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 # define __rcu          __attribute__((noderef, address_space(4)))
  21 # define __private      __attribute__((noderef))
  22 extern void __chk_user_ptr(const volatile void __user *);
  23 extern void __chk_io_ptr(const volatile void __iomem *);
  24 # define ACCESS_PRIVATE(p, member) (*((typeof((p)->member) __force *) &(p)->member))
  25 #else /* __CHECKER__ */
  26 # ifdef STRUCTLEAK_PLUGIN
  27 #  define __user __attribute__((user))
  28 # else
  29 #  define __user
  30 # endif
  31 # define __kernel
  32 # define __safe
  33 # define __force
  34 # define __nocast
  35 # define __iomem
  36 # define __chk_user_ptr(x) (void)0
  37 # define __chk_io_ptr(x) (void)0
  38 # define __builtin_warning(x, y...) (1)
  39 # define __must_hold(x)
  40 # define __acquires(x)
  41 # define __releases(x)
  42 # define __acquire(x) (void)0
  43 # define __release(x) (void)0
  44 # define __cond_lock(x,c) (c)
  45 # define __percpu
  46 # define __rcu
  47 # define __private
  48 # define ACCESS_PRIVATE(p, member) ((p)->member)
  49 #endif /* __CHECKER__ */
  50
  51 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
  52 #define ___PASTE(a,b) a##b
  53 #define __PASTE(a,b) ___PASTE(a,b)
  54
  55 #ifdef __KERNEL__
  56
  57 #ifdef __GNUC__
  58 #include <linux/compiler-gcc.h>
  59 #endif
  60
  61 #if defined(CC_USING_HOTPATCH) && !defined(__CHECKER__)
  62 #define notrace __attribute__((hotpatch(0,0)))
  63 #else
  64 #define notrace __attribute__((no_instrument_function))
  65 #endif
  66
  67 /* Intel compiler defines __GNUC__. So we will overwrite implementations
  68  * coming from above header files here
  69  */
  70 #ifdef __INTEL_COMPILER
  71 # include <linux/compiler-intel.h>
  72 #endif
  73
  74 /* Clang compiler defines __GNUC__. So we will overwrite implementations
  75  * coming from above header files here
  76  */
  77 #ifdef __clang__
  78 #include <linux/compiler-clang.h>
  79 #endif
  80
  81 /*
  82  * Generic compiler-dependent macros required for kernel
  83  * build go below this comment. Actual compiler/compiler version
  84  * specific implementations come from the above header files
  85  */
  86
  87 struct ftrace_branch_data {
  88         const char *func;
  89         const char *file;
  90         unsigned line;
  91         union {
  92                 struct {
  93                         unsigned long correct;
  94                         unsigned long incorrect;
  95                 };
  96                 struct {
  97                         unsigned long miss;
  98                         unsigned long hit;
  99                 };
 100                 unsigned long miss_hit[2];
 101         };
 102 };
 103
 104 struct ftrace_likely_data {
 105         struct ftrace_branch_data       data;
 106         unsigned long                   constant;
 107 };
 108
 109 /*
 110  * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
 111  * to disable branch tracing on a per file basis.
 112  */
 113 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
 114     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
 115 void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 116                           int expect, int is_constant);
 117
 118 #define likely_notrace(x)       __builtin_expect(!!(x), 1)
 119 #define unlikely_notrace(x)     __builtin_expect(!!(x), 0)
 120
 121 #define __branch_check__(x, expect, is_constant) ({                     \
 122                         int ______r;                                    \
 123                         static struct ftrace_likely_data                \
 124                                 __attribute__((__aligned__(4)))         \
 125                                 __attribute__((section("_ftrace_annotated_branch"))) \
 126                                 ______f = {                             \
 127                                 .data.func = __func__,                  \
 128                                 .data.file = __FILE__,                  \
 129                                 .data.line = __LINE__,                  \
 130                         };                                              \
 131                         ______r = __builtin_expect(!!(x), expect);      \
 132                         ftrace_likely_update(&______f, ______r,         \
 133                                              expect, is_constant);      \
 134                         ______r;                                        \
 135                 })
 136
 137 /*
 138  * Using __builtin_constant_p(x) to ignore cases where the return
 139  * value is always the same.  This idea is taken from a similar patch
 140  * written by Daniel Walker.
