1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * linux/percpu-defs.h - basic definitions for percpu areas
4 *
5 * DO NOT INCLUDE DIRECTLY OUTSIDE PERCPU IMPLEMENTATION PROPER.
6 *
7 * This file is separate from linux/percpu.h to avoid cyclic inclusion
8 * dependency from arch header files. Only to be included from
9 * asm/percpu.h.
10 *
11 * This file includes macros necessary to declare percpu sections and
12 * variables, and definitions of percpu accessors and operations. It
13 * should provide enough percpu features to arch header files even when
14 * they can only include asm/percpu.h to avoid cyclic inclusion dependency.
15 */
16
17 #ifndef _LINUX_PERCPU_DEFS_H
18 #define _LINUX_PERCPU_DEFS_H
19
20 #ifdef CONFIG_SMP
21
22 #ifdef MODULE
23 #define PER_CPU_SHARED_ALIGNED_SECTION ""
24 #define PER_CPU_ALIGNED_SECTION ""
25 #else
26 #define PER_CPU_SHARED_ALIGNED_SECTION "..shared_aligned"
27 #define PER_CPU_ALIGNED_SECTION "..shared_aligned"
28 #endif
29
30 #else
31
32 #define PER_CPU_SHARED_ALIGNED_SECTION ""
33 #define PER_CPU_ALIGNED_SECTION "..shared_aligned"
34
35 #endif
36
37 /*
38 * Base implementations of per-CPU variable declarations and definitions, where
39 * the section in which the variable is to be placed is provided by the
40 * 'sec' argument. This may be used to affect the parameters governing the
41 * variable's storage.
42 *
43 * NOTE! The sections for the DECLARE and for the DEFINE must match, lest
44 * linkage errors occur due the compiler generating the wrong code to access
45 * that section.
46 */
47 #define __PCPU_ATTRS(sec) \
48 __percpu __attribute__((section(PER_CPU_BASE_SECTION sec))) \
49 PER_CPU_ATTRIBUTES
50
51 #define __PCPU_DUMMY_ATTRS \
52 __section(".discard") __attribute__((unused))
53
54 /*
55 * s390 and alpha modules require percpu variables to be defined as
56 * weak to force the compiler to generate GOT based external
57 * references for them. This is necessary because percpu sections
58 * will be located outside of the usually addressable area.
59 *
60 * This definition puts the following two extra restrictions when
61 * defining percpu variables.
62 *
63 * 1. The symbol must be globally unique, even the static ones.
64 * 2. Static percpu variables cannot be defined inside a function.
65 *
66 * Archs which need weak percpu definitions should set
67 * CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU when necessary.
68 *
69 * To ensure that the generic code observes the above two
70 * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
71 * definition is used for all cases.
72 */
73 #if (defined(CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU) && defined(MODULE)) || \
74 defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
75 /*
76 * __pcpu_scope_* dummy variable is used to enforce scope. It
77 * receives the static modifier when it's used in front of
78 * DEFINE_PER_CPU() and will trigger build failure if
79 * DECLARE_PER_CPU() is used for the same variable.
80 *
81 * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
82 * such that hidden weak symbol collision, which will cause unrelated
83 * variables to share the same address, can be detected during build.
84 */
85 #define DECLARE_PER_CPU_SECTION(type, name, sec) \
86 extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
87 extern __PCPU_ATTRS(sec) __typeof__(type) name
88
89 #define DEFINE_PER_CPU_SECTION(type, name, sec) \
90 __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
91 extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
92 __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
93 extern __PCPU_ATTRS(sec) __typeof__(type) name; \
94 __PCPU_ATTRS(sec) __weak __typeof__(type) name
95 #else
96 /*
97 * Normal declaration and definition macros.
98 */
99 #define DECLARE_PER_CPU_SECTION(type, name, sec) \
100 extern __PCPU_ATTRS(sec) __typeof__(type) name
101
102 #define DEFINE_PER_CPU_SECTION(type, name, sec) \
103 __PCPU_ATTRS(sec) __typeof__(type) name
104 #endif
105
106 /*
107 * Variant on the per-CPU variable declaration/definition theme used for
108 * ordinary per-CPU variables.
109 */
110 #define DECLARE_PER_CPU(type, name) \
111 DECLARE_PER_CPU_SECTION(type, name, "")
112
113 #define DEFINE_PER_CPU(type, name) \
114 DEFINE_PER_CPU_SECTION(type, name, "")
115
116 /*
117 * Declaration/definition used for per-CPU variables that are frequently
118 * accessed and should be in a single cacheline.
