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 __pmem         __attribute__((noderef, address_space(5)))
  21 #ifdef CONFIG_SPARSE_RCU_POINTER
  22 # define __rcu          __attribute__((noderef, address_space(4)))
  23 #else /* CONFIG_SPARSE_RCU_POINTER */
  24 # define __rcu
  25 #endif /* CONFIG_SPARSE_RCU_POINTER */
  26 # define __private      __attribute__((noderef))
  27 extern void __chk_user_ptr(const volatile void __user *);
  28 extern void __chk_io_ptr(const volatile void __iomem *);
  29 # define ACCESS_PRIVATE(p, member) (*((typeof((p)->member) __force *) &(p)->member))
  30 #else /* __CHECKER__ */
  31 # define __user
  32 # define __kernel
  33 # define __safe
  34 # define __force
  35 # define __nocast
  36 # define __iomem
  37 # define __chk_user_ptr(x) (void)0
  38 # define __chk_io_ptr(x) (void)0
  39 # define __builtin_warning(x, y...) (1)
  40 # define __must_hold(x)
  41 # define __acquires(x)
  42 # define __releases(x)
  43 # define __acquire(x) (void)0
  44 # define __release(x) (void)0
  45 # define __cond_lock(x,c) (c)
  46 # define __percpu
  47 # define __rcu
  48 # define __pmem
  49 # define __private
  50 # define ACCESS_PRIVATE(p, member) ((p)->member)
  51 #endif /* __CHECKER__ */
  52
  53 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
  54 #define ___PASTE(a,b) a##b
  55 #define __PASTE(a,b) ___PASTE(a,b)
  56
  57 #ifdef __KERNEL__
  58
  59 #ifdef __GNUC__
  60 #include <linux/compiler-gcc.h>
  61 #endif
  62
  63 #if defined(CC_USING_HOTPATCH) && !defined(__CHECKER__)
  64 #define notrace __attribute__((hotpatch(0,0)))
  65 #else
  66 #define notrace __attribute__((no_instrument_function))
  67 #endif
  68
  69 /* Intel compiler defines __GNUC__. So we will overwrite implementations
  70  * coming from above header files here
  71  */
  72 #ifdef __INTEL_COMPILER
  73 # include <linux/compiler-intel.h>
  74 #endif
  75
  76 /* Clang compiler defines __GNUC__. So we will overwrite implementations
  77  * coming from above header files here
  78  */
  79 #ifdef __clang__
  80 #include <linux/compiler-clang.h>
  81 #endif
  82
  83 /*
  84  * Generic compiler-dependent macros required for kernel
  85  * build go below this comment. Actual compiler/compiler version
  86  * specific implementations come from the above header files
  87  */
  88
  89 struct ftrace_branch_data {
  90         const char *func;
  91         const char *file;
  92         unsigned line;
  93         union {
  94                 struct {
  95                         unsigned long correct;
  96                         unsigned long incorrect;
  97                 };
  98                 struct {
  99                         unsigned long miss;
 100                         unsigned long hit;
 101                 };
 102                 unsigned long miss_hit[2];
 103         };
 104 };
 105
 106 /*
 107  * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
 108  * to disable branch tracing on a per file basis.
 109  */
 110 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
 111     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
 112 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 113
 114 #define likely_notrace(x)       __builtin_expect(!!(x), 1)
 115 #define unlikely_notrace(x)     __builtin_expect(!!(x), 0)
 116
 117 #define __branch_check__(x, expect) ({                                  \
 118                         int ______r;                                    \
 119                         static struct ftrace_branch_data                \
 120                                 __attribute__((__aligned__(4)))         \
 121                                 __attribute__((section("_ftrace_annotated_branch"))) \
 122                                 ______f = {                             \
 123                                 .func = __func__,                       \
 124                                 .file = __FILE__,                       \
 125                                 .line = __LINE__,                       \
 126                         };                                              \
 127                         ______r = likely_notrace(x);                    \
 128                         ftrace_likely_update(&______f, ______r, expect); \
 129                         ______r;                                        \
 130                 })
 131
 132 /*
 133  * Using __builtin_constant_p(x) to ignore cases where the return
 134  * value is always the same.  This idea is taken from a similar patch
 135  * written by Daniel Walker.
