percpu-defs.h

  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 * 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)						\
220do {									\
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)						\
290do {									\
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)						\
302do {									\
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
312extern void __bad_size_call_parameter(void);
313
314#ifdef CONFIG_DEBUG_PREEMPT
315extern void __this_cpu_preempt_check(const char *op);
316#else
317static __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, ...)				\
366do {									\
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 */