 int events = 0;
1809 int e;
1810
1811 *delta_ptr = 0;
1812 *timestamp = 0;
1813
1814 ts = dpage->time_stamp;
1815
1816 for (e = 0; e < tail; e += rb_event_length(event)) {
1817
1818 event = (struct ring_buffer_event *)(dpage->data + e);
1819
1820 switch (event->type_len) {
1821
1822 case RINGBUF_TYPE_TIME_EXTEND:
1823 delta = rb_event_time_stamp(event);
1824 ts += delta;
1825 break;
1826
1827 case RINGBUF_TYPE_TIME_STAMP:
1828 delta = rb_event_time_stamp(event);
1829 delta = rb_fix_abs_ts(delta, ts);
1830 if (delta < ts) {
1831 *delta_ptr = delta;
1832 *timestamp = ts;
1833 return -1;
1834 }
1835 ts = delta;
1836 break;
1837
1838 case RINGBUF_TYPE_PADDING:
1839 if (event->time_delta == 1)
1840 break;
1841 fallthrough;
1842 case RINGBUF_TYPE_DATA:
1843 events++;
1844 ts += event->time_delta;
1845 break;
1846
1847 default:
1848 return -1;
1849 }
1850 }
1851 *timestamp = ts;
1852 return events;
1853 }
1854
rb_validate_buffer(struct buffer_data_page * dpage,int cpu)1855 static int rb_validate_buffer(struct buffer_data_page *dpage, int cpu)
1856 {
1857 unsigned long long ts;
1858 u64 delta;
1859 int tail;
1860
1861 tail = local_read(&dpage->commit);
1862 return rb_read_data_buffer(dpage, tail, cpu, &ts, &delta);
1863 }
1864
1865 /* If the meta data has been validated, now validate the events */
rb_meta_validate_events(struct ring_buffer_per_cpu * cpu_buffer)1866 static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer)
1867 {
1868 struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
1869 struct buffer_page *head_page;
1870 unsigned long entry_bytes = 0;
1871 unsigned long entries = 0;
1872 int ret;
1873 int i;
1874
1875 if (!meta || !meta->head_buffer)
1876 return;
1877
1878 /* Do the reader page first */
1879 ret = rb_validate_buffer(cpu_buffer->reader_page->page, cpu_buffer->cpu);
1880 if (ret < 0) {
1881 pr_info("Ring buffer reader page is invalid\n");
1882 goto invalid;
1883 }
1884 entries += ret;
1885 entry_bytes += local_read(&cpu_buffer->reader_page->page->commit);
1886 local_set(&cpu_buffer->reader_page->entries, ret);
1887
1888 head_page = cpu_buffer->head_page;
1889
1890 /* If the commit_buffer is the reader page, update the commit page */
1891 if (meta->commit_buffer == (unsigned long)cpu_buffer->reader_page->page) {
1892 cpu_buffer->commit_page = cpu_buffer->reader_page;
1893 /* Nothing more to do, the only page is the reader page */
1894 goto done;
1895 }
1896
1897 /* Iterate until finding the commit page */
1898 for (i = 0; i < meta->nr_subbufs + 1; i++, rb_inc_page(&head_page)) {
1899
1900 /* Reader page has already been done */
1901 if (head_page == cpu_buffer->reader_page)
1902 continue;
1903
1904 ret = rb_validate_buffer(head_page->page, cpu_buffer->cpu);
1905 if (ret < 0) {
1906 pr_info("Ring buffer meta [%d] invalid buffer page\n",
1907 cpu_buffer->cpu);
1908 goto invalid;
1909 }
1910
1911 /* If the buffer has content, update pages_touched */
1912 if (ret)
1913 local_inc(&cpu_buffer->pages_touched);
1914
1915 entries += ret;
1916 entry_bytes += local_read(&head_page->page->commit);
1917 local_set(&cpu_buffer->head_page->entries, ret);
1918
1919 if (head_page == cpu_buffer->commit_page)
1920 break;
1921 }
1922
1923 if (head_page != cpu_buffer->commit_page) {
1924 pr_info("Ring buffer meta [%d] commit page not found\n",
1925 cpu_buffer->cpu);
1926 goto invalid;
1927 }
1928 done:
1929 local_set(&cpu_buffer->entries, entries);
1930 local_set(&cpu_buffer->entries_bytes, entry_bytes);
1931
1932 pr_info("Ring buffer meta [%d] is from previous boot!\n", cpu_buffer->cpu);
1933 return;
1934
1935 invalid:
1936 /* The content of the buffers are invalid, reset the meta data */
1937 meta->head_buffer = 0;
1938 meta->commit_buffer = 0;
1939
1940 /* Reset the reader page */
1941 local_set(&cpu_buffer->reader_page->entries, 0);
1942 local_set(&cpu_buffer->reader_page->page->commit, 0);
1943
1944 /* Reset all the subbuffers */
1945 for (i = 0; i < meta->nr_subbufs - 1; i++, rb_inc_page(&head_page)) {
1946 local_set(&head_page->entries, 0);
1947 local_set(&head_page->page->commit, 0);
1948 }
1949 }
1950
rb_range_meta_init(struct trace_buffer * buffer,int nr_pages,int scratch_size)1951 static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages, int scratch_size)
1952 {
1953 struct ring_buffer_cpu_meta *meta;
1954 unsigned long *subbuf_mask;
1955 unsigned long delta;
1956 void *subbuf;
1957 bool valid = false;
1958 int cpu;
1959 int i;
1960
1961 /* Create a mask to test the subbuf array */
1962 subbuf_mask = bitmap_alloc(nr_pages + 1, GFP_KERNEL);
1963 /* If subbuf_mask fails to allocate, then rb_meta_valid() will return false */
1964
1965 if (rb_meta_init(buffer, scratch_size))
1966 valid = true;
1967
1968 for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
1969 void *next_meta;
1970
1971 meta = rb_range_meta(buffer, nr_pages, cpu);
1972
1973 if (valid && rb_cpu_meta_valid(meta, cpu, buffer, nr_pages, subbuf_mask)) {
1974 /* Make the mappings match the current address */
1975 subbuf = rb_subbufs_from_meta(meta);
1976 delta = (unsigned long)subbuf - meta->first_buffer;
1977 meta->first_buffer += delta;
1978 meta->head_buffer += delta;
1979 meta->commit_buffer += delta;
1980 continue;
1981 }
1982
1983 if (cpu < nr_cpu_ids - 1)
1984 next_meta = rb_range_meta(buffer, nr_pages, cpu + 1);
1985 else
1986 next_meta = (void *)buffer->range_addr_end;
1987
1988 memset(meta, 0, next_meta - (void *)meta);
1989
1990 meta->nr_subbufs = nr_pages + 1;
1991 meta->subbuf_size = PAGE_SIZE;
1992
1993 subbuf = rb_subbufs_from_meta(meta);
1994
1995 meta->first_buffer = (unsigned long)subbuf;
1996
1997 /*
1998 * The buffers[] array holds the order of the sub-buffers
1999 * that are after the meta data. The sub-buffers may
2000 * be swapped out when read and inserted into a different
2001 * location of the ring buffer. Although their addresses
2002 * remain the same, the buffers[] array contains the
2003 * index into the sub-buffers holding their actual order.
2004 */
2005 for (i = 0; i < meta->nr_subbufs; i++) {
2006 meta->buffers[i] = i;
2007 rb_init_page(subbuf);
2008 subbuf += meta->subbuf_size;
2009 }
2010 }
2011 bitmap_free(subbuf_mask);
2012 }
2013
rbm_start(struct seq_file * m,loff_t * pos)2014 static void *rbm_start(struct seq_file *m, loff_t *pos)
2015 {
2016 struct ring_buffer_per_cpu *cpu_buffer = m->private;
2017 struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
2018 unsigned long val;
2019
2020 if (!meta)
2021 return NULL;
2022
2023 if (*pos > meta->nr_subbufs)
2024 return NULL;
2025
2026 val = *pos;
2027 val++;
2028
2029 return (void *)val;
2030 }
2031
rbm_next(struct seq_file * m,void * v,loff_t * pos)2032 static void *rbm_next(struct seq_file *m, void *v, loff_t *pos)
2033 {
2034 (*pos)++;
2035
2036 return rbm_start(m, pos);
2037 }
2038
rbm_show(struct seq_file * m,void * v)2039 static int rbm_show(struct seq_file *m, void *v)
2040 {
2041 struct ring_buffer_per_cpu *cpu_buffer = m->private;
2042 struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
2043 unsigned long val = (unsigned long)v;
2044
2045 if (val == 1) {
2046 seq_printf(m, "head_buffer: %d\n",
2047 rb_meta_subbuf_idx(meta, (void *)meta->head_buffer));
2048 seq_printf(m, "commit_buffer: %d\n",
2049 rb_meta_subbuf_idx(meta, (void *)meta->commit_buffer));
2050 seq_printf(m, "subbuf_size: %d\n", meta->subbuf_size);
2051 seq_printf(m, "nr_subbufs: %d\n", meta->nr_subbufs);
2052 return 0;
2053 }
2054
2055 val -= 2;
2056 seq_printf(m, "buffer[%ld]: %d\n", val, meta->buffers[val]);
2057
2058 return 0;
2059 }
2060
rbm_stop(struct seq_file * m,void * p)2061 static void rbm_stop(struct seq_file *m, void *p)
2062 {
2063 }
2064
2065 static const struct seq_operations rb_meta_seq_ops = {
2066 .start = rbm_start,
2067 .next = rbm_next,
2068 .show = rbm_show,
2069 .stop = rbm_stop,
2070 };
2071
ring_buffer_meta_seq_init(struct file * file,struct trace_buffer * buffer,int cpu)2072 int ring_buffer_meta_seq_init(struct file *file, struct trace_buffer *buffer, int cpu)
2073 {
2074 struct seq_file *m;
2075 int ret;
2076
2077 ret = seq_open(file, &rb_meta_seq_ops);
2078 if (ret)
2079 return ret;
2080
2081 m = file->private_data;
2082 m->private = buffer->buffers[cpu];
2083
2084 return 0;
2085 }
2086
2087 /* Map the buffer_pages to the previous head and commit pages */
rb_meta_buffer_update(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * bpage)2088 static void rb_meta_buffer_update(struct ring_buffer_per_cpu *cpu_buffer,
2089 struct buffer_page *bpage)
2090 {
2091 struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
2092
2093 if (meta->head_buffer == (unsigned long)bpage->page)
2094 cpu_buffer->head_page = bpage;
2095
2096 if (meta->commit_buffer == (unsigned long)bpage->page) {
2097 cpu_buffer->commit_page = bpage;
2098 cpu_buffer->tail_page = bpage;
2099 }
2100 }
2101
__rb_allocate_pages(struct ring_buffer_per_cpu * cpu_buffer,long nr_pages,struct list_head * pages)2102 static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
2103 long nr_pages, struct list_head *pages)
2104 {
2105 struct trace_buffer *buffer = cpu_buffer->buffer;
2106 struct ring_buffer_cpu_meta *meta = NULL;
2107 struct buffer_page *bpage, *tmp;
2108 bool user_thread = current->mm != NULL;
2109 gfp_t mflags;
2110 long i;
2111
2112 /*
2113 * Check if the available memory is there first.
2114 * Note, si_mem_available() only gives us a rough estimate of available
2115 * memory. It may not be accurate. But we don't care, we just want
2116 * to prevent doing any allocation when it is obvious that it is
2117 * not going to succeed.
2118 */
2119 i = si_mem_available();
2120 if (i < nr_pages)
2121 return -ENOMEM;
2122
2123 /*
2124 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
2125 * gracefully without invoking oom-killer and the system is not
2126 * destabilized.
2127 */
2128 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
2129
2130 /*
2131 * If a user thread allocates too much, and si_mem_available()
2132 * reports there's enough memory, even though there is not.
2133 * Make sure the OOM killer kills this thread. This can happen
2134 * even with RETRY_MAYFAIL because another task may be doing
2135 * an allocation after this task has taken all memory.
2136 * This is the task the OOM killer needs to take out during this
2137 * loop, even if it was triggered by an allocation somewhere else.
2138 */
2139 if (user_thread)
2140 set_current_oom_origin();
2141
2142 if (buffer->range_addr_start)
2143 meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu);
2144
2145 for (i = 0; i < nr_pages; i++) {
2146 struct page *page;
2147
2148 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
2149 mflags, cpu_to_node(cpu_buffer->cpu));
2150 if (!bpage)
2151 goto free_pages;
2152
2153 rb_check_bpage(cpu_buffer, bpage);
2154
2155 /*
2156 * Append the pages as for mapped buffers we want to keep
2157 * the order
2158 */
2159 list_add_tail(&bpage->list, pages);
2160
2161 if (meta) {
2162 /* A range was given. Use that for the buffer page */
2163 bpage->page = rb_range_buffer(cpu_buffer, i + 1);
2164 if (!bpage->page)
2165 goto free_pages;
2166 /* If this is valid from a previous boot */
2167 if (meta->head_buffer)
2168 rb_meta_buffer_update(cpu_buffer, bpage);
2169 bpage->range = 1;
2170 bpage->id = i + 1;
2171 } else {
2172 page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
2173 mflags | __GFP_COMP | __GFP_ZERO,
2174 cpu_buffer->buffer->subbuf_order);
2175 if (!page)
2176 goto free_pages;
2177 bpage->page = page_address(page);
2178 rb_init_page(bpage->page);
2179 }
2180 bpage->order = cpu_buffer->buffer->subbuf_order;
2181
2182 if (user_thread && fatal_signal_pending(current))
2183 goto free_pages;
2184 }
2185 if (user_thread)
2186 clear_current_oom_origin();
2187
2188 return 0;
2189
2190 free_pages:
2191 list_for_each_entry_safe(bpage, tmp, pages, list) {
2192 list_del_init(&bpage->list);
2193 free_buffer_page(bpage);
2194 }
2195 if (user_thread)
2196 clear_current_oom_origin();
2197
2198 return -ENOMEM;
2199 }
2200
rb_allocate_pages(struct ring_buffer_per_cpu * cpu_buffer,unsigned long nr_pages)2201 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
2202 unsigned long nr_pages)
2203 {
2204 LIST_HEAD(pages);
2205
2206 WARN_ON(!nr_pages);
2207
2208 if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
2209 return -ENOMEM;
2210
2211 /*
2212 * The ring buffer page list is a circular list that does not
2213 * start and end with a list head. All page list items point to
2214 * other pages.
2215 */
2216 cpu_buffer->pages = pages.next;
2217 list_del(&pages);
2218
2219 cpu_buffer->nr_pages = nr_pages;
2220
2221 rb_check_pages(cpu_buffer);
2222
2223 return 0;
2224 }
2225
2226 static struct ring_buffer_per_cpu *
rb_allocate_cpu_buffer(struct trace_buffer * buffer,long nr_pages,int cpu)2227 rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
2228 {
2229 struct ring_buffer_per_cpu *cpu_buffer;
2230 struct ring_buffer_cpu_meta *meta;
2231 struct buffer_page *bpage;
2232 struct page *page;
2233 int ret;
2234
2235 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
2236 GFP_KERNEL, cpu_to_node(cpu));
2237 if (!cpu_buffer)
2238 return NULL;
2239
2240 cpu_buffer->cpu = cpu;
2241 cpu_buffer->buffer = buffer;
2242 raw_spin_lock_init(&cpu_buffer->reader_lock);
2243 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
2244 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
2245 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
2246 init_completion(&cpu_buffer->update_done);
2247 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
2248 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
2249 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
2250 mutex_init(&cpu_buffer->mapping_lock);
2251
2252 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
2253 GFP_KERNEL, cpu_to_node(cpu));
2254 if (!bpage)
2255 goto fail_free_buffer;
2256
2257 rb_check_bpage(cpu_buffer, bpage);
2258
2259 cpu_buffer->reader_page = bpage;
2260
2261 if (buffer->range_addr_start) {
2262 /*
2263 * Range mapped buffers have the same restrictions as memory
2264 * mapped ones do.
2265 */
2266 cpu_buffer->mapped = 1;
2267 cpu_buffer->ring_meta = rb_range_meta(buffer, nr_pages, cpu);
2268 bpage->page = rb_range_buffer(cpu_buffer, 0);
2269 if (!bpage->page)
2270 goto fail_free_reader;
2271 if (cpu_buffer->ring_meta->head_buffer)
2272 rb_meta_buffer_update(cpu_buffer, bpage);
2273 bpage->range = 1;
2274 } else {
2275 page = alloc_pages_node(cpu_to_node(cpu),
2276 GFP_KERNEL | __GFP_COMP | __GFP_ZERO,
2277 cpu_buffer->buffer->subbuf_order);
2278 if (!page)
2279 goto fail_free_reader;
2280 bpage->page = page_address(page);
2281 rb_init_page(bpage->page);
2282 }
2283
2284 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
2285 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2286
2287 ret = rb_allocate_pages(cpu_buffer, nr_pages);
2288 if (ret < 0)
2289 goto fail_free_reader;
2290
2291 rb_meta_validate_events(cpu_buffer);
2292
2293 /* If the boot meta was valid then this has already been updated */
2294 meta = cpu_buffer->ring_meta;
2295 if (!meta || !meta->head_buffer ||
2296 !cpu_buffer->head_page || !cpu_buffer->commit_page || !cpu_buffer->tail_page) {
2297 if (meta && meta->head_buffer &&
2298 (cpu_buffer->head_page || cpu_buffer->commit_page || cpu_buffer->tail_page)) {
2299 pr_warn("Ring buffer meta buffers not all mapped\n");
2300 if (!cpu_buffer->head_page)
2301 pr_warn(" Missing head_page\n");
2302 if (!cpu_buffer->commit_page)
2303 pr_warn(" Missing commit_page\n");
2304 if (!cpu_buffer->tail_page)
2305 pr_warn(" Missing tail_page\n");
2306 }
2307
2308 cpu_buffer->head_page
2309 = list_entry(cpu_buffer->pages, struct buffer_page, list);
2310 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
2311
2312 rb_head_page_activate(cpu_buffer);
2313
2314 if (cpu_buffer->ring_meta)
2315 meta->commit_buffer = meta->head_buffer;
2316 } else {
2317 /* The valid meta buffer still needs to activate the head page */
2318 rb_head_page_activate(cpu_buffer);
2319 }
2320
2321 return cpu_buffer;
2322
2323 fail_free_reader:
2324 free_buffer_page(cpu_buffer->reader_page);
2325
2326 fail_free_buffer:
2327 kfree(cpu_buffer);
2328 return NULL;
2329 }
2330
rb_free_cpu_buffer(struct ring_buffer_per_cpu * cpu_buffer)2331 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
2332 {
2333 struct list_head *head = cpu_buffer->pages;
2334 struct buffer_page *bpage, *tmp;
2335
2336 irq_work_sync(&cpu_buffer->irq_work.work);
2337
2338 free_buffer_page(cpu_buffer->reader_page);
2339
2340 if (head) {
2341 rb_head_page_deactivate(cpu_buffer);
2342
2343 list_for_each_entry_safe(bpage, tmp, head, list) {
2344 list_del_init(&bpage->list);
2345 free_buffer_page(bpage);
2346 }
2347 bpage = list_entry(head, struct buffer_page, list);
2348 free_buffer_page(bpage);
2349 }
2350
2351 free_page((unsigned long)cpu_buffer->free_page);
2352
2353 kfree(cpu_buffer);
2354 }
2355
alloc_buffer(unsigned long size,unsigned flags,int order,unsigned long start,unsigned long end,unsigned long scratch_size,struct lock_class_key * key)2356 static struct trace_buffer *alloc_buffer(unsigned long size, unsigned flags,
2357 int order, unsigned long start,
2358 unsigned long end,
2359 unsigned long scratch_size,
2360 struct lock_class_key *key)
2361 {
2362 struct trace_buffer *buffer;
2363 long nr_pages;
2364 int subbuf_size;
2365 int bsize;
2366 int cpu;
2367 int ret;
2368
2369 /* keep it in its own cache line */
2370 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
2371 GFP_KERNEL);
2372 if (!buffer)
2373 return NULL;
2374
2375 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
2376 goto fail_free_buffer;
2377
2378 buffer->subbuf_order = order;
2379 subbuf_size = (PAGE_SIZE << order);
2380 buffer->subbuf_size = subbuf_size - BUF_PAGE_HDR_SIZE;
2381
2382 /* Max payload is buffer page size - header (8bytes) */
2383 buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
2384
2385 buffer->flags = flags;
2386 buffer->clock = trace_clock_local;
2387 buffer->reader_lock_key = key;
2388
2389 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
2390 init_waitqueue_head(&buffer->irq_work.waiters);
2391
2392 buffer->cpus = nr_cpu_ids;
2393
2394 bsize = sizeof(void *) * nr_cpu_ids;
2395 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
2396 GFP_KERNEL);
2397 if (!buffer->buffers)
2398 goto fail_free_cpumask;
2399
2400 /* If start/end are specified, then that overrides size */
2401 if (start && end) {
2402 unsigned long buffers_start;
2403 unsigned long ptr;
2404 int n;
2405
2406 /* Make sure that start is word aligned */
2407 start = ALIGN(start, sizeof(long));
2408
2409 /* scratch_size needs to be aligned too */
2410 scratch_size = ALIGN(scratch_size, sizeof(long));
2411
2412 /* Subtract the buffer meta data and word aligned */
2413 buffers_start = start + sizeof(struct ring_buffer_cpu_meta);
2414 buffers_start = ALIGN(buffers_start, sizeof(long));
2415 buffers_start += scratch_size;
2416
2417 /* Calculate the size for the per CPU data */
2418 size = end - buffers_start;
2419 size = size / nr_cpu_ids;
2420
2421 /*
2422 * The number of sub-buffers (nr_pages) is determined by the
2423 * total size allocated minus the meta data size.
2424 * Then that is divided by the number of per CPU buffers
2425 * needed, plus account for the integer array index that
2426 * will be appended to the meta data.
2427 */
2428 nr_pages = (size - sizeof(struct ring_buffer_cpu_meta)) /
2429 (subbuf_size + sizeof(int));
2430 /* Need at least two pages plus the reader page */
2431 if (nr_pages < 3)
2432 goto fail_free_buffers;
2433
2434 again:
2435 /* Make sure that the size fits aligned */
2436 for (n = 0, ptr = buffers_start; n < nr_cpu_ids; n++) {
2437 ptr += sizeof(struct ring_buffer_cpu_meta) +
2438 sizeof(int) * nr_pages;
2439 ptr = ALIGN(ptr, subbuf_size);
2440 ptr += subbuf_size * nr_pages;
2441 }
2442 if (ptr > end) {
2443 if (nr_pages <= 3)
2444 goto fail_free_buffers;
2445 nr_pages--;
2446 goto again;
2447 }
2448
2449 /* nr_pages should not count the reader page */
2450 nr_pages--;
2451 buffer->range_addr_start = start;
2452 buffer->range_addr_end = end;
2453
2454 rb_range_meta_init(buffer, nr_pages, scratch_size);
2455 } else {
2456
2457 /* need at least two pages */
2458 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
2459 if (nr_pages < 2)
2460 nr_pages = 2;
2461 }
2462
2463 cpu = raw_smp_processor_id();
2464 cpumask_set_cpu(cpu, buffer->cpumask);
2465 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
2466 if (!buffer->buffers[cpu])
2467 goto fail_free_buffers;
2468
2469 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
2470 if (ret < 0)
2471 goto fail_free_buffers;
2472
2473 mutex_init(&buffer->mutex);
2474
2475 return buffer;
2476
2477 fail_free_buffers:
2478 for_each_buffer_cpu(buffer, cpu) {
2479 if (buffer->buffers[cpu])
2480 rb_free_cpu_buffer(buffer->buffers[cpu]);
2481 }
2482 kfree(buffer->buffers);
2483
2484 fail_free_cpumask:
2485 free_cpumask_var(buffer->cpumask);
2486
2487 fail_free_buffer:
2488 kfree(buffer);
2489 return NULL;
2490 }
2491
2492 /**
2493 * __ring_buffer_alloc - allocate a new ring_buffer
2494 * @size: the size in bytes per cpu that is needed.
2495 * @flags: attributes to set for the ring buffer.
2496 * @key: ring buffer reader_lock_key.
2497 *
2498 * Currently the only flag that is available is the RB_FL_OVERWRITE
2499 * flag. This flag means that the buffer will overwrite old data
2500 * when the buffer wraps. If this flag is not set, the buffer will
2501 * drop data when the tail hits the head.