119 *
120 * For use only by architecture and core code. Only use scalar or pointer
121 * types to maximize density.
122 */
123 #define DECLARE_PER_CPU_CACHE_HOT(type, name) \
124 DECLARE_PER_CPU_SECTION(type, name, "..hot.." #name)
125
126 #define DEFINE_PER_CPU_CACHE_HOT(type, name) \
127 DEFINE_PER_CPU_SECTION(type, name, "..hot.." #name)
128
129 /*
130 * Declaration/definition used for per-CPU variables that must be cacheline
131 * aligned under SMP conditions so that, whilst a particular instance of the
132 * data corresponds to a particular CPU, inefficiencies due to direct access by
133 * other CPUs are reduced by preventing the data from unnecessarily spanning
134 * cachelines.
135 *
136 * An example of this would be statistical data, where each CPU's set of data
137 * is updated by that CPU alone, but the data from across all CPUs is collated
138 * by a CPU processing a read from a proc file.
139 */
140 #define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \
141 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
142 ____cacheline_aligned_in_smp
143
144 #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \
145 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
146 ____cacheline_aligned_in_smp
147
148 #define DECLARE_PER_CPU_ALIGNED(type, name) \
149 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
150 ____cacheline_aligned
151
152 #define DEFINE_PER_CPU_ALIGNED(type, name) \
153 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
154 ____cacheline_aligned
155
156 /*
157 * Declaration/definition used for per-CPU variables that must be page aligned.
158 */
159 #define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \
160 DECLARE_PER_CPU_SECTION(type, name, "..page_aligned") \
161 __aligned(PAGE_SIZE)
162
163 #define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
164 DEFINE_PER_CPU_SECTION(type, name, "..page_aligned") \
165 __aligned(PAGE_SIZE)
166
167 /*
168 * Declaration/definition used for per-CPU variables that must be read mostly.
169 */
170 #define DECLARE_PER_CPU_READ_MOSTLY(type, name) \
171 DECLARE_PER_CPU_SECTION(type, name, "..read_mostly")
172
173 #define DEFINE_PER_CPU_READ_MOSTLY(type, name) \
174 DEFINE_PER_CPU_SECTION(type, name, "..read_mostly")
175
176 /*
177 * Declaration/definition used for per-CPU variables that should be accessed
178 * as decrypted when memory encryption is enabled in the guest.
179 */
180 #ifdef CONFIG_AMD_MEM_ENCRYPT
181 #define DECLARE_PER_CPU_DECRYPTED(type, name) \
182 DECLARE_PER_CPU_SECTION(type, name, "..decrypted")
183
184 #define DEFINE_PER_CPU_DECRYPTED(type, name) \
185 DEFINE_PER_CPU_SECTION(type, name, "..decrypted")
186 #else
187 #define DEFINE_PER_CPU_DECRYPTED(type, name) DEFINE_PER_CPU(type, name)
188 #endif
189
190 /*
191 * Intermodule exports for per-CPU variables. sparse forgets about
192 * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to
193 * noop if __CHECKER__.
194 */
195 #ifndef __CHECKER__
196 #define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var)
197 #define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var)
198 #else
199 #define EXPORT_PER_CPU_SYMBOL(var)
200 #define EXPORT_PER_CPU_SYMBOL_GPL(var)
201 #endif
202
203 /*
204 * Accessors and operations.
205 */
206 #ifndef __ASSEMBLY__
207
208 /*
209 * __verify_pcpu_ptr() verifies @ptr is a percpu pointer without evaluating
210 * @ptr and is invoked once before a percpu area is accessed by all
211 * accessors and operations. This is performed in the generic part of
212 * percpu and arch overrides don't need to worry about it; however, if an
213 * arch wants to implement an arch-specific percpu accessor or operation,
214 * it may use __verify_pcpu_ptr() to verify the parameters.
215 *
216 * + 0 is required in order to convert the pointer type from a
217 * potential array type to a pointer to a single item of the array.
218 */
219 #define __verify_pcpu_ptr(ptr) \
220 do { \
221 const void __percpu *__vpp_verify = (typeof((ptr) + 0))NULL; \
222 (void)__vpp_verify; \
223 } while (0)
224
225 #define PERCPU_PTR(__p) \
226 (TYPEOF_UNQUAL(*(__p)) __force __kernel *)((__force unsigned long)(__p))
227
228 #ifdef CONFIG_SMP
229
230 /*
231 * Add an offset to a pointer. Use RELOC_HIDE() to prevent the compiler
232 * from making incorrect assumptions about the pointer value.
