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Linux/include/linux/compiler.h

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  1 #ifndef __LINUX_COMPILER_H
  2 #define __LINUX_COMPILER_H
  3 
  4 #ifndef __ASSEMBLY__
  5 
  6 #ifdef __CHECKER__
  7 # define __user         __attribute__((noderef, address_space(1)))
  8 # define __kernel       __attribute__((address_space(0)))
  9 # define __safe         __attribute__((safe))
 10 # define __force        __attribute__((force))
 11 # define __nocast       __attribute__((nocast))
 12 # define __iomem        __attribute__((noderef, address_space(2)))
 13 # define __must_hold(x) __attribute__((context(x,1,1)))
 14 # define __acquires(x)  __attribute__((context(x,0,1)))
 15 # define __releases(x)  __attribute__((context(x,1,0)))
 16 # define __acquire(x)   __context__(x,1)
 17 # define __release(x)   __context__(x,-1)
 18 # define __cond_lock(x,c)       ((c) ? ({ __acquire(x); 1; }) : 0)
 19 # define __percpu       __attribute__((noderef, address_space(3)))
 20 #ifdef CONFIG_SPARSE_RCU_POINTER
 21 # define __rcu          __attribute__((noderef, address_space(4)))
 22 #else /* CONFIG_SPARSE_RCU_POINTER */
 23 # define __rcu
 24 #endif /* CONFIG_SPARSE_RCU_POINTER */
 25 # define __private      __attribute__((noderef))
 26 extern void __chk_user_ptr(const volatile void __user *);
 27 extern void __chk_io_ptr(const volatile void __iomem *);
 28 # define ACCESS_PRIVATE(p, member) (*((typeof((p)->member) __force *) &(p)->member))
 29 #else /* __CHECKER__ */
 30 # ifdef STRUCTLEAK_PLUGIN
 31 #  define __user __attribute__((user))
 32 # else
 33 #  define __user
 34 # endif
 35 # define __kernel
 36 # define __safe
 37 # define __force
 38 # define __nocast
 39 # define __iomem
 40 # define __chk_user_ptr(x) (void)0
 41 # define __chk_io_ptr(x) (void)0
 42 # define __builtin_warning(x, y...) (1)
 43 # define __must_hold(x)
 44 # define __acquires(x)
 45 # define __releases(x)
 46 # define __acquire(x) (void)0
 47 # define __release(x) (void)0
 48 # define __cond_lock(x,c) (c)
 49 # define __percpu
 50 # define __rcu
 51 # define __private
 52 # define ACCESS_PRIVATE(p, member) ((p)->member)
 53 #endif /* __CHECKER__ */
 54 
 55 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
 56 #define ___PASTE(a,b) a##b
 57 #define __PASTE(a,b) ___PASTE(a,b)
 58 
 59 #ifdef __KERNEL__
 60 
 61 #ifdef __GNUC__
 62 #include <linux/compiler-gcc.h>
 63 #endif
 64 
 65 #if defined(CC_USING_HOTPATCH) && !defined(__CHECKER__)
 66 #define notrace __attribute__((hotpatch(0,0)))
 67 #else
 68 #define notrace __attribute__((no_instrument_function))
 69 #endif
 70 
 71 /* Intel compiler defines __GNUC__. So we will overwrite implementations
 72  * coming from above header files here
 73  */
 74 #ifdef __INTEL_COMPILER
 75 # include <linux/compiler-intel.h>
 76 #endif
 77 
 78 /* Clang compiler defines __GNUC__. So we will overwrite implementations
 79  * coming from above header files here
 80  */
 81 #ifdef __clang__
 82 #include <linux/compiler-clang.h>
 83 #endif
 84 
 85 /*
 86  * Generic compiler-dependent macros required for kernel
 87  * build go below this comment. Actual compiler/compiler version
 88  * specific implementations come from the above header files
 89  */
 90 
 91 struct ftrace_branch_data {
 92         const char *func;
 93         const char *file;
 94         unsigned line;
 95         union {
 96                 struct {
 97                         unsigned long correct;
 98                         unsigned long incorrect;
 99                 };
100                 struct {
101                         unsigned long miss;
102                         unsigned long hit;
103                 };
104                 unsigned long miss_hit[2];
105         };
106 };
107 
108 struct ftrace_likely_data {
109         struct ftrace_branch_data       data;
110         unsigned long                   constant;
111 };
112 
113 /*
114  * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
115  * to disable branch tracing on a per file basis.