2502 */
__ring_buffer_alloc(unsigned long size,unsigned flags,struct lock_class_key * key)2503 struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
2504 struct lock_class_key *key)
2505 {
2506 /* Default buffer page size - one system page */
2507 return alloc_buffer(size, flags, 0, 0, 0, 0, key);
2508
2509 }
2510 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
2511
2512 /**
2513 * __ring_buffer_alloc_range - allocate a new ring_buffer from existing memory
2514 * @size: the size in bytes per cpu that is needed.
2515 * @flags: attributes to set for the ring buffer.
2516 * @order: sub-buffer order
2517 * @start: start of allocated range
2518 * @range_size: size of allocated range
2519 * @scratch_size: size of scratch area (for preallocated memory buffers)
2520 * @key: ring buffer reader_lock_key.
2521 *
2522 * Currently the only flag that is available is the RB_FL_OVERWRITE
2523 * flag. This flag means that the buffer will overwrite old data
2524 * when the buffer wraps. If this flag is not set, the buffer will
2525 * drop data when the tail hits the head.
2526 */
__ring_buffer_alloc_range(unsigned long size,unsigned flags,int order,unsigned long start,unsigned long range_size,unsigned long scratch_size,struct lock_class_key * key)2527 struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flags,
2528 int order, unsigned long start,
2529 unsigned long range_size,
2530 unsigned long scratch_size,
2531 struct lock_class_key *key)
2532 {
2533 return alloc_buffer(size, flags, order, start, start + range_size,
2534 scratch_size, key);
2535 }
2536
ring_buffer_meta_scratch(struct trace_buffer * buffer,unsigned int * size)2537 void *ring_buffer_meta_scratch(struct trace_buffer *buffer, unsigned int *size)
2538 {
2539 struct ring_buffer_meta *meta;
2540 void *ptr;
2541
2542 if (!buffer || !buffer->meta)
2543 return NULL;
2544
2545 meta = buffer->meta;
2546
2547 ptr = (void *)ALIGN((unsigned long)meta + sizeof(*meta), sizeof(long));
2548
2549 if (size)
2550 *size = (void *)meta + meta->buffers_offset - ptr;
2551
2552 return ptr;
2553 }
2554
2555 /**
2556 * ring_buffer_free - free a ring buffer.
2557 * @buffer: the buffer to free.
2558 */
2559 void
ring_buffer_free(struct trace_buffer * buffer)2560 ring_buffer_free(struct trace_buffer *buffer)
2561 {
2562 int cpu;
2563
2564 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
2565
2566 irq_work_sync(&buffer->irq_work.work);
2567
2568 for_each_buffer_cpu(buffer, cpu)
2569 rb_free_cpu_buffer(buffer->buffers[cpu]);
2570
2571 kfree(buffer->buffers);
2572 free_cpumask_var(buffer->cpumask);
2573
2574 kfree(buffer);
2575 }
2576 EXPORT_SYMBOL_GPL(ring_buffer_free);
2577
ring_buffer_set_clock(struct trace_buffer * buffer,u64 (* clock)(void))2578 void ring_buffer_set_clock(struct trace_buffer *buffer,
2579 u64 (*clock)(void))
2580 {
2581 buffer->clock = clock;
2582 }
2583
ring_buffer_set_time_stamp_abs(struct trace_buffer * buffer,bool abs)2584 void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
2585 {
2586 buffer->time_stamp_abs = abs;
2587 }
2588
ring_buffer_time_stamp_abs(struct trace_buffer * buffer)2589 bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
2590 {
2591 return buffer->time_stamp_abs;
2592 }
2593
rb_page_entries(struct buffer_page * bpage)2594 static inline unsigned long rb_page_entries(struct buffer_page *bpage)
2595 {
2596 return local_read(&bpage->entries) & RB_WRITE_MASK;
2597 }
2598
rb_page_write(struct buffer_page * bpage)2599 static inline unsigned long rb_page_write(struct buffer_page *bpage)
2600 {
2601 return local_read(&bpage->write) & RB_WRITE_MASK;
2602 }
2603
2604 static bool
rb_remove_pages(struct ring_buffer_per_cpu * cpu_buffer,unsigned long nr_pages)2605 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
2606 {
2607 struct list_head *tail_page, *to_remove, *next_page;
2608 struct buffer_page *to_remove_page, *tmp_iter_page;
2609 struct buffer_page *last_page, *first_page;
2610 unsigned long nr_removed;
2611 unsigned long head_bit;
2612 int page_entries;
2613
2614 head_bit = 0;
2615
2616 raw_spin_lock_irq(&cpu_buffer->reader_lock);
2617 atomic_inc(&cpu_buffer->record_disabled);
2618 /*
2619 * We don't race with the readers since we have acquired the reader
2620 * lock. We also don't race with writers after disabling recording.
2621 * This makes it easy to figure out the first and the last page to be
2622 * removed from the list. We unlink all the pages in between including
2623 * the first and last pages. This is done in a busy loop so that we
2624 * lose the least number of traces.
2625 * The pages are freed after we restart recording and unlock readers.
2626 */
2627 tail_page = &cpu_buffer->tail_page->list;
2628
2629 /*
2630 * tail page might be on reader page, we remove the next page
2631 * from the ring buffer
2632 */
2633 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
2634 tail_page = rb_list_head(tail_page->next);
2635 to_remove = tail_page;
2636
2637 /* start of pages to remove */
2638 first_page = list_entry(rb_list_head(to_remove->next),
2639 struct buffer_page, list);
2640
2641 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
2642 to_remove = rb_list_head(to_remove)->next;
2643 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
2644 }
2645 /* Read iterators need to reset themselves when some pages removed */
2646 cpu_buffer->pages_removed += nr_removed;
2647
2648 next_page = rb_list_head(to_remove)->next;
2649
2650 /*
2651 * Now we remove all pages between tail_page and next_page.
2652 * Make sure that we have head_bit value preserved for the
2653 * next page
2654 */
2655 tail_page->next = (struct list_head *)((unsigned long)next_page |
2656 head_bit);
2657 next_page = rb_list_head(next_page);
2658 next_page->prev = tail_page;
2659
2660 /* make sure pages points to a valid page in the ring buffer */
2661 cpu_buffer->pages = next_page;
2662 cpu_buffer->cnt++;
2663
2664 /* update head page */
2665 if (head_bit)
2666 cpu_buffer->head_page = list_entry(next_page,
2667 struct buffer_page, list);
2668
2669 /* pages are removed, resume tracing and then free the pages */
2670 atomic_dec(&cpu_buffer->record_disabled);
2671 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
2672
2673 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
2674
2675 /* last buffer page to remove */
2676 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
2677 list);
2678 tmp_iter_page = first_page;
2679
2680 do {
2681 cond_resched();
2682
2683 to_remove_page = tmp_iter_page;
2684 rb_inc_page(&tmp_iter_page);
2685
2686 /* update the counters */
2687 page_entries = rb_page_entries(to_remove_page);
2688 if (page_entries) {
2689 /*
2690 * If something was added to this page, it was full
2691 * since it is not the tail page. So we deduct the
2692 * bytes consumed in ring buffer from here.
2693 * Increment overrun to account for the lost events.
2694 */
2695 local_add(page_entries, &cpu_buffer->overrun);
2696 local_sub(rb_page_commit(to_remove_page), &cpu_buffer->entries_bytes);
2697 local_inc(&cpu_buffer->pages_lost);
2698 }
2699
2700 /*
2701 * We have already removed references to this list item, just
2702 * free up the buffer_page and its page
2703 */
2704 free_buffer_page(to_remove_page);
2705 nr_removed--;
2706
2707 } while (to_remove_page != last_page);
2708
2709 RB_WARN_ON(cpu_buffer, nr_removed);
2710
2711 return nr_removed == 0;
2712 }
2713
2714 static bool
rb_insert_pages(struct ring_buffer_per_cpu * cpu_buffer)2715 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
2716 {
2717 struct list_head *pages = &cpu_buffer->new_pages;
2718 unsigned long flags;
2719 bool success;
2720 int retries;
2721
2722 /* Can be called at early boot up, where interrupts must not been enabled */
2723 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2724 /*
2725 * We are holding the reader lock, so the reader page won't be swapped
2726 * in the ring buffer. Now we are racing with the writer trying to
2727 * move head page and the tail page.
2728 * We are going to adapt the reader page update process where:
2729 * 1. We first splice the start and end of list of new pages between
2730 * the head page and its previous page.
2731 * 2. We cmpxchg the prev_page->next to point from head page to the
2732 * start of new pages list.
2733 * 3. Finally, we update the head->prev to the end of new list.
2734 *
2735 * We will try this process 10 times, to make sure that we don't keep
2736 * spinning.
2737 */
2738 retries = 10;
2739 success = false;
2740 while (retries--) {
2741 struct list_head *head_page, *prev_page;
2742 struct list_head *last_page, *first_page;
2743 struct list_head *head_page_with_bit;
2744 struct buffer_page *hpage = rb_set_head_page(cpu_buffer);
2745
2746 if (!hpage)
2747 break;
2748 head_page = &hpage->list;
2749 prev_page = head_page->prev;
2750
2751 first_page = pages->next;
2752 last_page = pages->prev;
2753
2754 head_page_with_bit = (struct list_head *)
2755 ((unsigned long)head_page | RB_PAGE_HEAD);
2756
2757 last_page->next = head_page_with_bit;
2758 first_page->prev = prev_page;
2759
2760 /* caution: head_page_with_bit gets updated on cmpxchg failure */
2761 if (try_cmpxchg(&prev_page->next,
2762 &head_page_with_bit, first_page)) {
2763 /*
2764 * yay, we replaced the page pointer to our new list,
2765 * now, we just have to update to head page's prev
2766 * pointer to point to end of list
2767 */
2768 head_page->prev = last_page;
2769 cpu_buffer->cnt++;
2770 success = true;
2771 break;
2772 }
2773 }
2774
2775 if (success)
2776 INIT_LIST_HEAD(pages);
2777 /*
2778 * If we weren't successful in adding in new pages, warn and stop
2779 * tracing
2780 */
2781 RB_WARN_ON(cpu_buffer, !success);
2782 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2783
2784 /* free pages if they weren't inserted */
2785 if (!success) {
2786 struct buffer_page *bpage, *tmp;
2787 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2788 list) {
2789 list_del_init(&bpage->list);
2790 free_buffer_page(bpage);
2791 }
2792 }
2793 return success;
2794 }
2795
rb_update_pages(struct ring_buffer_per_cpu * cpu_buffer)2796 static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
2797 {
2798 bool success;
2799
2800 if (cpu_buffer->nr_pages_to_update > 0)
2801 success = rb_insert_pages(cpu_buffer);
2802 else
2803 success = rb_remove_pages(cpu_buffer,
2804 -cpu_buffer->nr_pages_to_update);
2805
2806 if (success)
2807 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2808 }
2809
update_pages_handler(struct work_struct * work)2810 static void update_pages_handler(struct work_struct *work)
2811 {
2812 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2813 struct ring_buffer_per_cpu, update_pages_work);
2814 rb_update_pages(cpu_buffer);
2815 complete(&cpu_buffer->update_done);
2816 }
2817
2818 /**
2819 * ring_buffer_resize - resize the ring buffer
2820 * @buffer: the buffer to resize.
2821 * @size: the new size.
2822 * @cpu_id: the cpu buffer to resize
2823 *
2824 * Minimum size is 2 * buffer->subbuf_size.
2825 *
2826 * Returns 0 on success and < 0 on failure.
2827 */
ring_buffer_resize(struct trace_buffer * buffer,unsigned long size,int cpu_id)2828 int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2829 int cpu_id)
2830 {
2831 struct ring_buffer_per_cpu *cpu_buffer;
2832 unsigned long nr_pages;
2833 int cpu, err;
2834
2835 /*
2836 * Always succeed at resizing a non-existent buffer:
2837 */
2838 if (!buffer)
2839 return 0;
2840
2841 /* Make sure the requested buffer exists */
2842 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2843 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2844 return 0;
2845
2846 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
2847
2848 /* we need a minimum of two pages */
2849 if (nr_pages < 2)
2850 nr_pages = 2;
2851
2852 /* prevent another thread from changing buffer sizes */
2853 mutex_lock(&buffer->mutex);
2854 atomic_inc(&buffer->resizing);
2855
2856 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2857 /*
2858 * Don't succeed if resizing is disabled, as a reader might be
2859 * manipulating the ring buffer and is expecting a sane state while
2860 * this is true.
2861 */
2862 for_each_buffer_cpu(buffer, cpu) {
2863 cpu_buffer = buffer->buffers[cpu];
2864 if (atomic_read(&cpu_buffer->resize_disabled)) {
2865 err = -EBUSY;
2866 goto out_err_unlock;
2867 }
2868 }
2869
2870 /* calculate the pages to update */
2871 for_each_buffer_cpu(buffer, cpu) {
2872 cpu_buffer = buffer->buffers[cpu];
2873
2874 cpu_buffer->nr_pages_to_update = nr_pages -
2875 cpu_buffer->nr_pages;
2876 /*
2877 * nothing more to do for removing pages or no update
2878 */
2879 if (cpu_buffer->nr_pages_to_update <= 0)
2880 continue;
2881 /*
2882 * to add pages, make sure all new pages can be
2883 * allocated without receiving ENOMEM
2884 */
2885 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2886 if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2887 &cpu_buffer->new_pages)) {
2888 /* not enough memory for new pages */
2889 err = -ENOMEM;
2890 goto out_err;
2891 }
2892
2893 cond_resched();
2894 }
2895
2896 cpus_read_lock();
2897 /*
2898 * Fire off all the required work handlers
2899 * We can't schedule on offline CPUs, but it's not necessary
2900 * since we can change their buffer sizes without any race.
2901 */
2902 for_each_buffer_cpu(buffer, cpu) {
2903 cpu_buffer = buffer->buffers[cpu];
2904 if (!cpu_buffer->nr_pages_to_update)
2905 continue;
2906
2907 /* Can't run something on an offline CPU. */
2908 if (!cpu_online(cpu)) {
2909 rb_update_pages(cpu_buffer);
2910 cpu_buffer->nr_pages_to_update = 0;
2911 } else {
2912 /* Run directly if possible. */
2913 migrate_disable();
2914 if (cpu != smp_processor_id()) {
2915 migrate_enable();
2916 schedule_work_on(cpu,
2917 &cpu_buffer->update_pages_work);
2918 } else {
2919 update_pages_handler(&cpu_buffer->update_pages_work);
2920 migrate_enable();
2921 }
2922 }
2923 }
2924
2925 /* wait for all the updates to complete */
2926 for_each_buffer_cpu(buffer, cpu) {
2927 cpu_buffer = buffer->buffers[cpu];
2928 if (!cpu_buffer->nr_pages_to_update)
2929 continue;
2930
2931 if (cpu_online(cpu))
2932 wait_for_completion(&cpu_buffer->update_done);
2933 cpu_buffer->nr_pages_to_update = 0;
2934 }
2935
2936 cpus_read_unlock();
2937 } else {
2938 cpu_buffer = buffer->buffers[cpu_id];
2939
2940 if (nr_pages == cpu_buffer->nr_pages)
2941 goto out;
2942
2943 /*
2944 * Don't succeed if resizing is disabled, as a reader might be
2945 * manipulating the ring buffer and is expecting a sane state while
2946 * this is true.
2947 */
2948 if (atomic_read(&cpu_buffer->resize_disabled)) {
2949 err = -EBUSY;
2950 goto out_err_unlock;
2951 }
2952
2953 cpu_buffer->nr_pages_to_update = nr_pages -
2954 cpu_buffer->nr_pages;
2955
2956 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2957 if (cpu_buffer->nr_pages_to_update > 0 &&
2958 __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2959 &cpu_buffer->new_pages)) {
2960 err = -ENOMEM;
2961 goto out_err;
2962 }
2963
2964 cpus_read_lock();
2965
2966 /* Can't run something on an offline CPU. */
2967 if (!cpu_online(cpu_id))
2968 rb_update_pages(cpu_buffer);
2969 else {
2970 /* Run directly if possible. */
2971 migrate_disable();
2972 if (cpu_id == smp_processor_id()) {
2973 rb_update_pages(cpu_buffer);
2974 migrate_enable();
2975 } else {
2976 migrate_enable();
2977 schedule_work_on(cpu_id,
2978 &cpu_buffer->update_pages_work);
2979 wait_for_completion(&cpu_buffer->update_done);
2980 }
2981 }
2982
2983 cpu_buffer->nr_pages_to_update = 0;
2984 cpus_read_unlock();
2985 }
2986
2987 out:
2988 /*
2989 * The ring buffer resize can happen with the ring buffer
2990 * enabled, so that the update disturbs the tracing as little
2991 * as possible. But if the buffer is disabled, we do not need
2992 * to worry about that, and we can take the time to verify
2993 * that the buffer is not corrupt.
2994 */
2995 if (atomic_read(&buffer->record_disabled)) {
2996 atomic_inc(&buffer->record_disabled);
2997 /*
2998 * Even though the buffer was disabled, we must make sure
2999 * that it is truly disabled before calling rb_check_pages.
3000 * There could have been a race between checking
3001 * record_disable and incrementing it.
3002 */
3003 synchronize_rcu();
3004 for_each_buffer_cpu(buffer, cpu) {
3005 cpu_buffer = buffer->buffers[cpu];
3006 rb_check_pages(cpu_buffer);
3007 }
3008 atomic_dec(&buffer->record_disabled);
3009 }
3010
3011 atomic_dec(&buffer->resizing);
3012 mutex_unlock(&buffer->mutex);
3013 return 0;
3014
3015 out_err:
3016 for_each_buffer_cpu(buffer, cpu) {
3017 struct buffer_page *bpage, *tmp;
3018
3019 cpu_buffer = buffer->buffers[cpu];
3020 cpu_buffer->nr_pages_to_update = 0;
3021
3022 if (list_empty(&cpu_buffer->new_pages))
3023 continue;
3024
3025 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
3026 list) {
3027 list_del_init(&bpage->list);
3028 free_buffer_page(bpage);
3029 }
3030 }
3031 out_err_unlock:
3032 atomic_dec(&buffer->resizing);
3033 mutex_unlock(&buffer->mutex);
3034 return err;
3035 }
3036 EXPORT_SYMBOL_GPL(ring_buffer_resize);
3037
ring_buffer_change_overwrite(struct trace_buffer * buffer,int val)3038 void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
3039 {
3040 mutex_lock(&buffer->mutex);
3041 if (val)
3042 buffer->flags |= RB_FL_OVERWRITE;
3043 else
3044 buffer->flags &= ~RB_FL_OVERWRITE;
3045 mutex_unlock(&buffer->mutex);
3046 }
3047 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
3048
__rb_page_index(struct buffer_page * bpage,unsigned index)3049 static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
3050 {
3051 return bpage->page->data + index;
3052 }
3053
3054 static __always_inline struct ring_buffer_event *
rb_reader_event(struct ring_buffer_per_cpu * cpu_buffer)3055 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
3056 {
3057 return __rb_page_index(cpu_buffer->reader_page,
3058 cpu_buffer->reader_page->read);
3059 }
3060
3061 static struct ring_buffer_event *
rb_iter_head_event(struct ring_buffer_iter * iter)3062 rb_iter_head_event(struct ring_buffer_iter *iter)
3063 {
3064 struct ring_buffer_event *event;
3065 struct buffer_page *iter_head_page = iter->head_page;
3066 unsigned long commit;
3067 unsigned length;
3068
3069 if (iter->head != iter->next_event)
3070 return iter->event;
3071
3072 /*
3073 * When the writer goes across pages, it issues a cmpxchg which
3074 * is a mb(), which will synchronize with the rmb here.
3075 * (see rb_tail_page_update() and __rb_reserve_next())
3076 */
3077 commit = rb_page_commit(iter_head_page);
3078 smp_rmb();
3079
3080 /* An event needs to be at least 8 bytes in size */
3081 if (iter->head > commit - 8)
3082 goto reset;
3083
3084 event = __rb_page_index(iter_head_page, iter->head);
3085 length = rb_event_length(event);
3086
3087 /*
3088 * READ_ONCE() doesn't work on functions and we don't want the
3089 * compiler doing any crazy optimizations with length.
3090 */
3091 barrier();
3092
3093 if ((iter->head + length) > commit || length > iter->event_size)
3094 /* Writer corrupted the read? */
3095 goto reset;
3096
3097 memcpy(iter->event, event, length);
3098 /*
3099 * If the page stamp is still the same after this rmb() then the
3100 * event was safely copied without the writer entering the page.
3101 */
3102 smp_rmb();
3103
3104 /* Make sure the page didn't change since we read this */
3105 if (iter->page_stamp != iter_head_page->page->time_stamp ||
3106 commit > rb_page_commit(iter_head_page))
3107 goto reset;
3108
3109 iter->next_event = iter->head + length;
3110 return iter->event;
3111 reset:
3112 /* Reset to the beginning */
3113 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
3114 iter->head = 0;
3115 iter->next_event = 0;
3116 iter->missed_events = 1;
3117 return NULL;
3118 }
3119
3120 /* Size is determined by what has been committed */
rb_page_size(struct buffer_page * bpage)3121 static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
3122 {
3123 return rb_page_commit(bpage) & ~RB_MISSED_MASK;
3124 }
3125
3126 static __always_inline unsigned
rb_commit_index(struct ring_buffer_per_cpu * cpu_buffer)3127 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
3128 {
3129 return rb_page_commit(cpu_buffer->commit_page);
3130 }
3131
3132 static __always_inline unsigned
rb_event_index(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event)3133 rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event)
3134 {
3135 unsigned long addr = (unsigned long)event;
3136
3137 addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1;
3138
3139 return addr - BUF_PAGE_HDR_SIZE;
3140 }
3141
rb_inc_iter(struct ring_buffer_iter * iter)3142 static void rb_inc_iter(struct ring_buffer_iter *iter)
3143 {
3144 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3145
3146 /*
3147 * The iterator could be on the reader page (it starts there).
3148 * But the head could have moved, since the reader was
3149 * found. Check for this case and assign the iterator
3150 * to the head page instead of next.
3151 */
3152 if (iter->head_page == cpu_buffer->reader_page)
3153 iter->head_page = rb_set_head_page(cpu_buffer);
3154 else
3155 rb_inc_page(&iter->head_page);
3156
3157 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
3158 iter->head = 0;
3159 iter->next_event = 0;
3160 }
3161
3162 /* Return the index into the sub-buffers for a given sub-buffer */
rb_meta_subbuf_idx(struct ring_buffer_cpu_meta * meta,void * subbuf)3163 static int rb_meta_subbuf_idx(struct ring_buffer_cpu_meta *meta, void *subbuf)
3164 {
3165 void *subbuf_array;
3166
3167 subbuf_array = (void *)meta + sizeof(int) * meta->nr_subbufs;
3168 subbuf_array = (void *)ALIGN((unsigned long)subbuf_array, meta->subbuf_size);
3169 return (subbuf - subbuf_array) / meta->subbuf_size;
3170 }
3171
rb_update_meta_head(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * next_page)3172 static void rb_update_meta_head(struct ring_buffer_per_cpu *cpu_buffer,
3173 struct buffer_page *next_page)
3174 {
3175 struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
3176 unsigned long old_head = (unsigned long)next_page->page;
3177 unsigned long new_head;
3178
3179 rb_inc_page(&next_page);
3180 new_head = (unsigned long)next_page->page;
3181
3182 /*
3183 * Only move it forward once, if something else came in and
3184 * moved it forward, then we don't want to touch it.
3185 */
3186 (void)cmpxchg(&meta->head_buffer, old_head, new_head);
3187 }
3188
rb_update_meta_reader(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * reader)3189 static void rb_update_meta_reader(struct ring_buffer_per_cpu *cpu_buffer,
3190 struct buffer_page *reader)
3191 {
3192 struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
3193 void *old_reader = cpu_buffer->reader_page->page;
3194 void *new_reader = reader->page;
3195 int id;
3196
3197 id = reader->id;
3198 cpu_buffer->reader_page->id = id;
3199 reader->id = 0;
3200
3201 meta->buffers[0] = rb_meta_subbuf_idx(meta, new_reader);
3202 meta->buffers[id] = rb_meta_subbuf_idx(meta, old_reader);
3203
3204 /* The head pointer is the one after the reader */
3205 rb_update_meta_head(cpu_buffer, reader);
3206 }
3207
3208 /*
3209 * rb_handle_head_page - writer hit the head page
3210 *
3211 * Returns: +1 to retry page
3212 * 0 to continue
3213 * -1 on error
3214 */
3215 static int
rb_handle_head_page(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * tail_page,struct buffer_page * next_page)3216 rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
3217 struct buffer_page *tail_page,
3218 struct buffer_page *next_page)
3219 {
3220 struct buffer_page *new_head;
3221 int entries;
3222 int type;
3223 int ret;
3224
3225 entries = rb_page_entries(next_page);
3226
3227 /*
3228 * The hard part is here. We need to move the head
3229 * forward, and protect against both readers on
3230 * other CPUs and writers coming in via interrupts.