 136  */
 137 # ifndef likely
 138 #  define likely(x)     (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1))
 139 # endif
 140 # ifndef unlikely
 141 #  define unlikely(x)   (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
 142 # endif
 143
 144 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 145 /*
 146  * "Define 'is'", Bill Clinton
 147  * "Define 'if'", Steven Rostedt
 148  */
 149 #define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
 150 #define __trace_if(cond) \
 151         if (__builtin_constant_p(!!(cond)) ? !!(cond) :                 \
 152         ({                                                              \
 153                 int ______r;                                            \
 154                 static struct ftrace_branch_data                        \
 155                         __attribute__((__aligned__(4)))                 \
 156                         __attribute__((section("_ftrace_branch")))      \
 157                         ______f = {                                     \
 158                                 .func = __func__,                       \
 159                                 .file = __FILE__,                       \
 160                                 .line = __LINE__,                       \
 161                         };                                              \
 162                 ______r = !!(cond);                                     \
 163                 ______f.miss_hit[______r]++;                                    \
 164                 ______r;                                                \
 165         }))
 166 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
 167
 168 #else
 169 # define likely(x)      __builtin_expect(!!(x), 1)
 170 # define unlikely(x)    __builtin_expect(!!(x), 0)
 171 #endif
 172
 173 /* Optimization barrier */
 174 #ifndef barrier
 175 # define barrier() __memory_barrier()
 176 #endif
 177
 178 #ifndef barrier_data
 179 # define barrier_data(ptr) barrier()
 180 #endif
 181
 182 /* Unreachable code */
 183 #ifndef unreachable
 184 # define unreachable() do { } while (1)
 185 #endif
 186
 187 #ifndef RELOC_HIDE
 188 # define RELOC_HIDE(ptr, off)                                   \
 189   ({ unsigned long __ptr;                                       \
 190      __ptr = (unsigned long) (ptr);                             \
 191     (typeof(ptr)) (__ptr + (off)); })
 192 #endif
 193
 194 #ifndef OPTIMIZER_HIDE_VAR
 195 #define OPTIMIZER_HIDE_VAR(var) barrier()
 196 #endif
 197
 198 /* Not-quite-unique ID. */
 199 #ifndef __UNIQUE_ID
 200 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 201 #endif
 202
 203 #include <uapi/linux/types.h>
 204
 205 #define __READ_ONCE_SIZE                                                \
 206 ({                                                                      \
 207         switch (size) {                                                 \
 208         case 1: *(__u8 *)res = *(volatile __u8 *)p; break;              \
 209         case 2: *(__u16 *)res = *(volatile __u16 *)p; break;            \
 210         case 4: *(__u32 *)res = *(volatile __u32 *)p; break;            \
 211         case 8: *(__u64 *)res = *(volatile __u64 *)p; break;            \
 212         default:                                                        \
 213                 barrier();                                              \
 214                 __builtin_memcpy((void *)res, (const void *)p, size);   \
 215                 barrier();                                              \
 216         }                                                               \
 217 })
 218
 219 static __always_inline
 220 void __read_once_size(const volatile void *p, void *res, int size)
 221 {
 222         __READ_ONCE_SIZE;
 223 }
 224
 225 #ifdef CONFIG_KASAN
 226 /*
 227  * This function is not 'inline' because __no_sanitize_address confilcts
 228  * with inlining. Attempt to inline it may cause a build failure.