116  */
117 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
118     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
119 void ftrace_likely_update(struct ftrace_likely_data *f, int val,
120                           int expect, int is_constant);
121 
122 #define likely_notrace(x)       __builtin_expect(!!(x), 1)
123 #define unlikely_notrace(x)     __builtin_expect(!!(x), 0)
124 
125 #define __branch_check__(x, expect, is_constant) ({                     \
126                         int ______r;                                    \
127                         static struct ftrace_likely_data                \
128                                 __attribute__((__aligned__(4)))         \
129                                 __attribute__((section("_ftrace_annotated_branch"))) \
130                                 ______f = {                             \
131                                 .data.func = __func__,                  \
132                                 .data.file = __FILE__,                  \
133                                 .data.line = __LINE__,                  \
134                         };                                              \
135                         ______r = __builtin_expect(!!(x), expect);      \
136                         ftrace_likely_update(&______f, ______r,         \
137                                              expect, is_constant);      \
138                         ______r;                                        \
139                 })
140 
141 /*
142  * Using __builtin_constant_p(x) to ignore cases where the return
143  * value is always the same.  This idea is taken from a similar patch
144  * written by Daniel Walker.
145  */
146 # ifndef likely
147 #  define likely(x)     (__branch_check__(x, 1, __builtin_constant_p(x)))
148 # endif
149 # ifndef unlikely
150 #  define unlikely(x)   (__branch_check__(x, 0, __builtin_constant_p(x)))
151 # endif
152 
153 #ifdef CONFIG_PROFILE_ALL_BRANCHES
154 /*
155  * "Define 'is'", Bill Clinton
156  * "Define 'if'", Steven Rostedt
157  */
158 #define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
159 #define __trace_if(cond) \
160         if (__builtin_constant_p(!!(cond)) ? !!(cond) :                 \
161         ({                                                              \
162                 int ______r;                                            \
163                 static struct ftrace_branch_data                        \
164                         __attribute__((__aligned__(4)))                 \
165                         __attribute__((section("_ftrace_branch")))      \
166                         ______f = {                                     \
167                                 .func = __func__,                       \
168                                 .file = __FILE__,                       \
169                                 .line = __LINE__,                       \
170                         };                                              \
171                 ______r = !!(cond);                                     \
172                 ______f.miss_hit[______r]++;                                    \
173                 ______r;                                                \
174         }))
175 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
176 
177 #else
178 # define likely(x)      __builtin_expect(!!(x), 1)
179 # define unlikely(x)    __builtin_expect(!!(x), 0)
180 #endif
181 
182 /* Optimization barrier */
183 #ifndef barrier
184 # define barrier() __memory_barrier()
185 #endif
186 
187 #ifndef barrier_data
188 # define barrier_data(ptr) barrier()
189 #endif
190 
191 /* Unreachable code */
192 #ifndef unreachable
193 # define unreachable() do { } while (1)
194 #endif
195 
196 /*
197  * KENTRY - kernel entry point
198  * This can be used to annotate symbols (functions or data) that are used
199  * without their linker symbol being referenced explicitly. For example,
200  * interrupt vector handlers, or functions in the kernel image that are found
201  * programatically.
202  *
203  * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
204  * are handled in their own way (with KEEP() in linker scripts).
205  *
206  * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
207  * linker script. For example an architecture could KEEP() its entire
208  * boot/exception vector code rather than annotate each function and data.