233 */
234 #define SHIFT_PERCPU_PTR(__p, __offset) \
235 RELOC_HIDE(PERCPU_PTR(__p), (__offset))
236
237 #define per_cpu_ptr(ptr, cpu) \
238 ({ \
239 __verify_pcpu_ptr(ptr); \
240 SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu))); \
241 })
242
243 #define raw_cpu_ptr(ptr) \
244 ({ \
245 __verify_pcpu_ptr(ptr); \
246 arch_raw_cpu_ptr(ptr); \
247 })
248
249 #ifdef CONFIG_DEBUG_PREEMPT
250 #define this_cpu_ptr(ptr) \
251 ({ \
252 __verify_pcpu_ptr(ptr); \
253 SHIFT_PERCPU_PTR(ptr, my_cpu_offset); \
254 })
255 #else
256 #define this_cpu_ptr(ptr) raw_cpu_ptr(ptr)
257 #endif
258
259 #else /* CONFIG_SMP */
260
261 #define per_cpu_ptr(ptr, cpu) \
262 ({ \
263 (void)(cpu); \
264 __verify_pcpu_ptr(ptr); \
265 PERCPU_PTR(ptr); \
266 })
267
268 #define raw_cpu_ptr(ptr) per_cpu_ptr(ptr, 0)
269 #define this_cpu_ptr(ptr) raw_cpu_ptr(ptr)
270
271 #endif /* CONFIG_SMP */
272
273 #define per_cpu(var, cpu) (*per_cpu_ptr(&(var), cpu))
274
275 /*
276 * Must be an lvalue. Since @var must be a simple identifier,
277 * we force a syntax error here if it isn't.
278 */
279 #define get_cpu_var(var) \
280 (*({ \
281 preempt_disable(); \
282 this_cpu_ptr(&var); \
283 }))
284
285 /*
286 * The weird & is necessary because sparse considers (void)(var) to be
287 * a direct dereference of percpu variable (var).
288 */
289 #define put_cpu_var(var) \
290 do { \
291 (void)&(var); \
292 preempt_enable(); \
293 } while (0)
294
295 #define get_cpu_ptr(var) \
296 ({ \
297 preempt_disable(); \
298 this_cpu_ptr(var); \
299 })
300
301 #define put_cpu_ptr(var) \
302 do { \
303 (void)(var); \
304 preempt_enable(); \
305 } while (0)
306
307 /*
308 * Branching function to split up a function into a set of functions that
309 * are called for different scalar sizes of the objects handled.
310 */
311
312 extern void __bad_size_call_parameter(void);
313
314 #ifdef CONFIG_DEBUG_PREEMPT
315 extern void __this_cpu_preempt_check(const char *op);
316 #else
__this_cpu_preempt_check(const char * op)317 static __always_inline void __this_cpu_preempt_check(const char *op) { }
318 #endif
319
320 #define __pcpu_size_call_return(stem, variable) \
321 ({ \
322 TYPEOF_UNQUAL(variable) pscr_ret__; \
323 __verify_pcpu_ptr(&(variable)); \
324 switch(sizeof(variable)) { \
325 case 1: pscr_ret__ = stem##1(variable); break; \
326 case 2: pscr_ret__ = stem##2(variable); break; \
327 case 4: pscr_ret__ = stem##4(variable); break; \
328 case 8: pscr_ret__ = stem##8(variable); break; \
329 default: \
330 __bad_size_call_parameter(); break; \
331 } \
332 pscr_ret__; \
333 })
334
335 #define __pcpu_size_call_return2(stem, variable, ...) \
336 ({ \
337 TYPEOF_UNQUAL(variable) pscr2_ret__; \
338 __verify_pcpu_ptr(&(variable)); \
339 switch(sizeof(variable)) { \
340 case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break; \
341 case 2: pscr2_ret__ = stem##2(variable, __VA_ARGS__); break; \
342 case 4: pscr2_ret__ = stem##4(variable, __VA_ARGS__); break; \
343 case 8: pscr2_ret__ = stem##8(variable, __VA_ARGS__); break; \
344 default: \
345 __bad_size_call_parameter(); break; \
346 } \
347 pscr2_ret__; \
348 })
349
350 #define __pcpu_size_call_return2bool(stem, variable, ...) \
351 ({ \
352 bool pscr2_ret__; \
353 __verify_pcpu_ptr(&(variable)); \
354 switch(sizeof(variable)) { \
355 case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break; \
356 case 2: pscr2_ret__ = stem##2(variable, __VA_ARGS__); break; \
357 case 4: pscr2_ret__ = stem##4(variable, __VA_ARGS__); break; \
358 case 8: pscr2_ret__ = stem##8(variable, __VA_ARGS__); break; \
359 default: \
360 __bad_size_call_parameter(); break; \
361 } \
362 pscr2_ret__; \
363 })
364
365 #define __pcpu_size_call(stem, variable, ...) \
366 do { \
367 __verify_pcpu_ptr(&(variable)); \
368 switch(sizeof(variable)) { \
369 case 1: stem##1(variable, __VA_ARGS__);break; \
370 case 2: stem##2(variable, __VA_ARGS__);break; \
371 case 4: stem##4(variable, __VA_ARGS__);break; \
372 case 8: stem##8(variable, __VA_ARGS__);break; \
373 default: \
374 __bad_size_call_parameter();break; \
375 } \
376 } while (0)
377
378 /*
379 * this_cpu operations (C) 2008-2013 Christoph Lameter <cl@gentwo.org>
380 *
381 * Optimized manipulation for memory allocated through the per cpu
382 * allocator or for addresses of per cpu variables.
