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#define PER_CPU_FIRST_SECTION "..first"
30
31#else
32
33#define PER_CPU_SHARED_ALIGNED_SECTION ""
34#define PER_CPU_ALIGNED_SECTION "..shared_aligned"
35#define PER_CPU_FIRST_SECTION ""
36
37#endif
38
39/*
40 * Base implementations of per-CPU variable declarations and definitions, where
41 * the section in which the variable is to be placed is provided by the
42 * 'sec' argument. This may be used to affect the parameters governing the
43 * variable's storage.
44 *
45 * NOTE! The sections for the DECLARE and for the DEFINE must match, lest
46 * linkage errors occur due the compiler generating the wrong code to access
47 * that section.
48 */
49#define __PCPU_ATTRS(sec) \
50 __percpu __attribute__((section(PER_CPU_BASE_SECTION sec))) \
51 PER_CPU_ATTRIBUTES
52
53#define __PCPU_DUMMY_ATTRS \
54 __section(".discard") __attribute__((unused))
55
56/*
57 * s390 and alpha modules require percpu variables to be defined as
58 * weak to force the compiler to generate GOT based external
59 * references for them. This is necessary because percpu sections
60 * will be located outside of the usually addressable area.
61 *
62 * This definition puts the following two extra restrictions when
63 * defining percpu variables.
64 *
65 * 1. The symbol must be globally unique, even the static ones.
66 * 2. Static percpu variables cannot be defined inside a function.
67 *
68 * Archs which need weak percpu definitions should define
69 * ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary.
70 *
71 * To ensure that the generic code observes the above two
72 * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
73 * definition is used for all cases.
74 */
75#if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
76/*
77 * __pcpu_scope_* dummy variable is used to enforce scope. It
78 * receives the static modifier when it's used in front of
79 * DEFINE_PER_CPU() and will trigger build failure if
80 * DECLARE_PER_CPU() is used for the same variable.
81 *
82 * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
83 * such that hidden weak symbol collision, which will cause unrelated
84 * variables to share the same address, can be detected during build.
85 */
86#define DECLARE_PER_CPU_SECTION(type, name, sec) \
87 extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
88 extern __PCPU_ATTRS(sec) __typeof__(type) name
89
90#define DEFINE_PER_CPU_SECTION(type, name, sec) \
91 __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
92 extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
93 __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
94 extern __PCPU_ATTRS(sec) __typeof__(type) name; \
95 __PCPU_ATTRS(sec) __weak __typeof__(type) name
96#else
97/*
98 * Normal declaration and definition macros.
99 */
100#define DECLARE_PER_CPU_SECTION(type, name, sec) \
101 extern __PCPU_ATTRS(sec) __typeof__(type) name
102
103#define DEFINE_PER_CPU_SECTION(type, name, sec) \
104 __PCPU_ATTRS(sec) __typeof__(type) name
105#endif
106
107/*
108 * Variant on the per-CPU variable declaration/definition theme used for
109 * ordinary per-CPU variables.
110 */
111#define DECLARE_PER_CPU(type, name) \
112 DECLARE_PER_CPU_SECTION(type, name, "")
113
114#define DEFINE_PER_CPU(type, name) \
115 DEFINE_PER_CPU_SECTION(type, name, "")
116
117/*
118 * Declaration/definition used for per-CPU variables that must come first in
119 * the set of variables.
120 */
121#define DECLARE_PER_CPU_FIRST(type, name) \
122 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
123
124#define DEFINE_PER_CPU_FIRST(type, name) \
125 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
126
127/*
128 * Declaration/definition used for per-CPU variables that must be cacheline
129 * aligned under SMP conditions so that, whilst a particular instance of the
130 * data corresponds to a particular CPU, inefficiencies due to direct access by
131 * other CPUs are reduced by preventing the data from unnecessarily spanning
132 * cachelines.
133 *
134 * An example of this would be statistical data, where each CPU's set of data
135 * is updated by that CPU alone, but the data from across all CPUs is collated
136 * by a CPU processing a read from a proc file.