3231 */
3232 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
3233 RB_PAGE_HEAD);
3234
3235 /*
3236 * type can be one of four:
3237 * NORMAL - an interrupt already moved it for us
3238 * HEAD - we are the first to get here.
3239 * UPDATE - we are the interrupt interrupting
3240 * a current move.
3241 * MOVED - a reader on another CPU moved the next
3242 * pointer to its reader page. Give up
3243 * and try again.
3244 */
3245
3246 switch (type) {
3247 case RB_PAGE_HEAD:
3248 /*
3249 * We changed the head to UPDATE, thus
3250 * it is our responsibility to update
3251 * the counters.
3252 */
3253 local_add(entries, &cpu_buffer->overrun);
3254 local_sub(rb_page_commit(next_page), &cpu_buffer->entries_bytes);
3255 local_inc(&cpu_buffer->pages_lost);
3256
3257 if (cpu_buffer->ring_meta)
3258 rb_update_meta_head(cpu_buffer, next_page);
3259 /*
3260 * The entries will be zeroed out when we move the
3261 * tail page.
3262 */
3263
3264 /* still more to do */
3265 break;
3266
3267 case RB_PAGE_UPDATE:
3268 /*
3269 * This is an interrupt that interrupt the
3270 * previous update. Still more to do.
3271 */
3272 break;
3273 case RB_PAGE_NORMAL:
3274 /*
3275 * An interrupt came in before the update
3276 * and processed this for us.
3277 * Nothing left to do.
3278 */
3279 return 1;
3280 case RB_PAGE_MOVED:
3281 /*
3282 * The reader is on another CPU and just did
3283 * a swap with our next_page.
3284 * Try again.
3285 */
3286 return 1;
3287 default:
3288 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
3289 return -1;
3290 }
3291
3292 /*
3293 * Now that we are here, the old head pointer is
3294 * set to UPDATE. This will keep the reader from
3295 * swapping the head page with the reader page.
3296 * The reader (on another CPU) will spin till
3297 * we are finished.
3298 *
3299 * We just need to protect against interrupts
3300 * doing the job. We will set the next pointer
3301 * to HEAD. After that, we set the old pointer
3302 * to NORMAL, but only if it was HEAD before.
3303 * otherwise we are an interrupt, and only
3304 * want the outer most commit to reset it.
3305 */
3306 new_head = next_page;
3307 rb_inc_page(&new_head);
3308
3309 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
3310 RB_PAGE_NORMAL);
3311
3312 /*
3313 * Valid returns are:
3314 * HEAD - an interrupt came in and already set it.
3315 * NORMAL - One of two things:
3316 * 1) We really set it.
3317 * 2) A bunch of interrupts came in and moved
3318 * the page forward again.
3319 */
3320 switch (ret) {
3321 case RB_PAGE_HEAD:
3322 case RB_PAGE_NORMAL:
3323 /* OK */
3324 break;
3325 default:
3326 RB_WARN_ON(cpu_buffer, 1);
3327 return -1;
3328 }
3329
3330 /*
3331 * It is possible that an interrupt came in,
3332 * set the head up, then more interrupts came in
3333 * and moved it again. When we get back here,
3334 * the page would have been set to NORMAL but we
3335 * just set it back to HEAD.
3336 *
3337 * How do you detect this? Well, if that happened
3338 * the tail page would have moved.
3339 */
3340 if (ret == RB_PAGE_NORMAL) {
3341 struct buffer_page *buffer_tail_page;
3342
3343 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
3344 /*
3345 * If the tail had moved passed next, then we need
3346 * to reset the pointer.
3347 */
3348 if (buffer_tail_page != tail_page &&
3349 buffer_tail_page != next_page)
3350 rb_head_page_set_normal(cpu_buffer, new_head,
3351 next_page,
3352 RB_PAGE_HEAD);
3353 }
3354
3355 /*
3356 * If this was the outer most commit (the one that
3357 * changed the original pointer from HEAD to UPDATE),
3358 * then it is up to us to reset it to NORMAL.
3359 */
3360 if (type == RB_PAGE_HEAD) {
3361 ret = rb_head_page_set_normal(cpu_buffer, next_page,
3362 tail_page,
3363 RB_PAGE_UPDATE);
3364 if (RB_WARN_ON(cpu_buffer,
3365 ret != RB_PAGE_UPDATE))
3366 return -1;
3367 }
3368
3369 return 0;
3370 }
3371
3372 static inline void
rb_reset_tail(struct ring_buffer_per_cpu * cpu_buffer,unsigned long tail,struct rb_event_info * info)3373 rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
3374 unsigned long tail, struct rb_event_info *info)
3375 {
3376 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
3377 struct buffer_page *tail_page = info->tail_page;
3378 struct ring_buffer_event *event;
3379 unsigned long length = info->length;
3380
3381 /*
3382 * Only the event that crossed the page boundary
3383 * must fill the old tail_page with padding.
3384 */
3385 if (tail >= bsize) {
3386 /*
3387 * If the page was filled, then we still need
3388 * to update the real_end. Reset it to zero
3389 * and the reader will ignore it.
3390 */
3391 if (tail == bsize)
3392 tail_page->real_end = 0;
3393
3394 local_sub(length, &tail_page->write);
3395 return;
3396 }
3397
3398 event = __rb_page_index(tail_page, tail);
3399
3400 /*
3401 * Save the original length to the meta data.
3402 * This will be used by the reader to add lost event
3403 * counter.
3404 */
3405 tail_page->real_end = tail;
3406
3407 /*
3408 * If this event is bigger than the minimum size, then
3409 * we need to be careful that we don't subtract the
3410 * write counter enough to allow another writer to slip
3411 * in on this page.
3412 * We put in a discarded commit instead, to make sure
3413 * that this space is not used again, and this space will
3414 * not be accounted into 'entries_bytes'.
3415 *
3416 * If we are less than the minimum size, we don't need to
3417 * worry about it.
3418 */
3419 if (tail > (bsize - RB_EVNT_MIN_SIZE)) {
3420 /* No room for any events */
3421
3422 /* Mark the rest of the page with padding */
3423 rb_event_set_padding(event);
3424
3425 /* Make sure the padding is visible before the write update */
3426 smp_wmb();
3427
3428 /* Set the write back to the previous setting */
3429 local_sub(length, &tail_page->write);
3430 return;
3431 }
3432
3433 /* Put in a discarded event */
3434 event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE;
3435 event->type_len = RINGBUF_TYPE_PADDING;
3436 /* time delta must be non zero */
3437 event->time_delta = 1;
3438
3439 /* account for padding bytes */
3440 local_add(bsize - tail, &cpu_buffer->entries_bytes);
3441
3442 /* Make sure the padding is visible before the tail_page->write update */
3443 smp_wmb();
3444
3445 /* Set write to end of buffer */
3446 length = (tail + length) - bsize;
3447 local_sub(length, &tail_page->write);
3448 }
3449
3450 static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
3451
3452 /*
3453 * This is the slow path, force gcc not to inline it.
3454 */
3455 static noinline struct ring_buffer_event *
rb_move_tail(struct ring_buffer_per_cpu * cpu_buffer,unsigned long tail,struct rb_event_info * info)3456 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
3457 unsigned long tail, struct rb_event_info *info)
3458 {
3459 struct buffer_page *tail_page = info->tail_page;
3460 struct buffer_page *commit_page = cpu_buffer->commit_page;
3461 struct trace_buffer *buffer = cpu_buffer->buffer;
3462 struct buffer_page *next_page;
3463 int ret;
3464
3465 next_page = tail_page;
3466
3467 rb_inc_page(&next_page);
3468
3469 /*
3470 * If for some reason, we had an interrupt storm that made
3471 * it all the way around the buffer, bail, and warn
3472 * about it.
3473 */
3474 if (unlikely(next_page == commit_page)) {
3475 local_inc(&cpu_buffer->commit_overrun);
3476 goto out_reset;
3477 }
3478
3479 /*
3480 * This is where the fun begins!
3481 *
3482 * We are fighting against races between a reader that
3483 * could be on another CPU trying to swap its reader
3484 * page with the buffer head.
3485 *
3486 * We are also fighting against interrupts coming in and
3487 * moving the head or tail on us as well.
3488 *
3489 * If the next page is the head page then we have filled
3490 * the buffer, unless the commit page is still on the
3491 * reader page.
3492 */
3493 if (rb_is_head_page(next_page, &tail_page->list)) {
3494
3495 /*
3496 * If the commit is not on the reader page, then
3497 * move the header page.
3498 */
3499 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
3500 /*
3501 * If we are not in overwrite mode,
3502 * this is easy, just stop here.
3503 */
3504 if (!(buffer->flags & RB_FL_OVERWRITE)) {
3505 local_inc(&cpu_buffer->dropped_events);
3506 goto out_reset;
3507 }
3508
3509 ret = rb_handle_head_page(cpu_buffer,
3510 tail_page,
3511 next_page);
3512 if (ret < 0)
3513 goto out_reset;
3514 if (ret)
3515 goto out_again;
3516 } else {
3517 /*
3518 * We need to be careful here too. The
3519 * commit page could still be on the reader
3520 * page. We could have a small buffer, and
3521 * have filled up the buffer with events
3522 * from interrupts and such, and wrapped.
3523 *
3524 * Note, if the tail page is also on the
3525 * reader_page, we let it move out.
3526 */
3527 if (unlikely((cpu_buffer->commit_page !=
3528 cpu_buffer->tail_page) &&
3529 (cpu_buffer->commit_page ==
3530 cpu_buffer->reader_page))) {
3531 local_inc(&cpu_buffer->commit_overrun);
3532 goto out_reset;
3533 }
3534 }
3535 }
3536
3537 rb_tail_page_update(cpu_buffer, tail_page, next_page);
3538
3539 out_again:
3540
3541 rb_reset_tail(cpu_buffer, tail, info);
3542
3543 /* Commit what we have for now. */
3544 rb_end_commit(cpu_buffer);
3545 /* rb_end_commit() decs committing */
3546 local_inc(&cpu_buffer->committing);
3547
3548 /* fail and let the caller try again */
3549 return ERR_PTR(-EAGAIN);
3550
3551 out_reset:
3552 /* reset write */
3553 rb_reset_tail(cpu_buffer, tail, info);
3554
3555 return NULL;
3556 }
3557
3558 /* Slow path */
3559 static struct ring_buffer_event *
rb_add_time_stamp(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event,u64 delta,bool abs)3560 rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3561 struct ring_buffer_event *event, u64 delta, bool abs)
3562 {
3563 if (abs)
3564 event->type_len = RINGBUF_TYPE_TIME_STAMP;
3565 else
3566 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
3567
3568 /* Not the first event on the page, or not delta? */
3569 if (abs || rb_event_index(cpu_buffer, event)) {
3570 event->time_delta = delta & TS_MASK;
3571 event->array[0] = delta >> TS_SHIFT;
3572 } else {
3573 /* nope, just zero it */
3574 event->time_delta = 0;
3575 event->array[0] = 0;
3576 }
3577
3578 return skip_time_extend(event);
3579 }
3580
3581 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
sched_clock_stable(void)3582 static inline bool sched_clock_stable(void)
3583 {
3584 return true;
3585 }
3586 #endif
3587
3588 static void
rb_check_timestamp(struct ring_buffer_per_cpu * cpu_buffer,struct rb_event_info * info)3589 rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
3590 struct rb_event_info *info)
3591 {
3592 u64 write_stamp;
3593
3594 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
3595 (unsigned long long)info->delta,
3596 (unsigned long long)info->ts,
3597 (unsigned long long)info->before,
3598 (unsigned long long)info->after,
3599 (unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}),
3600 sched_clock_stable() ? "" :
3601 "If you just came from a suspend/resume,\n"
3602 "please switch to the trace global clock:\n"
3603 " echo global > /sys/kernel/tracing/trace_clock\n"
3604 "or add trace_clock=global to the kernel command line\n");
3605 }
3606
rb_add_timestamp(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event ** event,struct rb_event_info * info,u64 * delta,unsigned int * length)3607 static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
3608 struct ring_buffer_event **event,
3609 struct rb_event_info *info,
3610 u64 *delta,
3611 unsigned int *length)
3612 {
3613 bool abs = info->add_timestamp &
3614 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
3615
3616 if (unlikely(info->delta > (1ULL << 59))) {
3617 /*
3618 * Some timers can use more than 59 bits, and when a timestamp
3619 * is added to the buffer, it will lose those bits.
3620 */
3621 if (abs && (info->ts & TS_MSB)) {
3622 info->delta &= ABS_TS_MASK;
3623
3624 /* did the clock go backwards */
3625 } else if (info->before == info->after && info->before > info->ts) {
3626 /* not interrupted */
3627 static int once;
3628
3629 /*
3630 * This is possible with a recalibrating of the TSC.
3631 * Do not produce a call stack, but just report it.
3632 */
3633 if (!once) {
3634 once++;
3635 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
3636 info->before, info->ts);
3637 }
3638 } else
3639 rb_check_timestamp(cpu_buffer, info);
3640 if (!abs)
3641 info->delta = 0;
3642 }
3643 *event = rb_add_time_stamp(cpu_buffer, *event, info->delta, abs);
3644 *length -= RB_LEN_TIME_EXTEND;
3645 *delta = 0;
3646 }
3647
3648 /**
3649 * rb_update_event - update event type and data
3650 * @cpu_buffer: The per cpu buffer of the @event
3651 * @event: the event to update
3652 * @info: The info to update the @event with (contains length and delta)
3653 *
3654 * Update the type and data fields of the @event. The length
3655 * is the actual size that is written to the ring buffer,
3656 * and with this, we can determine what to place into the
3657 * data field.
3658 */
3659 static void
rb_update_event(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event,struct rb_event_info * info)3660 rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
3661 struct ring_buffer_event *event,
3662 struct rb_event_info *info)
3663 {
3664 unsigned length = info->length;
3665 u64 delta = info->delta;
3666 unsigned int nest = local_read(&cpu_buffer->committing) - 1;
3667
3668 if (!WARN_ON_ONCE(nest >= MAX_NEST))
3669 cpu_buffer->event_stamp[nest] = info->ts;
3670
3671 /*
3672 * If we need to add a timestamp, then we
3673 * add it to the start of the reserved space.
3674 */
3675 if (unlikely(info->add_timestamp))
3676 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
3677
3678 event->time_delta = delta;
3679 length -= RB_EVNT_HDR_SIZE;
3680 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
3681 event->type_len = 0;
3682 event->array[0] = length;
3683 } else
3684 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
3685 }
3686
rb_calculate_event_length(unsigned length)3687 static unsigned rb_calculate_event_length(unsigned length)
3688 {
3689 struct ring_buffer_event event; /* Used only for sizeof array */
3690
3691 /* zero length can cause confusions */
3692 if (!length)
3693 length++;
3694
3695 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
3696 length += sizeof(event.array[0]);
3697
3698 length += RB_EVNT_HDR_SIZE;
3699 length = ALIGN(length, RB_ARCH_ALIGNMENT);
3700
3701 /*
3702 * In case the time delta is larger than the 27 bits for it
3703 * in the header, we need to add a timestamp. If another
3704 * event comes in when trying to discard this one to increase
3705 * the length, then the timestamp will be added in the allocated
3706 * space of this event. If length is bigger than the size needed
3707 * for the TIME_EXTEND, then padding has to be used. The events
3708 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
3709 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
3710 * As length is a multiple of 4, we only need to worry if it
3711 * is 12 (RB_LEN_TIME_EXTEND + 4).
3712 */
3713 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
3714 length += RB_ALIGNMENT;
3715
3716 return length;
3717 }
3718
3719 static inline bool
rb_try_to_discard(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event)3720 rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
3721 struct ring_buffer_event *event)
3722 {
3723 unsigned long new_index, old_index;
3724 struct buffer_page *bpage;
3725 unsigned long addr;
3726
3727 new_index = rb_event_index(cpu_buffer, event);
3728 old_index = new_index + rb_event_ts_length(event);
3729 addr = (unsigned long)event;
3730 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
3731
3732 bpage = READ_ONCE(cpu_buffer->tail_page);
3733
3734 /*
3735 * Make sure the tail_page is still the same and
3736 * the next write location is the end of this event
3737 */
3738 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
3739 unsigned long write_mask =
3740 local_read(&bpage->write) & ~RB_WRITE_MASK;
3741 unsigned long event_length = rb_event_length(event);
3742
3743 /*
3744 * For the before_stamp to be different than the write_stamp
3745 * to make sure that the next event adds an absolute
3746 * value and does not rely on the saved write stamp, which
3747 * is now going to be bogus.
3748 *
3749 * By setting the before_stamp to zero, the next event
3750 * is not going to use the write_stamp and will instead
3751 * create an absolute timestamp. This means there's no
3752 * reason to update the wirte_stamp!
3753 */
3754 rb_time_set(&cpu_buffer->before_stamp, 0);
3755
3756 /*
3757 * If an event were to come in now, it would see that the
3758 * write_stamp and the before_stamp are different, and assume
3759 * that this event just added itself before updating
3760 * the write stamp. The interrupting event will fix the
3761 * write stamp for us, and use an absolute timestamp.
3762 */
3763
3764 /*
3765 * This is on the tail page. It is possible that
3766 * a write could come in and move the tail page
3767 * and write to the next page. That is fine
3768 * because we just shorten what is on this page.
3769 */
3770 old_index += write_mask;
3771 new_index += write_mask;
3772
3773 /* caution: old_index gets updated on cmpxchg failure */
3774 if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) {
3775 /* update counters */
3776 local_sub(event_length, &cpu_buffer->entries_bytes);
3777 return true;
3778 }
3779 }
3780
3781 /* could not discard */
3782 return false;
3783 }
3784
rb_start_commit(struct ring_buffer_per_cpu * cpu_buffer)3785 static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
3786 {
3787 local_inc(&cpu_buffer->committing);
3788 local_inc(&cpu_buffer->commits);
3789 }
3790
3791 static __always_inline void
rb_set_commit_to_write(struct ring_buffer_per_cpu * cpu_buffer)3792 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
3793 {
3794 unsigned long max_count;
3795
3796 /*
3797 * We only race with interrupts and NMIs on this CPU.
3798 * If we own the commit event, then we can commit
3799 * all others that interrupted us, since the interruptions
3800 * are in stack format (they finish before they come
3801 * back to us). This allows us to do a simple loop to
3802 * assign the commit to the tail.
3803 */
3804 again:
3805 max_count = cpu_buffer->nr_pages * 100;
3806
3807 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
3808 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
3809 return;
3810 if (RB_WARN_ON(cpu_buffer,
3811 rb_is_reader_page(cpu_buffer->tail_page)))
3812 return;
3813 /*
3814 * No need for a memory barrier here, as the update
3815 * of the tail_page did it for this page.
3816 */
3817 local_set(&cpu_buffer->commit_page->page->commit,
3818 rb_page_write(cpu_buffer->commit_page));
3819 rb_inc_page(&cpu_buffer->commit_page);
3820 if (cpu_buffer->ring_meta) {
3821 struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
3822 meta->commit_buffer = (unsigned long)cpu_buffer->commit_page->page;
3823 }
3824 /* add barrier to keep gcc from optimizing too much */
3825 barrier();
3826 }
3827 while (rb_commit_index(cpu_buffer) !=
3828 rb_page_write(cpu_buffer->commit_page)) {
3829
3830 /* Make sure the readers see the content of what is committed. */
3831 smp_wmb();
3832 local_set(&cpu_buffer->commit_page->page->commit,
3833 rb_page_write(cpu_buffer->commit_page));
3834 RB_WARN_ON(cpu_buffer,
3835 local_read(&cpu_buffer->commit_page->page->commit) &
3836 ~RB_WRITE_MASK);
3837 barrier();
3838 }
3839
3840 /* again, keep gcc from optimizing */
3841 barrier();
3842
3843 /*
3844 * If an interrupt came in just after the first while loop
3845 * and pushed the tail page forward, we will be left with
3846 * a dangling commit that will never go forward.
3847 */
3848 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
3849 goto again;
3850 }
3851
rb_end_commit(struct ring_buffer_per_cpu * cpu_buffer)3852 static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
3853 {
3854 unsigned long commits;
3855
3856 if (RB_WARN_ON(cpu_buffer,
3857 !local_read(&cpu_buffer->committing)))
3858 return;
3859
3860 again:
3861 commits = local_read(&cpu_buffer->commits);
3862 /* synchronize with interrupts */
3863 barrier();
3864 if (local_read(&cpu_buffer->committing) == 1)
3865 rb_set_commit_to_write(cpu_buffer);
3866
3867 local_dec(&cpu_buffer->committing);
3868
3869 /* synchronize with interrupts */
3870 barrier();
3871
3872 /*
3873 * Need to account for interrupts coming in between the
3874 * updating of the commit page and the clearing of the
3875 * committing counter.
3876 */
3877 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3878 !local_read(&cpu_buffer->committing)) {
3879 local_inc(&cpu_buffer->committing);
3880 goto again;
3881 }
3882 }
3883
rb_event_discard(struct ring_buffer_event * event)3884 static inline void rb_event_discard(struct ring_buffer_event *event)
3885 {
3886 if (extended_time(event))
3887 event = skip_time_extend(event);
3888
3889 /* array[0] holds the actual length for the discarded event */
3890 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3891 event->type_len = RINGBUF_TYPE_PADDING;
3892 /* time delta must be non zero */
3893 if (!event->time_delta)
3894 event->time_delta = 1;
3895 }
3896
rb_commit(struct ring_buffer_per_cpu * cpu_buffer)3897 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer)
3898 {
3899 local_inc(&cpu_buffer->entries);
3900 rb_end_commit(cpu_buffer);
3901 }
3902
3903 static __always_inline void
rb_wakeups(struct trace_buffer * buffer,struct ring_buffer_per_cpu * cpu_buffer)3904 rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3905 {
3906 if (buffer->irq_work.waiters_pending) {
3907 buffer->irq_work.waiters_pending = false;
3908 /* irq_work_queue() supplies it's own memory barriers */
3909 irq_work_queue(&buffer->irq_work.work);
3910 }
3911
3912 if (cpu_buffer->irq_work.waiters_pending) {
3913 cpu_buffer->irq_work.waiters_pending = false;
3914 /* irq_work_queue() supplies it's own memory barriers */
3915 irq_work_queue(&cpu_buffer->irq_work.work);
3916 }
3917
3918 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3919 return;
3920
3921 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3922 return;
3923
3924 if (!cpu_buffer->irq_work.full_waiters_pending)
3925 return;
3926
3927 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3928
3929 if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
3930 return;
3931
3932 cpu_buffer->irq_work.wakeup_full = true;
3933 cpu_buffer->irq_work.full_waiters_pending = false;
3934 /* irq_work_queue() supplies it's own memory barriers */
3935 irq_work_queue(&cpu_buffer->irq_work.work);
3936 }
3937
3938 #ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3939 # define do_ring_buffer_record_recursion() \
3940 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3941 #else
3942 # define do_ring_buffer_record_recursion() do { } while (0)
3943 #endif
3944
3945 /*
3946 * The lock and unlock are done within a preempt disable section.
3947 * The current_context per_cpu variable can only be modified
3948 * by the current task between lock and unlock. But it can
3949 * be modified more than once via an interrupt. To pass this
3950 * information from the lock to the unlock without having to
3951 * access the 'in_interrupt()' functions again (which do show
3952 * a bit of overhead in something as critical as function tracing,
3953 * we use a bitmask trick.
3954 *
3955 * bit 1 = NMI context
3956 * bit 2 = IRQ context
3957 * bit 3 = SoftIRQ context
3958 * bit 4 = normal context.
3959 *
3960 * This works because this is the order of contexts that can
3961 * preempt other contexts. A SoftIRQ never preempts an IRQ
3962 * context.
3963 *
3964 * When the context is determined, the corresponding bit is
3965 * checked and set (if it was set, then a recursion of that context
3966 * happened).
3967 *
3968 * On unlock, we need to clear this bit. To do so, just subtract
3969 * 1 from the current_context and AND it to itself.
3970 *
3971 * (binary)
3972 * 101 - 1 = 100
3973 * 101 & 100 = 100 (clearing bit zero)
3974 *
3975 * 1010 - 1 = 1001
3976 * 1010 & 1001 = 1000 (clearing bit 1)
3977 *
3978 * The least significant bit can be cleared this way, and it
3979 * just so happens that it is the same bit corresponding to
3980 * the current context.
3981 *
3982 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3983 * is set when a recursion is detected at the current context, and if
3984 * the TRANSITION bit is already set, it will fail the recursion.