383 *
384 * These operation guarantee exclusivity of access for other operations
385 * on the *same* processor. The assumption is that per cpu data is only
386 * accessed by a single processor instance (the current one).
387 *
388 * The arch code can provide optimized implementation by defining macros
389 * for certain scalar sizes. F.e. provide this_cpu_add_2() to provide per
390 * cpu atomic operations for 2 byte sized RMW actions. If arch code does
391 * not provide operations for a scalar size then the fallback in the
392 * generic code will be used.
393 *
394 * cmpxchg_double replaces two adjacent scalars at once. The first two
395 * parameters are per cpu variables which have to be of the same size. A
396 * truth value is returned to indicate success or failure (since a double
397 * register result is difficult to handle). There is very limited hardware
398 * support for these operations, so only certain sizes may work.
399 */
400
401 /*
402 * Operations for contexts where we do not want to do any checks for
403 * preemptions. Unless strictly necessary, always use [__]this_cpu_*()
404 * instead.
405 *
406 * If there is no other protection through preempt disable and/or disabling
407 * interrupts then one of these RMW operations can show unexpected behavior
408 * because the execution thread was rescheduled on another processor or an
409 * interrupt occurred and the same percpu variable was modified from the
410 * interrupt context.
411 */
412 #define raw_cpu_read(pcp) __pcpu_size_call_return(raw_cpu_read_, pcp)
413 #define raw_cpu_write(pcp, val) __pcpu_size_call(raw_cpu_write_, pcp, val)
414 #define raw_cpu_add(pcp, val) __pcpu_size_call(raw_cpu_add_, pcp, val)
415 #define raw_cpu_and(pcp, val) __pcpu_size_call(raw_cpu_and_, pcp, val)
416 #define raw_cpu_or(pcp, val) __pcpu_size_call(raw_cpu_or_, pcp, val)
417 #define raw_cpu_add_return(pcp, val) __pcpu_size_call_return2(raw_cpu_add_return_, pcp, val)
418 #define raw_cpu_xchg(pcp, nval) __pcpu_size_call_return2(raw_cpu_xchg_, pcp, nval)
419 #define raw_cpu_cmpxchg(pcp, oval, nval) \
420 __pcpu_size_call_return2(raw_cpu_cmpxchg_, pcp, oval, nval)
421 #define raw_cpu_try_cmpxchg(pcp, ovalp, nval) \
422 __pcpu_size_call_return2bool(raw_cpu_try_cmpxchg_, pcp, ovalp, nval)
423 #define raw_cpu_sub(pcp, val) raw_cpu_add(pcp, -(val))
424 #define raw_cpu_inc(pcp) raw_cpu_add(pcp, 1)
425 #define raw_cpu_dec(pcp) raw_cpu_sub(pcp, 1)
426 #define raw_cpu_sub_return(pcp, val) raw_cpu_add_return(pcp, -(typeof(pcp))(val))
427 #define raw_cpu_inc_return(pcp) raw_cpu_add_return(pcp, 1)
428 #define raw_cpu_dec_return(pcp) raw_cpu_add_return(pcp, -1)
429
430 /*
431 * Operations for contexts that are safe from preemption/interrupts. These
432 * operations verify that preemption is disabled.
