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 __force_user   __force __user
   9 # define __kernel       __attribute__((address_space(0)))
  10 # define __force_kernel __force __kernel
  11 # define __safe         __attribute__((safe))
  12 # define __force        __attribute__((force))
  13 # define __nocast       __attribute__((nocast))
  14 # define __iomem        __attribute__((noderef, address_space(2)))
  15 # define __force_iomem  __force __iomem
  16 # define __must_hold(x) __attribute__((context(x,1,1)))
  17 # define __acquires(x)  __attribute__((context(x,0,1)))
  18 # define __releases(x)  __attribute__((context(x,1,0)))
  19 # define __acquire(x)   __context__(x,1)
  20 # define __release(x)   __context__(x,-1)
  21 # define __cond_lock(x,c)       ((c) ? ({ __acquire(x); 1; }) : 0)
  22 # define __percpu       __attribute__((noderef, address_space(3)))
  23 # define __force_percpu __force __percpu
  24 #ifdef CONFIG_SPARSE_RCU_POINTER
  25 # define __rcu          __attribute__((noderef, address_space(4)))
  26 # define __force_rcu    __force __rcu
  27 #else
  28 # define __rcu
  29 # define __force_rcu
  30 #endif
  31 extern void __chk_user_ptr(const volatile void __user *);
  32 extern void __chk_io_ptr(const volatile void __iomem *);
  33 #else
  34 # ifdef CHECKER_PLUGIN
  35 //#  define __user
  36 //#  define __force_user
  37 //#  define __kernel
  38 //#  define __force_kernel
  39 # else
  40 #  ifdef STRUCTLEAK_PLUGIN
  41 #   define __user __attribute__((user))
  42 #  else
  43 #   define __user
  44 #  endif
  45 #  define __force_user
  46 #  define __kernel
  47 #  define __force_kernel
  48 # endif
  49 # define __safe
  50 # define __force
  51 # define __nocast
  52 # define __iomem
  53 # define __force_iomem
  54 # define __chk_user_ptr(x) (void)0
  55 # define __chk_io_ptr(x) (void)0
  56 # define __builtin_warning(x, y...) (1)
  57 # define __must_hold(x)
  58 # define __acquires(x)
  59 # define __releases(x)
  60 # define __acquire(x) (void)0
  61 # define __release(x) (void)0
  62 # define __cond_lock(x,c) (c)
  63 # define __percpu
  64 # define __force_percpu
  65 # define __rcu
  66 # define __force_rcu
  67 #endif
  68
  69 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
  70 #define ___PASTE(a,b) a##b
  71 #define __PASTE(a,b) ___PASTE(a,b)
  72
  73 #ifdef __KERNEL__
  74
  75 #ifdef __GNUC__
  76 #include <linux/compiler-gcc.h>
  77 #endif
  78
  79 #define notrace __attribute__((no_instrument_function))
  80
  81 /* Intel compiler defines __GNUC__. So we will overwrite implementations
  82  * coming from above header files here
  83  */
  84 #ifdef __INTEL_COMPILER
  85 # include <linux/compiler-intel.h>
  86 #endif
  87
  88 /* Clang compiler defines __GNUC__. So we will overwrite implementations
  89  * coming from above header files here
  90  */
  91 #ifdef __clang__
  92 #include <linux/compiler-clang.h>
  93 #endif
  94
  95 /*
  96  * Generic compiler-dependent macros required for kernel
  97  * build go below this comment. Actual compiler/compiler version
  98  * specific implementations come from the above header files
  99  */
 100
 101 struct ftrace_branch_data {
 102         const char *func;
 103         const char *file;
 104         unsigned line;
 105         union {
 106                 struct {
 107                         unsigned long correct;
 108                         unsigned long incorrect;
 109                 };
 110                 struct {
 111                         unsigned long miss;
 112                         unsigned long hit;
 113                 };
 114                 unsigned long miss_hit[2];
 115         };
 116 };
 117
 118 /*
 119  * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
 120  * to disable branch tracing on a per file basis.
 121  */
 122 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
 123     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
 124 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 125
 126 #define likely_notrace(x)       __builtin_expect(!!(x), 1)
 127 #define unlikely_notrace(x)     __builtin_expect(!!(x), 0)
 128
 129 #define __branch_check__(x, expect) ({                                  \
 130                         int ______r;                                    \
 131                         static struct ftrace_branch_data                \
 132                                 __attribute__((__aligned__(4)))         \
 133                                 __attribute__((section("_ftrace_annotated_branch"))) \
 134                                 ______f = {                             \
 135                                 .func = __func__,                       \
 136                                 .file = __FILE__,                       \
 137                                 .line = __LINE__,                       \
 138                         };                                              \
 139                         ______r = likely_notrace(x);                    \
 140                         ftrace_likely_update(&______f, ______r, expect); \
 141                         ______r;                                        \
 142                 })
 143
 144 /*
 145  * Using __builtin_constant_p(x) to ignore cases where the return
 146  * value is always the same.  This idea is taken from a similar patch
 147  * written by Daniel Walker.