3985 * This is needed because there's a lag between the changing of
3986 * interrupt context and updating the preempt count. In this case,
3987 * a false positive will be found. To handle this, one extra recursion
3988 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3989 * bit is already set, then it is considered a recursion and the function
3990 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3991 *
3992 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3993 * to be cleared. Even if it wasn't the context that set it. That is,
3994 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3995 * is called before preempt_count() is updated, since the check will
3996 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3997 * NMI then comes in, it will set the NMI bit, but when the NMI code
3998 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3999 * and leave the NMI bit set. But this is fine, because the interrupt
4000 * code that set the TRANSITION bit will then clear the NMI bit when it
4001 * calls trace_recursive_unlock(). If another NMI comes in, it will
4002 * set the TRANSITION bit and continue.
4003 *
4004 * Note: The TRANSITION bit only handles a single transition between context.
4005 */
4006
4007 static __always_inline bool
trace_recursive_lock(struct ring_buffer_per_cpu * cpu_buffer)4008 trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
4009 {
4010 unsigned int val = cpu_buffer->current_context;
4011 int bit = interrupt_context_level();
4012
4013 bit = RB_CTX_NORMAL - bit;
4014
4015 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
4016 /*
4017 * It is possible that this was called by transitioning
4018 * between interrupt context, and preempt_count() has not
4019 * been updated yet. In this case, use the TRANSITION bit.
4020 */
4021 bit = RB_CTX_TRANSITION;
4022 if (val & (1 << (bit + cpu_buffer->nest))) {
4023 do_ring_buffer_record_recursion();
4024 return true;
4025 }
4026 }
4027
4028 val |= (1 << (bit + cpu_buffer->nest));
4029 cpu_buffer->current_context = val;
4030
4031 return false;
4032 }
4033
4034 static __always_inline void
trace_recursive_unlock(struct ring_buffer_per_cpu * cpu_buffer)4035 trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
4036 {
4037 cpu_buffer->current_context &=
4038 cpu_buffer->current_context - (1 << cpu_buffer->nest);
4039 }
4040
4041 /* The recursive locking above uses 5 bits */
4042 #define NESTED_BITS 5
4043
4044 /**
4045 * ring_buffer_nest_start - Allow to trace while nested
4046 * @buffer: The ring buffer to modify
4047 *
4048 * The ring buffer has a safety mechanism to prevent recursion.
4049 * But there may be a case where a trace needs to be done while
4050 * tracing something else. In this case, calling this function
4051 * will allow this function to nest within a currently active
4052 * ring_buffer_lock_reserve().
4053 *
4054 * Call this function before calling another ring_buffer_lock_reserve() and
4055 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
4056 */
ring_buffer_nest_start(struct trace_buffer * buffer)4057 void ring_buffer_nest_start(struct trace_buffer *buffer)
4058 {
4059 struct ring_buffer_per_cpu *cpu_buffer;
4060 int cpu;
4061
4062 /* Enabled by ring_buffer_nest_end() */
4063 preempt_disable_notrace();
4064 cpu = raw_smp_processor_id();
4065 cpu_buffer = buffer->buffers[cpu];
4066 /* This is the shift value for the above recursive locking */
4067 cpu_buffer->nest += NESTED_BITS;
4068 }
4069
4070 /**
4071 * ring_buffer_nest_end - Allow to trace while nested
4072 * @buffer: The ring buffer to modify
4073 *
4074 * Must be called after ring_buffer_nest_start() and after the
4075 * ring_buffer_unlock_commit().
4076 */
ring_buffer_nest_end(struct trace_buffer * buffer)4077 void ring_buffer_nest_end(struct trace_buffer *buffer)
4078 {
4079 struct ring_buffer_per_cpu *cpu_buffer;
4080 int cpu;
4081
4082 /* disabled by ring_buffer_nest_start() */
4083 cpu = raw_smp_processor_id();
4084 cpu_buffer = buffer->buffers[cpu];
4085 /* This is the shift value for the above recursive locking */
4086 cpu_buffer->nest -= NESTED_BITS;
4087 preempt_enable_notrace();
4088 }
4089
4090 /**
4091 * ring_buffer_unlock_commit - commit a reserved
4092 * @buffer: The buffer to commit to
4093 *
4094 * This commits the data to the ring buffer, and releases any locks held.
4095 *
4096 * Must be paired with ring_buffer_lock_reserve.
4097 */
ring_buffer_unlock_commit(struct trace_buffer * buffer)4098 int ring_buffer_unlock_commit(struct trace_buffer *buffer)
4099 {
4100 struct ring_buffer_per_cpu *cpu_buffer;
4101 int cpu = raw_smp_processor_id();
4102
4103 cpu_buffer = buffer->buffers[cpu];
4104
4105 rb_commit(cpu_buffer);
4106
4107 rb_wakeups(buffer, cpu_buffer);
4108
4109 trace_recursive_unlock(cpu_buffer);
4110
4111 preempt_enable_notrace();
4112
4113 return 0;
4114 }
4115 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
4116
4117 /* Special value to validate all deltas on a page. */
4118 #define CHECK_FULL_PAGE 1L
4119
4120 #ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
4121
show_irq_str(int bits)4122 static const char *show_irq_str(int bits)
4123 {
4124 const char *type[] = {
4125 ".", // 0
4126 "s", // 1
4127 "h", // 2
4128 "Hs", // 3
4129 "n", // 4
4130 "Ns", // 5
4131 "Nh", // 6
4132 "NHs", // 7
4133 };
4134
4135 return type[bits];
4136 }
4137
4138 /* Assume this is a trace event */
show_flags(struct ring_buffer_event * event)4139 static const char *show_flags(struct ring_buffer_event *event)
4140 {
4141 struct trace_entry *entry;
4142 int bits = 0;
4143
4144 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
4145 return "X";
4146
4147 entry = ring_buffer_event_data(event);
4148
4149 if (entry->flags & TRACE_FLAG_SOFTIRQ)
4150 bits |= 1;
4151
4152 if (entry->flags & TRACE_FLAG_HARDIRQ)
4153 bits |= 2;
4154
4155 if (entry->flags & TRACE_FLAG_NMI)
4156 bits |= 4;
4157
4158 return show_irq_str(bits);
4159 }
4160
show_irq(struct ring_buffer_event * event)4161 static const char *show_irq(struct ring_buffer_event *event)
4162 {
4163 struct trace_entry *entry;
4164
4165 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
4166 return "";
4167
4168 entry = ring_buffer_event_data(event);
4169 if (entry->flags & TRACE_FLAG_IRQS_OFF)
4170 return "d";
4171 return "";
4172 }
4173
show_interrupt_level(void)4174 static const char *show_interrupt_level(void)
4175 {
4176 unsigned long pc = preempt_count();
4177 unsigned char level = 0;
4178
4179 if (pc & SOFTIRQ_OFFSET)
4180 level |= 1;
4181
4182 if (pc & HARDIRQ_MASK)
4183 level |= 2;
4184
4185 if (pc & NMI_MASK)
4186 level |= 4;
4187
4188 return show_irq_str(level);
4189 }
4190
dump_buffer_page(struct buffer_data_page * bpage,struct rb_event_info * info,unsigned long tail)4191 static void dump_buffer_page(struct buffer_data_page *bpage,
4192 struct rb_event_info *info,
4193 unsigned long tail)
4194 {
4195 struct ring_buffer_event *event;
4196 u64 ts, delta;
4197 int e;
4198
4199 ts = bpage->time_stamp;
4200 pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
4201
4202 for (e = 0; e < tail; e += rb_event_length(event)) {
4203
4204 event = (struct ring_buffer_event *)(bpage->data + e);
4205
4206 switch (event->type_len) {
4207
4208 case RINGBUF_TYPE_TIME_EXTEND:
4209 delta = rb_event_time_stamp(event);
4210 ts += delta;
4211 pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
4212 e, ts, delta);
4213 break;
4214
4215 case RINGBUF_TYPE_TIME_STAMP:
4216 delta = rb_event_time_stamp(event);
4217 ts = rb_fix_abs_ts(delta, ts);
4218 pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n",
4219 e, ts, delta);
4220 break;
4221
4222 case RINGBUF_TYPE_PADDING:
4223 ts += event->time_delta;
4224 pr_warn(" 0x%x: [%lld] delta:%d PADDING\n",
4225 e, ts, event->time_delta);
4226 break;
4227
4228 case RINGBUF_TYPE_DATA:
4229 ts += event->time_delta;
4230 pr_warn(" 0x%x: [%lld] delta:%d %s%s\n",
4231 e, ts, event->time_delta,
4232 show_flags(event), show_irq(event));
4233 break;
4234
4235 default:
4236 break;
4237 }
4238 }
4239 pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e);
4240 }
4241
4242 static DEFINE_PER_CPU(atomic_t, checking);
4243 static atomic_t ts_dump;
4244
4245 #define buffer_warn_return(fmt, ...) \
4246 do { \
4247 /* If another report is happening, ignore this one */ \
4248 if (atomic_inc_return(&ts_dump) != 1) { \
4249 atomic_dec(&ts_dump); \
4250 goto out; \
4251 } \
4252 atomic_inc(&cpu_buffer->record_disabled); \
4253 pr_warn(fmt, ##__VA_ARGS__); \
4254 dump_buffer_page(bpage, info, tail); \
4255 atomic_dec(&ts_dump); \
4256 /* There's some cases in boot up that this can happen */ \
4257 if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \
4258 /* Do not re-enable checking */ \
4259 return; \
4260 } while (0)
4261
4262 /*
4263 * Check if the current event time stamp matches the deltas on
4264 * the buffer page.
4265 */
check_buffer(struct ring_buffer_per_cpu * cpu_buffer,struct rb_event_info * info,unsigned long tail)4266 static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
4267 struct rb_event_info *info,
4268 unsigned long tail)
4269 {
4270 struct buffer_data_page *bpage;
4271 u64 ts, delta;
4272 bool full = false;
4273 int ret;
4274
4275 bpage = info->tail_page->page;
4276
4277 if (tail == CHECK_FULL_PAGE) {
4278 full = true;
4279 tail = local_read(&bpage->commit);
4280 } else if (info->add_timestamp &
4281 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
4282 /* Ignore events with absolute time stamps */
4283 return;
4284 }
4285
4286 /*
4287 * Do not check the first event (skip possible extends too).
4288 * Also do not check if previous events have not been committed.
4289 */
4290 if (tail <= 8 || tail > local_read(&bpage->commit))
4291 return;
4292
4293 /*
4294 * If this interrupted another event,
4295 */
4296 if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
4297 goto out;
4298
4299 ret = rb_read_data_buffer(bpage, tail, cpu_buffer->cpu, &ts, &delta);
4300 if (ret < 0) {
4301 if (delta < ts) {
4302 buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n",
4303 cpu_buffer->cpu, ts, delta);
4304 goto out;
4305 }
4306 }
4307 if ((full && ts > info->ts) ||
4308 (!full && ts + info->delta != info->ts)) {
4309 buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n",
4310 cpu_buffer->cpu,
4311 ts + info->delta, info->ts, info->delta,
4312 info->before, info->after,
4313 full ? " (full)" : "", show_interrupt_level());
4314 }
4315 out:
4316 atomic_dec(this_cpu_ptr(&checking));
4317 }
4318 #else
check_buffer(struct ring_buffer_per_cpu * cpu_buffer,struct rb_event_info * info,unsigned long tail)4319 static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
4320 struct rb_event_info *info,
4321 unsigned long tail)
4322 {
4323 }
4324 #endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
4325
4326 static struct ring_buffer_event *
__rb_reserve_next(struct ring_buffer_per_cpu * cpu_buffer,struct rb_event_info * info)4327 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
4328 struct rb_event_info *info)
4329 {
4330 struct ring_buffer_event *event;
4331 struct buffer_page *tail_page;
4332 unsigned long tail, write, w;
4333
4334 /* Don't let the compiler play games with cpu_buffer->tail_page */
4335 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
4336
4337 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
4338 barrier();
4339 rb_time_read(&cpu_buffer->before_stamp, &info->before);
4340 rb_time_read(&cpu_buffer->write_stamp, &info->after);
4341 barrier();
4342 info->ts = rb_time_stamp(cpu_buffer->buffer);
4343
4344 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
4345 info->delta = info->ts;
4346 } else {
4347 /*
4348 * If interrupting an event time update, we may need an
4349 * absolute timestamp.
4350 * Don't bother if this is the start of a new page (w == 0).
4351 */
4352 if (!w) {
4353 /* Use the sub-buffer timestamp */
4354 info->delta = 0;
4355 } else if (unlikely(info->before != info->after)) {
4356 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
4357 info->length += RB_LEN_TIME_EXTEND;
4358 } else {
4359 info->delta = info->ts - info->after;
4360 if (unlikely(test_time_stamp(info->delta))) {
4361 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
4362 info->length += RB_LEN_TIME_EXTEND;
4363 }
4364 }
4365 }
4366
4367 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
4368
4369 /*C*/ write = local_add_return(info->length, &tail_page->write);
4370
4371 /* set write to only the index of the write */
4372 write &= RB_WRITE_MASK;
4373
4374 tail = write - info->length;
4375
4376 /* See if we shot pass the end of this buffer page */
4377 if (unlikely(write > cpu_buffer->buffer->subbuf_size)) {
4378 check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
4379 return rb_move_tail(cpu_buffer, tail, info);
4380 }
4381
4382 if (likely(tail == w)) {
4383 /* Nothing interrupted us between A and C */
4384 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
4385 /*
4386 * If something came in between C and D, the write stamp
4387 * may now not be in sync. But that's fine as the before_stamp
4388 * will be different and then next event will just be forced
4389 * to use an absolute timestamp.
4390 */
4391 if (likely(!(info->add_timestamp &
4392 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
4393 /* This did not interrupt any time update */
4394 info->delta = info->ts - info->after;
4395 else
4396 /* Just use full timestamp for interrupting event */
4397 info->delta = info->ts;
4398 check_buffer(cpu_buffer, info, tail);
4399 } else {
4400 u64 ts;
4401 /* SLOW PATH - Interrupted between A and C */
4402
4403 /* Save the old before_stamp */
4404 rb_time_read(&cpu_buffer->before_stamp, &info->before);
4405
4406 /*
4407 * Read a new timestamp and update the before_stamp to make
4408 * the next event after this one force using an absolute
4409 * timestamp. This is in case an interrupt were to come in
4410 * between E and F.
4411 */
4412 ts = rb_time_stamp(cpu_buffer->buffer);
4413 rb_time_set(&cpu_buffer->before_stamp, ts);
4414
4415 barrier();
4416 /*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after);
4417 barrier();
4418 /*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
4419 info->after == info->before && info->after < ts) {
4420 /*
4421 * Nothing came after this event between C and F, it is
4422 * safe to use info->after for the delta as it
4423 * matched info->before and is still valid.
4424 */
4425 info->delta = ts - info->after;
4426 } else {
4427 /*
4428 * Interrupted between C and F:
4429 * Lost the previous events time stamp. Just set the
4430 * delta to zero, and this will be the same time as
4431 * the event this event interrupted. And the events that
4432 * came after this will still be correct (as they would
4433 * have built their delta on the previous event.
4434 */
4435 info->delta = 0;
4436 }
4437 info->ts = ts;
4438 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
4439 }
4440
4441 /*
4442 * If this is the first commit on the page, then it has the same
4443 * timestamp as the page itself.
4444 */
4445 if (unlikely(!tail && !(info->add_timestamp &
4446 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
4447 info->delta = 0;
4448
4449 /* We reserved something on the buffer */
4450
4451 event = __rb_page_index(tail_page, tail);
4452 rb_update_event(cpu_buffer, event, info);
4453
4454 local_inc(&tail_page->entries);
4455
4456 /*
4457 * If this is the first commit on the page, then update
4458 * its timestamp.
4459 */
4460 if (unlikely(!tail))
4461 tail_page->page->time_stamp = info->ts;
4462
4463 /* account for these added bytes */
4464 local_add(info->length, &cpu_buffer->entries_bytes);
4465
4466 return event;
4467 }
4468
4469 static __always_inline struct ring_buffer_event *
rb_reserve_next_event(struct trace_buffer * buffer,struct ring_buffer_per_cpu * cpu_buffer,unsigned long length)4470 rb_reserve_next_event(struct trace_buffer *buffer,
4471 struct ring_buffer_per_cpu *cpu_buffer,
4472 unsigned long length)
4473 {
4474 struct ring_buffer_event *event;
4475 struct rb_event_info info;
4476 int nr_loops = 0;
4477 int add_ts_default;
4478
4479 /*
4480 * ring buffer does cmpxchg as well as atomic64 operations
4481 * (which some archs use locking for atomic64), make sure this
4482 * is safe in NMI context
4483 */
4484 if ((!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) ||
4485 IS_ENABLED(CONFIG_GENERIC_ATOMIC64)) &&
4486 (unlikely(in_nmi()))) {
4487 return NULL;
4488 }
4489
4490 rb_start_commit(cpu_buffer);
4491 /* The commit page can not change after this */
4492
4493 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4494 /*
4495 * Due to the ability to swap a cpu buffer from a buffer
4496 * it is possible it was swapped before we committed.
4497 * (committing stops a swap). We check for it here and
4498 * if it happened, we have to fail the write.
4499 */
4500 barrier();
4501 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
4502 local_dec(&cpu_buffer->committing);
4503 local_dec(&cpu_buffer->commits);
4504 return NULL;
4505 }
4506 #endif
4507
4508 info.length = rb_calculate_event_length(length);
4509
4510 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
4511 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
4512 info.length += RB_LEN_TIME_EXTEND;
4513 if (info.length > cpu_buffer->buffer->max_data_size)
4514 goto out_fail;
4515 } else {
4516 add_ts_default = RB_ADD_STAMP_NONE;
4517 }
4518
4519 again:
4520 info.add_timestamp = add_ts_default;
4521 info.delta = 0;
4522
4523 /*
4524 * We allow for interrupts to reenter here and do a trace.
4525 * If one does, it will cause this original code to loop
4526 * back here. Even with heavy interrupts happening, this
4527 * should only happen a few times in a row. If this happens
4528 * 1000 times in a row, there must be either an interrupt
4529 * storm or we have something buggy.
4530 * Bail!
4531 */
4532 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
4533 goto out_fail;
4534
4535 event = __rb_reserve_next(cpu_buffer, &info);
4536
4537 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
4538 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
4539 info.length -= RB_LEN_TIME_EXTEND;
4540 goto again;
4541 }
4542
4543 if (likely(event))
4544 return event;
4545 out_fail:
4546 rb_end_commit(cpu_buffer);
4547 return NULL;
4548 }
4549
4550 /**
4551 * ring_buffer_lock_reserve - reserve a part of the buffer
4552 * @buffer: the ring buffer to reserve from
4553 * @length: the length of the data to reserve (excluding event header)
4554 *
4555 * Returns a reserved event on the ring buffer to copy directly to.
4556 * The user of this interface will need to get the body to write into
4557 * and can use the ring_buffer_event_data() interface.
4558 *
4559 * The length is the length of the data needed, not the event length
4560 * which also includes the event header.
4561 *
4562 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
4563 * If NULL is returned, then nothing has been allocated or locked.
4564 */
4565 struct ring_buffer_event *
ring_buffer_lock_reserve(struct trace_buffer * buffer,unsigned long length)4566 ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
4567 {
4568 struct ring_buffer_per_cpu *cpu_buffer;
4569 struct ring_buffer_event *event;
4570 int cpu;
4571
4572 /* If we are tracing schedule, we don't want to recurse */
4573 preempt_disable_notrace();
4574
4575 if (unlikely(atomic_read(&buffer->record_disabled)))
4576 goto out;
4577
4578 cpu = raw_smp_processor_id();
4579
4580 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
4581 goto out;
4582
4583 cpu_buffer = buffer->buffers[cpu];
4584
4585 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
4586 goto out;
4587
4588 if (unlikely(length > buffer->max_data_size))
4589 goto out;
4590
4591 if (unlikely(trace_recursive_lock(cpu_buffer)))
4592 goto out;
4593
4594 event = rb_reserve_next_event(buffer, cpu_buffer, length);
4595 if (!event)
4596 goto out_unlock;
4597
4598 return event;
4599
4600 out_unlock:
4601 trace_recursive_unlock(cpu_buffer);
4602 out:
4603 preempt_enable_notrace();
4604 return NULL;
4605 }
4606 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
4607
4608 /*
4609 * Decrement the entries to the page that an event is on.
4610 * The event does not even need to exist, only the pointer
4611 * to the page it is on. This may only be called before the commit
4612 * takes place.
4613 */
4614 static inline void
rb_decrement_entry(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event)4615 rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
4616 struct ring_buffer_event *event)
4617 {
4618 unsigned long addr = (unsigned long)event;
4619 struct buffer_page *bpage = cpu_buffer->commit_page;
4620 struct buffer_page *start;
4621
4622 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
4623
4624 /* Do the likely case first */
4625 if (likely(bpage->page == (void *)addr)) {
4626 local_dec(&bpage->entries);
4627 return;
4628 }
4629
4630 /*
4631 * Because the commit page may be on the reader page we
4632 * start with the next page and check the end loop there.
4633 */
4634 rb_inc_page(&bpage);
4635 start = bpage;
4636 do {
4637 if (bpage->page == (void *)addr) {
4638 local_dec(&bpage->entries);
4639 return;
4640 }
4641 rb_inc_page(&bpage);
4642 } while (bpage != start);
4643
4644 /* commit not part of this buffer?? */
4645 RB_WARN_ON(cpu_buffer, 1);
4646 }
4647
4648 /**
4649 * ring_buffer_discard_commit - discard an event that has not been committed
4650 * @buffer: the ring buffer
4651 * @event: non committed event to discard
4652 *
4653 * Sometimes an event that is in the ring buffer needs to be ignored.
4654 * This function lets the user discard an event in the ring buffer
4655 * and then that event will not be read later.
4656 *
4657 * This function only works if it is called before the item has been
4658 * committed. It will try to free the event from the ring buffer
4659 * if another event has not been added behind it.
4660 *
4661 * If another event has been added behind it, it will set the event
4662 * up as discarded, and perform the commit.
4663 *
4664 * If this function is called, do not call ring_buffer_unlock_commit on
4665 * the event.
4666 */
ring_buffer_discard_commit(struct trace_buffer * buffer,struct ring_buffer_event * event)4667 void ring_buffer_discard_commit(struct trace_buffer *buffer,
4668 struct ring_buffer_event *event)
4669 {
4670 struct ring_buffer_per_cpu *cpu_buffer;
4671 int cpu;
4672
4673 /* The event is discarded regardless */
4674 rb_event_discard(event);
4675
4676 cpu = smp_processor_id();
4677 cpu_buffer = buffer->buffers[cpu];
4678
4679 /*
4680 * This must only be called if the event has not been
4681 * committed yet. Thus we can assume that preemption
4682 * is still disabled.
4683 */
4684 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
4685
4686 rb_decrement_entry(cpu_buffer, event);
4687 if (rb_try_to_discard(cpu_buffer, event))
4688 goto out;
4689
4690 out:
4691 rb_end_commit(cpu_buffer);
4692
4693 trace_recursive_unlock(cpu_buffer);
4694
4695 preempt_enable_notrace();
4696
4697 }
4698 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
4699
4700 /**
4701 * ring_buffer_write - write data to the buffer without reserving
4702 * @buffer: The ring buffer to write to.
4703 * @length: The length of the data being written (excluding the event header)
4704 * @data: The data to write to the buffer.
4705 *
4706 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
4707 * one function. If you already have the data to write to the buffer, it
4708 * may be easier to simply call this function.
4709 *
4710 * Note, like ring_buffer_lock_reserve, the length is the length of the data
4711 * and not the length of the event which would hold the header.
4712 */
ring_buffer_write(struct trace_buffer * buffer,unsigned long length,void * data)4713 int ring_buffer_write(struct trace_buffer *buffer,
4714 unsigned long length,
4715 void *data)
4716 {
4717 struct ring_buffer_per_cpu *cpu_buffer;
4718 struct ring_buffer_event *event;
4719 void *body;
4720 int ret = -EBUSY;
4721 int cpu;
4722
4723 preempt_disable_notrace();
4724
4725 if (atomic_read(&buffer->record_disabled))
4726 goto out;
4727
4728 cpu = raw_smp_processor_id();
4729
4730 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4731 goto out;
4732
4733 cpu_buffer = buffer->buffers[cpu];
4734
4735 if (atomic_read(&cpu_buffer->record_disabled))
4736 goto out;
4737
4738 if (length > buffer->max_data_size)
4739 goto out;
4740
4741 if (unlikely(trace_recursive_lock(cpu_buffer)))
4742 goto out;
4743
4744 event = rb_reserve_next_event(buffer, cpu_buffer, length);
4745 if (!event)
4746 goto out_unlock;
4747
4748 body = rb_event_data(event);
4749
4750 memcpy(body, data, length);
4751
4752 rb_commit(cpu_buffer);
4753
4754 rb_wakeups(buffer, cpu_buffer);
4755
4756 ret = 0;
4757
4758 out_unlock:
4759 trace_recursive_unlock(cpu_buffer);
4760
4761 out:
4762 preempt_enable_notrace();
4763
4764 return ret;
4765 }
4766 EXPORT_SYMBOL_GPL(ring_buffer_write);
4767
4768 /*
4769 * The total entries in the ring buffer is the running counter
4770 * of entries entered into the ring buffer, minus the sum of
4771 * the entries read from the ring buffer and the number of
4772 * entries that were overwritten.
