include/linux/compiler.h

   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
  23 # define __rcu
  24 #endif
  25 extern void __chk_user_ptr(const volatile void __user *);
  26 extern void __chk_io_ptr(const volatile void __iomem *);
  27 #else
  28 # define __user
  29 # define __kernel
  30 # define __safe
  31 # define __force
  32 # define __nocast
  33 # define __iomem
  34 # define __chk_user_ptr(x) (void)0
  35 # define __chk_io_ptr(x) (void)0
  36 # define __builtin_warning(x, y...) (1)
  37 # define __must_hold(x)
  38 # define __acquires(x)
  39 # define __releases(x)
  40 # define __acquire(x) (void)0
  41 # define __release(x) (void)0
  42 # define __cond_lock(x,c) (c)
  43 # define __percpu
  44 # define __rcu
  45 #endif
  46
  47 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
  48 #define ___PASTE(a,b) a##b
  49 #define __PASTE(a,b) ___PASTE(a,b)
  50
  51 #ifdef __KERNEL__
  52
  53 #ifdef __GNUC__
  54 #include <linux/compiler-gcc.h>
  55 #endif
  56
  57 #ifdef CC_USING_HOTPATCH
  58 #define notrace __attribute__((hotpatch(0,0)))
  59 #else
  60 #define notrace __attribute__((no_instrument_function))
  61 #endif
  62
  63 /* Intel compiler defines __GNUC__. So we will overwrite implementations
  64  * coming from above header files here
  65  */
  66 #ifdef __INTEL_COMPILER
  67 # include <linux/compiler-intel.h>
  68 #endif
  69
  70 /* Clang compiler defines __GNUC__. So we will overwrite implementations
  71  * coming from above header files here
  72  */
  73 #ifdef __clang__
  74 #include <linux/compiler-clang.h>
  75 #endif
  76
  77 /*
  78  * Generic compiler-dependent macros required for kernel
  79  * build go below this comment. Actual compiler/compiler version
  80  * specific implementations come from the above header files
  81  */
  82
  83 struct ftrace_branch_data {
  84         const char *func;
  85         const char *file;
  86         unsigned line;
  87         union {
  88                 struct {
  89                         unsigned long correct;
  90                         unsigned long incorrect;
  91                 };
  92                 struct {
  93                         unsigned long miss;
  94                         unsigned long hit;
  95                 };
  96                 unsigned long miss_hit[2];
  97         };
  98 };
  99
 100 /*
 101  * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
 102  * to disable branch tracing on a per file basis.
 103  */
 104 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
 105     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
 106 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 107
 108 #define likely_notrace(x)       __builtin_expect(!!(x), 1)
 109 #define unlikely_notrace(x)     __builtin_expect(!!(x), 0)
 110
 111 #define __branch_check__(x, expect) ({                                  \
 112                         int ______r;                                    \
 113                         static struct ftrace_branch_data                \
 114                                 __attribute__((__aligned__(4)))         \
 115                                 __attribute__((section("_ftrace_annotated_branch"))) \
 116                                 ______f = {                             \
 117                                 .func = __func__,                       \
 118                                 .file = __FILE__,                       \
 119                                 .line = __LINE__,                       \
 120                         };                                              \
 121                         ______r = likely_notrace(x);                    \
 122                         ftrace_likely_update(&______f, ______r, expect); \
 123                         ______r;                                        \
 124                 })
 125
 126 /*
 127  * Using __builtin_constant_p(x) to ignore cases where the return
 128  * value is always the same.  This idea is taken from a similar patch
 129  * written by Daniel Walker.
