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