433 */
434 #define __this_cpu_read(pcp) \
435 ({ \
436 __this_cpu_preempt_check("read"); \
437 raw_cpu_read(pcp); \
438 })
439
440 #define __this_cpu_write(pcp, val) \
441 ({ \
442 __this_cpu_preempt_check("write"); \
443 raw_cpu_write(pcp, val); \
444 })
445
446 #define __this_cpu_add(pcp, val) \
447 ({ \
448 __this_cpu_preempt_check("add"); \
449 raw_cpu_add(pcp, val); \
450 })
451
452 #define __this_cpu_and(pcp, val) \
453 ({ \
454 __this_cpu_preempt_check("and"); \
455 raw_cpu_and(pcp, val); \
456 })
457
458 #define __this_cpu_or(pcp, val) \
459 ({ \
460 __this_cpu_preempt_check("or"); \
461 raw_cpu_or(pcp, val); \
462 })
463
464 #define __this_cpu_add_return(pcp, val) \
465 ({ \
466 __this_cpu_preempt_check("add_return"); \
467 raw_cpu_add_return(pcp, val); \
468 })
469
470 #define __this_cpu_xchg(pcp, nval) \
471 ({ \
472 __this_cpu_preempt_check("xchg"); \
473 raw_cpu_xchg(pcp, nval); \
474 })
475
476 #define __this_cpu_cmpxchg(pcp, oval, nval) \
477 ({ \
478 __this_cpu_preempt_check("cmpxchg"); \
479 raw_cpu_cmpxchg(pcp, oval, nval); \
480 })
481
482 #define __this_cpu_try_cmpxchg(pcp, ovalp, nval) \
483 ({ \
484 __this_cpu_preempt_check("try_cmpxchg"); \
485 raw_cpu_try_cmpxchg(pcp, ovalp, nval); \
486 })
487
488 #define __this_cpu_sub(pcp, val) __this_cpu_add(pcp, -(typeof(pcp))(val))
489 #define __this_cpu_inc(pcp) __this_cpu_add(pcp, 1)
490 #define __this_cpu_dec(pcp) __this_cpu_sub(pcp, 1)
491 #define __this_cpu_sub_return(pcp, val) __this_cpu_add_return(pcp, -(typeof(pcp))(val))
492 #define __this_cpu_inc_return(pcp) __this_cpu_add_return(pcp, 1)
493 #define __this_cpu_dec_return(pcp) __this_cpu_add_return(pcp, -1)
494
495 /*
496 * Operations with implied preemption/interrupt protection. These
497 * operations can be used without worrying about preemption or interrupt.
498 */
499 #define this_cpu_read(pcp) __pcpu_size_call_return(this_cpu_read_, pcp)
500 #define this_cpu_write(pcp, val) __pcpu_size_call(this_cpu_write_, pcp, val)
501 #define this_cpu_add(pcp, val) __pcpu_size_call(this_cpu_add_, pcp, val)
502 #define this_cpu_and(pcp, val) __pcpu_size_call(this_cpu_and_, pcp, val)
503 #define this_cpu_or(pcp, val) __pcpu_size_call(this_cpu_or_, pcp, val)
504 #define this_cpu_add_return(pcp, val) __pcpu_size_call_return2(this_cpu_add_return_, pcp, val)
505 #define this_cpu_xchg(pcp, nval) __pcpu_size_call_return2(this_cpu_xchg_, pcp, nval)
506 #define this_cpu_cmpxchg(pcp, oval, nval) \
507 __pcpu_size_call_return2(this_cpu_cmpxchg_, pcp, oval, nval)
508 #define this_cpu_try_cmpxchg(pcp, ovalp, nval) \
509 __pcpu_size_call_return2bool(this_cpu_try_cmpxchg_, pcp, ovalp, nval)
510 #define this_cpu_sub(pcp, val) this_cpu_add(pcp, -(typeof(pcp))(val))
511 #define this_cpu_inc(pcp) this_cpu_add(pcp, 1)
512 #define this_cpu_dec(pcp) this_cpu_sub(pcp, 1)
513 #define this_cpu_sub_return(pcp, val) this_cpu_add_return(pcp, -(typeof(pcp))(val))
514 #define this_cpu_inc_return(pcp) this_cpu_add_return(pcp, 1)
515 #define this_cpu_dec_return(pcp) this_cpu_add_return(pcp, -1)
516
517 #endif /* __ASSEMBLY__ */
518 #endif /* _LINUX_PERCPU_DEFS_H */
519