209  */
210 #ifndef KENTRY
211 # define KENTRY(sym)                                            \
212         extern typeof(sym) sym;                                 \
213         static const unsigned long __kentry_##sym               \
214         __used                                                  \
215         __attribute__((section("___kentry" "+" #sym ), used))   \
216         = (unsigned long)&sym;
217 #endif
218 
219 #ifndef RELOC_HIDE
220 # define RELOC_HIDE(ptr, off)                                   \
221   ({ unsigned long __ptr;                                       \
222      __ptr = (unsigned long) (ptr);                             \
223     (typeof(ptr)) (__ptr + (off)); })
224 #endif
225 
226 #ifndef OPTIMIZER_HIDE_VAR
227 #define OPTIMIZER_HIDE_VAR(var) barrier()
228 #endif
229 
230 /* Not-quite-unique ID. */
231 #ifndef __UNIQUE_ID
232 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
233 #endif
234 
235 #include <uapi/linux/types.h>
236 
237 #define __READ_ONCE_SIZE                                                \
238 ({                                                                      \
239         switch (size) {                                                 \
240         case 1: *(__u8 *)res = *(volatile __u8 *)p; break;              \
241         case 2: *(__u16 *)res = *(volatile __u16 *)p; break;            \
242         case 4: *(__u32 *)res = *(volatile __u32 *)p; break;            \
243         case 8: *(__u64 *)res = *(volatile __u64 *)p; break;            \
244         default:                                                        \
245                 barrier();                                              \
246                 __builtin_memcpy((void *)res, (const void *)p, size);   \
247                 barrier();                                              \
248         }                                                               \
249 })
250 
251 static __always_inline
252 void __read_once_size(const volatile void *p, void *res, int size)
253 {
254         __READ_ONCE_SIZE;
255 }
256 
257 #ifdef CONFIG_KASAN
258 /*
259  * This function is not 'inline' because __no_sanitize_address confilcts
260  * with inlining. Attempt to inline it may cause a build failure.
261  *      https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
262  * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
263  */
264 static __no_sanitize_address __maybe_unused
265 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
266 {
267         __READ_ONCE_SIZE;
268 }
269 #else
270 static __always_inline
271 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
272 {
273         __READ_ONCE_SIZE;
274 }
275 #endif
276 
277 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
278 {
279         switch (size) {
280         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
281         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
282         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
283         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
284         default:
285                 barrier();
286                 __builtin_memcpy((void *)p, (const void *)res, size);
287                 barrier();
288         }
289 }
290 
291 /*
292  * Prevent the compiler from merging or refetching reads or writes. The
293  * compiler is also forbidden from reordering successive instances of
294  * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
295  * compiler is aware of some particular ordering.  One way to make the
296  * compiler aware of ordering is to put the two invocations of READ_ONCE,
297  * WRITE_ONCE or ACCESS_ONCE() in different C statements.
298  *
299  * In contrast to ACCESS_ONCE these two macros will also work on aggregate
300  * data types like structs or unions. If the size of the accessed data
301  * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
302  * READ_ONCE() and WRITE_ONCE() will fall back to memcpy(). There's at
303  * least two memcpy()s: one for the __builtin_memcpy() and then one for
304  * the macro doing the copy of variable - '__u' allocated on the stack.
305  *
306  * Their two major use cases are: (1) Mediating communication between
307  * process-level code and irq/NMI handlers, all running on the same CPU,
308  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
309  * mutilate accesses that either do not require ordering or that interact
310  * with an explicit memory barrier or atomic instruction that provides the
311  * required ordering.
312  */
313 
314 #define __READ_ONCE(x, check)                                           \
315 ({                                                                      \
316         union { typeof(x) __val; char __c[1]; } __u;                    \
317         if (check)                                                      \
318                 __read_once_size(&(x), __u.__c, sizeof(x));             \
319         else                                                            \
320                 __read_once_size_nocheck(&(x), __u.__c, sizeof(x));     \
321         __u.__val;                                                      \
322 })
323 #define READ_ONCE(x) __READ_ONCE(x, 1)
324 
325 /*
326  * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
327  * to hide memory access from KASAN.
