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