 141  */
 142 # ifndef likely
 143 #  define likely(x)     (__branch_check__(x, 1, __builtin_constant_p(x)))
 144 # endif
 145 # ifndef unlikely
 146 #  define unlikely(x)   (__branch_check__(x, 0, __builtin_constant_p(x)))
 147 # endif
 148
 149 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 150 /*
 151  * "Define 'is'", Bill Clinton
 152  * "Define 'if'", Steven Rostedt
 153  */
 154 #define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
 155 #define __trace_if(cond) \
 156         if (__builtin_constant_p(!!(cond)) ? !!(cond) :                 \
 157         ({                                                              \
 158                 int ______r;                                            \
 159                 static struct ftrace_branch_data                        \
 160                         __attribute__((__aligned__(4)))                 \
 161                         __attribute__((section("_ftrace_branch")))      \
 162                         ______f = {                                     \
 163                                 .func = __func__,                       \
 164                                 .file = __FILE__,                       \
 165                                 .line = __LINE__,                       \
 166                         };                                              \
 167                 ______r = !!(cond);                                     \
 168                 ______f.miss_hit[______r]++;                                    \
 169                 ______r;                                                \
 170         }))
 171 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
 172
 173 #else
 174 # define likely(x)      __builtin_expect(!!(x), 1)
 175 # define unlikely(x)    __builtin_expect(!!(x), 0)
 176 #endif
 177
 178 /* Optimization barrier */
 179 #ifndef barrier
 180 # define barrier() __memory_barrier()
 181 #endif
 182
 183 #ifndef barrier_data
 184 # define barrier_data(ptr) barrier()
 185 #endif
 186
 187 /* Unreachable code */
 188 #ifndef unreachable
 189 # define unreachable() do { } while (1)
 190 #endif
 191
 192 /*
 193  * KENTRY - kernel entry point
 194  * This can be used to annotate symbols (functions or data) that are used
 195  * without their linker symbol being referenced explicitly. For example,
 196  * interrupt vector handlers, or functions in the kernel image that are found
 197  * programatically.
 198  *
 199  * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
 200  * are handled in their own way (with KEEP() in linker scripts).
 201  *
 202  * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
 203  * linker script. For example an architecture could KEEP() its entire
 204  * boot/exception vector code rather than annotate each function and data.
 205  */
 206 #ifndef KENTRY
 207 # define KENTRY(sym)                                            \
 208         extern typeof(sym) sym;                                 \
 209         static const unsigned long __kentry_##sym               \
 210         __used                                                  \
 211         __attribute__((section("___kentry" "+" #sym ), used))   \
 212         = (unsigned long)&sym;
 213 #endif
 214
 215 #ifndef RELOC_HIDE
 216 # define RELOC_HIDE(ptr, off)                                   \
 217   ({ unsigned long __ptr;                                       \
 218      __ptr = (unsigned long) (ptr);                             \
 219     (typeof(ptr)) (__ptr + (off)); })
 220 #endif
 221
 222 #ifndef OPTIMIZER_HIDE_VAR
 223 #define OPTIMIZER_HIDE_VAR(var) barrier()
 224 #endif
 225
 226 /* Not-quite-unique ID. */
 227 #ifndef __UNIQUE_ID
 228 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 229 #endif
 230
 231 #include <uapi/linux/types.h>
 232
 233 #define __READ_ONCE_SIZE                                                \
 234 ({                                                                      \
 235         switch (size) {                                                 \
 236         case 1: *(__u8 *)res = *(volatile __u8 *)p; break;              \
 237         case 2: *(__u16 *)res = *(volatile __u16 *)p; break;            \
 238         case 4: *(__u32 *)res = *(volatile __u32 *)p; break;            \
 239         case 8: *(__u64 *)res = *(volatile __u64 *)p; break;            \
 240         default:                                                        \
 241                 barrier();                                              \
 242                 __builtin_memcpy((void *)res, (const void *)p, size);   \
 243                 barrier();                                              \
 244         }                                                               \
 245 })
 246
 247 static __always_inline
 248 void __read_once_size(const volatile void *p, void *res, int size)
 249 {
 250         __READ_ONCE_SIZE;
 251 }
 252
 253 #ifdef CONFIG_KASAN
 254 /*
 255  * This function is not 'inline' because __no_sanitize_address confilcts
 256  * with inlining. Attempt to inline it may cause a build failure.
