linux/include/linux/compiler.h
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   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
  23# define __rcu
  24#endif
  25extern void __chk_user_ptr(const volatile void __user *);
  26extern void __chk_io_ptr(const volatile void __iomem *);
  27#else
  28# define __user
  29# define __kernel
  30# define __safe
  31# define __force
  32# define __nocast
  33# define __iomem
  34# define __chk_user_ptr(x) (void)0
  35# define __chk_io_ptr(x) (void)0
  36# define __builtin_warning(x, y...) (1)
  37# define __must_hold(x)
  38# define __acquires(x)
  39# define __releases(x)
  40# define __acquire(x) (void)0
  41# define __release(x) (void)0
  42# define __cond_lock(x,c) (c)
  43# define __percpu
  44# define __rcu
  45#endif
  46
  47/* Indirect macros required for expanded argument pasting, eg. __LINE__. */
  48#define ___PASTE(a,b) a##b
  49#define __PASTE(a,b) ___PASTE(a,b)
  50
  51#ifdef __KERNEL__
  52
  53#ifdef __GNUC__
  54#include <linux/compiler-gcc.h>
  55#endif
  56
  57#define notrace __attribute__((no_instrument_function))
  58
  59/* Intel compiler defines __GNUC__. So we will overwrite implementations
  60 * coming from above header files here
  61 */
  62#ifdef __INTEL_COMPILER
  63# include <linux/compiler-intel.h>
  64#endif
  65
  66/* Clang compiler defines __GNUC__. So we will overwrite implementations
  67 * coming from above header files here
  68 */
  69#ifdef __clang__
  70#include <linux/compiler-clang.h>
  71#endif
  72
  73/*
  74 * Generic compiler-dependent macros required for kernel
  75 * build go below this comment. Actual compiler/compiler version
  76 * specific implementations come from the above header files
  77 */
  78
  79struct ftrace_branch_data {
  80        const char *func;
  81        const char *file;
  82        unsigned line;
  83        union {
  84                struct {
  85                        unsigned long correct;
  86                        unsigned long incorrect;
  87                };
  88                struct {
  89                        unsigned long miss;
  90                        unsigned long hit;
  91                };
  92                unsigned long miss_hit[2];
  93        };
  94};
  95
  96/*
  97 * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
  98 * to disable branch tracing on a per file basis.
  99 */
 100#if defined(CONFIG_TRACE_BRANCH_PROFILING) \
 101    && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
 102void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 103
 104#define likely_notrace(x)       __builtin_expect(!!(x), 1)
 105#define unlikely_notrace(x)     __builtin_expect(!!(x), 0)
 106
 107#define __branch_check__(x, expect) ({                                  \
 108                        int ______r;                                    \
 109                        static struct ftrace_branch_data                \
 110                                __attribute__((__aligned__(4)))         \
 111                                __attribute__((section("_ftrace_annotated_branch"))) \
 112                                ______f = {                             \
 113                                .func = __func__,                       \
 114                                .file = __FILE__,                       \
 115                                .line = __LINE__,                       \
 116                        };                                              \
 117                        ______r = likely_notrace(x);                    \
 118                        ftrace_likely_update(&______f, ______r, expect); \
 119                        ______r;                                        \
 120                })
 121
 122/*
 123 * Using __builtin_constant_p(x) to ignore cases where the return
 124 * value is always the same.  This idea is taken from a similar patch
 125 * written by Daniel Walker.