 130  */
 131 # ifndef likely
 132 #  define likely(x)     (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1))
 133 # endif
 134 # ifndef unlikely
 135 #  define unlikely(x)   (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
 136 # endif
 137
 138 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 139 /*
 140  * "Define 'is'", Bill Clinton
 141  * "Define 'if'", Steven Rostedt
 142  */
 143 #define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
 144 #define __trace_if(cond) \
 145         if (__builtin_constant_p((cond)) ? !!(cond) :                   \
 146         ({                                                              \
 147                 int ______r;                                            \
 148                 static struct ftrace_branch_data                        \
 149                         __attribute__((__aligned__(4)))                 \
 150                         __attribute__((section("_ftrace_branch")))      \
 151                         ______f = {                                     \
 152                                 .func = __func__,                       \
 153                                 .file = __FILE__,                       \
 154                                 .line = __LINE__,                       \
 155                         };                                              \
 156                 ______r = !!(cond);                                     \
 157                 ______f.miss_hit[______r]++;                                    \
 158                 ______r;                                                \
 159         }))
 160 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
 161
 162 #else
 163 # define likely(x)      __builtin_expect(!!(x), 1)
 164 # define unlikely(x)    __builtin_expect(!!(x), 0)
 165 #endif
 166
 167 /* Optimization barrier */
 168 #ifndef barrier
 169 # define barrier() __memory_barrier()
 170 #endif
 171
 172 /* Unreachable code */
 173 #ifndef unreachable
 174 # define unreachable() do { } while (1)
 175 #endif
 176
 177 #ifndef RELOC_HIDE
 178 # define RELOC_HIDE(ptr, off)                                   \
 179   ({ unsigned long __ptr;                                       \
 180      __ptr = (unsigned long) (ptr);                             \
 181     (typeof(ptr)) (__ptr + (off)); })
 182 #endif
 183
 184 #ifndef OPTIMIZER_HIDE_VAR
 185 #define OPTIMIZER_HIDE_VAR(var) barrier()
 186 #endif
 187
 188 /* Not-quite-unique ID. */
 189 #ifndef __UNIQUE_ID
 190 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 191 #endif
 192
 193 #include <uapi/linux/types.h>
 194
 195 static __always_inline void data_access_exceeds_word_size(void)
 196 #ifdef __compiletime_warning
 197 __compiletime_warning("data access exceeds word size and won't be atomic")
 198 #endif
 199 ;
 200
 201 static __always_inline void data_access_exceeds_word_size(void)
 202 {
 203 }
 204
 205 static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
 206 {
 207         switch (size) {
 208         case 1: *(__u8 *)res = *(volatile __u8 *)p; break;
 209         case 2: *(__u16 *)res = *(volatile __u16 *)p; break;
 210         case 4: *(__u32 *)res = *(volatile __u32 *)p; break;
 211 #ifdef CONFIG_64BIT
 212         case 8: *(__u64 *)res = *(volatile __u64 *)p; break;
 213 #endif
 214         default:
 215                 barrier();
 216                 __builtin_memcpy((void *)res, (const void *)p, size);
 217                 data_access_exceeds_word_size();
 218                 barrier();
 219         }
 220 }
 221
 222 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 223 {
 224         switch (size) {
 225         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
 226         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
 227         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
 228 #ifdef CONFIG_64BIT
 229         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
 230 #endif
 231         default:
 232                 barrier();
 233                 __builtin_memcpy((void *)p, (const void *)res, size);
 234                 data_access_exceeds_word_size();
 235                 barrier();
 236         }
 237 }
 238
 239 /*
 240  * Prevent the compiler from merging or refetching reads or writes. The
 241  * compiler is also forbidden from reordering successive instances of
 242  * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
 243  * compiler is aware of some particular ordering.  One way to make the
 244  * compiler aware of ordering is to put the two invocations of READ_ONCE,
 245  * WRITE_ONCE or ACCESS_ONCE() in different C statements.
 246  *
 247  * In contrast to ACCESS_ONCE these two macros will also work on aggregate
 248  * data types like structs or unions. If the size of the accessed data
 249  * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
 250  * READ_ONCE() and WRITE_ONCE()  will fall back to memcpy and print a
 251  * compile-time warning.
 252  *
 253  * Their two major use cases are: (1) Mediating communication between
 254  * process-level code and irq/NMI handlers, all running on the same CPU,
 255  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 256  * mutilate accesses that either do not require ordering or that interact
 257  * with an explicit memory barrier or atomic instruction that provides the
 258  * required ordering.