 148  */
 149 # ifndef likely
 150 #  define likely(x)     (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1))
 151 # endif
 152 # ifndef unlikely
 153 #  define unlikely(x)   (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
 154 # endif
 155
 156 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 157 /*
 158  * "Define 'is'", Bill Clinton
 159  * "Define 'if'", Steven Rostedt
 160  */
 161 #define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
 162 #define __trace_if(cond) \
 163         if (__builtin_constant_p((cond)) ? !!(cond) :                   \
 164         ({                                                              \
 165                 int ______r;                                            \
 166                 static struct ftrace_branch_data                        \
 167                         __attribute__((__aligned__(4)))                 \
 168                         __attribute__((section("_ftrace_branch")))      \
 169                         ______f = {                                     \
 170                                 .func = __func__,                       \
 171                                 .file = __FILE__,                       \
 172                                 .line = __LINE__,                       \
 173                         };                                              \
 174                 ______r = !!(cond);                                     \
 175                 ______f.miss_hit[______r]++;                                    \
 176                 ______r;                                                \
 177         }))
 178 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
 179
 180 #else
 181 # define likely(x)      __builtin_expect(!!(x), 1)
 182 # define unlikely(x)    __builtin_expect(!!(x), 0)
 183 #endif
 184
 185 /* Optimization barrier */
 186 #ifndef barrier
 187 # define barrier() __memory_barrier()
 188 #endif
 189
 190 /* Unreachable code */
 191 #ifndef unreachable
 192 # define unreachable() do { } while (1)
 193 #endif
 194
 195 #ifndef RELOC_HIDE
 196 # define RELOC_HIDE(ptr, off)                                   \
 197   ({ unsigned long __ptr;                                       \
 198      __ptr = (unsigned long) (ptr);                             \
 199     (typeof(ptr)) (__ptr + (off)); })
 200 #endif
 201
 202 #ifndef OPTIMIZER_HIDE_VAR
 203 #define OPTIMIZER_HIDE_VAR(var) barrier()
 204 #endif
 205
 206 /* Not-quite-unique ID. */
 207 #ifndef __UNIQUE_ID
 208 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 209 #endif
 210
 211 #include <uapi/linux/types.h>
 212
 213 static __always_inline void data_access_exceeds_word_size(void)
 214 #ifdef __compiletime_warning
 215 __compiletime_warning("data access exceeds word size and won't be atomic")
 216 #endif
 217 ;
 218
 219 static __always_inline void data_access_exceeds_word_size(void)
 220 {
 221 }
 222
 223 static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
 224 {
 225         switch (size) {
 226         case 1: *(__u8 *)res = *(const volatile __u8 *)p; break;
 227         case 2: *(__u16 *)res = *(const volatile __u16 *)p; break;
 228         case 4: *(__u32 *)res = *(const volatile __u32 *)p; break;
 229 #ifdef CONFIG_64BIT
 230         case 8: *(__u64 *)res = *(const volatile __u64 *)p; break;
 231 #endif
 232         default:
 233                 barrier();
 234                 __builtin_memcpy(res, (const void *)p, size);
 235                 data_access_exceeds_word_size();
 236                 barrier();
 237         }
 238 }
 239
 240 static __always_inline void __write_once_size(volatile void *p, const void *res, int size)
 241 {
 242         switch (size) {
 243         case 1: *(volatile __u8 *)p = *(const __u8 *)res; break;
 244         case 2: *(volatile __u16 *)p = *(const __u16 *)res; break;
 245         case 4: *(volatile __u32 *)p = *(const __u32 *)res; break;
 246 #ifdef CONFIG_64BIT
 247         case 8: *(volatile __u64 *)p = *(const __u64 *)res; break;
 248 #endif
 249         default:
 250                 barrier();
 251                 __builtin_memcpy((void *)p, res, size);
 252                 data_access_exceeds_word_size();
 253                 barrier();
 254         }
 255 }
 256
 257 /*
 258  * Prevent the compiler from merging or refetching reads or writes. The
 259  * compiler is also forbidden from reordering successive instances of
 260  * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
 261  * compiler is aware of some particular ordering.  One way to make the
 262  * compiler aware of ordering is to put the two invocations of READ_ONCE,
 263  * WRITE_ONCE or ACCESS_ONCE() in different C statements.
