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 #ifdef CONFIG_STACK_VALIDATION
 189 #define annotate_reachable() ({                                         \
 190         asm("%c0:\n\t"                                                  \
 191             ".pushsection .discard.reachable\n\t"                       \
 192             ".long %c0b - .\n\t"                                        \
 193             ".popsection\n\t" : : "i" (__LINE__));                      \
 194 })
 195 #define annotate_unreachable() ({                                       \
 196         asm("%c0:\n\t"                                                  \
 197             ".pushsection .discard.unreachable\n\t"                     \
 198             ".long %c0b - .\n\t"                                        \
 199             ".popsection\n\t" : : "i" (__LINE__));                      \
 200 })
 201 #define ASM_UNREACHABLE                                                 \
 202         "999:\n\t"                                                      \
 203         ".pushsection .discard.unreachable\n\t"                         \
 204         ".long 999b - .\n\t"                                            \
 205         ".popsection\n\t"
 206 #else
 207 #define annotate_reachable()
 208 #define annotate_unreachable()
 209 #endif
 210
 211 #ifndef ASM_UNREACHABLE
 212 # define ASM_UNREACHABLE
 213 #endif
 214 #ifndef unreachable
 215 # define unreachable() do { annotate_reachable(); do { } while (1); } while (0)
 216 #endif
 217
 218 /*
 219  * KENTRY - kernel entry point
 220  * This can be used to annotate symbols (functions or data) that are used
 221  * without their linker symbol being referenced explicitly. For example,
 222  * interrupt vector handlers, or functions in the kernel image that are found
 223  * programatically.
 224  *
 225  * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
 226  * are handled in their own way (with KEEP() in linker scripts).
 227  *
 228  * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
 229  * linker script. For example an architecture could KEEP() its entire
 230  * boot/exception vector code rather than annotate each function and data.
 231  */
 232 #ifndef KENTRY
 233 # define KENTRY(sym)                                            \
 234         extern typeof(sym) sym;                                 \
 235         static const unsigned long __kentry_##sym               \
 236         __used                                                  \
 237         __attribute__((section("___kentry" "+" #sym ), used))   \
 238         = (unsigned long)&sym;
 239 #endif
 240
 241 #ifndef RELOC_HIDE
 242 # define RELOC_HIDE(ptr, off)                                   \
 243   ({ unsigned long __ptr;                                       \
 244      __ptr = (unsigned long) (ptr);                             \
 245     (typeof(ptr)) (__ptr + (off)); })
 246 #endif
 247
 248 #ifndef OPTIMIZER_HIDE_VAR
 249 #define OPTIMIZER_HIDE_VAR(var) barrier()
 250 #endif
 251
 252 /* Not-quite-unique ID. */
 253 #ifndef __UNIQUE_ID
 254 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 255 #endif
 256
 257 #include <uapi/linux/types.h>
 258
 259 #define __READ_ONCE_SIZE                                                \
 260 ({                                                                      \
 261         switch (size) {                                                 \
 262         case 1: *(__u8 *)res = *(volatile __u8 *)p; break;              \
 263         case 2: *(__u16 *)res = *(volatile __u16 *)p; break;            \
 264         case 4: *(__u32 *)res = *(volatile __u32 *)p; break;            \
 265         case 8: *(__u64 *)res = *(volatile __u64 *)p; break;            \
 266         default:                                                        \
 267                 barrier();                                              \
 268                 __builtin_memcpy((void *)res, (const void *)p, size);   \
 269                 barrier();                                              \
 270         }                                                               \
 271 })
 272
 273 static __always_inline
 274 void __read_once_size(const volatile void *p, void *res, int size)
 275 {
 276         __READ_ONCE_SIZE;
 277 }
 278
 279 #ifdef CONFIG_KASAN
 280 /*
 281  * This function is not 'inline' because __no_sanitize_address confilcts
 282  * with inlining. Attempt to inline it may cause a build failure.