 259  */
 260
 261 #define READ_ONCE(x) \
 262         ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
 263
 264 #define WRITE_ONCE(x, val) \
 265         ({ typeof(x) __val = (val); __write_once_size(&(x), &__val, sizeof(__val)); __val; })
 266
 267 #endif /* __KERNEL__ */
 268
 269 #endif /* __ASSEMBLY__ */
 270
 271 #ifdef __KERNEL__
 272 /*
 273  * Allow us to mark functions as 'deprecated' and have gcc emit a nice
 274  * warning for each use, in hopes of speeding the functions removal.
 275  * Usage is:
 276  *              int __deprecated foo(void)
 277  */
 278 #ifndef __deprecated
 279 # define __deprecated           /* unimplemented */
 280 #endif
 281
 282 #ifdef MODULE
 283 #define __deprecated_for_modules __deprecated
 284 #else
 285 #define __deprecated_for_modules
 286 #endif
 287
 288 #ifndef __must_check
 289 #define __must_check
 290 #endif
 291
 292 #ifndef CONFIG_ENABLE_MUST_CHECK
 293 #undef __must_check
 294 #define __must_check
 295 #endif
 296 #ifndef CONFIG_ENABLE_WARN_DEPRECATED
 297 #undef __deprecated
 298 #undef __deprecated_for_modules
 299 #define __deprecated
 300 #define __deprecated_for_modules
 301 #endif
 302
 303 /*
 304  * Allow us to avoid 'defined but not used' warnings on functions and data,
 305  * as well as force them to be emitted to the assembly file.
 306  *
 307  * As of gcc 3.4, static functions that are not marked with attribute((used))
 308  * may be elided from the assembly file.  As of gcc 3.4, static data not so
 309  * marked will not be elided, but this may change in a future gcc version.
 310  *
 311  * NOTE: Because distributions shipped with a backported unit-at-a-time
 312  * compiler in gcc 3.3, we must define __used to be __attribute__((used))
 313  * for gcc >=3.3 instead of 3.4.
 314  *
 315  * In prior versions of gcc, such functions and data would be emitted, but
 316  * would be warned about except with attribute((unused)).
 317  *
 318  * Mark functions that are referenced only in inline assembly as __used so
 319  * the code is emitted even though it appears to be unreferenced.
 320  */
 321 #ifndef __used
 322 # define __used                 /* unimplemented */
 323 #endif
 324
 325 #ifndef __maybe_unused
 326 # define __maybe_unused         /* unimplemented */
 327 #endif
 328
 329 #ifndef __always_unused
 330 # define __always_unused        /* unimplemented */
 331 #endif
 332
 333 #ifndef noinline
 334 #define noinline
 335 #endif
 336
 337 /*
 338  * Rather then using noinline to prevent stack consumption, use
 339  * noinline_for_stack instead.  For documentation reasons.
 340  */
 341 #define noinline_for_stack noinline
 342
 343 #ifndef __always_inline
 344 #define __always_inline inline
 345 #endif
 346
 347 #endif /* __KERNEL__ */
 348
 349 /*
 350  * From the GCC manual:
 351  *
 352  * Many functions do not examine any values except their arguments,
 353  * and have no effects except the return value.  Basically this is
 354  * just slightly more strict class than the `pure' attribute above,
 355  * since function is not allowed to read global memory.
 356  *
 357  * Note that a function that has pointer arguments and examines the
 358  * data pointed to must _not_ be declared `const'.  Likewise, a
 359  * function that calls a non-`const' function usually must not be
 360  * `const'.  It does not make sense for a `const' function to return
 361  * `void'.
 362  */
 363 #ifndef __attribute_const__
 364 # define __attribute_const__    /* unimplemented */
 365 #endif
 366
 367 /*
 368  * Tell gcc if a function is cold. The compiler will assume any path
 369  * directly leading to the call is unlikely.