4773 */
4774 static inline unsigned long
rb_num_of_entries(struct ring_buffer_per_cpu * cpu_buffer)4775 rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4776 {
4777 return local_read(&cpu_buffer->entries) -
4778 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4779 }
4780
rb_per_cpu_empty(struct ring_buffer_per_cpu * cpu_buffer)4781 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
4782 {
4783 return !rb_num_of_entries(cpu_buffer);
4784 }
4785
4786 /**
4787 * ring_buffer_record_disable - stop all writes into the buffer
4788 * @buffer: The ring buffer to stop writes to.
4789 *
4790 * This prevents all writes to the buffer. Any attempt to write
4791 * to the buffer after this will fail and return NULL.
4792 *
4793 * The caller should call synchronize_rcu() after this.
4794 */
ring_buffer_record_disable(struct trace_buffer * buffer)4795 void ring_buffer_record_disable(struct trace_buffer *buffer)
4796 {
4797 atomic_inc(&buffer->record_disabled);
4798 }
4799 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
4800
4801 /**
4802 * ring_buffer_record_enable - enable writes to the buffer
4803 * @buffer: The ring buffer to enable writes
4804 *
4805 * Note, multiple disables will need the same number of enables
4806 * to truly enable the writing (much like preempt_disable).
4807 */
ring_buffer_record_enable(struct trace_buffer * buffer)4808 void ring_buffer_record_enable(struct trace_buffer *buffer)
4809 {
4810 atomic_dec(&buffer->record_disabled);
4811 }
4812 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
4813
4814 /**
4815 * ring_buffer_record_off - stop all writes into the buffer
4816 * @buffer: The ring buffer to stop writes to.
4817 *
4818 * This prevents all writes to the buffer. Any attempt to write
4819 * to the buffer after this will fail and return NULL.
4820 *
4821 * This is different than ring_buffer_record_disable() as
4822 * it works like an on/off switch, where as the disable() version
4823 * must be paired with a enable().
4824 */
ring_buffer_record_off(struct trace_buffer * buffer)4825 void ring_buffer_record_off(struct trace_buffer *buffer)
4826 {
4827 unsigned int rd;
4828 unsigned int new_rd;
4829
4830 rd = atomic_read(&buffer->record_disabled);
4831 do {
4832 new_rd = rd | RB_BUFFER_OFF;
4833 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4834 }
4835 EXPORT_SYMBOL_GPL(ring_buffer_record_off);
4836
4837 /**
4838 * ring_buffer_record_on - restart writes into the buffer
4839 * @buffer: The ring buffer to start writes to.
4840 *
4841 * This enables all writes to the buffer that was disabled by
4842 * ring_buffer_record_off().
4843 *
4844 * This is different than ring_buffer_record_enable() as
4845 * it works like an on/off switch, where as the enable() version
4846 * must be paired with a disable().
4847 */
ring_buffer_record_on(struct trace_buffer * buffer)4848 void ring_buffer_record_on(struct trace_buffer *buffer)
4849 {
4850 unsigned int rd;
4851 unsigned int new_rd;
4852
4853 rd = atomic_read(&buffer->record_disabled);
4854 do {
4855 new_rd = rd & ~RB_BUFFER_OFF;
4856 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4857 }
4858 EXPORT_SYMBOL_GPL(ring_buffer_record_on);
4859
4860 /**
4861 * ring_buffer_record_is_on - return true if the ring buffer can write
4862 * @buffer: The ring buffer to see if write is enabled
4863 *
4864 * Returns true if the ring buffer is in a state that it accepts writes.
4865 */
ring_buffer_record_is_on(struct trace_buffer * buffer)4866 bool ring_buffer_record_is_on(struct trace_buffer *buffer)
4867 {
4868 return !atomic_read(&buffer->record_disabled);
4869 }
4870
4871 /**
4872 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
4873 * @buffer: The ring buffer to see if write is set enabled
4874 *
4875 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
4876 * Note that this does NOT mean it is in a writable state.
4877 *
4878 * It may return true when the ring buffer has been disabled by
4879 * ring_buffer_record_disable(), as that is a temporary disabling of
4880 * the ring buffer.
4881 */
ring_buffer_record_is_set_on(struct trace_buffer * buffer)4882 bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
4883 {
4884 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
4885 }
4886
4887 /**
4888 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4889 * @buffer: The ring buffer to stop writes to.
4890 * @cpu: The CPU buffer to stop
4891 *
4892 * This prevents all writes to the buffer. Any attempt to write
4893 * to the buffer after this will fail and return NULL.
4894 *
4895 * The caller should call synchronize_rcu() after this.
4896 */
ring_buffer_record_disable_cpu(struct trace_buffer * buffer,int cpu)4897 void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4898 {
4899 struct ring_buffer_per_cpu *cpu_buffer;
4900
4901 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4902 return;
4903
4904 cpu_buffer = buffer->buffers[cpu];
4905 atomic_inc(&cpu_buffer->record_disabled);
4906 }
4907 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4908
4909 /**
4910 * ring_buffer_record_enable_cpu - enable writes to the buffer
4911 * @buffer: The ring buffer to enable writes
4912 * @cpu: The CPU to enable.
4913 *
4914 * Note, multiple disables will need the same number of enables
4915 * to truly enable the writing (much like preempt_disable).
4916 */
ring_buffer_record_enable_cpu(struct trace_buffer * buffer,int cpu)4917 void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4918 {
4919 struct ring_buffer_per_cpu *cpu_buffer;
4920
4921 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4922 return;
4923
4924 cpu_buffer = buffer->buffers[cpu];
4925 atomic_dec(&cpu_buffer->record_disabled);
4926 }
4927 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4928
4929 /**
4930 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4931 * @buffer: The ring buffer
4932 * @cpu: The per CPU buffer to read from.
4933 */
ring_buffer_oldest_event_ts(struct trace_buffer * buffer,int cpu)4934 u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4935 {
4936 unsigned long flags;
4937 struct ring_buffer_per_cpu *cpu_buffer;
4938 struct buffer_page *bpage;
4939 u64 ret = 0;
4940
4941 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4942 return 0;
4943
4944 cpu_buffer = buffer->buffers[cpu];
4945 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4946 /*
4947 * if the tail is on reader_page, oldest time stamp is on the reader
4948 * page
4949 */
4950 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4951 bpage = cpu_buffer->reader_page;
4952 else
4953 bpage = rb_set_head_page(cpu_buffer);
4954 if (bpage)
4955 ret = bpage->page->time_stamp;
4956 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4957
4958 return ret;
4959 }
4960 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4961
4962 /**
4963 * ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer
4964 * @buffer: The ring buffer
4965 * @cpu: The per CPU buffer to read from.
4966 */
ring_buffer_bytes_cpu(struct trace_buffer * buffer,int cpu)4967 unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4968 {
4969 struct ring_buffer_per_cpu *cpu_buffer;
4970 unsigned long ret;
4971
4972 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4973 return 0;
4974
4975 cpu_buffer = buffer->buffers[cpu];
4976 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4977
4978 return ret;
4979 }
4980 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4981
4982 /**
4983 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4984 * @buffer: The ring buffer
4985 * @cpu: The per CPU buffer to get the entries from.
4986 */
ring_buffer_entries_cpu(struct trace_buffer * buffer,int cpu)4987 unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4988 {
4989 struct ring_buffer_per_cpu *cpu_buffer;
4990
4991 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4992 return 0;
4993
4994 cpu_buffer = buffer->buffers[cpu];
4995
4996 return rb_num_of_entries(cpu_buffer);
4997 }
4998 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4999
5000 /**
5001 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
5002 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
5003 * @buffer: The ring buffer
5004 * @cpu: The per CPU buffer to get the number of overruns from
5005 */
ring_buffer_overrun_cpu(struct trace_buffer * buffer,int cpu)5006 unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
5007 {
5008 struct ring_buffer_per_cpu *cpu_buffer;
5009 unsigned long ret;
5010
5011 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5012 return 0;
5013
5014 cpu_buffer = buffer->buffers[cpu];
5015 ret = local_read(&cpu_buffer->overrun);
5016
5017 return ret;
5018 }
5019 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
5020
5021 /**
5022 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
5023 * commits failing due to the buffer wrapping around while there are uncommitted
5024 * events, such as during an interrupt storm.
5025 * @buffer: The ring buffer
5026 * @cpu: The per CPU buffer to get the number of overruns from
5027 */
5028 unsigned long
ring_buffer_commit_overrun_cpu(struct trace_buffer * buffer,int cpu)5029 ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
5030 {
5031 struct ring_buffer_per_cpu *cpu_buffer;
5032 unsigned long ret;
5033
5034 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5035 return 0;
5036
5037 cpu_buffer = buffer->buffers[cpu];
5038 ret = local_read(&cpu_buffer->commit_overrun);
5039
5040 return ret;
5041 }
5042 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
5043
5044 /**
5045 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
5046 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
5047 * @buffer: The ring buffer
5048 * @cpu: The per CPU buffer to get the number of overruns from
5049 */
5050 unsigned long
ring_buffer_dropped_events_cpu(struct trace_buffer * buffer,int cpu)5051 ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
5052 {
5053 struct ring_buffer_per_cpu *cpu_buffer;
5054 unsigned long ret;
5055
5056 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5057 return 0;
5058
5059 cpu_buffer = buffer->buffers[cpu];
5060 ret = local_read(&cpu_buffer->dropped_events);
5061
5062 return ret;
5063 }
5064 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
5065
5066 /**
5067 * ring_buffer_read_events_cpu - get the number of events successfully read
5068 * @buffer: The ring buffer
5069 * @cpu: The per CPU buffer to get the number of events read
5070 */
5071 unsigned long
ring_buffer_read_events_cpu(struct trace_buffer * buffer,int cpu)5072 ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
5073 {
5074 struct ring_buffer_per_cpu *cpu_buffer;
5075
5076 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5077 return 0;
5078
5079 cpu_buffer = buffer->buffers[cpu];
5080 return cpu_buffer->read;
5081 }
5082 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
5083
5084 /**
5085 * ring_buffer_entries - get the number of entries in a buffer
5086 * @buffer: The ring buffer
5087 *
5088 * Returns the total number of entries in the ring buffer
5089 * (all CPU entries)
5090 */
ring_buffer_entries(struct trace_buffer * buffer)5091 unsigned long ring_buffer_entries(struct trace_buffer *buffer)
5092 {
5093 struct ring_buffer_per_cpu *cpu_buffer;
5094 unsigned long entries = 0;
5095 int cpu;
5096
5097 /* if you care about this being correct, lock the buffer */
5098 for_each_buffer_cpu(buffer, cpu) {
5099 cpu_buffer = buffer->buffers[cpu];
5100 entries += rb_num_of_entries(cpu_buffer);
5101 }
5102
5103 return entries;
5104 }
5105 EXPORT_SYMBOL_GPL(ring_buffer_entries);
5106
5107 /**
5108 * ring_buffer_overruns - get the number of overruns in buffer
5109 * @buffer: The ring buffer
5110 *
5111 * Returns the total number of overruns in the ring buffer
5112 * (all CPU entries)
5113 */
ring_buffer_overruns(struct trace_buffer * buffer)5114 unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
5115 {
5116 struct ring_buffer_per_cpu *cpu_buffer;
5117 unsigned long overruns = 0;
5118 int cpu;
5119
5120 /* if you care about this being correct, lock the buffer */
5121 for_each_buffer_cpu(buffer, cpu) {
5122 cpu_buffer = buffer->buffers[cpu];
5123 overruns += local_read(&cpu_buffer->overrun);
5124 }
5125
5126 return overruns;
5127 }
5128 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
5129
rb_iter_reset(struct ring_buffer_iter * iter)5130 static void rb_iter_reset(struct ring_buffer_iter *iter)
5131 {
5132 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5133
5134 /* Iterator usage is expected to have record disabled */
5135 iter->head_page = cpu_buffer->reader_page;
5136 iter->head = cpu_buffer->reader_page->read;
5137 iter->next_event = iter->head;
5138
5139 iter->cache_reader_page = iter->head_page;
5140 iter->cache_read = cpu_buffer->read;
5141 iter->cache_pages_removed = cpu_buffer->pages_removed;
5142
5143 if (iter->head) {
5144 iter->read_stamp = cpu_buffer->read_stamp;
5145 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
5146 } else {
5147 iter->read_stamp = iter->head_page->page->time_stamp;
5148 iter->page_stamp = iter->read_stamp;
5149 }
5150 }
5151
5152 /**
5153 * ring_buffer_iter_reset - reset an iterator
5154 * @iter: The iterator to reset
5155 *
5156 * Resets the iterator, so that it will start from the beginning
5157 * again.
5158 */
ring_buffer_iter_reset(struct ring_buffer_iter * iter)5159 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
5160 {
5161 struct ring_buffer_per_cpu *cpu_buffer;
5162 unsigned long flags;
5163
5164 if (!iter)
5165 return;
5166
5167 cpu_buffer = iter->cpu_buffer;
5168
5169 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5170 rb_iter_reset(iter);
5171 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5172 }
5173 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
5174
5175 /**
5176 * ring_buffer_iter_empty - check if an iterator has no more to read
5177 * @iter: The iterator to check
5178 */
ring_buffer_iter_empty(struct ring_buffer_iter * iter)5179 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
5180 {
5181 struct ring_buffer_per_cpu *cpu_buffer;
5182 struct buffer_page *reader;
5183 struct buffer_page *head_page;
5184 struct buffer_page *commit_page;
5185 struct buffer_page *curr_commit_page;
5186 unsigned commit;
5187 u64 curr_commit_ts;
5188 u64 commit_ts;
5189
5190 cpu_buffer = iter->cpu_buffer;
5191 reader = cpu_buffer->reader_page;
5192 head_page = cpu_buffer->head_page;
5193 commit_page = READ_ONCE(cpu_buffer->commit_page);
5194 commit_ts = commit_page->page->time_stamp;
5195
5196 /*
5197 * When the writer goes across pages, it issues a cmpxchg which
5198 * is a mb(), which will synchronize with the rmb here.
5199 * (see rb_tail_page_update())
5200 */
5201 smp_rmb();
5202 commit = rb_page_commit(commit_page);
5203 /* We want to make sure that the commit page doesn't change */
5204 smp_rmb();
5205
5206 /* Make sure commit page didn't change */
5207 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
5208 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
5209
5210 /* If the commit page changed, then there's more data */
5211 if (curr_commit_page != commit_page ||
5212 curr_commit_ts != commit_ts)
5213 return 0;
5214
5215 /* Still racy, as it may return a false positive, but that's OK */
5216 return ((iter->head_page == commit_page && iter->head >= commit) ||
5217 (iter->head_page == reader && commit_page == head_page &&
5218 head_page->read == commit &&
5219 iter->head == rb_page_size(cpu_buffer->reader_page)));
5220 }
5221 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
5222
5223 static void
rb_update_read_stamp(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event)5224 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
5225 struct ring_buffer_event *event)
5226 {
5227 u64 delta;
5228
5229 switch (event->type_len) {
5230 case RINGBUF_TYPE_PADDING:
5231 return;
5232
5233 case RINGBUF_TYPE_TIME_EXTEND:
5234 delta = rb_event_time_stamp(event);
5235 cpu_buffer->read_stamp += delta;
5236 return;
5237
5238 case RINGBUF_TYPE_TIME_STAMP:
5239 delta = rb_event_time_stamp(event);
5240 delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp);
5241 cpu_buffer->read_stamp = delta;
5242 return;
5243
5244 case RINGBUF_TYPE_DATA:
5245 cpu_buffer->read_stamp += event->time_delta;
5246 return;
5247
5248 default:
5249 RB_WARN_ON(cpu_buffer, 1);
5250 }
5251 }
5252
5253 static void
rb_update_iter_read_stamp(struct ring_buffer_iter * iter,struct ring_buffer_event * event)5254 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
5255 struct ring_buffer_event *event)
5256 {
5257 u64 delta;
5258
5259 switch (event->type_len) {
5260 case RINGBUF_TYPE_PADDING:
5261 return;
5262
5263 case RINGBUF_TYPE_TIME_EXTEND:
5264 delta = rb_event_time_stamp(event);
5265 iter->read_stamp += delta;
5266 return;
5267
5268 case RINGBUF_TYPE_TIME_STAMP:
5269 delta = rb_event_time_stamp(event);
5270 delta = rb_fix_abs_ts(delta, iter->read_stamp);
5271 iter->read_stamp = delta;
5272 return;
5273
5274 case RINGBUF_TYPE_DATA:
5275 iter->read_stamp += event->time_delta;
5276 return;
5277
5278 default:
5279 RB_WARN_ON(iter->cpu_buffer, 1);
5280 }
5281 }
5282
5283 static struct buffer_page *
rb_get_reader_page(struct ring_buffer_per_cpu * cpu_buffer)5284 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
5285 {
5286 struct buffer_page *reader = NULL;
5287 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
5288 unsigned long overwrite;
5289 unsigned long flags;
5290 int nr_loops = 0;
5291 bool ret;
5292
5293 local_irq_save(flags);
5294 arch_spin_lock(&cpu_buffer->lock);
5295
5296 again:
5297 /*
5298 * This should normally only loop twice. But because the
5299 * start of the reader inserts an empty page, it causes
5300 * a case where we will loop three times. There should be no
5301 * reason to loop four times (that I know of).
5302 */
5303 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
5304 reader = NULL;
5305 goto out;
5306 }
5307
5308 reader = cpu_buffer->reader_page;
5309
5310 /* If there's more to read, return this page */
5311 if (cpu_buffer->reader_page->read < rb_page_size(reader))
5312 goto out;
5313
5314 /* Never should we have an index greater than the size */
5315 if (RB_WARN_ON(cpu_buffer,
5316 cpu_buffer->reader_page->read > rb_page_size(reader)))
5317 goto out;
5318
5319 /* check if we caught up to the tail */
5320 reader = NULL;
5321 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
5322 goto out;
5323
5324 /* Don't bother swapping if the ring buffer is empty */
5325 if (rb_num_of_entries(cpu_buffer) == 0)
5326 goto out;
5327
5328 /*
5329 * Reset the reader page to size zero.
5330 */
5331 local_set(&cpu_buffer->reader_page->write, 0);
5332 local_set(&cpu_buffer->reader_page->entries, 0);
5333 local_set(&cpu_buffer->reader_page->page->commit, 0);
5334 cpu_buffer->reader_page->real_end = 0;
5335
5336 spin:
5337 /*
5338 * Splice the empty reader page into the list around the head.
5339 */
5340 reader = rb_set_head_page(cpu_buffer);
5341 if (!reader)
5342 goto out;
5343 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
5344 cpu_buffer->reader_page->list.prev = reader->list.prev;
5345
5346 /*
5347 * cpu_buffer->pages just needs to point to the buffer, it
5348 * has no specific buffer page to point to. Lets move it out
5349 * of our way so we don't accidentally swap it.
5350 */
5351 cpu_buffer->pages = reader->list.prev;
5352
5353 /* The reader page will be pointing to the new head */
5354 rb_set_list_to_head(&cpu_buffer->reader_page->list);
5355
5356 /*
5357 * We want to make sure we read the overruns after we set up our
5358 * pointers to the next object. The writer side does a
5359 * cmpxchg to cross pages which acts as the mb on the writer
5360 * side. Note, the reader will constantly fail the swap
5361 * while the writer is updating the pointers, so this
5362 * guarantees that the overwrite recorded here is the one we
5363 * want to compare with the last_overrun.
5364 */
5365 smp_mb();
5366 overwrite = local_read(&(cpu_buffer->overrun));
5367
5368 /*
5369 * Here's the tricky part.
5370 *
5371 * We need to move the pointer past the header page.
5372 * But we can only do that if a writer is not currently
5373 * moving it. The page before the header page has the
5374 * flag bit '1' set if it is pointing to the page we want.
5375 * but if the writer is in the process of moving it
5376 * then it will be '2' or already moved '0'.
5377 */
5378
5379 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
5380
5381 /*
5382 * If we did not convert it, then we must try again.
5383 */
5384 if (!ret)
5385 goto spin;
5386
5387 if (cpu_buffer->ring_meta)
5388 rb_update_meta_reader(cpu_buffer, reader);
5389
5390 /*
5391 * Yay! We succeeded in replacing the page.
5392 *
5393 * Now make the new head point back to the reader page.
5394 */
5395 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
5396 rb_inc_page(&cpu_buffer->head_page);
5397
5398 cpu_buffer->cnt++;
5399 local_inc(&cpu_buffer->pages_read);
5400
5401 /* Finally update the reader page to the new head */
5402 cpu_buffer->reader_page = reader;
5403 cpu_buffer->reader_page->read = 0;
5404
5405 if (overwrite != cpu_buffer->last_overrun) {
5406 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
5407 cpu_buffer->last_overrun = overwrite;
5408 }
5409
5410 goto again;
5411
5412 out:
5413 /* Update the read_stamp on the first event */
5414 if (reader && reader->read == 0)
5415 cpu_buffer->read_stamp = reader->page->time_stamp;
5416
5417 arch_spin_unlock(&cpu_buffer->lock);
5418 local_irq_restore(flags);
5419
5420 /*
5421 * The writer has preempt disable, wait for it. But not forever
5422 * Although, 1 second is pretty much "forever"
5423 */
5424 #define USECS_WAIT 1000000
5425 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
5426 /* If the write is past the end of page, a writer is still updating it */
5427 if (likely(!reader || rb_page_write(reader) <= bsize))
5428 break;
5429
5430 udelay(1);
5431
5432 /* Get the latest version of the reader write value */
5433 smp_rmb();
5434 }
5435
5436 /* The writer is not moving forward? Something is wrong */
5437 if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
5438 reader = NULL;
5439
5440 /*
5441 * Make sure we see any padding after the write update
5442 * (see rb_reset_tail()).
5443 *
5444 * In addition, a writer may be writing on the reader page
5445 * if the page has not been fully filled, so the read barrier
5446 * is also needed to make sure we see the content of what is
5447 * committed by the writer (see rb_set_commit_to_write()).
5448 */
5449 smp_rmb();
5450
5451
5452 return reader;
5453 }
5454
rb_advance_reader(struct ring_buffer_per_cpu * cpu_buffer)5455 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
5456 {
5457 struct ring_buffer_event *event;
5458 struct buffer_page *reader;
5459 unsigned length;
5460
5461 reader = rb_get_reader_page(cpu_buffer);
5462
5463 /* This function should not be called when buffer is empty */
5464 if (RB_WARN_ON(cpu_buffer, !reader))
5465 return;
5466
5467 event = rb_reader_event(cpu_buffer);
5468
5469 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
5470 cpu_buffer->read++;
5471
5472 rb_update_read_stamp(cpu_buffer, event);
5473
5474 length = rb_event_length(event);
5475 cpu_buffer->reader_page->read += length;
5476 cpu_buffer->read_bytes += length;
5477 }
5478
rb_advance_iter(struct ring_buffer_iter * iter)5479 static void rb_advance_iter(struct ring_buffer_iter *iter)
5480 {
5481 struct ring_buffer_per_cpu *cpu_buffer;
5482
5483 cpu_buffer = iter->cpu_buffer;
5484
5485 /* If head == next_event then we need to jump to the next event */
5486 if (iter->head == iter->next_event) {
5487 /* If the event gets overwritten again, there's nothing to do */
5488 if (rb_iter_head_event(iter) == NULL)
5489 return;
5490 }
5491
5492 iter->head = iter->next_event;
5493
5494 /*
5495 * Check if we are at the end of the buffer.