 283  *      https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
 284  * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
 285  */
 286 static __no_sanitize_address __maybe_unused
 287 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
 288 {
 289         __READ_ONCE_SIZE;
 290 }
 291 #else
 292 static __always_inline
 293 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
 294 {
 295         __READ_ONCE_SIZE;
 296 }
 297 #endif
 298
 299 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 300 {
 301         switch (size) {
 302         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
 303         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
 304         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
 305         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
 306         default:
 307                 barrier();
 308                 __builtin_memcpy((void *)p, (const void *)res, size);
 309                 barrier();
 310         }
 311 }
 312
 313 /*
 314  * Prevent the compiler from merging or refetching reads or writes. The
 315  * compiler is also forbidden from reordering successive instances of
 316  * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
 317  * compiler is aware of some particular ordering.  One way to make the
 318  * compiler aware of ordering is to put the two invocations of READ_ONCE,
 319  * WRITE_ONCE or ACCESS_ONCE() in different C statements.
 320  *
 321  * In contrast to ACCESS_ONCE these two macros will also work on aggregate
 322  * data types like structs or unions. If the size of the accessed data
 323  * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
 324  * READ_ONCE() and WRITE_ONCE() will fall back to memcpy(). There's at
 325  * least two memcpy()s: one for the __builtin_memcpy() and then one for
 326  * the macro doing the copy of variable - '__u' allocated on the stack.
 327  *
 328  * Their two major use cases are: (1) Mediating communication between
 329  * process-level code and irq/NMI handlers, all running on the same CPU,
 330  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 331  * mutilate accesses that either do not require ordering or that interact
 332  * with an explicit memory barrier or atomic instruction that provides the
 333  * required ordering.
 334  */
 335
 336 #define __READ_ONCE(x, check)                                           \
 337 ({                                                                      \
 338         union { typeof(x) __val; char __c[1]; } __u;                    \
 339         if (check)                                                      \
 340                 __read_once_size(&(x), __u.__c, sizeof(x));             \
 341         else                                                            \
 342                 __read_once_size_nocheck(&(x), __u.__c, sizeof(x));     \
 343         __u.__val;                                                      \
 344 })
 345 #define READ_ONCE(x) __READ_ONCE(x, 1)
 346
 347 /*
 348  * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
 349  * to hide memory access from KASAN.
 350  */
 351 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
 352
 353 #define WRITE_ONCE(x, val) \
 354 ({                                                      \
 355         union { typeof(x) __val; char __c[1]; } __u =   \
 356                 { .__val = (__force typeof(x)) (val) }; \
 357         __write_once_size(&(x), __u.__c, sizeof(x));    \
 358         __u.__val;                                      \
 359 })
 360
 361 #endif /* __KERNEL__ */
 362
 363 #endif /* __ASSEMBLY__ */
 364
 365 #ifdef __KERNEL__
 366 /*
 367  * Allow us to mark functions as 'deprecated' and have gcc emit a nice
 368  * warning for each use, in hopes of speeding the functions removal.
 369  * Usage is:
 370  *              int __deprecated foo(void)
 371  */
 372 #ifndef __deprecated
 373 # define __deprecated           /* unimplemented */
 374 #endif
 375
 376 #ifdef MODULE
 377 #define __deprecated_for_modules __deprecated
 378 #else
 379 #define __deprecated_for_modules
 380 #endif
 381
 382 #ifndef __must_check
 383 #define __must_check
 384 #endif
 385
 386 #ifndef CONFIG_ENABLE_MUST_CHECK
 387 #undef __must_check
 388 #define __must_check
 389 #endif
 390 #ifndef CONFIG_ENABLE_WARN_DEPRECATED
 391 #undef __deprecated
 392 #undef __deprecated_for_modules
 393 #define __deprecated
 394 #define __deprecated_for_modules
 395 #endif
 396
 397 #ifndef __malloc
 398 #define __malloc
 399 #endif
 400
 401 /*
 402  * Allow us to avoid 'defined but not used' warnings on functions and data,
 403  * as well as force them to be emitted to the assembly file.