328  */
329 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
330 
331 #define WRITE_ONCE(x, val) \
332 ({                                                      \
333         union { typeof(x) __val; char __c[1]; } __u =   \
334                 { .__val = (__force typeof(x)) (val) }; \
335         __write_once_size(&(x), __u.__c, sizeof(x));    \
336         __u.__val;                                      \
337 })
338 
339 #endif /* __KERNEL__ */
340 
341 #endif /* __ASSEMBLY__ */
342 
343 #ifdef __KERNEL__
344 /*
345  * Allow us to mark functions as 'deprecated' and have gcc emit a nice
346  * warning for each use, in hopes of speeding the functions removal.
347  * Usage is:
348  *              int __deprecated foo(void)
349  */
350 #ifndef __deprecated
351 # define __deprecated           /* unimplemented */
352 #endif
353 
354 #ifdef MODULE
355 #define __deprecated_for_modules __deprecated
356 #else
357 #define __deprecated_for_modules
358 #endif
359 
360 #ifndef __must_check
361 #define __must_check
362 #endif
363 
364 #ifndef CONFIG_ENABLE_MUST_CHECK
365 #undef __must_check
366 #define __must_check
367 #endif
368 #ifndef CONFIG_ENABLE_WARN_DEPRECATED
369 #undef __deprecated
370 #undef __deprecated_for_modules
371 #define __deprecated
372 #define __deprecated_for_modules
373 #endif
374 
375 #ifndef __malloc
376 #define __malloc
377 #endif
378 
379 /*
380  * Allow us to avoid 'defined but not used' warnings on functions and data,
381  * as well as force them to be emitted to the assembly file.
382  *
383  * As of gcc 3.4, static functions that are not marked with attribute((used))
384  * may be elided from the assembly file.  As of gcc 3.4, static data not so
385  * marked will not be elided, but this may change in a future gcc version.
386  *
387  * NOTE: Because distributions shipped with a backported unit-at-a-time
388  * compiler in gcc 3.3, we must define __used to be __attribute__((used))
389  * for gcc >=3.3 instead of 3.4.
390  *
391  * In prior versions of gcc, such functions and data would be emitted, but
392  * would be warned about except with attribute((unused)).
393  *
394  * Mark functions that are referenced only in inline assembly as __used so
395  * the code is emitted even though it appears to be unreferenced.
396  */
397 #ifndef __used
398 # define __used                 /* unimplemented */
399 #endif
400 
401 #ifndef __maybe_unused
402 # define __maybe_unused         /* unimplemented */
403 #endif
404 
405 #ifndef __always_unused
406 # define __always_unused        /* unimplemented */
407 #endif
408 
409 #ifndef noinline
410 #define noinline
411 #endif
412 
413 /*
414  * Rather then using noinline to prevent stack consumption, use
415  * noinline_for_stack instead.  For documentation reasons.
416  */
417 #define noinline_for_stack noinline
418 
419 #ifndef __always_inline
420 #define __always_inline inline
421 #endif
422 
423 #endif /* __KERNEL__ */
424 
425 /*
426  * From the GCC manual:
427  *
428  * Many functions do not examine any values except their arguments,
429  * and have no effects except the return value.  Basically this is
430  * just slightly more strict class than the `pure' attribute above,
431  * since function is not allowed to read global memory.
432  *
433  * Note that a function that has pointer arguments and examines the
434  * data pointed to must _not_ be declared `const'.  Likewise, a
435  * function that calls a non-`const' function usually must not be
436  * `const'.  It does not make sense for a `const' function to return
437  * `void'.
438  */
439 #ifndef __attribute_const__
440 # define __attribute_const__    /* unimplemented */
441 #endif
442 
443 #ifndef __latent_entropy
444 # define __latent_entropy
445 #endif
446 
447 /*
448  * Tell gcc if a function is cold. The compiler will assume any path
449  * directly leading to the call is unlikely.
450  */
451 
452 #ifndef __cold
453 #define __cold
454 #endif
455 
456 /* Simple shorthand for a section definition */
457 #ifndef __section
458 # define __section(S) __attribute__ ((__section__(#S)))
459 #endif
460 
461 #ifndef __visible
462 #define __visible
463 #endif
464 
465 /*
466  * Assume alignment of return value.
467  */
468 #ifndef __assume_aligned
469 #define __assume_aligned(a, ...)