137 */
138#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \
139 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
140 ____cacheline_aligned_in_smp
141
142#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \
143 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
144 ____cacheline_aligned_in_smp
145
146#define DECLARE_PER_CPU_ALIGNED(type, name) \
147 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
148 ____cacheline_aligned
149
150#define DEFINE_PER_CPU_ALIGNED(type, name) \
151 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
152 ____cacheline_aligned
153
154/*
155 * Declaration/definition used for per-CPU variables that must be page aligned.
156 */
157#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \
158 DECLARE_PER_CPU_SECTION(type, name, "..page_aligned") \
159 __aligned(PAGE_SIZE)
160
161#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
162 DEFINE_PER_CPU_SECTION(type, name, "..page_aligned") \
163 __aligned(PAGE_SIZE)
164
165/*
166 * Declaration/definition used for per-CPU variables that must be read mostly.
167 */
168#define DECLARE_PER_CPU_READ_MOSTLY(type, name) \
169 DECLARE_PER_CPU_SECTION(type, name, "..read_mostly")
170
171#define DEFINE_PER_CPU_READ_MOSTLY(type, name) \
172 DEFINE_PER_CPU_SECTION(type, name, "..read_mostly")
173
174/*
175 * Declaration/definition used for per-CPU variables that should be accessed
176 * as decrypted when memory encryption is enabled in the guest.
177 */
178#ifdef CONFIG_AMD_MEM_ENCRYPT
179#define DECLARE_PER_CPU_DECRYPTED(type, name) \
180 DECLARE_PER_CPU_SECTION(type, name, "..decrypted")
181
182#define DEFINE_PER_CPU_DECRYPTED(type, name) \
183 DEFINE_PER_CPU_SECTION(type, name, "..decrypted")
184#else
185#define DEFINE_PER_CPU_DECRYPTED(type, name) DEFINE_PER_CPU(type, name)
186#endif
187
188/*
189 * Intermodule exports for per-CPU variables. sparse forgets about
190 * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to
191 * noop if __CHECKER__.
192 */
193#ifndef __CHECKER__
194#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var)
195#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var)
196#else
197#define EXPORT_PER_CPU_SYMBOL(var)
198#define EXPORT_PER_CPU_SYMBOL_GPL(var)
199#endif
200
201/*
202 * Accessors and operations.
203 */
204#ifndef __ASSEMBLY__
205
206/*
207 * __verify_pcpu_ptr() verifies @ptr is a percpu pointer without evaluating
208 * @ptr and is invoked once before a percpu area is accessed by all
209 * accessors and operations. This is performed in the generic part of
210 * percpu and arch overrides don't need to worry about it; however, if an
211 * arch wants to implement an arch-specific percpu accessor or operation,
212 * it may use __verify_pcpu_ptr() to verify the parameters.
213 *
214 * + 0 is required in order to convert the pointer type from a
215 * potential array type to a pointer to a single item of the array.
216 */
217#define __verify_pcpu_ptr(ptr) \
218do { \
219 const void __percpu *__vpp_verify = (typeof((ptr) + 0))NULL; \
220 (void)__vpp_verify; \
221} while (0)
222
223#ifdef CONFIG_SMP
224
225/*
226 * Add an offset to a pointer but keep the pointer as-is. Use RELOC_HIDE()
227 * to prevent the compiler from making incorrect assumptions about the
228 * pointer value. The weird cast keeps both GCC and sparse happy.
229 */
230#define SHIFT_PERCPU_PTR(__p, __offset) \
231 RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset))
232
233#define per_cpu_ptr(ptr, cpu) \
234({ \
235 __verify_pcpu_ptr(ptr); \
236 SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu))); \
237})
238
239#define raw_cpu_ptr(ptr) \
240({ \
241 __verify_pcpu_ptr(ptr); \
242 arch_raw_cpu_ptr(ptr); \
243})
244
245#ifdef CONFIG_DEBUG_PREEMPT
246#define this_cpu_ptr(ptr) \
247({ \
248 __verify_pcpu_ptr(ptr); \
249 SHIFT_PERCPU_PTR(ptr, my_cpu_offset); \
250})
251#else
252#define this_cpu_ptr(ptr) raw_cpu_ptr(ptr)
253#endif
254
255#else /* CONFIG_SMP */
256
257#define VERIFY_PERCPU_PTR(__p) \
258({ \
259 __verify_pcpu_ptr(__p); \
260 (typeof(*(__p)) __kernel __force *)(__p); \
261})
262
263#define per_cpu_ptr(ptr, cpu) ({ (void)(cpu); VERIFY_PERCPU_PTR(ptr); })
264#define raw_cpu_ptr(ptr) per_cpu_ptr(ptr, 0)
265#define this_cpu_ptr(ptr) raw_cpu_ptr(ptr)
266
267#endif /* CONFIG_SMP */
268
269#define per_cpu(var, cpu) (*per_cpu_ptr(&(var), cpu))
270
271/*
272 * Must be an lvalue. Since @var must be a simple identifier,
273 * we force a syntax error here if it isn't.