 404  *
 405  * As of gcc 3.4, static functions that are not marked with attribute((used))
 406  * may be elided from the assembly file.  As of gcc 3.4, static data not so
 407  * marked will not be elided, but this may change in a future gcc version.
 408  *
 409  * NOTE: Because distributions shipped with a backported unit-at-a-time
 410  * compiler in gcc 3.3, we must define __used to be __attribute__((used))
 411  * for gcc >=3.3 instead of 3.4.
 412  *
 413  * In prior versions of gcc, such functions and data would be emitted, but
 414  * would be warned about except with attribute((unused)).
 415  *
 416  * Mark functions that are referenced only in inline assembly as __used so
 417  * the code is emitted even though it appears to be unreferenced.
 418  */
 419 #ifndef __used
 420 # define __used                 /* unimplemented */
 421 #endif
 422
 423 #ifndef __maybe_unused
 424 # define __maybe_unused         /* unimplemented */
 425 #endif
 426
 427 #ifndef __always_unused
 428 # define __always_unused        /* unimplemented */
 429 #endif
 430
 431 #ifndef noinline
 432 #define noinline
 433 #endif
 434
 435 /*
 436  * Rather then using noinline to prevent stack consumption, use
 437  * noinline_for_stack instead.  For documentation reasons.
 438  */
 439 #define noinline_for_stack noinline
 440
 441 #ifndef __always_inline
 442 #define __always_inline inline
 443 #endif
 444
 445 #endif /* __KERNEL__ */
 446
 447 /*
 448  * From the GCC manual:
 449  *
 450  * Many functions do not examine any values except their arguments,
 451  * and have no effects except the return value.  Basically this is
 452  * just slightly more strict class than the `pure' attribute above,
 453  * since function is not allowed to read global memory.
 454  *
 455  * Note that a function that has pointer arguments and examines the
 456  * data pointed to must _not_ be declared `const'.  Likewise, a
 457  * function that calls a non-`const' function usually must not be
 458  * `const'.  It does not make sense for a `const' function to return
 459  * `void'.
 460  */
 461 #ifndef __attribute_const__
 462 # define __attribute_const__    /* unimplemented */
 463 #endif
 464
 465 #ifndef __designated_init
 466 # define __designated_init
 467 #endif
 468
 469 #ifndef __latent_entropy
 470 # define __latent_entropy
 471 #endif
 472
 473 #ifndef __randomize_layout
 474 # define __randomize_layout __designated_init
 475 #endif
 476
 477 #ifndef __no_randomize_layout
 478 # define __no_randomize_layout
 479 #endif
 480
 481 #ifndef randomized_struct_fields_start
 482 # define randomized_struct_fields_start
 483 # define randomized_struct_fields_end
 484 #endif
 485
 486 /*
 487  * Tell gcc if a function is cold. The compiler will assume any path
 488  * directly leading to the call is unlikely.
 489  */
 490
 491 #ifndef __cold
 492 #define __cold
 493 #endif
 494
 495 /* Simple shorthand for a section definition */
 496 #ifndef __section
 497 # define __section(S) __attribute__ ((__section__(#S)))
 498 #endif
 499
 500 #ifndef __visible
 501 #define __visible
 502 #endif
 503
 504 #ifndef __nostackprotector
 505 # define __nostackprotector
 506 #endif
 507
 508 /*
 509  * Assume alignment of return value.
 510  */
 511 #ifndef __assume_aligned
 512 #define __assume_aligned(a, ...)