5496 */
5497 if (iter->next_event >= rb_page_size(iter->head_page)) {
5498 /* discarded commits can make the page empty */
5499 if (iter->head_page == cpu_buffer->commit_page)
5500 return;
5501 rb_inc_iter(iter);
5502 return;
5503 }
5504
5505 rb_update_iter_read_stamp(iter, iter->event);
5506 }
5507
rb_lost_events(struct ring_buffer_per_cpu * cpu_buffer)5508 static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
5509 {
5510 return cpu_buffer->lost_events;
5511 }
5512
5513 static struct ring_buffer_event *
rb_buffer_peek(struct ring_buffer_per_cpu * cpu_buffer,u64 * ts,unsigned long * lost_events)5514 rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
5515 unsigned long *lost_events)
5516 {
5517 struct ring_buffer_event *event;
5518 struct buffer_page *reader;
5519 int nr_loops = 0;
5520
5521 if (ts)
5522 *ts = 0;
5523 again:
5524 /*
5525 * We repeat when a time extend is encountered.
5526 * Since the time extend is always attached to a data event,
5527 * we should never loop more than once.
5528 * (We never hit the following condition more than twice).
5529 */
5530 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
5531 return NULL;
5532
5533 reader = rb_get_reader_page(cpu_buffer);
5534 if (!reader)
5535 return NULL;
5536
5537 event = rb_reader_event(cpu_buffer);
5538
5539 switch (event->type_len) {
5540 case RINGBUF_TYPE_PADDING:
5541 if (rb_null_event(event))
5542 RB_WARN_ON(cpu_buffer, 1);
5543 /*
5544 * Because the writer could be discarding every
5545 * event it creates (which would probably be bad)
5546 * if we were to go back to "again" then we may never
5547 * catch up, and will trigger the warn on, or lock
5548 * the box. Return the padding, and we will release
5549 * the current locks, and try again.
5550 */
5551 return event;
5552
5553 case RINGBUF_TYPE_TIME_EXTEND:
5554 /* Internal data, OK to advance */
5555 rb_advance_reader(cpu_buffer);
5556 goto again;
5557
5558 case RINGBUF_TYPE_TIME_STAMP:
5559 if (ts) {
5560 *ts = rb_event_time_stamp(event);
5561 *ts = rb_fix_abs_ts(*ts, reader->page->time_stamp);
5562 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
5563 cpu_buffer->cpu, ts);
5564 }
5565 /* Internal data, OK to advance */
5566 rb_advance_reader(cpu_buffer);
5567 goto again;
5568
5569 case RINGBUF_TYPE_DATA:
5570 if (ts && !(*ts)) {
5571 *ts = cpu_buffer->read_stamp + event->time_delta;
5572 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
5573 cpu_buffer->cpu, ts);
5574 }
5575 if (lost_events)
5576 *lost_events = rb_lost_events(cpu_buffer);
5577 return event;
5578
5579 default:
5580 RB_WARN_ON(cpu_buffer, 1);
5581 }
5582
5583 return NULL;
5584 }
5585 EXPORT_SYMBOL_GPL(ring_buffer_peek);
5586
5587 static struct ring_buffer_event *
rb_iter_peek(struct ring_buffer_iter * iter,u64 * ts)5588 rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
5589 {
5590 struct trace_buffer *buffer;
5591 struct ring_buffer_per_cpu *cpu_buffer;
5592 struct ring_buffer_event *event;
5593 int nr_loops = 0;
5594
5595 if (ts)
5596 *ts = 0;
5597
5598 cpu_buffer = iter->cpu_buffer;
5599 buffer = cpu_buffer->buffer;
5600
5601 /*
5602 * Check if someone performed a consuming read to the buffer
5603 * or removed some pages from the buffer. In these cases,
5604 * iterator was invalidated and we need to reset it.
5605 */
5606 if (unlikely(iter->cache_read != cpu_buffer->read ||
5607 iter->cache_reader_page != cpu_buffer->reader_page ||
5608 iter->cache_pages_removed != cpu_buffer->pages_removed))
5609 rb_iter_reset(iter);
5610
5611 again:
5612 if (ring_buffer_iter_empty(iter))
5613 return NULL;
5614
5615 /*
5616 * As the writer can mess with what the iterator is trying
5617 * to read, just give up if we fail to get an event after
5618 * three tries. The iterator is not as reliable when reading
5619 * the ring buffer with an active write as the consumer is.
5620 * Do not warn if the three failures is reached.
5621 */
5622 if (++nr_loops > 3)
5623 return NULL;
5624
5625 if (rb_per_cpu_empty(cpu_buffer))
5626 return NULL;
5627
5628 if (iter->head >= rb_page_size(iter->head_page)) {
5629 rb_inc_iter(iter);
5630 goto again;
5631 }
5632
5633 event = rb_iter_head_event(iter);
5634 if (!event)
5635 goto again;
5636
5637 switch (event->type_len) {
5638 case RINGBUF_TYPE_PADDING:
5639 if (rb_null_event(event)) {
5640 rb_inc_iter(iter);
5641 goto again;
5642 }
5643 rb_advance_iter(iter);
5644 return event;
5645
5646 case RINGBUF_TYPE_TIME_EXTEND:
5647 /* Internal data, OK to advance */
5648 rb_advance_iter(iter);
5649 goto again;
5650
5651 case RINGBUF_TYPE_TIME_STAMP:
5652 if (ts) {
5653 *ts = rb_event_time_stamp(event);
5654 *ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp);
5655 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
5656 cpu_buffer->cpu, ts);
5657 }
5658 /* Internal data, OK to advance */
5659 rb_advance_iter(iter);
5660 goto again;
5661
5662 case RINGBUF_TYPE_DATA:
5663 if (ts && !(*ts)) {
5664 *ts = iter->read_stamp + event->time_delta;
5665 ring_buffer_normalize_time_stamp(buffer,
5666 cpu_buffer->cpu, ts);
5667 }
5668 return event;
5669
5670 default:
5671 RB_WARN_ON(cpu_buffer, 1);
5672 }
5673
5674 return NULL;
5675 }
5676 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
5677
rb_reader_lock(struct ring_buffer_per_cpu * cpu_buffer)5678 static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
5679 {
5680 if (likely(!in_nmi())) {
5681 raw_spin_lock(&cpu_buffer->reader_lock);
5682 return true;
5683 }
5684
5685 /*
5686 * If an NMI die dumps out the content of the ring buffer
5687 * trylock must be used to prevent a deadlock if the NMI
5688 * preempted a task that holds the ring buffer locks. If
5689 * we get the lock then all is fine, if not, then continue
5690 * to do the read, but this can corrupt the ring buffer,
5691 * so it must be permanently disabled from future writes.
5692 * Reading from NMI is a oneshot deal.
5693 */
5694 if (raw_spin_trylock(&cpu_buffer->reader_lock))
5695 return true;
5696
5697 /* Continue without locking, but disable the ring buffer */
5698 atomic_inc(&cpu_buffer->record_disabled);
5699 return false;
5700 }
5701
5702 static inline void
rb_reader_unlock(struct ring_buffer_per_cpu * cpu_buffer,bool locked)5703 rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
5704 {
5705 if (likely(locked))
5706 raw_spin_unlock(&cpu_buffer->reader_lock);
5707 }
5708
5709 /**
5710 * ring_buffer_peek - peek at the next event to be read
5711 * @buffer: The ring buffer to read
5712 * @cpu: The cpu to peak at
5713 * @ts: The timestamp counter of this event.
5714 * @lost_events: a variable to store if events were lost (may be NULL)
5715 *
5716 * This will return the event that will be read next, but does
5717 * not consume the data.
5718 */
5719 struct ring_buffer_event *
ring_buffer_peek(struct trace_buffer * buffer,int cpu,u64 * ts,unsigned long * lost_events)5720 ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
5721 unsigned long *lost_events)
5722 {
5723 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5724 struct ring_buffer_event *event;
5725 unsigned long flags;
5726 bool dolock;
5727
5728 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5729 return NULL;
5730
5731 again:
5732 local_irq_save(flags);
5733 dolock = rb_reader_lock(cpu_buffer);
5734 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5735 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5736 rb_advance_reader(cpu_buffer);
5737 rb_reader_unlock(cpu_buffer, dolock);
5738 local_irq_restore(flags);
5739
5740 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5741 goto again;
5742
5743 return event;
5744 }
5745
5746 /** ring_buffer_iter_dropped - report if there are dropped events
5747 * @iter: The ring buffer iterator
5748 *
5749 * Returns true if there was dropped events since the last peek.
5750 */
ring_buffer_iter_dropped(struct ring_buffer_iter * iter)5751 bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
5752 {
5753 bool ret = iter->missed_events != 0;
5754
5755 iter->missed_events = 0;
5756 return ret;
5757 }
5758 EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
5759
5760 /**
5761 * ring_buffer_iter_peek - peek at the next event to be read
5762 * @iter: The ring buffer iterator
5763 * @ts: The timestamp counter of this event.
5764 *
5765 * This will return the event that will be read next, but does
5766 * not increment the iterator.
5767 */
5768 struct ring_buffer_event *
ring_buffer_iter_peek(struct ring_buffer_iter * iter,u64 * ts)5769 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
5770 {
5771 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5772 struct ring_buffer_event *event;
5773 unsigned long flags;
5774
5775 again:
5776 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5777 event = rb_iter_peek(iter, ts);
5778 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5779
5780 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5781 goto again;
5782
5783 return event;
5784 }
5785
5786 /**
5787 * ring_buffer_consume - return an event and consume it
5788 * @buffer: The ring buffer to get the next event from
5789 * @cpu: the cpu to read the buffer from
5790 * @ts: a variable to store the timestamp (may be NULL)
5791 * @lost_events: a variable to store if events were lost (may be NULL)
5792 *
5793 * Returns the next event in the ring buffer, and that event is consumed.
5794 * Meaning, that sequential reads will keep returning a different event,
5795 * and eventually empty the ring buffer if the producer is slower.
5796 */
5797 struct ring_buffer_event *
ring_buffer_consume(struct trace_buffer * buffer,int cpu,u64 * ts,unsigned long * lost_events)5798 ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
5799 unsigned long *lost_events)
5800 {
5801 struct ring_buffer_per_cpu *cpu_buffer;
5802 struct ring_buffer_event *event = NULL;
5803 unsigned long flags;
5804 bool dolock;
5805
5806 again:
5807 /* might be called in atomic */
5808 preempt_disable();
5809
5810 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5811 goto out;
5812
5813 cpu_buffer = buffer->buffers[cpu];
5814 local_irq_save(flags);
5815 dolock = rb_reader_lock(cpu_buffer);
5816
5817 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5818 if (event) {
5819 cpu_buffer->lost_events = 0;
5820 rb_advance_reader(cpu_buffer);
5821 }
5822
5823 rb_reader_unlock(cpu_buffer, dolock);
5824 local_irq_restore(flags);
5825
5826 out:
5827 preempt_enable();
5828
5829 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5830 goto again;
5831
5832 return event;
5833 }
5834 EXPORT_SYMBOL_GPL(ring_buffer_consume);
5835
5836 /**
5837 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
5838 * @buffer: The ring buffer to read from
5839 * @cpu: The cpu buffer to iterate over
5840 * @flags: gfp flags to use for memory allocation
5841 *
5842 * This performs the initial preparations necessary to iterate
5843 * through the buffer. Memory is allocated, buffer resizing
5844 * is disabled, and the iterator pointer is returned to the caller.
5845 *
5846 * After a sequence of ring_buffer_read_prepare calls, the user is
5847 * expected to make at least one call to ring_buffer_read_prepare_sync.
5848 * Afterwards, ring_buffer_read_start is invoked to get things going
5849 * for real.
5850 *
5851 * This overall must be paired with ring_buffer_read_finish.
5852 */
5853 struct ring_buffer_iter *
ring_buffer_read_prepare(struct trace_buffer * buffer,int cpu,gfp_t flags)5854 ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
5855 {
5856 struct ring_buffer_per_cpu *cpu_buffer;
5857 struct ring_buffer_iter *iter;
5858
5859 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5860 return NULL;
5861
5862 iter = kzalloc(sizeof(*iter), flags);
5863 if (!iter)
5864 return NULL;
5865
5866 /* Holds the entire event: data and meta data */
5867 iter->event_size = buffer->subbuf_size;
5868 iter->event = kmalloc(iter->event_size, flags);
5869 if (!iter->event) {
5870 kfree(iter);
5871 return NULL;
5872 }
5873
5874 cpu_buffer = buffer->buffers[cpu];
5875
5876 iter->cpu_buffer = cpu_buffer;
5877
5878 atomic_inc(&cpu_buffer->resize_disabled);
5879
5880 return iter;
5881 }
5882 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
5883
5884 /**
5885 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
5886 *
5887 * All previously invoked ring_buffer_read_prepare calls to prepare
5888 * iterators will be synchronized. Afterwards, read_buffer_read_start
5889 * calls on those iterators are allowed.
5890 */
5891 void
ring_buffer_read_prepare_sync(void)5892 ring_buffer_read_prepare_sync(void)
5893 {
5894 synchronize_rcu();
5895 }
5896 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
5897
5898 /**
5899 * ring_buffer_read_start - start a non consuming read of the buffer
5900 * @iter: The iterator returned by ring_buffer_read_prepare
5901 *
5902 * This finalizes the startup of an iteration through the buffer.
5903 * The iterator comes from a call to ring_buffer_read_prepare and
5904 * an intervening ring_buffer_read_prepare_sync must have been
5905 * performed.
5906 *
5907 * Must be paired with ring_buffer_read_finish.
5908 */
5909 void
ring_buffer_read_start(struct ring_buffer_iter * iter)5910 ring_buffer_read_start(struct ring_buffer_iter *iter)
5911 {
5912 struct ring_buffer_per_cpu *cpu_buffer;
5913 unsigned long flags;
5914
5915 if (!iter)
5916 return;
5917
5918 cpu_buffer = iter->cpu_buffer;
5919
5920 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5921 arch_spin_lock(&cpu_buffer->lock);
5922 rb_iter_reset(iter);
5923 arch_spin_unlock(&cpu_buffer->lock);
5924 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5925 }
5926 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5927
5928 /**
5929 * ring_buffer_read_finish - finish reading the iterator of the buffer
5930 * @iter: The iterator retrieved by ring_buffer_start
5931 *
5932 * This re-enables resizing of the buffer, and frees the iterator.
5933 */
5934 void
ring_buffer_read_finish(struct ring_buffer_iter * iter)5935 ring_buffer_read_finish(struct ring_buffer_iter *iter)
5936 {
5937 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5938
5939 /* Use this opportunity to check the integrity of the ring buffer. */
5940 rb_check_pages(cpu_buffer);
5941
5942 atomic_dec(&cpu_buffer->resize_disabled);
5943 kfree(iter->event);
5944 kfree(iter);
5945 }
5946 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5947
5948 /**
5949 * ring_buffer_iter_advance - advance the iterator to the next location
5950 * @iter: The ring buffer iterator
5951 *
5952 * Move the location of the iterator such that the next read will
5953 * be the next location of the iterator.
5954 */
ring_buffer_iter_advance(struct ring_buffer_iter * iter)5955 void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5956 {
5957 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5958 unsigned long flags;
5959
5960 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5961
5962 rb_advance_iter(iter);
5963
5964 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5965 }
5966 EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5967
5968 /**
5969 * ring_buffer_size - return the size of the ring buffer (in bytes)
5970 * @buffer: The ring buffer.
5971 * @cpu: The CPU to get ring buffer size from.
5972 */
ring_buffer_size(struct trace_buffer * buffer,int cpu)5973 unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5974 {
5975 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5976 return 0;
5977
5978 return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages;
5979 }
5980 EXPORT_SYMBOL_GPL(ring_buffer_size);
5981
5982 /**
5983 * ring_buffer_max_event_size - return the max data size of an event
5984 * @buffer: The ring buffer.
5985 *
5986 * Returns the maximum size an event can be.
5987 */
ring_buffer_max_event_size(struct trace_buffer * buffer)5988 unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer)
5989 {
5990 /* If abs timestamp is requested, events have a timestamp too */
5991 if (ring_buffer_time_stamp_abs(buffer))
5992 return buffer->max_data_size - RB_LEN_TIME_EXTEND;
5993 return buffer->max_data_size;
5994 }
5995 EXPORT_SYMBOL_GPL(ring_buffer_max_event_size);
5996
rb_clear_buffer_page(struct buffer_page * page)5997 static void rb_clear_buffer_page(struct buffer_page *page)
5998 {
5999 local_set(&page->write, 0);
6000 local_set(&page->entries, 0);
6001 rb_init_page(page->page);
6002 page->read = 0;
6003 }
6004
rb_update_meta_page(struct ring_buffer_per_cpu * cpu_buffer)6005 static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
6006 {
6007 struct trace_buffer_meta *meta = cpu_buffer->meta_page;
6008
6009 if (!meta)
6010 return;
6011
6012 meta->reader.read = cpu_buffer->reader_page->read;
6013 meta->reader.id = cpu_buffer->reader_page->id;
6014 meta->reader.lost_events = cpu_buffer->lost_events;
6015
6016 meta->entries = local_read(&cpu_buffer->entries);
6017 meta->overrun = local_read(&cpu_buffer->overrun);
6018 meta->read = cpu_buffer->read;
6019
6020 /* Some archs do not have data cache coherency between kernel and user-space */
6021 flush_kernel_vmap_range(cpu_buffer->meta_page, PAGE_SIZE);
6022 }
6023
6024 static void
rb_reset_cpu(struct ring_buffer_per_cpu * cpu_buffer)6025 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
6026 {
6027 struct buffer_page *page;
6028
6029 rb_head_page_deactivate(cpu_buffer);
6030
6031 cpu_buffer->head_page
6032 = list_entry(cpu_buffer->pages, struct buffer_page, list);
6033 rb_clear_buffer_page(cpu_buffer->head_page);
6034 list_for_each_entry(page, cpu_buffer->pages, list) {
6035 rb_clear_buffer_page(page);
6036 }
6037
6038 cpu_buffer->tail_page = cpu_buffer->head_page;
6039 cpu_buffer->commit_page = cpu_buffer->head_page;
6040
6041 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
6042 INIT_LIST_HEAD(&cpu_buffer->new_pages);
6043 rb_clear_buffer_page(cpu_buffer->reader_page);
6044
6045 local_set(&cpu_buffer->entries_bytes, 0);
6046 local_set(&cpu_buffer->overrun, 0);
6047 local_set(&cpu_buffer->commit_overrun, 0);
6048 local_set(&cpu_buffer->dropped_events, 0);
6049 local_set(&cpu_buffer->entries, 0);
6050 local_set(&cpu_buffer->committing, 0);
6051 local_set(&cpu_buffer->commits, 0);
6052 local_set(&cpu_buffer->pages_touched, 0);
6053 local_set(&cpu_buffer->pages_lost, 0);
6054 local_set(&cpu_buffer->pages_read, 0);
6055 cpu_buffer->last_pages_touch = 0;
6056 cpu_buffer->shortest_full = 0;
6057 cpu_buffer->read = 0;
6058 cpu_buffer->read_bytes = 0;
6059
6060 rb_time_set(&cpu_buffer->write_stamp, 0);
6061 rb_time_set(&cpu_buffer->before_stamp, 0);
6062
6063 memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
6064
6065 cpu_buffer->lost_events = 0;
6066 cpu_buffer->last_overrun = 0;
6067
6068 rb_head_page_activate(cpu_buffer);
6069 cpu_buffer->pages_removed = 0;
6070
6071 if (cpu_buffer->mapped) {
6072 rb_update_meta_page(cpu_buffer);
6073 if (cpu_buffer->ring_meta) {
6074 struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
6075 meta->commit_buffer = meta->head_buffer;
6076 }
6077 }
6078 }
6079
6080 /* Must have disabled the cpu buffer then done a synchronize_rcu */
reset_disabled_cpu_buffer(struct ring_buffer_per_cpu * cpu_buffer)6081 static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
6082 {
6083 unsigned long flags;
6084
6085 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6086
6087 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
6088 goto out;
6089
6090 arch_spin_lock(&cpu_buffer->lock);
6091
6092 rb_reset_cpu(cpu_buffer);
6093
6094 arch_spin_unlock(&cpu_buffer->lock);
6095
6096 out:
6097 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
6098 }
6099
6100 /**
6101 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
6102 * @buffer: The ring buffer to reset a per cpu buffer of
6103 * @cpu: The CPU buffer to be reset
6104 */
ring_buffer_reset_cpu(struct trace_buffer * buffer,int cpu)6105 void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
6106 {
6107 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
6108
6109 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6110 return;
6111
6112 /* prevent another thread from changing buffer sizes */
6113 mutex_lock(&buffer->mutex);
6114
6115 atomic_inc(&cpu_buffer->resize_disabled);
6116 atomic_inc(&cpu_buffer->record_disabled);
6117
6118 /* Make sure all commits have finished */
6119 synchronize_rcu();
6120
6121 reset_disabled_cpu_buffer(cpu_buffer);
6122
6123 atomic_dec(&cpu_buffer->record_disabled);
6124 atomic_dec(&cpu_buffer->resize_disabled);
6125
6126 mutex_unlock(&buffer->mutex);
6127 }
6128 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
6129
6130 /* Flag to ensure proper resetting of atomic variables */
6131 #define RESET_BIT (1 << 30)
6132
6133 /**
6134 * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
6135 * @buffer: The ring buffer to reset a per cpu buffer of
6136 */
ring_buffer_reset_online_cpus(struct trace_buffer * buffer)6137 void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
6138 {
6139 struct ring_buffer_per_cpu *cpu_buffer;
6140 int cpu;
6141
6142 /* prevent another thread from changing buffer sizes */
6143 mutex_lock(&buffer->mutex);
6144
6145 for_each_online_buffer_cpu(buffer, cpu) {
6146 cpu_buffer = buffer->buffers[cpu];
6147
6148 atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
6149 atomic_inc(&cpu_buffer->record_disabled);
6150 }
6151
6152 /* Make sure all commits have finished */
6153 synchronize_rcu();
6154
6155 for_each_buffer_cpu(buffer, cpu) {
6156 cpu_buffer = buffer->buffers[cpu];
6157
6158 /*
6159 * If a CPU came online during the synchronize_rcu(), then
6160 * ignore it.
6161 */
6162 if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
6163 continue;
6164
6165 reset_disabled_cpu_buffer(cpu_buffer);
6166
6167 atomic_dec(&cpu_buffer->record_disabled);
6168 atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
6169 }
6170
6171 mutex_unlock(&buffer->mutex);
6172 }
6173
6174 /**
6175 * ring_buffer_reset - reset a ring buffer
6176 * @buffer: The ring buffer to reset all cpu buffers
6177 */
ring_buffer_reset(struct trace_buffer * buffer)6178 void ring_buffer_reset(struct trace_buffer *buffer)
6179 {
6180 struct ring_buffer_per_cpu *cpu_buffer;
6181 int cpu;
6182
6183 /* prevent another thread from changing buffer sizes */
6184 mutex_lock(&buffer->mutex);
6185
6186 for_each_buffer_cpu(buffer, cpu) {
6187 cpu_buffer = buffer->buffers[cpu];
6188
6189 atomic_inc(&cpu_buffer->resize_disabled);
6190 atomic_inc(&cpu_buffer->record_disabled);
6191 }
6192
6193 /* Make sure all commits have finished */
6194 synchronize_rcu();
6195
6196 for_each_buffer_cpu(buffer, cpu) {
6197 cpu_buffer = buffer->buffers[cpu];
6198
6199 reset_disabled_cpu_buffer(cpu_buffer);
6200
6201 atomic_dec(&cpu_buffer->record_disabled);
6202 atomic_dec(&cpu_buffer->resize_disabled);
6203 }
6204
6205 mutex_unlock(&buffer->mutex);
6206 }
6207 EXPORT_SYMBOL_GPL(ring_buffer_reset);
6208
6209 /**
6210 * ring_buffer_empty - is the ring buffer empty?
6211 * @buffer: The ring buffer to test
6212 */
ring_buffer_empty(struct trace_buffer * buffer)6213 bool ring_buffer_empty(struct trace_buffer *buffer)
6214 {
6215 struct ring_buffer_per_cpu *cpu_buffer;
6216 unsigned long flags;
6217 bool dolock;
6218 bool ret;
6219 int cpu;
6220
6221 /* yes this is racy, but if you don't like the race, lock the buffer */
6222 for_each_buffer_cpu(buffer, cpu) {
6223 cpu_buffer = buffer->buffers[cpu];
6224 local_irq_save(flags);
6225 dolock = rb_reader_lock(cpu_buffer);
6226 ret = rb_per_cpu_empty(cpu_buffer);
6227 rb_reader_unlock(cpu_buffer, dolock);
6228 local_irq_restore(flags);
6229
6230 if (!ret)
6231 return false;
6232 }
6233
6234 return true;
6235 }
6236 EXPORT_SYMBOL_GPL(ring_buffer_empty);
6237
6238 /**
6239 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
6240 * @buffer: The ring buffer
6241 * @cpu: The CPU buffer to test
6242 */
ring_buffer_empty_cpu(struct trace_buffer * buffer,int cpu)6243 bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
6244 {
6245 struct ring_buffer_per_cpu *cpu_buffer;
6246 unsigned long flags;
6247 bool dolock;
6248 bool ret;
6249
6250 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6251 return true;
6252
6253 cpu_buffer = buffer->buffers[cpu];
6254 local_irq_save(flags);
6255 dolock = rb_reader_lock(cpu_buffer);
6256 ret = rb_per_cpu_empty(cpu_buffer);
6257 rb_reader_unlock(cpu_buffer, dolock);
6258 local_irq_restore(flags);
6259
6260 return ret;
6261 }
6262 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
6263
6264 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
6265 /**
6266 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
6267 * @buffer_a: One buffer to swap with
6268 * @buffer_b: The other buffer to swap with
6269 * @cpu: the CPU of the buffers to swap
6270 *
6271 * This function is useful for tracers that want to take a "snapshot"
6272 * of a CPU buffer and has another back up buffer lying around.
