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