 229  *      https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
 230  * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
 231  */
 232 static __no_sanitize_address __maybe_unused
 233 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
 234 {
 235         __READ_ONCE_SIZE;
 236 }
 237 #else
 238 static __always_inline
 239 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
 240 {
 241         __READ_ONCE_SIZE;
 242 }
 243 #endif
 244
 245 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 246 {
 247         switch (size) {
 248         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
 249         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
 250         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
 251         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
 252         default:
 253                 barrier();
 254                 __builtin_memcpy((void *)p, (const void *)res, size);
 255                 barrier();
 256         }
 257 }
 258
 259 /*
 260  * Prevent the compiler from merging or refetching reads or writes. The
 261  * compiler is also forbidden from reordering successive instances of
 262  * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
 263  * compiler is aware of some particular ordering.  One way to make the
 264  * compiler aware of ordering is to put the two invocations of READ_ONCE,
 265  * WRITE_ONCE or ACCESS_ONCE() in different C statements.
 266  *
 267  * In contrast to ACCESS_ONCE these two macros will also work on aggregate
 268  * data types like structs or unions. If the size of the accessed data
 269  * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
 270  * READ_ONCE() and WRITE_ONCE() will fall back to memcpy(). There's at
 271  * least two memcpy()s: one for the __builtin_memcpy() and then one for
 272  * the macro doing the copy of variable - '__u' allocated on the stack.
 273  *
 274  * Their two major use cases are: (1) Mediating communication between
 275  * process-level code and irq/NMI handlers, all running on the same CPU,
 276  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 277  * mutilate accesses that either do not require ordering or that interact
 278  * with an explicit memory barrier or atomic instruction that provides the
 279  * required ordering.
 280  */
 281
 282 #define __READ_ONCE(x, check)                                           \
 283 ({                                                                      \
 284         union { typeof(x) __val; char __c[1]; } __u;                    \
 285         if (check)                                                      \
 286                 __read_once_size(&(x), __u.__c, sizeof(x));             \
 287         else                                                            \
 288                 __read_once_size_nocheck(&(x), __u.__c, sizeof(x));     \
 289         __u.__val;                                                      \
 290 })
 291 #define READ_ONCE(x) __READ_ONCE(x, 1)
 292
 293 /*
 294  * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
 295  * to hide memory access from KASAN.
 296  */
 297 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
 298
 299 #define WRITE_ONCE(x, val) \
 300 ({                                                      \
 301         union { typeof(x) __val; char __c[1]; } __u =   \
 302                 { .__val = (__force typeof(x)) (val) }; \
 303         __write_once_size(&(x), __u.__c, sizeof(x));    \
 304         __u.__val;                                      \
 305 })
 306
 307 /**
 308  * smp_cond_acquire() - Spin wait for cond with ACQUIRE ordering
 309  * @cond: boolean expression to wait for
 310  *
 311  * Equivalent to using smp_load_acquire() on the condition variable but employs
 312  * the control dependency of the wait to reduce the barrier on many platforms.
 313  *
 314  * The control dependency provides a LOAD->STORE order, the additional RMB
 315  * provides LOAD->LOAD order, together they provide LOAD->{LOAD,STORE} order,
 316  * aka. ACQUIRE.
 317  */
 318 #define smp_cond_acquire(cond)  do {            \
 319         while (!(cond))                         \
 320                 cpu_relax();                    \
 321         smp_rmb(); /* ctrl + rmb := acquire */  \
 322 } while (0)
 323
 324 #endif /* __KERNEL__ */
 325
 326 #endif /* __ASSEMBLY__ */
 327
 328 #ifdef __KERNEL__
 329 /*
 330  * Allow us to mark functions as 'deprecated' and have gcc emit a nice
 331  * warning for each use, in hopes of speeding the functions removal.
