LXR linux/tools/include/linux/compiler.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef _TOOLS_LINUX_COMPILER_H_
   3#define _TOOLS_LINUX_COMPILER_H_
   4
   5#ifdef __GNUC__
   6#include <linux/compiler-gcc.h>
   7#endif
   8
   9#ifndef __compiletime_error
  10# define __compiletime_error(message)
  11#endif
  12
  13#ifdef __OPTIMIZE__
  14# define __compiletime_assert(condition, msg, prefix, suffix)           \
  15        do {                                                            \
  16                extern void prefix ## suffix(void) __compiletime_error(msg); \
  17                if (!(condition))                                       \
  18                        prefix ## suffix();                             \
  19        } while (0)
  20#else
  21# define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
  22#endif
  23
  24#define _compiletime_assert(condition, msg, prefix, suffix) \
  25        __compiletime_assert(condition, msg, prefix, suffix)
  26
  27/**
  28 * compiletime_assert - break build and emit msg if condition is false
  29 * @condition: a compile-time constant condition to check
  30 * @msg:       a message to emit if condition is false
  31 *
  32 * In tradition of POSIX assert, this macro will break the build if the
  33 * supplied condition is *false*, emitting the supplied error message if the
  34 * compiler has support to do so.
  35 */
  36#define compiletime_assert(condition, msg) \
  37        _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
  38
  39/* Optimization barrier */
  40/* The "volatile" is due to gcc bugs */
  41#define barrier() __asm__ __volatile__("": : :"memory")
  42
  43#ifndef __always_inline
  44# define __always_inline        inline __attribute__((always_inline))
  45#endif
  46
  47#ifndef noinline
  48#define noinline
  49#endif
  50
  51/* Are two types/vars the same type (ignoring qualifiers)? */
  52#ifndef __same_type
  53# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
  54#endif
  55
  56#ifdef __ANDROID__
  57/*
  58 * FIXME: Big hammer to get rid of tons of:
  59 *   "warning: always_inline function might not be inlinable"
  60 *
  61 * At least on android-ndk-r12/platforms/android-24/arch-arm
  62 */
  63#undef __always_inline
  64#define __always_inline inline
  65#endif
  66
  67#define __user
  68#define __rcu
  69#define __read_mostly
  70
  71#ifndef __attribute_const__
  72# define __attribute_const__
  73#endif
  74
  75#ifndef __maybe_unused
  76# define __maybe_unused         __attribute__((unused))
  77#endif
  78
  79#ifndef __used
  80# define __used         __attribute__((__unused__))
  81#endif
  82
  83#ifndef __packed
  84# define __packed               __attribute__((__packed__))
  85#endif
  86
  87#ifndef __force
  88# define __force
  89#endif
  90
  91#ifndef __weak
  92# define __weak                 __attribute__((weak))
  93#endif
  94
  95#ifndef likely
  96# define likely(x)              __builtin_expect(!!(x), 1)
  97#endif
  98
  99#ifndef unlikely
 100# define unlikely(x)            __builtin_expect(!!(x), 0)
 101#endif
 102
 103#ifndef __init
 104# define __init
 105#endif
 106
 107#ifndef noinline
 108# define noinline
 109#endif
 110
 111#include <linux/types.h>
 112
 113/*
 114 * Following functions are taken from kernel sources and
 115 * break aliasing rules in their original form.
 116 *
 117 * While kernel is compiled with -fno-strict-aliasing,
 118 * perf uses -Wstrict-aliasing=3 which makes build fail
 119 * under gcc 4.4.
 120 *
 121 * Using extra __may_alias__ type to allow aliasing
 122 * in this case.
 123 */
 124typedef __u8  __attribute__((__may_alias__))  __u8_alias_t;
 125typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
 126typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
 127typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
 128
 129static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
 130{
 131        switch (size) {
 132        case 1: *(__u8_alias_t  *) res = *(volatile __u8_alias_t  *) p; break;
 133        case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
 134        case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
 135        case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
 136        default:
 137                barrier();
 138                __builtin_memcpy((void *)res, (const void *)p, size);
 139                barrier();
 140        }
 141}
 142
 143static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 144{
 145        switch (size) {
 146        case 1: *(volatile  __u8_alias_t *) p = *(__u8_alias_t  *) res; break;
 147        case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
 148        case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
 149        case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
 150        default:
 151                barrier();
 152                __builtin_memcpy((void *)p, (const void *)res, size);
 153                barrier();
 154        }
 155}
 156
 157/*
 158 * Prevent the compiler from merging or refetching reads or writes. The
 159 * compiler is also forbidden from reordering successive instances of
 160 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
 161 * particular ordering. One way to make the compiler aware of ordering is to
 162 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
 163 * statements.
 164 *
 165 * These two macros will also work on aggregate data types like structs or
 166 * unions. If the size of the accessed data type exceeds the word size of
 167 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
 168 * fall back to memcpy and print a compile-time warning.
 169 *
 170 * Their two major use cases are: (1) Mediating communication between
 171 * process-level code and irq/NMI handlers, all running on the same CPU,
 172 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
 173 * mutilate accesses that either do not require ordering or that interact
 174 * with an explicit memory barrier or atomic instruction that provides the
 175 * required ordering.
 176 */
 177
 178#define READ_ONCE(x)                                    \
 179({                                                      \
 180        union { typeof(x) __val; char __c[1]; } __u =   \
 181                { .__c = { 0 } };                       \
 182        __read_once_size(&(x), __u.__c, sizeof(x));     \
 183        __u.__val;                                      \
 184})
 185
 186#define WRITE_ONCE(x, val)                              \
 187({                                                      \
 188        union { typeof(x) __val; char __c[1]; } __u =   \
 189                { .__val = (val) };                     \
 190        __write_once_size(&(x), __u.__c, sizeof(x));    \
 191        __u.__val;                                      \
 192})
 193
 194
 195#ifndef __fallthrough
 196# define __fallthrough
 197#endif
 198
 199/* Indirect macros required for expanded argument pasting, eg. __LINE__. */
 200#define ___PASTE(a, b) a##b
 201#define __PASTE(a, b) ___PASTE(a, b)
 202
 203#endif /* _TOOLS_LINUX_COMPILER_H */
 204