 257  *      https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
 258  * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
 259  */
 260 static __no_sanitize_address __maybe_unused
 261 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
 262 {
 263         __READ_ONCE_SIZE;
 264 }
 265 #else
 266 static __always_inline
 267 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
 268 {
 269         __READ_ONCE_SIZE;
 270 }
 271 #endif
 272
 273 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 274 {
 275         switch (size) {
 276         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
 277         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
 278         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
 279         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
 280         default:
 281                 barrier();
 282                 __builtin_memcpy((void *)p, (const void *)res, size);
 283                 barrier();
 284         }
 285 }
 286
 287 /*
 288  * Prevent the compiler from merging or refetching reads or writes. The
 289  * compiler is also forbidden from reordering successive instances of
 290  * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
 291  * compiler is aware of some particular ordering.  One way to make the
 292  * compiler aware of ordering is to put the two invocations of READ_ONCE,
 293  * WRITE_ONCE or ACCESS_ONCE() in different C statements.
 294  *
 295  * In contrast to ACCESS_ONCE these two macros will also work on aggregate
 296  * data types like structs or unions. If the size of the accessed data
 297  * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
 298  * READ_ONCE() and WRITE_ONCE() will fall back to memcpy(). There's at
 299  * least two memcpy()s: one for the __builtin_memcpy() and then one for
 300  * the macro doing the copy of variable - '__u' allocated on the stack.
 301  *
 302  * Their two major use cases are: (1) Mediating communication between
 303  * process-level code and irq/NMI handlers, all running on the same CPU,
 304  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 305  * mutilate accesses that either do not require ordering or that interact
 306  * with an explicit memory barrier or atomic instruction that provides the
 307  * required ordering.
 308  */
 309
 310 #define __READ_ONCE(x, check)                                           \
 311 ({                                                                      \
 312         union { typeof(x) __val; char __c[1]; } __u;                    \
 313         if (check)                                                      \
 314                 __read_once_size(&(x), __u.__c, sizeof(x));             \
 315         else                                                            \
 316                 __read_once_size_nocheck(&(x), __u.__c, sizeof(x));     \
 317         smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
 318         __u.__val;                                                      \
 319 })
 320 #define READ_ONCE(x) __READ_ONCE(x, 1)
 321
 322 /*
 323  * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
 324  * to hide memory access from KASAN.
 325  */
 326 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
 327
 328 #define WRITE_ONCE(x, val) \
 329 ({                                                      \
 330         union { typeof(x) __val; char __c[1]; } __u =   \
 331                 { .__val = (__force typeof(x)) (val) }; \
 332         __write_once_size(&(x), __u.__c, sizeof(x));    \
 333         __u.__val;                                      \
 334 })
 335
 336 #endif /* __KERNEL__ */
 337
 338 #endif /* __ASSEMBLY__ */
 339
 340 #ifdef __KERNEL__
 341 /*
 342  * Allow us to mark functions as 'deprecated' and have gcc emit a nice
 343  * warning for each use, in hopes of speeding the functions removal.
 344  * Usage is:
 345  *              int __deprecated foo(void)
 346  */
 347 #ifndef __deprecated
 348 # define __deprecated           /* unimplemented */
 349 #endif
 350
 351 #ifdef MODULE
 352 #define __deprecated_for_modules __deprecated
 353 #else
 354 #define __deprecated_for_modules
 355 #endif
 356
 357 #ifndef __must_check
 358 #define __must_check
 359 #endif
 360
 361 #ifndef CONFIG_ENABLE_MUST_CHECK
 362 #undef __must_check
 363 #define __must_check
 364 #endif
 365 #ifndef CONFIG_ENABLE_WARN_DEPRECATED
 366 #undef __deprecated
 367 #undef __deprecated_for_modules
 368 #define __deprecated
 369 #define __deprecated_for_modules
 370 #endif
 371
 372 #ifndef __malloc
 373 #define __malloc
 374 #endif
 375
 376 /*
 377  * Allow us to avoid 'defined but not used' warnings on functions and data,
 378  * as well as force them to be emitted to the assembly file.