274 */
275#define get_cpu_var(var) \
276(*({ \
277 preempt_disable(); \
278 this_cpu_ptr(&var); \
279}))
280
281/*
282 * The weird & is necessary because sparse considers (void)(var) to be
283 * a direct dereference of percpu variable (var).
284 */
285#define put_cpu_var(var) \
286do { \
287 (void)&(var); \
288 preempt_enable(); \
289} while (0)
290
291#define get_cpu_ptr(var) \
292({ \
293 preempt_disable(); \
294 this_cpu_ptr(var); \
295})
296
297#define put_cpu_ptr(var) \
298do { \
299 (void)(var); \
300 preempt_enable(); \
301} while (0)
302
303/*
304 * Branching function to split up a function into a set of functions that
305 * are called for different scalar sizes of the objects handled.
306 */
307
308extern void __bad_size_call_parameter(void);
309
310#ifdef CONFIG_DEBUG_PREEMPT
311extern void __this_cpu_preempt_check(const char *op);
312#else
313static inline void __this_cpu_preempt_check(const char *op) { }
314#endif
315
316#define __pcpu_size_call_return(stem, variable) \
317({ \
318 typeof(variable) pscr_ret__; \
319 __verify_pcpu_ptr(&(variable)); \
320 switch(sizeof(variable)) { \
321 case 1: pscr_ret__ = stem##1(variable); break; \
322 case 2: pscr_ret__ = stem##2(variable); break; \
323 case 4: pscr_ret__ = stem##4(variable); break; \
324 case 8: pscr_ret__ = stem##8(variable); break; \
325 default: \
326 __bad_size_call_parameter(); break; \
327 } \
328 pscr_ret__; \
329})
330
331#define __pcpu_size_call_return2(stem, variable, ...) \
332({ \
333 typeof(variable) pscr2_ret__; \
334 __verify_pcpu_ptr(&(variable)); \
335 switch(sizeof(variable)) { \
336 case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break; \
337 case 2: pscr2_ret__ = stem##2(variable, __VA_ARGS__); break; \
338 case 4: pscr2_ret__ = stem##4(variable, __VA_ARGS__); break; \
339 case 8: pscr2_ret__ = stem##8(variable, __VA_ARGS__); break; \
340 default: \
341 __bad_size_call_parameter(); break; \
342 } \
343 pscr2_ret__; \
344})
345
346/*
347 * Special handling for cmpxchg_double. cmpxchg_double is passed two
348 * percpu variables. The first has to be aligned to a double word
349 * boundary and the second has to follow directly thereafter.
350 * We enforce this on all architectures even if they don't support
351 * a double cmpxchg instruction, since it's a cheap requirement, and it
352 * avoids breaking the requirement for architectures with the instruction.
