1 #ifndef _LINUX_TRACEPOINT_H
2 #define _LINUX_TRACEPOINT_H
3
4 /*
5 * Kernel Tracepoint API.
6 *
7 * See Documentation/trace/tracepoints.txt.
8 *
9 * (C) Copyright 2008 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
10 *
11 * Heavily inspired from the Linux Kernel Markers.
12 *
13 * This file is released under the GPLv2.
14 * See the file COPYING for more details.
15 */
16
17 #include <linux/errno.h>
18 #include <linux/types.h>
19 #include <linux/rcupdate.h>
20 #include <linux/jump_label.h>
21
22 struct module;
23 struct tracepoint;
24
25 struct tracepoint_func {
26 void *func;
27 void *data;
28 };
29
30 struct tracepoint {
31 const char *name; /* Tracepoint name */
32 struct jump_label_key key;
33 void (*regfunc)(void);
34 void (*unregfunc)(void);
35 struct tracepoint_func __rcu *funcs;
36 };
37
38 /*
39 * Connect a probe to a tracepoint.
40 * Internal API, should not be used directly.
41 */
42 extern int tracepoint_probe_register(const char *name, void *probe, void *data);
43
44 /*
45 * Disconnect a probe from a tracepoint.
46 * Internal API, should not be used directly.
47 */
48 extern int
49 tracepoint_probe_unregister(const char *name, void *probe, void *data);
50
51 extern int tracepoint_probe_register_noupdate(const char *name, void *probe,
52 void *data);
53 extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
54 void *data);
55 extern void tracepoint_probe_update_all(void);
56
57 #ifdef CONFIG_MODULES
58 struct tp_module {
59 struct list_head list;
60 unsigned int num_tracepoints;
61 struct tracepoint * const *tracepoints_ptrs;
62 };
63 #endif /* CONFIG_MODULES */
64
65 struct tracepoint_iter {
66 #ifdef CONFIG_MODULES
67 struct tp_module *module;
68 #endif /* CONFIG_MODULES */
69 struct tracepoint * const *tracepoint;
70 };
71
72 extern void tracepoint_iter_start(struct tracepoint_iter *iter);
73 extern void tracepoint_iter_next(struct tracepoint_iter *iter);
74 extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
75 extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
76
77 /*
78 * tracepoint_synchronize_unregister must be called between the last tracepoint
79 * probe unregistration and the end of module exit to make sure there is no
80 * caller executing a probe when it is freed.
81 */
tracepoint_synchronize_unregister(void)82 static inline void tracepoint_synchronize_unregister(void)
83 {
84 synchronize_sched();
85 }
86
87 #define PARAMS(args...) args
88
89 #endif /* _LINUX_TRACEPOINT_H */
90
91 /*
92 * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
93 * file ifdef protection.
94 * This is due to the way trace events work. If a file includes two
95 * trace event headers under one "CREATE_TRACE_POINTS" the first include
96 * will override the TRACE_EVENT and break the second include.
97 */
98
99 #ifndef DECLARE_TRACE
100
101 #define TP_PROTO(args...) args
102 #define TP_ARGS(args...) args
103 #define TP_CONDITION(args...) args
104
105 #ifdef CONFIG_TRACEPOINTS
106
107 /*
108 * it_func[0] is never NULL because there is at least one element in the array
109 * when the array itself is non NULL.
110 *
111 * Note, the proto and args passed in includes "__data" as the first parameter.
112 * The reason for this is to handle the "void" prototype. If a tracepoint
113 * has a "void" prototype, then it is invalid to declare a function
114 * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
115 * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
116 */
117 #define __DO_TRACE(tp, proto, args, cond) \
118 do { \
119 struct tracepoint_func *it_func_ptr; \
120 void *it_func; \
121 void *__data; \
122 \
123 if (!(cond)) \
124 return; \
125 rcu_read_lock_sched_notrace(); \
126 it_func_ptr = rcu_dereference_sched((tp)->funcs); \
127 if (it_func_ptr) { \
128 do { \
129 it_func = (it_func_ptr)->func; \
130 __data = (it_func_ptr)->data; \
131 ((void(*)(proto))(it_func))(args); \
132 } while ((++it_func_ptr)->func); \
133 } \
134 rcu_read_unlock_sched_notrace(); \
135 } while (0)
136
137 /*
138 * Make sure the alignment of the structure in the __tracepoints section will
139 * not add unwanted padding between the beginning of the section and the
140 * structure. Force alignment to the same alignment as the section start.