 126 */
 127# ifndef likely
 128#  define likely(x)     (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1))
 129# endif
 130# ifndef unlikely
 131#  define unlikely(x)   (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
 132# endif
 133
 134#ifdef CONFIG_PROFILE_ALL_BRANCHES
 135/*
 136 * "Define 'is'", Bill Clinton
 137 * "Define 'if'", Steven Rostedt
 138 */
 139#define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
 140#define __trace_if(cond) \
 141        if (__builtin_constant_p((cond)) ? !!(cond) :                   \
 142        ({                                                              \
 143                int ______r;                                            \
 144                static struct ftrace_branch_data                        \
 145                        __attribute__((__aligned__(4)))                 \
 146                        __attribute__((section("_ftrace_branch")))      \
 147                        ______f = {                                     \
 148                                .func = __func__,                       \
 149                                .file = __FILE__,                       \
 150                                .line = __LINE__,                       \
 151                        };                                              \
 152                ______r = !!(cond);                                     \
 153                ______f.miss_hit[______r]++;                                    \
 154                ______r;                                                \
 155        }))
 156#endif /* CONFIG_PROFILE_ALL_BRANCHES */
 157
 158#else
 159# define likely(x)      __builtin_expect(!!(x), 1)
 160# define unlikely(x)    __builtin_expect(!!(x), 0)
 161#endif
 162
 163/* Optimization barrier */
 164#ifndef barrier
 165# define barrier() __memory_barrier()
 166#endif
 167
 168/* Unreachable code */
 169#ifndef unreachable
 170# define unreachable() do { } while (1)
 171#endif
 172
 173#ifndef RELOC_HIDE
 174# define RELOC_HIDE(ptr, off)                                   \
 175  ({ unsigned long __ptr;                                       \
 176     __ptr = (unsigned long) (ptr);                             \
 177    (typeof(ptr)) (__ptr + (off)); })
 178#endif
 179
 180#ifndef OPTIMIZER_HIDE_VAR
 181#define OPTIMIZER_HIDE_VAR(var) barrier()
 182#endif
 183
 184/* Not-quite-unique ID. */
 185#ifndef __UNIQUE_ID
 186# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 187#endif
 188
 189#include <uapi/linux/types.h>
 190
 191static __always_inline void data_access_exceeds_word_size(void)
 192#ifdef __compiletime_warning
 193__compiletime_warning("data access exceeds word size and won't be atomic")
 194#endif
 195;
 196
 197static __always_inline void data_access_exceeds_word_size(void)
 198{
 199}
 200
 201static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
 202{
 203        switch (size) {
 204        case 1: *(__u8 *)res = *(volatile __u8 *)p; break;
 205        case 2: *(__u16 *)res = *(volatile __u16 *)p; break;
 206        case 4: *(__u32 *)res = *(volatile __u32 *)p; break;
 207#ifdef CONFIG_64BIT
 208        case 8: *(__u64 *)res = *(volatile __u64 *)p; break;
 209#endif
 210        default:
 211                barrier();
 212                __builtin_memcpy((void *)res, (const void *)p, size);
 213                data_access_exceeds_word_size();
 214                barrier();
 215        }
 216}
 217
 218static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 219{
 220        switch (size) {
 221        case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
 222        case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
 223        case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
 224#ifdef CONFIG_64BIT
 225        case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
 226#endif
 227        default:
 228                barrier();
 229                __builtin_memcpy((void *)p, (const void *)res, size);
 230                data_access_exceeds_word_size();
 231                barrier();
 232        }
 233}
 234
 235/*
 236 * Prevent the compiler from merging or refetching reads or writes. The
 237 * compiler is also forbidden from reordering successive instances of
 238 * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
 239 * compiler is aware of some particular ordering.  One way to make the
 240 * compiler aware of ordering is to put the two invocations of READ_ONCE,
 241 * WRITE_ONCE or ACCESS_ONCE() in different C statements.
 242 *
 243 * In contrast to ACCESS_ONCE these two macros will also work on aggregate
 244 * data types like structs or unions. If the size of the accessed data
 245 * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
 246 * READ_ONCE() and WRITE_ONCE()  will fall back to memcpy and print a
 247 * compile-time warning.
 248 *
 249 * Their two major use cases are: (1) Mediating communication between
 250 * process-level code and irq/NMI handlers, all running on the same CPU,
 251 * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 252 * mutilate accesses that either do not require ordering or that interact
 253 * with an explicit memory barrier or atomic instruction that provides the
 254 * required ordering.
