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