 379  *
 380  * As of gcc 3.4, static functions that are not marked with attribute((used))
 381  * may be elided from the assembly file.  As of gcc 3.4, static data not so
 382  * marked will not be elided, but this may change in a future gcc version.
 383  *
 384  * NOTE: Because distributions shipped with a backported unit-at-a-time
 385  * compiler in gcc 3.3, we must define __used to be __attribute__((used))
 386  * for gcc >=3.3 instead of 3.4.
 387  *
 388  * In prior versions of gcc, such functions and data would be emitted, but
 389  * would be warned about except with attribute((unused)).
 390  *
 391  * Mark functions that are referenced only in inline assembly as __used so
 392  * the code is emitted even though it appears to be unreferenced.
 393  */
 394 #ifndef __used
 395 # define __used                 /* unimplemented */
 396 #endif
 397
 398 #ifndef __maybe_unused
 399 # define __maybe_unused         /* unimplemented */
 400 #endif
 401
 402 #ifndef __always_unused
 403 # define __always_unused        /* unimplemented */
 404 #endif
 405
 406 #ifndef noinline
 407 #define noinline
 408 #endif
 409
 410 /*
 411  * Rather then using noinline to prevent stack consumption, use
 412  * noinline_for_stack instead.  For documentation reasons.
 413  */
 414 #define noinline_for_stack noinline
 415
 416 #ifndef __always_inline
 417 #define __always_inline inline
 418 #endif
 419
 420 #endif /* __KERNEL__ */
 421
 422 /*
 423  * From the GCC manual:
 424  *
 425  * Many functions do not examine any values except their arguments,
 426  * and have no effects except the return value.  Basically this is
 427  * just slightly more strict class than the `pure' attribute above,
 428  * since function is not allowed to read global memory.
 429  *
 430  * Note that a function that has pointer arguments and examines the
 431  * data pointed to must _not_ be declared `const'.  Likewise, a
 432  * function that calls a non-`const' function usually must not be
 433  * `const'.  It does not make sense for a `const' function to return
 434  * `void'.
 435  */
 436 #ifndef __attribute_const__
 437 # define __attribute_const__    /* unimplemented */
 438 #endif
 439
 440 #ifndef __designated_init
 441 # define __designated_init
 442 #endif
 443
 444 #ifndef __latent_entropy
 445 # define __latent_entropy
 446 #endif
 447
 448 #ifndef __randomize_layout
 449 # define __randomize_layout __designated_init
 450 #endif
 451
 452 #ifndef __no_randomize_layout
 453 # define __no_randomize_layout
 454 #endif
 455
 456 #ifndef randomized_struct_fields_start
 457 # define randomized_struct_fields_start
 458 # define randomized_struct_fields_end
 459 #endif
 460
 461 /*
 462  * Tell gcc if a function is cold. The compiler will assume any path
 463  * directly leading to the call is unlikely.
 464  */
 465
 466 #ifndef __cold
 467 #define __cold
 468 #endif
 469
 470 /* Simple shorthand for a section definition */
 471 #ifndef __section
 472 # define __section(S) __attribute__ ((__section__(#S)))
 473 #endif
 474
 475 #ifndef __visible
 476 #define __visible
 477 #endif
 478
 479 /*
 480  * Assume alignment of return value.
 481  */
 482 #ifndef __assume_aligned
 483 #define __assume_aligned(a, ...)