6273 * it is expected that the tracer handles the cpu buffer not being
6274 * used at the moment.
6275 */
ring_buffer_swap_cpu(struct trace_buffer * buffer_a,struct trace_buffer * buffer_b,int cpu)6276 int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
6277 struct trace_buffer *buffer_b, int cpu)
6278 {
6279 struct ring_buffer_per_cpu *cpu_buffer_a;
6280 struct ring_buffer_per_cpu *cpu_buffer_b;
6281 int ret = -EINVAL;
6282
6283 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
6284 !cpumask_test_cpu(cpu, buffer_b->cpumask))
6285 goto out;
6286
6287 cpu_buffer_a = buffer_a->buffers[cpu];
6288 cpu_buffer_b = buffer_b->buffers[cpu];
6289
6290 /* It's up to the callers to not try to swap mapped buffers */
6291 if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped)) {
6292 ret = -EBUSY;
6293 goto out;
6294 }
6295
6296 /* At least make sure the two buffers are somewhat the same */
6297 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
6298 goto out;
6299
6300 if (buffer_a->subbuf_order != buffer_b->subbuf_order)
6301 goto out;
6302
6303 ret = -EAGAIN;
6304
6305 if (atomic_read(&buffer_a->record_disabled))
6306 goto out;
6307
6308 if (atomic_read(&buffer_b->record_disabled))
6309 goto out;
6310
6311 if (atomic_read(&cpu_buffer_a->record_disabled))
6312 goto out;
6313
6314 if (atomic_read(&cpu_buffer_b->record_disabled))
6315 goto out;
6316
6317 /*
6318 * We can't do a synchronize_rcu here because this
6319 * function can be called in atomic context.
6320 * Normally this will be called from the same CPU as cpu.
6321 * If not it's up to the caller to protect this.
6322 */
6323 atomic_inc(&cpu_buffer_a->record_disabled);
6324 atomic_inc(&cpu_buffer_b->record_disabled);
6325
6326 ret = -EBUSY;
6327 if (local_read(&cpu_buffer_a->committing))
6328 goto out_dec;
6329 if (local_read(&cpu_buffer_b->committing))
6330 goto out_dec;
6331
6332 /*
6333 * When resize is in progress, we cannot swap it because
6334 * it will mess the state of the cpu buffer.
6335 */
6336 if (atomic_read(&buffer_a->resizing))
6337 goto out_dec;
6338 if (atomic_read(&buffer_b->resizing))
6339 goto out_dec;
6340
6341 buffer_a->buffers[cpu] = cpu_buffer_b;
6342 buffer_b->buffers[cpu] = cpu_buffer_a;
6343
6344 cpu_buffer_b->buffer = buffer_a;
6345 cpu_buffer_a->buffer = buffer_b;
6346
6347 ret = 0;
6348
6349 out_dec:
6350 atomic_dec(&cpu_buffer_a->record_disabled);
6351 atomic_dec(&cpu_buffer_b->record_disabled);
6352 out:
6353 return ret;
6354 }
6355 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
6356 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
6357
6358 /**
6359 * ring_buffer_alloc_read_page - allocate a page to read from buffer
6360 * @buffer: the buffer to allocate for.
6361 * @cpu: the cpu buffer to allocate.
6362 *
6363 * This function is used in conjunction with ring_buffer_read_page.
6364 * When reading a full page from the ring buffer, these functions
6365 * can be used to speed up the process. The calling function should
6366 * allocate a few pages first with this function. Then when it
6367 * needs to get pages from the ring buffer, it passes the result
6368 * of this function into ring_buffer_read_page, which will swap
6369 * the page that was allocated, with the read page of the buffer.
6370 *
6371 * Returns:
6372 * The page allocated, or ERR_PTR
6373 */
6374 struct buffer_data_read_page *
ring_buffer_alloc_read_page(struct trace_buffer * buffer,int cpu)6375 ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
6376 {
6377 struct ring_buffer_per_cpu *cpu_buffer;
6378 struct buffer_data_read_page *bpage = NULL;
6379 unsigned long flags;
6380 struct page *page;
6381
6382 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6383 return ERR_PTR(-ENODEV);
6384
6385 bpage = kzalloc(sizeof(*bpage), GFP_KERNEL);
6386 if (!bpage)
6387 return ERR_PTR(-ENOMEM);
6388
6389 bpage->order = buffer->subbuf_order;
6390 cpu_buffer = buffer->buffers[cpu];
6391 local_irq_save(flags);
6392 arch_spin_lock(&cpu_buffer->lock);
6393
6394 if (cpu_buffer->free_page) {
6395 bpage->data = cpu_buffer->free_page;
6396 cpu_buffer->free_page = NULL;
6397 }
6398
6399 arch_spin_unlock(&cpu_buffer->lock);
6400 local_irq_restore(flags);
6401
6402 if (bpage->data)
6403 goto out;
6404
6405 page = alloc_pages_node(cpu_to_node(cpu),
6406 GFP_KERNEL | __GFP_NORETRY | __GFP_COMP | __GFP_ZERO,
6407 cpu_buffer->buffer->subbuf_order);
6408 if (!page) {
6409 kfree(bpage);
6410 return ERR_PTR(-ENOMEM);
6411 }
6412
6413 bpage->data = page_address(page);
6414
6415 out:
6416 rb_init_page(bpage->data);
6417
6418 return bpage;
6419 }
6420 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
6421
6422 /**
6423 * ring_buffer_free_read_page - free an allocated read page
6424 * @buffer: the buffer the page was allocate for
6425 * @cpu: the cpu buffer the page came from
6426 * @data_page: the page to free
6427 *
6428 * Free a page allocated from ring_buffer_alloc_read_page.
6429 */
ring_buffer_free_read_page(struct trace_buffer * buffer,int cpu,struct buffer_data_read_page * data_page)6430 void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu,
6431 struct buffer_data_read_page *data_page)
6432 {
6433 struct ring_buffer_per_cpu *cpu_buffer;
6434 struct buffer_data_page *bpage = data_page->data;
6435 struct page *page = virt_to_page(bpage);
6436 unsigned long flags;
6437
6438 if (!buffer || !buffer->buffers || !buffer->buffers[cpu])
6439 return;
6440
6441 cpu_buffer = buffer->buffers[cpu];
6442
6443 /*
6444 * If the page is still in use someplace else, or order of the page
6445 * is different from the subbuffer order of the buffer -
6446 * we can't reuse it
6447 */
6448 if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order)
6449 goto out;
6450
6451 local_irq_save(flags);
6452 arch_spin_lock(&cpu_buffer->lock);
6453
6454 if (!cpu_buffer->free_page) {
6455 cpu_buffer->free_page = bpage;
6456 bpage = NULL;
6457 }
6458
6459 arch_spin_unlock(&cpu_buffer->lock);
6460 local_irq_restore(flags);
6461
6462 out:
6463 free_pages((unsigned long)bpage, data_page->order);
6464 kfree(data_page);
6465 }
6466 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
6467
6468 /**
6469 * ring_buffer_read_page - extract a page from the ring buffer
6470 * @buffer: buffer to extract from
6471 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
6472 * @len: amount to extract
6473 * @cpu: the cpu of the buffer to extract
6474 * @full: should the extraction only happen when the page is full.
6475 *
6476 * This function will pull out a page from the ring buffer and consume it.
6477 * @data_page must be the address of the variable that was returned
6478 * from ring_buffer_alloc_read_page. This is because the page might be used
6479 * to swap with a page in the ring buffer.
6480 *
6481 * for example:
6482 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
6483 * if (IS_ERR(rpage))
6484 * return PTR_ERR(rpage);
6485 * ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0);
6486 * if (ret >= 0)
6487 * process_page(ring_buffer_read_page_data(rpage), ret);
6488 * ring_buffer_free_read_page(buffer, cpu, rpage);
6489 *
6490 * When @full is set, the function will not return true unless
6491 * the writer is off the reader page.
6492 *
6493 * Note: it is up to the calling functions to handle sleeps and wakeups.
6494 * The ring buffer can be used anywhere in the kernel and can not
6495 * blindly call wake_up. The layer that uses the ring buffer must be
6496 * responsible for that.
6497 *
6498 * Returns:
6499 * >=0 if data has been transferred, returns the offset of consumed data.
6500 * <0 if no data has been transferred.
6501 */
ring_buffer_read_page(struct trace_buffer * buffer,struct buffer_data_read_page * data_page,size_t len,int cpu,int full)6502 int ring_buffer_read_page(struct trace_buffer *buffer,
6503 struct buffer_data_read_page *data_page,
6504 size_t len, int cpu, int full)
6505 {
6506 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
6507 struct ring_buffer_event *event;
6508 struct buffer_data_page *bpage;
6509 struct buffer_page *reader;
6510 unsigned long missed_events;
6511 unsigned long flags;
6512 unsigned int commit;
6513 unsigned int read;
6514 u64 save_timestamp;
6515 int ret = -1;
6516
6517 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6518 goto out;
6519
6520 /*
6521 * If len is not big enough to hold the page header, then
6522 * we can not copy anything.
6523 */
6524 if (len <= BUF_PAGE_HDR_SIZE)
6525 goto out;
6526
6527 len -= BUF_PAGE_HDR_SIZE;
6528
6529 if (!data_page || !data_page->data)
6530 goto out;
6531 if (data_page->order != buffer->subbuf_order)
6532 goto out;
6533
6534 bpage = data_page->data;
6535 if (!bpage)
6536 goto out;
6537
6538 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6539
6540 reader = rb_get_reader_page(cpu_buffer);
6541 if (!reader)
6542 goto out_unlock;
6543
6544 event = rb_reader_event(cpu_buffer);
6545
6546 read = reader->read;
6547 commit = rb_page_size(reader);
6548
6549 /* Check if any events were dropped */
6550 missed_events = cpu_buffer->lost_events;
6551
6552 /*
6553 * If this page has been partially read or
6554 * if len is not big enough to read the rest of the page or
6555 * a writer is still on the page, then
6556 * we must copy the data from the page to the buffer.
6557 * Otherwise, we can simply swap the page with the one passed in.
6558 */
6559 if (read || (len < (commit - read)) ||
6560 cpu_buffer->reader_page == cpu_buffer->commit_page ||
6561 cpu_buffer->mapped) {
6562 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
6563 unsigned int rpos = read;
6564 unsigned int pos = 0;
6565 unsigned int size;
6566
6567 /*
6568 * If a full page is expected, this can still be returned
6569 * if there's been a previous partial read and the
6570 * rest of the page can be read and the commit page is off
6571 * the reader page.
6572 */
6573 if (full &&
6574 (!read || (len < (commit - read)) ||
6575 cpu_buffer->reader_page == cpu_buffer->commit_page))
6576 goto out_unlock;
6577
6578 if (len > (commit - read))
6579 len = (commit - read);
6580
6581 /* Always keep the time extend and data together */
6582 size = rb_event_ts_length(event);
6583
6584 if (len < size)
6585 goto out_unlock;
6586
6587 /* save the current timestamp, since the user will need it */
6588 save_timestamp = cpu_buffer->read_stamp;
6589
6590 /* Need to copy one event at a time */
6591 do {
6592 /* We need the size of one event, because
6593 * rb_advance_reader only advances by one event,
6594 * whereas rb_event_ts_length may include the size of
6595 * one or two events.
6596 * We have already ensured there's enough space if this
6597 * is a time extend. */
6598 size = rb_event_length(event);
6599 memcpy(bpage->data + pos, rpage->data + rpos, size);
6600
6601 len -= size;
6602
6603 rb_advance_reader(cpu_buffer);
6604 rpos = reader->read;
6605 pos += size;
6606
6607 if (rpos >= commit)
6608 break;
6609
6610 event = rb_reader_event(cpu_buffer);
6611 /* Always keep the time extend and data together */
6612 size = rb_event_ts_length(event);
6613 } while (len >= size);
6614
6615 /* update bpage */
6616 local_set(&bpage->commit, pos);
6617 bpage->time_stamp = save_timestamp;
6618
6619 /* we copied everything to the beginning */
6620 read = 0;
6621 } else {
6622 /* update the entry counter */
6623 cpu_buffer->read += rb_page_entries(reader);
6624 cpu_buffer->read_bytes += rb_page_size(reader);
6625
6626 /* swap the pages */
6627 rb_init_page(bpage);
6628 bpage = reader->page;
6629 reader->page = data_page->data;
6630 local_set(&reader->write, 0);
6631 local_set(&reader->entries, 0);
6632 reader->read = 0;
6633 data_page->data = bpage;
6634
6635 /*
6636 * Use the real_end for the data size,
6637 * This gives us a chance to store the lost events
6638 * on the page.
6639 */
6640 if (reader->real_end)
6641 local_set(&bpage->commit, reader->real_end);
6642 }
6643 ret = read;
6644
6645 cpu_buffer->lost_events = 0;
6646
6647 commit = local_read(&bpage->commit);
6648 /*
6649 * Set a flag in the commit field if we lost events
6650 */
6651 if (missed_events) {
6652 /* If there is room at the end of the page to save the
6653 * missed events, then record it there.
6654 */
6655 if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
6656 memcpy(&bpage->data[commit], &missed_events,
6657 sizeof(missed_events));
6658 local_add(RB_MISSED_STORED, &bpage->commit);
6659 commit += sizeof(missed_events);
6660 }
6661 local_add(RB_MISSED_EVENTS, &bpage->commit);
6662 }
6663
6664 /*
6665 * This page may be off to user land. Zero it out here.
6666 */
6667 if (commit < buffer->subbuf_size)
6668 memset(&bpage->data[commit], 0, buffer->subbuf_size - commit);
6669
6670 out_unlock:
6671 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
6672
6673 out:
6674 return ret;
6675 }
6676 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
6677
6678 /**
6679 * ring_buffer_read_page_data - get pointer to the data in the page.
6680 * @page: the page to get the data from
6681 *
6682 * Returns pointer to the actual data in this page.
6683 */
ring_buffer_read_page_data(struct buffer_data_read_page * page)6684 void *ring_buffer_read_page_data(struct buffer_data_read_page *page)
6685 {
6686 return page->data;
6687 }
6688 EXPORT_SYMBOL_GPL(ring_buffer_read_page_data);
6689
6690 /**
6691 * ring_buffer_subbuf_size_get - get size of the sub buffer.
6692 * @buffer: the buffer to get the sub buffer size from
6693 *
6694 * Returns size of the sub buffer, in bytes.
6695 */
ring_buffer_subbuf_size_get(struct trace_buffer * buffer)6696 int ring_buffer_subbuf_size_get(struct trace_buffer *buffer)
6697 {
6698 return buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
6699 }
6700 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get);
6701
6702 /**
6703 * ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page.
6704 * @buffer: The ring_buffer to get the system sub page order from
6705 *
6706 * By default, one ring buffer sub page equals to one system page. This parameter
6707 * is configurable, per ring buffer. The size of the ring buffer sub page can be
6708 * extended, but must be an order of system page size.
6709 *
6710 * Returns the order of buffer sub page size, in system pages:
6711 * 0 means the sub buffer size is 1 system page and so forth.
6712 * In case of an error < 0 is returned.
6713 */
ring_buffer_subbuf_order_get(struct trace_buffer * buffer)6714 int ring_buffer_subbuf_order_get(struct trace_buffer *buffer)
6715 {
6716 if (!buffer)
6717 return -EINVAL;
6718
6719 return buffer->subbuf_order;
6720 }
6721 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get);
6722
6723 /**
6724 * ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
6725 * @buffer: The ring_buffer to set the new page size.
6726 * @order: Order of the system pages in one sub buffer page
6727 *
6728 * By default, one ring buffer pages equals to one system page. This API can be
6729 * used to set new size of the ring buffer page. The size must be order of
6730 * system page size, that's why the input parameter @order is the order of
6731 * system pages that are allocated for one ring buffer page:
6732 * 0 - 1 system page
6733 * 1 - 2 system pages
6734 * 3 - 4 system pages
6735 * ...
6736 *
6737 * Returns 0 on success or < 0 in case of an error.
6738 */
ring_buffer_subbuf_order_set(struct trace_buffer * buffer,int order)6739 int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
6740 {
6741 struct ring_buffer_per_cpu *cpu_buffer;
6742 struct buffer_page *bpage, *tmp;
6743 int old_order, old_size;
6744 int nr_pages;
6745 int psize;
6746 int err;
6747 int cpu;
6748
6749 if (!buffer || order < 0)
6750 return -EINVAL;
6751
6752 if (buffer->subbuf_order == order)
6753 return 0;
6754
6755 psize = (1 << order) * PAGE_SIZE;
6756 if (psize <= BUF_PAGE_HDR_SIZE)
6757 return -EINVAL;
6758
6759 /* Size of a subbuf cannot be greater than the write counter */
6760 if (psize > RB_WRITE_MASK + 1)
6761 return -EINVAL;
6762
6763 old_order = buffer->subbuf_order;
6764 old_size = buffer->subbuf_size;
6765
6766 /* prevent another thread from changing buffer sizes */
6767 mutex_lock(&buffer->mutex);
6768 atomic_inc(&buffer->record_disabled);
6769
6770 /* Make sure all commits have finished */
6771 synchronize_rcu();
6772
6773 buffer->subbuf_order = order;
6774 buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
6775
6776 /* Make sure all new buffers are allocated, before deleting the old ones */
6777 for_each_buffer_cpu(buffer, cpu) {
6778
6779 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6780 continue;
6781
6782 cpu_buffer = buffer->buffers[cpu];
6783
6784 if (cpu_buffer->mapped) {
6785 err = -EBUSY;
6786 goto error;
6787 }
6788
6789 /* Update the number of pages to match the new size */
6790 nr_pages = old_size * buffer->buffers[cpu]->nr_pages;
6791 nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
6792
6793 /* we need a minimum of two pages */
6794 if (nr_pages < 2)
6795 nr_pages = 2;
6796
6797 cpu_buffer->nr_pages_to_update = nr_pages;
6798
6799 /* Include the reader page */
6800 nr_pages++;
6801
6802 /* Allocate the new size buffer */
6803 INIT_LIST_HEAD(&cpu_buffer->new_pages);
6804 if (__rb_allocate_pages(cpu_buffer, nr_pages,
6805 &cpu_buffer->new_pages)) {
6806 /* not enough memory for new pages */
6807 err = -ENOMEM;
6808 goto error;
6809 }
6810 }
6811
6812 for_each_buffer_cpu(buffer, cpu) {
6813 struct buffer_data_page *old_free_data_page;
6814 struct list_head old_pages;
6815 unsigned long flags;
6816
6817 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6818 continue;
6819
6820 cpu_buffer = buffer->buffers[cpu];
6821
6822 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6823
6824 /* Clear the head bit to make the link list normal to read */
6825 rb_head_page_deactivate(cpu_buffer);
6826
6827 /*
6828 * Collect buffers from the cpu_buffer pages list and the
6829 * reader_page on old_pages, so they can be freed later when not
6830 * under a spinlock. The pages list is a linked list with no
6831 * head, adding old_pages turns it into a regular list with
6832 * old_pages being the head.
6833 */
6834 list_add(&old_pages, cpu_buffer->pages);
6835 list_add(&cpu_buffer->reader_page->list, &old_pages);
6836
6837 /* One page was allocated for the reader page */
6838 cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next,
6839 struct buffer_page, list);
6840 list_del_init(&cpu_buffer->reader_page->list);
6841
6842 /* Install the new pages, remove the head from the list */
6843 cpu_buffer->pages = cpu_buffer->new_pages.next;
6844 list_del_init(&cpu_buffer->new_pages);
6845 cpu_buffer->cnt++;
6846
6847 cpu_buffer->head_page
6848 = list_entry(cpu_buffer->pages, struct buffer_page, list);
6849 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
6850
6851 cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update;
6852 cpu_buffer->nr_pages_to_update = 0;
6853
6854 old_free_data_page = cpu_buffer->free_page;
6855 cpu_buffer->free_page = NULL;
6856
6857 rb_head_page_activate(cpu_buffer);
6858
6859 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
6860
6861 /* Free old sub buffers */
6862 list_for_each_entry_safe(bpage, tmp, &old_pages, list) {
6863 list_del_init(&bpage->list);
6864 free_buffer_page(bpage);
6865 }
6866 free_pages((unsigned long)old_free_data_page, old_order);
6867
6868 rb_check_pages(cpu_buffer);
6869 }
6870
6871 atomic_dec(&buffer->record_disabled);
6872 mutex_unlock(&buffer->mutex);
6873
6874 return 0;
6875
6876 error:
6877 buffer->subbuf_order = old_order;
6878 buffer->subbuf_size = old_size;
6879
6880 atomic_dec(&buffer->record_disabled);
6881 mutex_unlock(&buffer->mutex);
6882
6883 for_each_buffer_cpu(buffer, cpu) {
6884 cpu_buffer = buffer->buffers[cpu];
6885
6886 if (!cpu_buffer->nr_pages_to_update)
6887 continue;
6888
6889 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) {
6890 list_del_init(&bpage->list);
6891 free_buffer_page(bpage);
6892 }
6893 }
6894
6895 return err;
6896 }
6897 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set);
6898
rb_alloc_meta_page(struct ring_buffer_per_cpu * cpu_buffer)6899 static int rb_alloc_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
6900 {
6901 struct page *page;
6902
6903 if (cpu_buffer->meta_page)
6904 return 0;
6905
6906 page = alloc_page(GFP_USER | __GFP_ZERO);
6907 if (!page)
6908 return -ENOMEM;
6909
6910 cpu_buffer->meta_page = page_to_virt(page);
6911
6912 return 0;
6913 }
6914
rb_free_meta_page(struct ring_buffer_per_cpu * cpu_buffer)6915 static void rb_free_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
6916 {
6917 unsigned long addr = (unsigned long)cpu_buffer->meta_page;
6918
6919 free_page(addr);
6920 cpu_buffer->meta_page = NULL;
6921 }
6922
rb_setup_ids_meta_page(struct ring_buffer_per_cpu * cpu_buffer,unsigned long * subbuf_ids)6923 static void rb_setup_ids_meta_page(struct ring_buffer_per_cpu *cpu_buffer,
6924 unsigned long *subbuf_ids)
6925 {
6926 struct trace_buffer_meta *meta = cpu_buffer->meta_page;
6927 unsigned int nr_subbufs = cpu_buffer->nr_pages + 1;
6928 struct buffer_page *first_subbuf, *subbuf;
6929 int id = 0;
6930
6931 subbuf_ids[id] = (unsigned long)cpu_buffer->reader_page->page;
6932 cpu_buffer->reader_page->id = id++;
6933
6934 first_subbuf = subbuf = rb_set_head_page(cpu_buffer);
6935 do {
6936 if (WARN_ON(id >= nr_subbufs))
6937 break;
6938
6939 subbuf_ids[id] = (unsigned long)subbuf->page;
6940 subbuf->id = id;
6941
6942 rb_inc_page(&subbuf);
6943 id++;
6944 } while (subbuf != first_subbuf);
6945
6946 /* install subbuf ID to kern VA translation */
6947 cpu_buffer->subbuf_ids = subbuf_ids;
6948
6949 meta->meta_struct_len = sizeof(*meta);
6950 meta->nr_subbufs = nr_subbufs;
6951 meta->subbuf_size = cpu_buffer->buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
6952 meta->meta_page_size = meta->subbuf_size;
6953
6954 rb_update_meta_page(cpu_buffer);
6955 }
6956
6957 static struct ring_buffer_per_cpu *
rb_get_mapped_buffer(struct trace_buffer * buffer,int cpu)6958 rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu)
6959 {
6960 struct ring_buffer_per_cpu *cpu_buffer;
6961
6962 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6963 return ERR_PTR(-EINVAL);
6964
6965 cpu_buffer = buffer->buffers[cpu];
6966
6967 mutex_lock(&cpu_buffer->mapping_lock);
6968
6969 if (!cpu_buffer->user_mapped) {
6970 mutex_unlock(&cpu_buffer->mapping_lock);
6971 return ERR_PTR(-ENODEV);
6972 }
6973
6974 return cpu_buffer;
6975 }
6976
rb_put_mapped_buffer(struct ring_buffer_per_cpu * cpu_buffer)6977 static void rb_put_mapped_buffer(struct ring_buffer_per_cpu *cpu_buffer)
6978 {
6979 mutex_unlock(&cpu_buffer->mapping_lock);
6980 }
6981
6982 /*
6983 * Fast-path for rb_buffer_(un)map(). Called whenever the meta-page doesn't need
6984 * to be set-up or torn-down.