 255 */
 256
 257#define READ_ONCE(x) \
 258        ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
 259
 260#define WRITE_ONCE(x, val) \
 261        ({ typeof(x) __val = (val); __write_once_size(&(x), &__val, sizeof(__val)); __val; })
 262
 263#endif /* __KERNEL__ */
 264
 265#endif /* __ASSEMBLY__ */
 266
 267#ifdef __KERNEL__
 268/*
 269 * Allow us to mark functions as 'deprecated' and have gcc emit a nice
 270 * warning for each use, in hopes of speeding the functions removal.
 271 * Usage is:
 272 *              int __deprecated foo(void)
 273 */
 274#ifndef __deprecated
 275# define __deprecated           /* unimplemented */
 276#endif
 277
 278#ifdef MODULE
 279#define __deprecated_for_modules __deprecated
 280#else
 281#define __deprecated_for_modules
 282#endif
 283
 284#ifndef __must_check
 285#define __must_check
 286#endif
 287
 288#ifndef CONFIG_ENABLE_MUST_CHECK
 289#undef __must_check
 290#define __must_check
 291#endif
 292#ifndef CONFIG_ENABLE_WARN_DEPRECATED
 293#undef __deprecated
 294#undef __deprecated_for_modules
 295#define __deprecated
 296#define __deprecated_for_modules
 297#endif
 298
 299/*
 300 * Allow us to avoid 'defined but not used' warnings on functions and data,
 301 * as well as force them to be emitted to the assembly file.
 302 *
 303 * As of gcc 3.4, static functions that are not marked with attribute((used))
 304 * may be elided from the assembly file.  As of gcc 3.4, static data not so
 305 * marked will not be elided, but this may change in a future gcc version.
 306 *
 307 * NOTE: Because distributions shipped with a backported unit-at-a-time
 308 * compiler in gcc 3.3, we must define __used to be __attribute__((used))
 309 * for gcc >=3.3 instead of 3.4.
 310 *
 311 * In prior versions of gcc, such functions and data would be emitted, but
 312 * would be warned about except with attribute((unused)).
 313 *
 314 * Mark functions that are referenced only in inline assembly as __used so
 315 * the code is emitted even though it appears to be unreferenced.
 316 */
 317#ifndef __used
 318# define __used                 /* unimplemented */
 319#endif
 320
 321#ifndef __maybe_unused
 322# define __maybe_unused         /* unimplemented */
 323#endif
 324
 325#ifndef __always_unused
 326# define __always_unused        /* unimplemented */
 327#endif
 328
 329#ifndef noinline
 330#define noinline
 331#endif
 332
 333/*
 334 * Rather then using noinline to prevent stack consumption, use
 335 * noinline_for_stack instead.  For documentation reasons.
 336 */
 337#define noinline_for_stack noinline
 338
 339#ifndef __always_inline
 340#define __always_inline inline
 341#endif
 342
 343#endif /* __KERNEL__ */
 344
 345/*
 346 * From the GCC manual:
 347 *
 348 * Many functions do not examine any values except their arguments,
 349 * and have no effects except the return value.  Basically this is
 350 * just slightly more strict class than the `pure' attribute above,
 351 * since function is not allowed to read global memory.
 352 *
 353 * Note that a function that has pointer arguments and examines the
 354 * data pointed to must _not_ be declared `const'.  Likewise, a
 355 * function that calls a non-`const' function usually must not be
 356 * `const'.  It does not make sense for a `const' function to return
 357 * `void'.
 358 */
 359#ifndef __attribute_const__
 360# define __attribute_const__    /* unimplemented */
 361#endif
 362
 363/*
 364 * Tell gcc if a function is cold. The compiler will assume any path
 365 * directly leading to the call is unlikely.