 513 #endif
 514
 515
 516 /* Are two types/vars the same type (ignoring qualifiers)? */
 517 #ifndef __same_type
 518 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 519 #endif
 520
 521 /* Is this type a native word size -- useful for atomic operations */
 522 #ifndef __native_word
 523 # define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 524 #endif
 525
 526 /* Compile time object size, -1 for unknown */
 527 #ifndef __compiletime_object_size
 528 # define __compiletime_object_size(obj) -1
 529 #endif
 530 #ifndef __compiletime_warning
 531 # define __compiletime_warning(message)
 532 #endif
 533 #ifndef __compiletime_error
 534 # define __compiletime_error(message)
 535 /*
 536  * Sparse complains of variable sized arrays due to the temporary variable in
 537  * __compiletime_assert. Unfortunately we can't just expand it out to make
 538  * sparse see a constant array size without breaking compiletime_assert on old
 539  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
 540  */
 541 # ifndef __CHECKER__
 542 #  define __compiletime_error_fallback(condition) \
 543         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 544 # endif
 545 #endif
 546 #ifndef __compiletime_error_fallback
 547 # define __compiletime_error_fallback(condition) do { } while (0)
 548 #endif
 549
 550 #ifdef __OPTIMIZE__
 551 # define __compiletime_assert(condition, msg, prefix, suffix)           \
 552         do {                                                            \
 553                 bool __cond = !(condition);                             \
 554                 extern void prefix ## suffix(void) __compiletime_error(msg); \
 555                 if (__cond)                                             \
 556                         prefix ## suffix();                             \
 557                 __compiletime_error_fallback(__cond);                   \
 558         } while (0)
 559 #else
 560 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
 561 #endif
 562
 563 #define _compiletime_assert(condition, msg, prefix, suffix) \
 564         __compiletime_assert(condition, msg, prefix, suffix)
 565
 566 /**
 567  * compiletime_assert - break build and emit msg if condition is false
 568  * @condition: a compile-time constant condition to check
 569  * @msg:       a message to emit if condition is false
 570  *
 571  * In tradition of POSIX assert, this macro will break the build if the
 572  * supplied condition is *false*, emitting the supplied error message if the
 573  * compiler has support to do so.
 574  */
 575 #define compiletime_assert(condition, msg) \
 576         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 577
 578 #define compiletime_assert_atomic_type(t)                               \
 579         compiletime_assert(__native_word(t),                            \
 580                 "Need native word sized stores/loads for atomicity.")
 581
 582 /*
 583  * Prevent the compiler from merging or refetching accesses.  The compiler
 584  * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 585  * but only when the compiler is aware of some particular ordering.  One way
 586  * to make the compiler aware of ordering is to put the two invocations of
 587  * ACCESS_ONCE() in different C statements.
 588  *
 589  * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
 590  * on a union member will work as long as the size of the member matches the
 591  * size of the union and the size is smaller than word size.
 592  *
 593  * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
 594  * between process-level code and irq/NMI handlers, all running on the same CPU,
 595  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 596  * mutilate accesses that either do not require ordering or that interact
 597  * with an explicit memory barrier or atomic instruction that provides the
 598  * required ordering.
 599  *
 600  * If possible use READ_ONCE()/WRITE_ONCE() instead.
 601  */
 602 #define __ACCESS_ONCE(x) ({ \
 603          __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
 604         (volatile typeof(x) *)&(x); })
 605 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
 606
 607 /**
 608  * lockless_dereference() - safely load a pointer for later dereference
 609  * @p: The pointer to load
 610  *
 611  * Similar to rcu_dereference(), but for situations where the pointed-to
 612  * object's lifetime is managed by something other than RCU.  That
 613  * "something other" might be reference counting or simple immortality.
 614  *
 615  * The seemingly unused variable ___typecheck_p validates that @p is
 616  * indeed a pointer type by using a pointer to typeof(*p) as the type.
 617  * Taking a pointer to typeof(*p) again is needed in case p is void *.
 618  */
 619 #define lockless_dereference(p) \
 620 ({ \
 621         typeof(p) _________p1 = READ_ONCE(p); \
 622         typeof(*(p)) *___typecheck_p __maybe_unused; \
 623         smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
 624         (_________p1); \
 625 })
 626
 627 #endif /* __LINUX_COMPILER_H */