353 */
354#define __pcpu_double_call_return_bool(stem, pcp1, pcp2, ...) \
355({ \
356 bool pdcrb_ret__; \
357 __verify_pcpu_ptr(&(pcp1)); \
358 BUILD_BUG_ON(sizeof(pcp1) != sizeof(pcp2)); \
359 VM_BUG_ON((unsigned long)(&(pcp1)) % (2 * sizeof(pcp1))); \
360 VM_BUG_ON((unsigned long)(&(pcp2)) != \
361 (unsigned long)(&(pcp1)) + sizeof(pcp1)); \
362 switch(sizeof(pcp1)) { \
363 case 1: pdcrb_ret__ = stem##1(pcp1, pcp2, __VA_ARGS__); break; \
364 case 2: pdcrb_ret__ = stem##2(pcp1, pcp2, __VA_ARGS__); break; \
365 case 4: pdcrb_ret__ = stem##4(pcp1, pcp2, __VA_ARGS__); break; \
366 case 8: pdcrb_ret__ = stem##8(pcp1, pcp2, __VA_ARGS__); break; \
367 default: \
368 __bad_size_call_parameter(); break; \
369 } \
370 pdcrb_ret__; \
371})
372
373#define __pcpu_size_call(stem, variable, ...) \
374do { \
375 __verify_pcpu_ptr(&(variable)); \
376 switch(sizeof(variable)) { \
377 case 1: stem##1(variable, __VA_ARGS__);break; \
378 case 2: stem##2(variable, __VA_ARGS__);break; \
379 case 4: stem##4(variable, __VA_ARGS__);break; \
380 case 8: stem##8(variable, __VA_ARGS__);break; \
381 default: \
382 __bad_size_call_parameter();break; \
383 } \
384} while (0)
385
386/*
387 * this_cpu operations (C) 2008-2013 Christoph Lameter <cl@linux.com>
388 *
389 * Optimized manipulation for memory allocated through the per cpu
390 * allocator or for addresses of per cpu variables.
391 *
392 * These operation guarantee exclusivity of access for other operations
393 * on the *same* processor. The assumption is that per cpu data is only
394 * accessed by a single processor instance (the current one).
395 *
396 * The arch code can provide optimized implementation by defining macros
397 * for certain scalar sizes. F.e. provide this_cpu_add_2() to provide per
398 * cpu atomic operations for 2 byte sized RMW actions. If arch code does
399 * not provide operations for a scalar size then the fallback in the
400 * generic code will be used.
401 *
402 * cmpxchg_double replaces two adjacent scalars at once. The first two
403 * parameters are per cpu variables which have to be of the same size. A
404 * truth value is returned to indicate success or failure (since a double
405 * register result is difficult to handle). There is very limited hardware
406 * support for these operations, so only certain sizes may work.
407 */
408
409/*
410 * Operations for contexts where we do not want to do any checks for
411 * preemptions. Unless strictly necessary, always use [__]this_cpu_*()
412 * instead.
413 *
414 * If there is no other protection through preempt disable and/or disabling
415 * interrupts then one of these RMW operations can show unexpected behavior
416 * because the execution thread was rescheduled on another processor or an
417 * interrupt occurred and the same percpu variable was modified from the
418 * interrupt context.
419 */
420#define raw_cpu_read(pcp) __pcpu_size_call_return(raw_cpu_read_, pcp)
421#define raw_cpu_write(pcp, val) __pcpu_size_call(raw_cpu_write_, pcp, val)
422#define raw_cpu_add(pcp, val) __pcpu_size_call(raw_cpu_add_, pcp, val)
423#define raw_cpu_and(pcp, val) __pcpu_size_call(raw_cpu_and_, pcp, val)
424#define raw_cpu_or(pcp, val) __pcpu_size_call(raw_cpu_or_, pcp, val)
425#define raw_cpu_add_return(pcp, val) __pcpu_size_call_return2(raw_cpu_add_return_, pcp, val)
426#define raw_cpu_xchg(pcp, nval) __pcpu_size_call_return2(raw_cpu_xchg_, pcp, nval)
427#define raw_cpu_cmpxchg(pcp, oval, nval) \
428 __pcpu_size_call_return2(raw_cpu_cmpxchg_, pcp, oval, nval)
429#define raw_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
430 __pcpu_double_call_return_bool(raw_cpu_cmpxchg_double_, pcp1, pcp2, oval1, oval2, nval1, nval2)
431
432#define raw_cpu_sub(pcp, val) raw_cpu_add(pcp, -(val))
433#define raw_cpu_inc(pcp) raw_cpu_add(pcp, 1)
434#define raw_cpu_dec(pcp) raw_cpu_sub(pcp, 1)
435#define raw_cpu_sub_return(pcp, val) raw_cpu_add_return(pcp, -(typeof(pcp))(val))
436#define raw_cpu_inc_return(pcp) raw_cpu_add_return(pcp, 1)
437#define raw_cpu_dec_return(pcp) raw_cpu_add_return(pcp, -1)
438
439/*
440 * Operations for contexts that are safe from preemption/interrupts. These
441 * operations verify that preemption is disabled.