 332  * Usage is:
 333  *              int __deprecated foo(void)
 334  */
 335 #ifndef __deprecated
 336 # define __deprecated           /* unimplemented */
 337 #endif
 338
 339 #ifdef MODULE
 340 #define __deprecated_for_modules __deprecated
 341 #else
 342 #define __deprecated_for_modules
 343 #endif
 344
 345 #ifndef __must_check
 346 #define __must_check
 347 #endif
 348
 349 #ifndef CONFIG_ENABLE_MUST_CHECK
 350 #undef __must_check
 351 #define __must_check
 352 #endif
 353 #ifndef CONFIG_ENABLE_WARN_DEPRECATED
 354 #undef __deprecated
 355 #undef __deprecated_for_modules
 356 #define __deprecated
 357 #define __deprecated_for_modules
 358 #endif
 359
 360 /*
 361  * Allow us to avoid 'defined but not used' warnings on functions and data,
 362  * as well as force them to be emitted to the assembly file.
 363  *
 364  * As of gcc 3.4, static functions that are not marked with attribute((used))
 365  * may be elided from the assembly file.  As of gcc 3.4, static data not so
 366  * marked will not be elided, but this may change in a future gcc version.
 367  *
 368  * NOTE: Because distributions shipped with a backported unit-at-a-time
 369  * compiler in gcc 3.3, we must define __used to be __attribute__((used))
 370  * for gcc >=3.3 instead of 3.4.
 371  *
 372  * In prior versions of gcc, such functions and data would be emitted, but
 373  * would be warned about except with attribute((unused)).
 374  *
 375  * Mark functions that are referenced only in inline assembly as __used so
 376  * the code is emitted even though it appears to be unreferenced.
 377  */
 378 #ifndef __used
 379 # define __used                 /* unimplemented */
 380 #endif
 381
 382 #ifndef __maybe_unused
 383 # define __maybe_unused         /* unimplemented */
 384 #endif
 385
 386 #ifndef __always_unused
 387 # define __always_unused        /* unimplemented */
 388 #endif
 389
 390 #ifndef noinline
 391 #define noinline
 392 #endif
 393
 394 /*
 395  * Rather then using noinline to prevent stack consumption, use
 396  * noinline_for_stack instead.  For documentation reasons.
 397  */
 398 #define noinline_for_stack noinline
 399
 400 #ifndef __always_inline
 401 #define __always_inline inline
 402 #endif
 403
 404 #endif /* __KERNEL__ */
 405
 406 /*
 407  * From the GCC manual:
 408  *
 409  * Many functions do not examine any values except their arguments,
 410  * and have no effects except the return value.  Basically this is
 411  * just slightly more strict class than the `pure' attribute above,
 412  * since function is not allowed to read global memory.
 413  *
 414  * Note that a function that has pointer arguments and examines the
 415  * data pointed to must _not_ be declared `const'.  Likewise, a
 416  * function that calls a non-`const' function usually must not be
 417  * `const'.  It does not make sense for a `const' function to return
 418  * `void'.
 419  */
 420 #ifndef __attribute_const__
 421 # define __attribute_const__    /* unimplemented */
 422 #endif
 423
 424 /*
 425  * Tell gcc if a function is cold. The compiler will assume any path
 426  * directly leading to the call is unlikely.
 427  */
 428
 429 #ifndef __cold
 430 #define __cold
 431 #endif
 432
 433 /* Simple shorthand for a section definition */
 434 #ifndef __section
 435 # define __section(S) __attribute__ ((__section__(#S)))
 436 #endif
 437
 438 #ifndef __visible
 439 #define __visible
 440 #endif
 441
 442 /*
 443  * Assume alignment of return value.
 444  */
 445 #ifndef __assume_aligned
 446 #define __assume_aligned(a, ...)