 264  *
 265  * In contrast to ACCESS_ONCE these two macros will also work on aggregate
 266  * data types like structs or unions. If the size of the accessed data
 267  * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
 268  * READ_ONCE() and WRITE_ONCE()  will fall back to memcpy and print a
 269  * compile-time warning.
 270  *
 271  * Their two major use cases are: (1) Mediating communication between
 272  * process-level code and irq/NMI handlers, all running on the same CPU,
 273  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 274  * mutilate accesses that either do not require ordering or that interact
 275  * with an explicit memory barrier or atomic instruction that provides the
 276  * required ordering.
 277  */
 278
 279 #define READ_ONCE(x) \
 280         ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
 281
 282 #define WRITE_ONCE(x, val) \
 283         ({ typeof(x) __val = (val); __write_once_size(&(x), &__val, sizeof(__val)); __val; })
 284
 285 #endif /* __KERNEL__ */
 286
 287 #endif /* __ASSEMBLY__ */
 288
 289 #ifdef __KERNEL__
 290 /*
 291  * Allow us to mark functions as 'deprecated' and have gcc emit a nice
 292  * warning for each use, in hopes of speeding the functions removal.
 293  * Usage is:
 294  *              int __deprecated foo(void)
 295  */
 296 #ifndef __deprecated
 297 # define __deprecated           /* unimplemented */
 298 #endif
 299
 300 #ifdef MODULE
 301 #define __deprecated_for_modules __deprecated
 302 #else
 303 #define __deprecated_for_modules
 304 #endif
 305
 306 #ifndef __must_check
 307 #define __must_check
 308 #endif
 309
 310 #ifndef CONFIG_ENABLE_MUST_CHECK
 311 #undef __must_check
 312 #define __must_check
 313 #endif
 314 #ifndef CONFIG_ENABLE_WARN_DEPRECATED
 315 #undef __deprecated
 316 #undef __deprecated_for_modules
 317 #define __deprecated
 318 #define __deprecated_for_modules
 319 #endif
 320
 321 /*
 322  * Allow us to avoid 'defined but not used' warnings on functions and data,
 323  * as well as force them to be emitted to the assembly file.
 324  *
 325  * As of gcc 3.4, static functions that are not marked with attribute((used))
 326  * may be elided from the assembly file.  As of gcc 3.4, static data not so
 327  * marked will not be elided, but this may change in a future gcc version.
 328  *
 329  * NOTE: Because distributions shipped with a backported unit-at-a-time
 330  * compiler in gcc 3.3, we must define __used to be __attribute__((used))
 331  * for gcc >=3.3 instead of 3.4.
 332  *
 333  * In prior versions of gcc, such functions and data would be emitted, but
 334  * would be warned about except with attribute((unused)).
 335  *
 336  * Mark functions that are referenced only in inline assembly as __used so
 337  * the code is emitted even though it appears to be unreferenced.
 338  */
 339 #ifndef __used
 340 # define __used                 /* unimplemented */
 341 #endif
 342
 343 #ifndef __maybe_unused
 344 # define __maybe_unused         /* unimplemented */
 345 #endif
 346
 347 #ifndef __always_unused
 348 # define __always_unused        /* unimplemented */
 349 #endif
 350
 351 #ifndef noinline
 352 #define noinline
 353 #endif
 354
 355 /*
 356  * Rather then using noinline to prevent stack consumption, use
 357  * noinline_for_stack instead.  For documentation reasons.
 358  */
 359 #define noinline_for_stack noinline
 360
 361 #ifndef __always_inline
 362 #define __always_inline inline
 363 #endif
 364
 365 #endif /* __KERNEL__ */
 366
 367 /*
 368  * From the GCC manual:
 369  *
 370  * Many functions do not examine any values except their arguments,
 371  * and have no effects except the return value.  Basically this is
 372  * just slightly more strict class than the `pure' attribute above,
 373  * since function is not allowed to read global memory.
 374  *
 375  * Note that a function that has pointer arguments and examines the
 376  * data pointed to must _not_ be declared `const'.  Likewise, a
 377  * function that calls a non-`const' function usually must not be
 378  * `const'.  It does not make sense for a `const' function to return
 379  * `void'.
 380  */
 381 #ifndef __attribute_const__
 382 # define __attribute_const__    /* unimplemented */
 383 #endif
 384
 385 #ifndef __randomize_layout
 386 # define __randomize_layout
 387 #endif
 388
 389 #ifndef __no_randomize_layout
 390 # define __no_randomize_layout
 391 #endif
 392
 393 #ifndef __no_const
 394 # define __no_const
 395 #endif
 396
 397 #ifndef __do_const
 398 # define __do_const
 399 #endif
 400
 401 #ifndef __size_overflow
 402 # define __size_overflow(...)
 403 #endif
 404
 405 #ifndef __intentional_overflow
 406 # define __intentional_overflow(...)