442 */
443#define __this_cpu_read(pcp) \
444({ \
445 __this_cpu_preempt_check("read"); \
446 raw_cpu_read(pcp); \
447})
448
449#define __this_cpu_write(pcp, val) \
450({ \
451 __this_cpu_preempt_check("write"); \
452 raw_cpu_write(pcp, val); \
453})
454
455#define __this_cpu_add(pcp, val) \
456({ \
457 __this_cpu_preempt_check("add"); \
458 raw_cpu_add(pcp, val); \
459})
460
461#define __this_cpu_and(pcp, val) \
462({ \
463 __this_cpu_preempt_check("and"); \
464 raw_cpu_and(pcp, val); \
465})
466
467#define __this_cpu_or(pcp, val) \
468({ \
469 __this_cpu_preempt_check("or"); \
470 raw_cpu_or(pcp, val); \
471})
472
473#define __this_cpu_add_return(pcp, val) \
474({ \
475 __this_cpu_preempt_check("add_return"); \
476 raw_cpu_add_return(pcp, val); \
477})
478
479#define __this_cpu_xchg(pcp, nval) \
480({ \
481 __this_cpu_preempt_check("xchg"); \
482 raw_cpu_xchg(pcp, nval); \
483})
484
485#define __this_cpu_cmpxchg(pcp, oval, nval) \
486({ \
487 __this_cpu_preempt_check("cmpxchg"); \
488 raw_cpu_cmpxchg(pcp, oval, nval); \
489})
490
491#define __this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
492({ __this_cpu_preempt_check("cmpxchg_double"); \
493 raw_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2); \
494})
495
496#define __this_cpu_sub(pcp, val) __this_cpu_add(pcp, -(typeof(pcp))(val))
497#define __this_cpu_inc(pcp) __this_cpu_add(pcp, 1)
498#define __this_cpu_dec(pcp) __this_cpu_sub(pcp, 1)
499#define __this_cpu_sub_return(pcp, val) __this_cpu_add_return(pcp, -(typeof(pcp))(val))
500#define __this_cpu_inc_return(pcp) __this_cpu_add_return(pcp, 1)
501#define __this_cpu_dec_return(pcp) __this_cpu_add_return(pcp, -1)
502
503/*
504 * Operations with implied preemption/interrupt protection. These
505 * operations can be used without worrying about preemption or interrupt.
506 */
507#define this_cpu_read(pcp) __pcpu_size_call_return(this_cpu_read_, pcp)
508#define this_cpu_write(pcp, val) __pcpu_size_call(this_cpu_write_, pcp, val)
509#define this_cpu_add(pcp, val) __pcpu_size_call(this_cpu_add_, pcp, val)
510#define this_cpu_and(pcp, val) __pcpu_size_call(this_cpu_and_, pcp, val)
511#define this_cpu_or(pcp, val) __pcpu_size_call(this_cpu_or_, pcp, val)
512#define this_cpu_add_return(pcp, val) __pcpu_size_call_return2(this_cpu_add_return_, pcp, val)
513#define this_cpu_xchg(pcp, nval) __pcpu_size_call_return2(this_cpu_xchg_, pcp, nval)
514#define this_cpu_cmpxchg(pcp, oval, nval) \
515 __pcpu_size_call_return2(this_cpu_cmpxchg_, pcp, oval, nval)
516#define this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
517 __pcpu_double_call_return_bool(this_cpu_cmpxchg_double_, pcp1, pcp2, oval1, oval2, nval1, nval2)
518
519#define this_cpu_sub(pcp, val) this_cpu_add(pcp, -(typeof(pcp))(val))
520#define this_cpu_inc(pcp) this_cpu_add(pcp, 1)
521#define this_cpu_dec(pcp) this_cpu_sub(pcp, 1)
522#define this_cpu_sub_return(pcp, val) this_cpu_add_return(pcp, -(typeof(pcp))(val))
523#define this_cpu_inc_return(pcp) this_cpu_add_return(pcp, 1)
524#define this_cpu_dec_return(pcp) this_cpu_add_return(pcp, -1)
525
526#endif /* __ASSEMBLY__ */
527#endif /* _LINUX_PERCPU_DEFS_H */
528

source code of linux/include/linux/percpu-defs.h