 447 #endif
 448
 449
 450 /* Are two types/vars the same type (ignoring qualifiers)? */
 451 #ifndef __same_type
 452 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 453 #endif
 454
 455 /* Is this type a native word size -- useful for atomic operations */
 456 #ifndef __native_word
 457 # define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 458 #endif
 459
 460 /* Compile time object size, -1 for unknown */
 461 #ifndef __compiletime_object_size
 462 # define __compiletime_object_size(obj) -1
 463 #endif
 464 #ifndef __compiletime_warning
 465 # define __compiletime_warning(message)
 466 #endif
 467 #ifndef __compiletime_error
 468 # define __compiletime_error(message)
 469 /*
 470  * Sparse complains of variable sized arrays due to the temporary variable in
 471  * __compiletime_assert. Unfortunately we can't just expand it out to make
 472  * sparse see a constant array size without breaking compiletime_assert on old
 473  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
 474  */
 475 # ifndef __CHECKER__
 476 #  define __compiletime_error_fallback(condition) \
 477         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 478 # endif
 479 #endif
 480 #ifndef __compiletime_error_fallback
 481 # define __compiletime_error_fallback(condition) do { } while (0)
 482 #endif
 483
 484 #define __compiletime_assert(condition, msg, prefix, suffix)            \
 485         do {                                                            \
 486                 bool __cond = !(condition);                             \
 487                 extern void prefix ## suffix(void) __compiletime_error(msg); \
 488                 if (__cond)                                             \
 489                         prefix ## suffix();                             \
 490                 __compiletime_error_fallback(__cond);                   \
 491         } while (0)
 492
 493 #define _compiletime_assert(condition, msg, prefix, suffix) \
 494         __compiletime_assert(condition, msg, prefix, suffix)
 495
 496 /**
 497  * compiletime_assert - break build and emit msg if condition is false
 498  * @condition: a compile-time constant condition to check
 499  * @msg:       a message to emit if condition is false
 500  *
 501  * In tradition of POSIX assert, this macro will break the build if the
 502  * supplied condition is *false*, emitting the supplied error message if the
 503  * compiler has support to do so.
 504  */
 505 #define compiletime_assert(condition, msg) \
 506         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 507
 508 #define compiletime_assert_atomic_type(t)                               \
 509         compiletime_assert(__native_word(t),                            \
 510                 "Need native word sized stores/loads for atomicity.")
 511
 512 /*
 513  * Prevent the compiler from merging or refetching accesses.  The compiler
 514  * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 515  * but only when the compiler is aware of some particular ordering.  One way
 516  * to make the compiler aware of ordering is to put the two invocations of
 517  * ACCESS_ONCE() in different C statements.
 518  *
 519  * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
 520  * on a union member will work as long as the size of the member matches the
 521  * size of the union and the size is smaller than word size.
 522  *
 523  * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
 524  * between process-level code and irq/NMI handlers, all running on the same CPU,
 525  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 526  * mutilate accesses that either do not require ordering or that interact
 527  * with an explicit memory barrier or atomic instruction that provides the
 528  * required ordering.
 529  *
 530  * If possible use READ_ONCE()/WRITE_ONCE() instead.
 531  */
 532 #define __ACCESS_ONCE(x) ({ \
 533          __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
 534         (volatile typeof(x) *)&(x); })
 535 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
 536
 537 /**
 538  * lockless_dereference() - safely load a pointer for later dereference
 539  * @p: The pointer to load
 540  *
 541  * Similar to rcu_dereference(), but for situations where the pointed-to
 542  * object's lifetime is managed by something other than RCU.  That
 543  * "something other" might be reference counting or simple immortality.
 544  */
 545 #define lockless_dereference(p) \
 546 ({ \
 547         typeof(p) _________p1 = READ_ONCE(p); \
 548         smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
 549         (_________p1); \
 550 })
 551
 552 /* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
 553 #ifdef CONFIG_KPROBES
 554 # define __kprobes      __attribute__((__section__(".kprobes.text")))
 555 # define nokprobe_inline        __always_inline
 556 #else
 557 # define __kprobes
 558 # define nokprobe_inline        inline
 559 #endif
 560 #endif /* __LINUX_COMPILER_H */