 370  */
 371
 372 #ifndef __cold
 373 #define __cold
 374 #endif
 375
 376 /* Simple shorthand for a section definition */
 377 #ifndef __section
 378 # define __section(S) __attribute__ ((__section__(#S)))
 379 #endif
 380
 381 #ifndef __visible
 382 #define __visible
 383 #endif
 384
 385 /* Are two types/vars the same type (ignoring qualifiers)? */
 386 #ifndef __same_type
 387 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 388 #endif
 389
 390 /* Is this type a native word size -- useful for atomic operations */
 391 #ifndef __native_word
 392 # define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 393 #endif
 394
 395 /* Compile time object size, -1 for unknown */
 396 #ifndef __compiletime_object_size
 397 # define __compiletime_object_size(obj) -1
 398 #endif
 399 #ifndef __compiletime_warning
 400 # define __compiletime_warning(message)
 401 #endif
 402 #ifndef __compiletime_error
 403 # define __compiletime_error(message)
 404 /*
 405  * Sparse complains of variable sized arrays due to the temporary variable in
 406  * __compiletime_assert. Unfortunately we can't just expand it out to make
 407  * sparse see a constant array size without breaking compiletime_assert on old
 408  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
 409  */
 410 # ifndef __CHECKER__
 411 #  define __compiletime_error_fallback(condition) \
 412         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 413 # endif
 414 #endif
 415 #ifndef __compiletime_error_fallback
 416 # define __compiletime_error_fallback(condition) do { } while (0)
 417 #endif
 418
 419 #define __compiletime_assert(condition, msg, prefix, suffix)            \
 420         do {                                                            \
 421                 bool __cond = !(condition);                             \
 422                 extern void prefix ## suffix(void) __compiletime_error(msg); \
 423                 if (__cond)                                             \
 424                         prefix ## suffix();                             \
 425                 __compiletime_error_fallback(__cond);                   \
 426         } while (0)
 427
 428 #define _compiletime_assert(condition, msg, prefix, suffix) \
 429         __compiletime_assert(condition, msg, prefix, suffix)
 430
 431 /**
 432  * compiletime_assert - break build and emit msg if condition is false
 433  * @condition: a compile-time constant condition to check
 434  * @msg:       a message to emit if condition is false
 435  *
 436  * In tradition of POSIX assert, this macro will break the build if the
 437  * supplied condition is *false*, emitting the supplied error message if the
 438  * compiler has support to do so.
 439  */
 440 #define compiletime_assert(condition, msg) \
 441         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 442
 443 #define compiletime_assert_atomic_type(t)                               \
 444         compiletime_assert(__native_word(t),                            \
 445                 "Need native word sized stores/loads for atomicity.")
 446
 447 /*
 448  * Prevent the compiler from merging or refetching accesses.  The compiler
 449  * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 450  * but only when the compiler is aware of some particular ordering.  One way
 451  * to make the compiler aware of ordering is to put the two invocations of
 452  * ACCESS_ONCE() in different C statements.
 453  *
 454  * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
 455  * on a union member will work as long as the size of the member matches the
 456  * size of the union and the size is smaller than word size.
 457  *
 458  * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
 459  * between process-level code and irq/NMI handlers, all running on the same CPU,
 460  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 461  * mutilate accesses that either do not require ordering or that interact
 462  * with an explicit memory barrier or atomic instruction that provides the
 463  * required ordering.
 464  *
 465  * If possible use READ_ONCE/ASSIGN_ONCE instead.
 466  */
 467 #define __ACCESS_ONCE(x) ({ \
 468          __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
 469         (volatile typeof(x) *)&(x); })
 470 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
 471
 472 /* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
 473 #ifdef CONFIG_KPROBES
 474 # define __kprobes      __attribute__((__section__(".kprobes.text")))
 475 # define nokprobe_inline        __always_inline
 476 #else
 477 # define __kprobes
 478 # define nokprobe_inline        inline
 479 #endif
 480 #endif /* __LINUX_COMPILER_H */