141 */
142 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
143 extern struct tracepoint __tracepoint_##name; \
144 static inline void trace_##name(proto) \
145 { \
146 if (static_branch(&__tracepoint_##name.key)) \
147 __DO_TRACE(&__tracepoint_##name, \
148 TP_PROTO(data_proto), \
149 TP_ARGS(data_args), \
150 TP_CONDITION(cond)); \
151 } \
152 static inline int \
153 register_trace_##name(void (*probe)(data_proto), void *data) \
154 { \
155 return tracepoint_probe_register(#name, (void *)probe, \
156 data); \
157 } \
158 static inline int \
159 unregister_trace_##name(void (*probe)(data_proto), void *data) \
160 { \
161 return tracepoint_probe_unregister(#name, (void *)probe, \
162 data); \
163 } \
164 static inline void \
165 check_trace_callback_type_##name(void (*cb)(data_proto)) \
166 { \
167 }
168
169 /*
170 * We have no guarantee that gcc and the linker won't up-align the tracepoint
171 * structures, so we create an array of pointers that will be used for iteration
172 * on the tracepoints.
173 */
174 #define DEFINE_TRACE_FN(name, reg, unreg) \
175 static const char __tpstrtab_##name[] \
176 __attribute__((section("__tracepoints_strings"))) = #name; \
177 struct tracepoint __tracepoint_##name \
178 __attribute__((section("__tracepoints"))) = \
179 { __tpstrtab_##name, JUMP_LABEL_INIT, reg, unreg, NULL };\
180 static struct tracepoint * const __tracepoint_ptr_##name __used \
181 __attribute__((section("__tracepoints_ptrs"))) = \
182 &__tracepoint_##name;
183
184 #define DEFINE_TRACE(name) \
185 DEFINE_TRACE_FN(name, NULL, NULL);
186
187 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name) \
188 EXPORT_SYMBOL_GPL(__tracepoint_##name)
189 #define EXPORT_TRACEPOINT_SYMBOL(name) \
190 EXPORT_SYMBOL(__tracepoint_##name)
191
192 #else /* !CONFIG_TRACEPOINTS */
193 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
194 static inline void trace_##name(proto) \
195 { } \
196 static inline int \
197 register_trace_##name(void (*probe)(data_proto), \
198 void *data) \
199 { \
200 return -ENOSYS; \
201 } \
202 static inline int \
203 unregister_trace_##name(void (*probe)(data_proto), \
204 void *data) \
205 { \
206 return -ENOSYS; \
207 } \
208 static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
209 { \
210 }
211
212 #define DEFINE_TRACE_FN(name, reg, unreg)
213 #define DEFINE_TRACE(name)
214 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
215 #define EXPORT_TRACEPOINT_SYMBOL(name)
216
217 #endif /* CONFIG_TRACEPOINTS */
218
219 /*
220 * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
221 * (void). "void" is a special value in a function prototype and can
222 * not be combined with other arguments. Since the DECLARE_TRACE()
223 * macro adds a data element at the beginning of the prototype,
224 * we need a way to differentiate "(void *data, proto)" from
225 * "(void *data, void)". The second prototype is invalid.
226 *
227 * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
228 * and "void *__data" as the callback prototype.
229 *
230 * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
231 * "void *__data, proto" as the callback prototype.
232 */
233 #define DECLARE_TRACE_NOARGS(name) \
234 __DECLARE_TRACE(name, void, , 1, void *__data, __data)
235
236 #define DECLARE_TRACE(name, proto, args) \
237 __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1, \
238 PARAMS(void *__data, proto), \
239 PARAMS(__data, args))
240
241 #define DECLARE_TRACE_CONDITION(name, proto, args, cond) \
242 __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
243 PARAMS(void *__data, proto), \
244 PARAMS(__data, args))
245
246 #define TRACE_EVENT_FLAGS(event, flag)
247
248 #endif /* DECLARE_TRACE */
249
250 #ifndef TRACE_EVENT
251 /*
252 * For use with the TRACE_EVENT macro:
253 *
254 * We define a tracepoint, its arguments, its printk format
255 * and its 'fast binay record' layout.