 366 */
 367
 368#ifndef __cold
 369#define __cold
 370#endif
 371
 372/* Simple shorthand for a section definition */
 373#ifndef __section
 374# define __section(S) __attribute__ ((__section__(#S)))
 375#endif
 376
 377#ifndef __visible
 378#define __visible
 379#endif
 380
 381/* Are two types/vars the same type (ignoring qualifiers)? */
 382#ifndef __same_type
 383# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 384#endif
 385
 386/* Is this type a native word size -- useful for atomic operations */
 387#ifndef __native_word
 388# define __native_word(t) (sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 389#endif
 390
 391/* Compile time object size, -1 for unknown */
 392#ifndef __compiletime_object_size
 393# define __compiletime_object_size(obj) -1
 394#endif
 395#ifndef __compiletime_warning
 396# define __compiletime_warning(message)
 397#endif
 398#ifndef __compiletime_error
 399# define __compiletime_error(message)
 400/*
 401 * Sparse complains of variable sized arrays due to the temporary variable in
 402 * __compiletime_assert. Unfortunately we can't just expand it out to make
 403 * sparse see a constant array size without breaking compiletime_assert on old
 404 * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
 405 */
 406# ifndef __CHECKER__
 407#  define __compiletime_error_fallback(condition) \
 408        do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 409# endif
 410#endif
 411#ifndef __compiletime_error_fallback
 412# define __compiletime_error_fallback(condition) do { } while (0)
 413#endif
 414
 415#define __compiletime_assert(condition, msg, prefix, suffix)            \
 416        do {                                                            \
 417                bool __cond = !(condition);                             \
 418                extern void prefix ## suffix(void) __compiletime_error(msg); \
 419                if (__cond)                                             \
 420                        prefix ## suffix();                             \
 421                __compiletime_error_fallback(__cond);                   \
 422        } while (0)
 423
 424#define _compiletime_assert(condition, msg, prefix, suffix) \
 425        __compiletime_assert(condition, msg, prefix, suffix)
 426
 427/**
 428 * compiletime_assert - break build and emit msg if condition is false
 429 * @condition: a compile-time constant condition to check
 430 * @msg:       a message to emit if condition is false
 431 *
 432 * In tradition of POSIX assert, this macro will break the build if the
 433 * supplied condition is *false*, emitting the supplied error message if the
 434 * compiler has support to do so.
 435 */
 436#define compiletime_assert(condition, msg) \
 437        _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 438
 439#define compiletime_assert_atomic_type(t)                               \
 440        compiletime_assert(__native_word(t),                            \
 441                "Need native word sized stores/loads for atomicity.")
 442
 443/*
 444 * Prevent the compiler from merging or refetching accesses.  The compiler
 445 * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 446 * but only when the compiler is aware of some particular ordering.  One way
 447 * to make the compiler aware of ordering is to put the two invocations of
 448 * ACCESS_ONCE() in different C statements.
 449 *
 450 * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
 451 * on a union member will work as long as the size of the member matches the
 452 * size of the union and the size is smaller than word size.
 453 *
 454 * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
 455 * between process-level code and irq/NMI handlers, all running on the same CPU,
 456 * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 457 * mutilate accesses that either do not require ordering or that interact
 458 * with an explicit memory barrier or atomic instruction that provides the
 459 * required ordering.
 460 *
 461 * If possible use READ_ONCE/ASSIGN_ONCE instead.
 462 */
 463#define __ACCESS_ONCE(x) ({ \
 464         __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
 465        (volatile typeof(x) *)&(x); })
 466#define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
 467
 468/* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
 469#ifdef CONFIG_KPROBES
 470# define __kprobes      __attribute__((__section__(".kprobes.text")))
 471# define nokprobe_inline        __always_inline
 472#else
 473# define __kprobes
 474# define nokprobe_inline        inline
 475#endif
 476#endif /* __LINUX_COMPILER_H */
 477
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