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