256 *
257 * Firstly, name your tracepoint via TRACE_EVENT(name : the
258 * 'subsystem_event' notation is fine.
259 *
260 * Think about this whole construct as the
261 * 'trace_sched_switch() function' from now on.
262 *
263 *
264 * TRACE_EVENT(sched_switch,
265 *
266 * *
267 * * A function has a regular function arguments
268 * * prototype, declare it via TP_PROTO():
269 * *
270 *
271 * TP_PROTO(struct rq *rq, struct task_struct *prev,
272 * struct task_struct *next),
273 *
274 * *
275 * * Define the call signature of the 'function'.
276 * * (Design sidenote: we use this instead of a
277 * * TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
278 * *
279 *
280 * TP_ARGS(rq, prev, next),
281 *
282 * *
283 * * Fast binary tracing: define the trace record via
284 * * TP_STRUCT__entry(). You can think about it like a
285 * * regular C structure local variable definition.
286 * *
287 * * This is how the trace record is structured and will
288 * * be saved into the ring buffer. These are the fields
289 * * that will be exposed to user-space in
290 * * /sys/kernel/debug/tracing/events/<*>/format.
291 * *
292 * * The declared 'local variable' is called '__entry'
293 * *
294 * * __field(pid_t, prev_prid) is equivalent to a standard declariton:
295 * *
296 * * pid_t prev_pid;
297 * *
298 * * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
299 * *
300 * * char prev_comm[TASK_COMM_LEN];
301 * *
302 *
303 * TP_STRUCT__entry(
304 * __array( char, prev_comm, TASK_COMM_LEN )
305 * __field( pid_t, prev_pid )
306 * __field( int, prev_prio )
307 * __array( char, next_comm, TASK_COMM_LEN )
308 * __field( pid_t, next_pid )
309 * __field( int, next_prio )
310 * ),
311 *
312 * *
313 * * Assign the entry into the trace record, by embedding
314 * * a full C statement block into TP_fast_assign(). You
315 * * can refer to the trace record as '__entry' -
316 * * otherwise you can put arbitrary C code in here.
317 * *
318 * * Note: this C code will execute every time a trace event
319 * * happens, on an active tracepoint.
320 * *
321 *
322 * TP_fast_assign(
323 * memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
324 * __entry->prev_pid = prev->pid;
325 * __entry->prev_prio = prev->prio;
326 * memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
327 * __entry->next_pid = next->pid;
328 * __entry->next_prio = next->prio;
329 * ),
330 *
331 * *
332 * * Formatted output of a trace record via TP_printk().
333 * * This is how the tracepoint will appear under ftrace
334 * * plugins that make use of this tracepoint.
335 * *
336 * * (raw-binary tracing wont actually perform this step.)
337 * *
338 *
339 * TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
340 * __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
341 * __entry->next_comm, __entry->next_pid, __entry->next_prio),
342 *
343 * );
344 *
345 * This macro construct is thus used for the regular printk format
346 * tracing setup, it is used to construct a function pointer based
347 * tracepoint callback (this is used by programmatic plugins and
348 * can also by used by generic instrumentation like SystemTap), and
349 * it is also used to expose a structured trace record in
350 * /sys/kernel/debug/tracing/events/.
351 *
352 * A set of (un)registration functions can be passed to the variant
353 * TRACE_EVENT_FN to perform any (un)registration work.
354 */
355
356 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
357 #define DEFINE_EVENT(template, name, proto, args) \
358 DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
359 #define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
360 DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
361 #define DEFINE_EVENT_CONDITION(template, name, proto, \
362 args, cond) \
363 DECLARE_TRACE_CONDITION(name, PARAMS(proto), \
364 PARAMS(args), PARAMS(cond))
365
366 #define TRACE_EVENT(name, proto, args, struct, assign, print) \
367 DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
368 #define TRACE_EVENT_FN(name, proto, args, struct, \
369 assign, print, reg, unreg) \
370 DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
371 #define TRACE_EVENT_CONDITION(name, proto, args, cond, \
372 struct, assign, print) \
373 DECLARE_TRACE_CONDITION(name, PARAMS(proto), \
374 PARAMS(args), PARAMS(cond))
375
376 #define TRACE_EVENT_FLAGS(event, flag)
377
378 #endif /* ifdef TRACE_EVENT (see note above) */
379