470 #endif
471 
472 
473 /* Are two types/vars the same type (ignoring qualifiers)? */
474 #ifndef __same_type
475 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
476 #endif
477 
478 /* Is this type a native word size -- useful for atomic operations */
479 #ifndef __native_word
480 # define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
481 #endif
482 
483 /* Compile time object size, -1 for unknown */
484 #ifndef __compiletime_object_size
485 # define __compiletime_object_size(obj) -1
486 #endif
487 #ifndef __compiletime_warning
488 # define __compiletime_warning(message)
489 #endif
490 #ifndef __compiletime_error
491 # define __compiletime_error(message)
492 /*
493  * Sparse complains of variable sized arrays due to the temporary variable in
494  * __compiletime_assert. Unfortunately we can't just expand it out to make
495  * sparse see a constant array size without breaking compiletime_assert on old
496  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
497  */
498 # ifndef __CHECKER__
499 #  define __compiletime_error_fallback(condition) \
500         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
501 # endif
502 #endif
503 #ifndef __compiletime_error_fallback
504 # define __compiletime_error_fallback(condition) do { } while (0)
505 #endif
506 
507 #define __compiletime_assert(condition, msg, prefix, suffix)            \
508         do {                                                            \
509                 bool __cond = !(condition);                             \
510                 extern void prefix ## suffix(void) __compiletime_error(msg); \
511                 if (__cond)                                             \
512                         prefix ## suffix();                             \
513                 __compiletime_error_fallback(__cond);                   \
514         } while (0)
515 
516 #define _compiletime_assert(condition, msg, prefix, suffix) \
517         __compiletime_assert(condition, msg, prefix, suffix)
518 
519 /**
520  * compiletime_assert - break build and emit msg if condition is false
521  * @condition: a compile-time constant condition to check
522  * @msg:       a message to emit if condition is false
523  *
524  * In tradition of POSIX assert, this macro will break the build if the
525  * supplied condition is *false*, emitting the supplied error message if the
526  * compiler has support to do so.
527  */
528 #define compiletime_assert(condition, msg) \
529         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
530 
531 #define compiletime_assert_atomic_type(t)                               \
532         compiletime_assert(__native_word(t),                            \
533                 "Need native word sized stores/loads for atomicity.")
534 
535 /*
536  * Prevent the compiler from merging or refetching accesses.  The compiler
537  * is also forbidden from reordering successive instances of ACCESS_ONCE(),
538  * but only when the compiler is aware of some particular ordering.  One way
539  * to make the compiler aware of ordering is to put the two invocations of
540  * ACCESS_ONCE() in different C statements.
541  *
542  * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
543  * on a union member will work as long as the size of the member matches the
544  * size of the union and the size is smaller than word size.
545  *
546  * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
547  * between process-level code and irq/NMI handlers, all running on the same CPU,
548  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
549  * mutilate accesses that either do not require ordering or that interact
550  * with an explicit memory barrier or atomic instruction that provides the
551  * required ordering.
552  *
553  * If possible use READ_ONCE()/WRITE_ONCE() instead.
554  */
555 #define __ACCESS_ONCE(x) ({ \
556          __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
557         (volatile typeof(x) *)&(x); })
558 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
559 
560 /**
561  * lockless_dereference() - safely load a pointer for later dereference
562  * @p: The pointer to load
563  *
564  * Similar to rcu_dereference(), but for situations where the pointed-to
565  * object's lifetime is managed by something other than RCU.  That
566  * "something other" might be reference counting or simple immortality.
567  *
568  * The seemingly unused variable ___typecheck_p validates that @p is
569  * indeed a pointer type by using a pointer to typeof(*p) as the type.
570  * Taking a pointer to typeof(*p) again is needed in case p is void *.
571  */
572 #define lockless_dereference(p) \
573 ({ \
574         typeof(p) _________p1 = READ_ONCE(p); \
575         typeof(*(p)) *___typecheck_p __maybe_unused; \
576         smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
577         (_________p1); \
578 })
579 
580 #endif /* __LINUX_COMPILER_H */
581 

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