6985 */
__rb_inc_dec_mapped(struct ring_buffer_per_cpu * cpu_buffer,bool inc)6986 static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer,
6987 bool inc)
6988 {
6989 unsigned long flags;
6990
6991 lockdep_assert_held(&cpu_buffer->mapping_lock);
6992
6993 /* mapped is always greater or equal to user_mapped */
6994 if (WARN_ON(cpu_buffer->mapped < cpu_buffer->user_mapped))
6995 return -EINVAL;
6996
6997 if (inc && cpu_buffer->mapped == UINT_MAX)
6998 return -EBUSY;
6999
7000 if (WARN_ON(!inc && cpu_buffer->user_mapped == 0))
7001 return -EINVAL;
7002
7003 mutex_lock(&cpu_buffer->buffer->mutex);
7004 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7005
7006 if (inc) {
7007 cpu_buffer->user_mapped++;
7008 cpu_buffer->mapped++;
7009 } else {
7010 cpu_buffer->user_mapped--;
7011 cpu_buffer->mapped--;
7012 }
7013
7014 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7015 mutex_unlock(&cpu_buffer->buffer->mutex);
7016
7017 return 0;
7018 }
7019
7020 /*
7021 * +--------------+ pgoff == 0
7022 * | meta page |
7023 * +--------------+ pgoff == 1
7024 * | subbuffer 0 |
7025 * | |
7026 * +--------------+ pgoff == (1 + (1 << subbuf_order))
7027 * | subbuffer 1 |
7028 * | |
7029 * ...
7030 */
7031 #ifdef CONFIG_MMU
__rb_map_vma(struct ring_buffer_per_cpu * cpu_buffer,struct vm_area_struct * vma)7032 static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
7033 struct vm_area_struct *vma)
7034 {
7035 unsigned long nr_subbufs, nr_pages, nr_vma_pages, pgoff = vma->vm_pgoff;
7036 unsigned int subbuf_pages, subbuf_order;
7037 struct page **pages;
7038 int p = 0, s = 0;
7039 int err;
7040
7041 /* Refuse MP_PRIVATE or writable mappings */
7042 if (vma->vm_flags & VM_WRITE || vma->vm_flags & VM_EXEC ||
7043 !(vma->vm_flags & VM_MAYSHARE))
7044 return -EPERM;
7045
7046 subbuf_order = cpu_buffer->buffer->subbuf_order;
7047 subbuf_pages = 1 << subbuf_order;
7048
7049 if (subbuf_order && pgoff % subbuf_pages)
7050 return -EINVAL;
7051
7052 /*
7053 * Make sure the mapping cannot become writable later. Also tell the VM
7054 * to not touch these pages (VM_DONTCOPY | VM_DONTEXPAND).
7055 */
7056 vm_flags_mod(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP,
7057 VM_MAYWRITE);
7058
7059 lockdep_assert_held(&cpu_buffer->mapping_lock);
7060
7061 nr_subbufs = cpu_buffer->nr_pages + 1; /* + reader-subbuf */
7062 nr_pages = ((nr_subbufs + 1) << subbuf_order); /* + meta-page */
7063 if (nr_pages <= pgoff)
7064 return -EINVAL;
7065
7066 nr_pages -= pgoff;
7067
7068 nr_vma_pages = vma_pages(vma);
7069 if (!nr_vma_pages || nr_vma_pages > nr_pages)
7070 return -EINVAL;
7071
7072 nr_pages = nr_vma_pages;
7073
7074 pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
7075 if (!pages)
7076 return -ENOMEM;
7077
7078 if (!pgoff) {
7079 unsigned long meta_page_padding;
7080
7081 pages[p++] = virt_to_page(cpu_buffer->meta_page);
7082
7083 /*
7084 * Pad with the zero-page to align the meta-page with the
7085 * sub-buffers.
7086 */
7087 meta_page_padding = subbuf_pages - 1;
7088 while (meta_page_padding-- && p < nr_pages) {
7089 unsigned long __maybe_unused zero_addr =
7090 vma->vm_start + (PAGE_SIZE * p);
7091
7092 pages[p++] = ZERO_PAGE(zero_addr);
7093 }
7094 } else {
7095 /* Skip the meta-page */
7096 pgoff -= subbuf_pages;
7097
7098 s += pgoff / subbuf_pages;
7099 }
7100
7101 while (p < nr_pages) {
7102 struct page *page;
7103 int off = 0;
7104
7105 if (WARN_ON_ONCE(s >= nr_subbufs)) {
7106 err = -EINVAL;
7107 goto out;
7108 }
7109
7110 page = virt_to_page((void *)cpu_buffer->subbuf_ids[s]);
7111
7112 for (; off < (1 << (subbuf_order)); off++, page++) {
7113 if (p >= nr_pages)
7114 break;
7115
7116 pages[p++] = page;
7117 }
7118 s++;
7119 }
7120
7121 err = vm_insert_pages(vma, vma->vm_start, pages, &nr_pages);
7122
7123 out:
7124 kfree(pages);
7125
7126 return err;
7127 }
7128 #else
__rb_map_vma(struct ring_buffer_per_cpu * cpu_buffer,struct vm_area_struct * vma)7129 static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
7130 struct vm_area_struct *vma)
7131 {
7132 return -EOPNOTSUPP;
7133 }
7134 #endif
7135
ring_buffer_map(struct trace_buffer * buffer,int cpu,struct vm_area_struct * vma)7136 int ring_buffer_map(struct trace_buffer *buffer, int cpu,
7137 struct vm_area_struct *vma)
7138 {
7139 struct ring_buffer_per_cpu *cpu_buffer;
7140 unsigned long flags, *subbuf_ids;
7141 int err = 0;
7142
7143 if (!cpumask_test_cpu(cpu, buffer->cpumask))
7144 return -EINVAL;
7145
7146 cpu_buffer = buffer->buffers[cpu];
7147
7148 mutex_lock(&cpu_buffer->mapping_lock);
7149
7150 if (cpu_buffer->user_mapped) {
7151 err = __rb_map_vma(cpu_buffer, vma);
7152 if (!err)
7153 err = __rb_inc_dec_mapped(cpu_buffer, true);
7154 mutex_unlock(&cpu_buffer->mapping_lock);
7155 return err;
7156 }
7157
7158 /* prevent another thread from changing buffer/sub-buffer sizes */
7159 mutex_lock(&buffer->mutex);
7160
7161 err = rb_alloc_meta_page(cpu_buffer);
7162 if (err)
7163 goto unlock;
7164
7165 /* subbuf_ids include the reader while nr_pages does not */
7166 subbuf_ids = kcalloc(cpu_buffer->nr_pages + 1, sizeof(*subbuf_ids), GFP_KERNEL);
7167 if (!subbuf_ids) {
7168 rb_free_meta_page(cpu_buffer);
7169 err = -ENOMEM;
7170 goto unlock;
7171 }
7172
7173 atomic_inc(&cpu_buffer->resize_disabled);
7174
7175 /*
7176 * Lock all readers to block any subbuf swap until the subbuf IDs are
7177 * assigned.
7178 */
7179 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7180 rb_setup_ids_meta_page(cpu_buffer, subbuf_ids);
7181
7182 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7183
7184 err = __rb_map_vma(cpu_buffer, vma);
7185 if (!err) {
7186 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7187 /* This is the first time it is mapped by user */
7188 cpu_buffer->mapped++;
7189 cpu_buffer->user_mapped = 1;
7190 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7191 } else {
7192 kfree(cpu_buffer->subbuf_ids);
7193 cpu_buffer->subbuf_ids = NULL;
7194 rb_free_meta_page(cpu_buffer);
7195 atomic_dec(&cpu_buffer->resize_disabled);
7196 }
7197
7198 unlock:
7199 mutex_unlock(&buffer->mutex);
7200 mutex_unlock(&cpu_buffer->mapping_lock);
7201
7202 return err;
7203 }
7204
ring_buffer_unmap(struct trace_buffer * buffer,int cpu)7205 int ring_buffer_unmap(struct trace_buffer *buffer, int cpu)
7206 {
7207 struct ring_buffer_per_cpu *cpu_buffer;
7208 unsigned long flags;
7209 int err = 0;
7210
7211 if (!cpumask_test_cpu(cpu, buffer->cpumask))
7212 return -EINVAL;
7213
7214 cpu_buffer = buffer->buffers[cpu];
7215
7216 mutex_lock(&cpu_buffer->mapping_lock);
7217
7218 if (!cpu_buffer->user_mapped) {
7219 err = -ENODEV;
7220 goto out;
7221 } else if (cpu_buffer->user_mapped > 1) {
7222 __rb_inc_dec_mapped(cpu_buffer, false);
7223 goto out;
7224 }
7225
7226 mutex_lock(&buffer->mutex);
7227 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7228
7229 /* This is the last user space mapping */
7230 if (!WARN_ON_ONCE(cpu_buffer->mapped < cpu_buffer->user_mapped))
7231 cpu_buffer->mapped--;
7232 cpu_buffer->user_mapped = 0;
7233
7234 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7235
7236 kfree(cpu_buffer->subbuf_ids);
7237 cpu_buffer->subbuf_ids = NULL;
7238 rb_free_meta_page(cpu_buffer);
7239 atomic_dec(&cpu_buffer->resize_disabled);
7240
7241 mutex_unlock(&buffer->mutex);
7242
7243 out:
7244 mutex_unlock(&cpu_buffer->mapping_lock);
7245
7246 return err;
7247 }
7248
ring_buffer_map_get_reader(struct trace_buffer * buffer,int cpu)7249 int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu)
7250 {
7251 struct ring_buffer_per_cpu *cpu_buffer;
7252 struct buffer_page *reader;
7253 unsigned long missed_events;
7254 unsigned long reader_size;
7255 unsigned long flags;
7256
7257 cpu_buffer = rb_get_mapped_buffer(buffer, cpu);
7258 if (IS_ERR(cpu_buffer))
7259 return (int)PTR_ERR(cpu_buffer);
7260
7261 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7262
7263 consume:
7264 if (rb_per_cpu_empty(cpu_buffer))
7265 goto out;
7266
7267 reader_size = rb_page_size(cpu_buffer->reader_page);
7268
7269 /*
7270 * There are data to be read on the current reader page, we can
7271 * return to the caller. But before that, we assume the latter will read
7272 * everything. Let's update the kernel reader accordingly.
7273 */
7274 if (cpu_buffer->reader_page->read < reader_size) {
7275 while (cpu_buffer->reader_page->read < reader_size)
7276 rb_advance_reader(cpu_buffer);
7277 goto out;
7278 }
7279
7280 reader = rb_get_reader_page(cpu_buffer);
7281 if (WARN_ON(!reader))
7282 goto out;
7283
7284 /* Check if any events were dropped */
7285 missed_events = cpu_buffer->lost_events;
7286
7287 if (cpu_buffer->reader_page != cpu_buffer->commit_page) {
7288 if (missed_events) {
7289 struct buffer_data_page *bpage = reader->page;
7290 unsigned int commit;
7291 /*
7292 * Use the real_end for the data size,
7293 * This gives us a chance to store the lost events
7294 * on the page.
7295 */
7296 if (reader->real_end)
7297 local_set(&bpage->commit, reader->real_end);
7298 /*
7299 * If there is room at the end of the page to save the
7300 * missed events, then record it there.
7301 */
7302 commit = rb_page_size(reader);
7303 if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
7304 memcpy(&bpage->data[commit], &missed_events,
7305 sizeof(missed_events));
7306 local_add(RB_MISSED_STORED, &bpage->commit);
7307 }
7308 local_add(RB_MISSED_EVENTS, &bpage->commit);
7309 }
7310 } else {
7311 /*
7312 * There really shouldn't be any missed events if the commit
7313 * is on the reader page.
7314 */
7315 WARN_ON_ONCE(missed_events);
7316 }
7317
7318 cpu_buffer->lost_events = 0;
7319
7320 goto consume;
7321
7322 out:
7323 /* Some archs do not have data cache coherency between kernel and user-space */
7324 flush_kernel_vmap_range(cpu_buffer->reader_page->page,
7325 buffer->subbuf_size + BUF_PAGE_HDR_SIZE);
7326
7327 rb_update_meta_page(cpu_buffer);
7328
7329 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7330 rb_put_mapped_buffer(cpu_buffer);
7331
7332 return 0;
7333 }
7334
7335 /*
7336 * We only allocate new buffers, never free them if the CPU goes down.
7337 * If we were to free the buffer, then the user would lose any trace that was in
7338 * the buffer.
7339 */
trace_rb_cpu_prepare(unsigned int cpu,struct hlist_node * node)7340 int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
7341 {
7342 struct trace_buffer *buffer;
7343 long nr_pages_same;
7344 int cpu_i;
7345 unsigned long nr_pages;
7346
7347 buffer = container_of(node, struct trace_buffer, node);
7348 if (cpumask_test_cpu(cpu, buffer->cpumask))
7349 return 0;
7350
7351 nr_pages = 0;
7352 nr_pages_same = 1;
7353 /* check if all cpu sizes are same */
7354 for_each_buffer_cpu(buffer, cpu_i) {
7355 /* fill in the size from first enabled cpu */
7356 if (nr_pages == 0)
7357 nr_pages = buffer->buffers[cpu_i]->nr_pages;
7358 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
7359 nr_pages_same = 0;
7360 break;
7361 }
7362 }
7363 /* allocate minimum pages, user can later expand it */
7364 if (!nr_pages_same)
7365 nr_pages = 2;
7366 buffer->buffers[cpu] =
7367 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
7368 if (!buffer->buffers[cpu]) {
7369 WARN(1, "failed to allocate ring buffer on CPU %u\n",
7370 cpu);
7371 return -ENOMEM;
7372 }
7373 smp_wmb();
7374 cpumask_set_cpu(cpu, buffer->cpumask);
7375 return 0;
7376 }
7377
7378 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
7379 /*
7380 * This is a basic integrity check of the ring buffer.
7381 * Late in the boot cycle this test will run when configured in.
7382 * It will kick off a thread per CPU that will go into a loop
7383 * writing to the per cpu ring buffer various sizes of data.
7384 * Some of the data will be large items, some small.
7385 *
7386 * Another thread is created that goes into a spin, sending out
7387 * IPIs to the other CPUs to also write into the ring buffer.
7388 * this is to test the nesting ability of the buffer.
7389 *
7390 * Basic stats are recorded and reported. If something in the
7391 * ring buffer should happen that's not expected, a big warning
7392 * is displayed and all ring buffers are disabled.
7393 */
7394 static struct task_struct *rb_threads[NR_CPUS] __initdata;
7395
7396 struct rb_test_data {
7397 struct trace_buffer *buffer;
7398 unsigned long events;
7399 unsigned long bytes_written;
7400 unsigned long bytes_alloc;
7401 unsigned long bytes_dropped;
7402 unsigned long events_nested;
7403 unsigned long bytes_written_nested;
7404 unsigned long bytes_alloc_nested;
7405 unsigned long bytes_dropped_nested;
7406 int min_size_nested;
7407 int max_size_nested;
7408 int max_size;
7409 int min_size;
7410 int cpu;
7411 int cnt;
7412 };
7413
7414 static struct rb_test_data rb_data[NR_CPUS] __initdata;
7415
7416 /* 1 meg per cpu */
7417 #define RB_TEST_BUFFER_SIZE 1048576
7418
7419 static char rb_string[] __initdata =
7420 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
7421 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
7422 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
7423
7424 static bool rb_test_started __initdata;
7425
7426 struct rb_item {
7427 int size;
7428 char str[];
7429 };
7430
rb_write_something(struct rb_test_data * data,bool nested)7431 static __init int rb_write_something(struct rb_test_data *data, bool nested)
7432 {
7433 struct ring_buffer_event *event;
7434 struct rb_item *item;
7435 bool started;
7436 int event_len;
7437 int size;
7438 int len;
7439 int cnt;
7440
7441 /* Have nested writes different that what is written */
7442 cnt = data->cnt + (nested ? 27 : 0);
7443
7444 /* Multiply cnt by ~e, to make some unique increment */
7445 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
7446
7447 len = size + sizeof(struct rb_item);
7448
7449 started = rb_test_started;
7450 /* read rb_test_started before checking buffer enabled */
7451 smp_rmb();
7452
7453 event = ring_buffer_lock_reserve(data->buffer, len);
7454 if (!event) {
7455 /* Ignore dropped events before test starts. */
7456 if (started) {
7457 if (nested)
7458 data->bytes_dropped_nested += len;
7459 else
7460 data->bytes_dropped += len;
7461 }
7462 return len;
7463 }
7464
7465 event_len = ring_buffer_event_length(event);
7466
7467 if (RB_WARN_ON(data->buffer, event_len < len))
7468 goto out;
7469
7470 item = ring_buffer_event_data(event);
7471 item->size = size;
7472 memcpy(item->str, rb_string, size);
7473
7474 if (nested) {
7475 data->bytes_alloc_nested += event_len;
7476 data->bytes_written_nested += len;
7477 data->events_nested++;
7478 if (!data->min_size_nested || len < data->min_size_nested)
7479 data->min_size_nested = len;
7480 if (len > data->max_size_nested)
7481 data->max_size_nested = len;
7482 } else {
7483 data->bytes_alloc += event_len;
7484 data->bytes_written += len;
7485 data->events++;
7486 if (!data->min_size || len < data->min_size)
7487 data->max_size = len;
7488 if (len > data->max_size)
7489 data->max_size = len;
7490 }
7491
7492 out:
7493 ring_buffer_unlock_commit(data->buffer);
7494
7495 return 0;
7496 }
7497
rb_test(void * arg)7498 static __init int rb_test(void *arg)
7499 {
7500 struct rb_test_data *data = arg;
7501
7502 while (!kthread_should_stop()) {
7503 rb_write_something(data, false);
7504 data->cnt++;
7505
7506 set_current_state(TASK_INTERRUPTIBLE);
7507 /* Now sleep between a min of 100-300us and a max of 1ms */
7508 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
7509 }
7510
7511 return 0;
7512 }
7513
rb_ipi(void * ignore)7514 static __init void rb_ipi(void *ignore)
7515 {
7516 struct rb_test_data *data;
7517 int cpu = smp_processor_id();
7518
7519 data = &rb_data[cpu];
7520 rb_write_something(data, true);
7521 }
7522
rb_hammer_test(void * arg)7523 static __init int rb_hammer_test(void *arg)
7524 {
7525 while (!kthread_should_stop()) {
7526
7527 /* Send an IPI to all cpus to write data! */
7528 smp_call_function(rb_ipi, NULL, 1);
7529 /* No sleep, but for non preempt, let others run */
7530 schedule();
7531 }
7532
7533 return 0;
7534 }
7535
test_ringbuffer(void)7536 static __init int test_ringbuffer(void)
7537 {
7538 struct task_struct *rb_hammer;
7539 struct trace_buffer *buffer;
7540 int cpu;
7541 int ret = 0;
7542
7543 if (security_locked_down(LOCKDOWN_TRACEFS)) {
7544 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
7545 return 0;
7546 }
7547
7548 pr_info("Running ring buffer tests...\n");
7549
7550 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
7551 if (WARN_ON(!buffer))
7552 return 0;
7553
7554 /* Disable buffer so that threads can't write to it yet */
7555 ring_buffer_record_off(buffer);
7556
7557 for_each_online_cpu(cpu) {
7558 rb_data[cpu].buffer = buffer;
7559 rb_data[cpu].cpu = cpu;
7560 rb_data[cpu].cnt = cpu;
7561 rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu],
7562 cpu, "rbtester/%u");
7563 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
7564 pr_cont("FAILED\n");
7565 ret = PTR_ERR(rb_threads[cpu]);
7566 goto out_free;
7567 }
7568 }
7569
7570 /* Now create the rb hammer! */
7571 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
7572 if (WARN_ON(IS_ERR(rb_hammer))) {
7573 pr_cont("FAILED\n");
7574 ret = PTR_ERR(rb_hammer);
7575 goto out_free;
7576 }
7577
7578 ring_buffer_record_on(buffer);
7579 /*
7580 * Show buffer is enabled before setting rb_test_started.
7581 * Yes there's a small race window where events could be
7582 * dropped and the thread wont catch it. But when a ring
7583 * buffer gets enabled, there will always be some kind of
7584 * delay before other CPUs see it. Thus, we don't care about
7585 * those dropped events. We care about events dropped after
7586 * the threads see that the buffer is active.
7587 */
7588 smp_wmb();
7589 rb_test_started = true;
7590
7591 set_current_state(TASK_INTERRUPTIBLE);
7592 /* Just run for 10 seconds */;
7593 schedule_timeout(10 * HZ);
7594
7595 kthread_stop(rb_hammer);
7596
7597 out_free:
7598 for_each_online_cpu(cpu) {
7599 if (!rb_threads[cpu])
7600 break;
7601 kthread_stop(rb_threads[cpu]);
7602 }
7603 if (ret) {
7604 ring_buffer_free(buffer);
7605 return ret;
7606 }
7607
7608 /* Report! */
7609 pr_info("finished\n");
7610 for_each_online_cpu(cpu) {
7611 struct ring_buffer_event *event;
7612 struct rb_test_data *data = &rb_data[cpu];
7613 struct rb_item *item;
7614 unsigned long total_events;
7615 unsigned long total_dropped;
7616 unsigned long total_written;
7617 unsigned long total_alloc;
7618 unsigned long total_read = 0;
7619 unsigned long total_size = 0;
7620 unsigned long total_len = 0;
7621 unsigned long total_lost = 0;
7622 unsigned long lost;
7623 int big_event_size;
7624 int small_event_size;
7625
7626 ret = -1;
7627
7628 total_events = data->events + data->events_nested;
7629 total_written = data->bytes_written + data->bytes_written_nested;
7630 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
7631 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
7632
7633 big_event_size = data->max_size + data->max_size_nested;
7634 small_event_size = data->min_size + data->min_size_nested;
7635
7636 pr_info("CPU %d:\n", cpu);
7637 pr_info(" events: %ld\n", total_events);
7638 pr_info(" dropped bytes: %ld\n", total_dropped);
7639 pr_info(" alloced bytes: %ld\n", total_alloc);
7640 pr_info(" written bytes: %ld\n", total_written);
7641 pr_info(" biggest event: %d\n", big_event_size);
7642 pr_info(" smallest event: %d\n", small_event_size);
7643
7644 if (RB_WARN_ON(buffer, total_dropped))
7645 break;
7646
7647 ret = 0;
7648
7649 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
7650 total_lost += lost;
7651 item = ring_buffer_event_data(event);
7652 total_len += ring_buffer_event_length(event);
7653 total_size += item->size + sizeof(struct rb_item);
7654 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
7655 pr_info("FAILED!\n");
7656 pr_info("buffer had: %.*s\n", item->size, item->str);
7657 pr_info("expected: %.*s\n", item->size, rb_string);
7658 RB_WARN_ON(buffer, 1);
7659 ret = -1;
7660 break;
7661 }
7662 total_read++;
7663 }
7664 if (ret)
7665 break;
7666
7667 ret = -1;
7668
7669 pr_info(" read events: %ld\n", total_read);
7670 pr_info(" lost events: %ld\n", total_lost);
7671 pr_info(" total events: %ld\n", total_lost + total_read);
7672 pr_info(" recorded len bytes: %ld\n", total_len);
7673 pr_info(" recorded size bytes: %ld\n", total_size);
7674 if (total_lost) {
7675 pr_info(" With dropped events, record len and size may not match\n"
7676 " alloced and written from above\n");
7677 } else {
7678 if (RB_WARN_ON(buffer, total_len != total_alloc ||
7679 total_size != total_written))
7680 break;
7681 }
7682 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
7683 break;
7684
7685 ret = 0;
7686 }
7687 if (!ret)
7688 pr_info("Ring buffer PASSED!\n");
7689
7690 ring_buffer_free(buffer);
7691 return 0;
7692 }
7693
7694 late_initcall(test_ringbuffer);
7695 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
7696