 484 #endif
 485
 486
 487 /* Are two types/vars the same type (ignoring qualifiers)? */
 488 #ifndef __same_type
 489 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 490 #endif
 491
 492 /* Is this type a native word size -- useful for atomic operations */
 493 #ifndef __native_word
 494 # define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 495 #endif
 496
 497 /* Compile time object size, -1 for unknown */
 498 #ifndef __compiletime_object_size
 499 # define __compiletime_object_size(obj) -1
 500 #endif
 501 #ifndef __compiletime_warning
 502 # define __compiletime_warning(message)
 503 #endif
 504 #ifndef __compiletime_error
 505 # define __compiletime_error(message)
 506 /*
 507  * Sparse complains of variable sized arrays due to the temporary variable in
 508  * __compiletime_assert. Unfortunately we can't just expand it out to make
 509  * sparse see a constant array size without breaking compiletime_assert on old
 510  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
 511  */
 512 # ifndef __CHECKER__
 513 #  define __compiletime_error_fallback(condition) \
 514         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 515 # endif
 516 #endif
 517 #ifndef __compiletime_error_fallback
 518 # define __compiletime_error_fallback(condition) do { } while (0)
 519 #endif
 520
 521 #ifdef __OPTIMIZE__
 522 # define __compiletime_assert(condition, msg, prefix, suffix)           \
 523         do {                                                            \
 524                 bool __cond = !(condition);                             \
 525                 extern void prefix ## suffix(void) __compiletime_error(msg); \
 526                 if (__cond)                                             \
 527                         prefix ## suffix();                             \
 528                 __compiletime_error_fallback(__cond);                   \
 529         } while (0)
 530 #else
 531 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
 532 #endif
 533
 534 #define _compiletime_assert(condition, msg, prefix, suffix) \
 535         __compiletime_assert(condition, msg, prefix, suffix)
 536
 537 /**
 538  * compiletime_assert - break build and emit msg if condition is false
 539  * @condition: a compile-time constant condition to check
 540  * @msg:       a message to emit if condition is false
 541  *
 542  * In tradition of POSIX assert, this macro will break the build if the
 543  * supplied condition is *false*, emitting the supplied error message if the
 544  * compiler has support to do so.
 545  */
 546 #define compiletime_assert(condition, msg) \
 547         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 548
 549 #define compiletime_assert_atomic_type(t)                               \
 550         compiletime_assert(__native_word(t),                            \
 551                 "Need native word sized stores/loads for atomicity.")
 552
 553 /*
 554  * Prevent the compiler from merging or refetching accesses.  The compiler
 555  * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 556  * but only when the compiler is aware of some particular ordering.  One way
 557  * to make the compiler aware of ordering is to put the two invocations of
 558  * ACCESS_ONCE() in different C statements.
 559  *
 560  * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
 561  * on a union member will work as long as the size of the member matches the
 562  * size of the union and the size is smaller than word size.
 563  *
 564  * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
 565  * between process-level code and irq/NMI handlers, all running on the same CPU,
 566  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 567  * mutilate accesses that either do not require ordering or that interact
 568  * with an explicit memory barrier or atomic instruction that provides the
 569  * required ordering.
 570  *
 571  * If possible use READ_ONCE()/WRITE_ONCE() instead.
 572  */
 573 #define __ACCESS_ONCE(x) ({ \
 574          __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
 575         (volatile typeof(x) *)&(x); })
 576 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
 577
 578 /**
 579  * lockless_dereference() - safely load a pointer for later dereference
 580  * @p: The pointer to load
 581  *
 582  * Similar to rcu_dereference(), but for situations where the pointed-to
 583  * object's lifetime is managed by something other than RCU.  That
 584  * "something other" might be reference counting or simple immortality.
 585  *
 586  * The seemingly unused variable ___typecheck_p validates that @p is
 587  * indeed a pointer type by using a pointer to typeof(*p) as the type.
 588  * Taking a pointer to typeof(*p) again is needed in case p is void *.
 589  */
 590 #define lockless_dereference(p) \
 591 ({ \
 592         typeof(p) _________p1 = READ_ONCE(p); \
 593         typeof(*(p)) *___typecheck_p __maybe_unused; \
 594         smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
 595         (_________p1); \
 596 })
 597
 598 #endif /* __LINUX_COMPILER_H */