 407 #endif
 408
 409 #ifndef __latent_entropy
 410 # define __latent_entropy
 411 #endif
 412
 413 /*
 414  * Tell gcc if a function is cold. The compiler will assume any path
 415  * directly leading to the call is unlikely.
 416  */
 417
 418 #ifndef __cold
 419 #define __cold
 420 #endif
 421
 422 #ifndef __alloc_size
 423 #define __alloc_size(...)
 424 #endif
 425
 426 #ifndef __bos
 427 #define __bos(ptr, arg)
 428 #endif
 429
 430 #ifndef __bos0
 431 #define __bos0(ptr)
 432 #endif
 433
 434 #ifndef __bos1
 435 #define __bos1(ptr)
 436 #endif
 437
 438 /* Simple shorthand for a section definition */
 439 #ifndef __section
 440 # define __section(S) __attribute__ ((__section__(#S)))
 441 #endif
 442
 443 #ifndef __visible
 444 #define __visible
 445 #endif
 446
 447 /* Are two types/vars the same type (ignoring qualifiers)? */
 448 #ifndef __same_type
 449 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 450 #endif
 451
 452 /* Is this type a native word size -- useful for atomic operations */
 453 #ifndef __native_word
 454 # define __native_word(t) (sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 455 #endif
 456
 457 /* Compile time object size, -1 for unknown */
 458 #ifndef __compiletime_object_size
 459 # define __compiletime_object_size(obj) -1
 460 #endif
 461 #ifndef __compiletime_warning
 462 # define __compiletime_warning(message)
 463 #endif
 464 #ifndef __compiletime_error
 465 # define __compiletime_error(message)
 466 /*
 467  * Sparse complains of variable sized arrays due to the temporary variable in
 468  * __compiletime_assert. Unfortunately we can't just expand it out to make
 469  * sparse see a constant array size without breaking compiletime_assert on old
 470  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
 471  */
 472 # ifndef __CHECKER__
 473 #  define __compiletime_error_fallback(condition) \
 474         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 475 # endif
 476 #endif
 477 #ifndef __compiletime_error_fallback
 478 # define __compiletime_error_fallback(condition) do { } while (0)
 479 #endif
 480
 481 #define __compiletime_assert(condition, msg, prefix, suffix)            \
 482         do {                                                            \
 483                 bool __cond = !(condition);                             \
 484                 extern void prefix ## suffix(void) __compiletime_error(msg); \
 485                 if (__cond)                                             \
 486                         prefix ## suffix();                             \
 487                 __compiletime_error_fallback(__cond);                   \
 488         } while (0)
 489
 490 #define _compiletime_assert(condition, msg, prefix, suffix) \
 491         __compiletime_assert(condition, msg, prefix, suffix)
 492
 493 /**
 494  * compiletime_assert - break build and emit msg if condition is false
 495  * @condition: a compile-time constant condition to check
 496  * @msg:       a message to emit if condition is false
 497  *
 498  * In tradition of POSIX assert, this macro will break the build if the
 499  * supplied condition is *false*, emitting the supplied error message if the
 500  * compiler has support to do so.
 501  */
 502 #define compiletime_assert(condition, msg) \
 503         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 504
 505 #define compiletime_assert_atomic_type(t)                               \
 506         compiletime_assert(__native_word(t),                            \
 507                 "Need native word sized stores/loads for atomicity.")
 508
 509 /*
 510  * Prevent the compiler from merging or refetching accesses.  The compiler
 511  * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 512  * but only when the compiler is aware of some particular ordering.  One way
 513  * to make the compiler aware of ordering is to put the two invocations of
 514  * ACCESS_ONCE() in different C statements.
 515  *
 516  * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
 517  * on a union member will work as long as the size of the member matches the
 518  * size of the union and the size is smaller than word size.
 519  *
 520  * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
 521  * between process-level code and irq/NMI handlers, all running on the same CPU,
 522  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 523  * mutilate accesses that either do not require ordering or that interact
 524  * with an explicit memory barrier or atomic instruction that provides the
 525  * required ordering.
 526  *
 527  * If possible use READ_ONCE/ASSIGN_ONCE instead.
 528  */
 529 #define __ACCESS_ONCE(x) ({ \
 530          __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
 531         (volatile const typeof(x) *)&(x); })
 532 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
 533 #define ACCESS_ONCE_RW(x) (*(volatile typeof(x) *)&(x))
 534
 535 /* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
 536 #ifdef CONFIG_KPROBES
 537 # define __kprobes      __attribute__((__section__(".kprobes.text")))
 538 # define nokprobe_inline        __always_inline
 539 #else
 540 # define __kprobes
 541 # define nokprobe_inline        inline
 542 #endif
 543 #endif /* __LINUX_COMPILER_H */