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 #define uninitialized_var(x) x = *(&(x))
 112
 113 #include <linux/types.h>
 114
 115 /*
 116  * Following functions are taken from kernel sources and
 117  * break aliasing rules in their original form.
 118  *
 119  * While kernel is compiled with -fno-strict-aliasing,
 120  * perf uses -Wstrict-aliasing=3 which makes build fail
 121  * under gcc 4.4.
 122  *
 123  * Using extra __may_alias__ type to allow aliasing
 124  * in this case.
 125  */
 126 typedef __u8  __attribute__((__may_alias__))  __u8_alias_t;
 127 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
 128 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
 129 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
 130
 131 static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
 132 {
 133         switch (size) {
 134         case 1: *(__u8_alias_t  *) res = *(volatile __u8_alias_t  *) p; break;
 135         case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
 136         case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
 137         case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
 138         default:
 139                 barrier();
 140                 __builtin_memcpy((void *)res, (const void *)p, size);
 141                 barrier();
 142         }
 143 }
 144
 145 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 146 {
 147         switch (size) {
 148         case 1: *(volatile  __u8_alias_t *) p = *(__u8_alias_t  *) res; break;
 149         case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
 150         case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
 151         case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
 152         default:
 153                 barrier();
 154                 __builtin_memcpy((void *)p, (const void *)res, size);
 155                 barrier();
 156         }
 157 }
 158
 159 /*
 160  * Prevent the compiler from merging or refetching reads or writes. The
 161  * compiler is also forbidden from reordering successive instances of
 162  * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
 163  * particular ordering. One way to make the compiler aware of ordering is to
 164  * put the two invocations of READ_ONCE or WRITE_ONCE in different C
 165  * statements.
 166  *
 167  * These two macros will also work on aggregate data types like structs or
 168  * unions. If the size of the accessed data type exceeds the word size of
 169  * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
 170  * fall back to memcpy and print a compile-time warning.
 171  *
 172  * Their two major use cases are: (1) Mediating communication between
 173  * process-level code and irq/NMI handlers, all running on the same CPU,
 174  * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
 175  * mutilate accesses that either do not require ordering or that interact
 176  * with an explicit memory barrier or atomic instruction that provides the
 177  * required ordering.
 178  */
 179
 180 #define READ_ONCE(x)                                    \
 181 ({                                                      \
 182         union { typeof(x) __val; char __c[1]; } __u =   \
 183                 { .__c = { 0 } };                       \
 184         __read_once_size(&(x), __u.__c, sizeof(x));     \
 185         __u.__val;                                      \
 186 })
 187
 188 #define WRITE_ONCE(x, val)                              \
 189 ({                                                      \
 190         union { typeof(x) __val; char __c[1]; } __u =   \
 191                 { .__val = (val) };                     \
 192         __write_once_size(&(x), __u.__c, sizeof(x));    \
 193         __u.__val;                                      \
 194 })
 195
 196
 197 #ifndef __fallthrough
 198 # define __fallthrough
 199 #endif
 200
 201 #endif /* _TOOLS_LINUX_COMPILER_H */