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 #ifndef __ASSEMBLY__
   6
   7 #include <linux/compiler_types.h>
   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 __always_unused
  48 #define __always_unused __attribute__((__unused__))
  49 #endif
  50
  51 #ifndef __noreturn
  52 #define __noreturn __attribute__((__noreturn__))
  53 #endif
  54
  55 #ifndef unreachable
  56 #define unreachable() __builtin_unreachable()
  57 #endif
  58
  59 #ifndef noinline
  60 #define noinline
  61 #endif
  62
  63 #ifndef __nocf_check
  64 #define __nocf_check __attribute__((nocf_check))
  65 #endif
  66
  67 #ifndef __naked
  68 #define __naked __attribute__((__naked__))
  69 #endif
  70
  71 /* Are two types/vars the same type (ignoring qualifiers)? */
  72 #ifndef __same_type
  73 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
  74 #endif
  75
  76 /*
  77  * This returns a constant expression while determining if an argument is
  78  * a constant expression, most importantly without evaluating the argument.
  79  * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
  80  */
  81 #define __is_constexpr(x) \
  82         (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
  83
  84 #ifdef __ANDROID__
  85 /*
  86  * FIXME: Big hammer to get rid of tons of:
  87  *   "warning: always_inline function might not be inlinable"
  88  *
  89  * At least on android-ndk-r12/platforms/android-24/arch-arm
  90  */
  91 #undef __always_inline
  92 #define __always_inline inline
  93 #endif
  94
  95 #define __user
  96 #define __rcu
  97 #define __read_mostly
  98
  99 #ifndef __attribute_const__
 100 # define __attribute_const__
 101 #endif
 102
 103 #ifndef __maybe_unused
 104 # define __maybe_unused         __attribute__((unused))
 105 #endif
 106
 107 #ifndef __used
 108 # define __used         __attribute__((__unused__))
 109 #endif
 110
 111 #ifndef __packed
 112 # define __packed               __attribute__((__packed__))
 113 #endif
 114
 115 #ifndef __force
 116 # define __force
 117 #endif
 118
 119 #ifndef __weak
 120 # define __weak                 __attribute__((weak))
 121 #endif
 122
 123 #ifndef likely
 124 # define likely(x)              __builtin_expect(!!(x), 1)
 125 #endif
 126
 127 #ifndef unlikely
 128 # define unlikely(x)            __builtin_expect(!!(x), 0)
 129 #endif
 130
 131 #include <linux/types.h>
 132
 133 /*
 134  * Following functions are taken from kernel sources and
 135  * break aliasing rules in their original form.
 136  *
 137  * While kernel is compiled with -fno-strict-aliasing,
 138  * perf uses -Wstrict-aliasing=3 which makes build fail
 139  * under gcc 4.4.
 140  *
 141  * Using extra __may_alias__ type to allow aliasing
 142  * in this case.
 143  */
 144 typedef __u8  __attribute__((__may_alias__))  __u8_alias_t;
 145 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
 146 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
 147 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
 148
 149 static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
 150 {
 151         switch (size) {
 152         case 1: *(__u8_alias_t  *) res = *(volatile __u8_alias_t  *) p; break;
 153         case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
 154         case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
 155         case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
 156         default:
 157                 barrier();
 158                 __builtin_memcpy((void *)res, (const void *)p, size);
 159                 barrier();
 160         }
 161 }
 162
 163 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 164 {
 165         switch (size) {
 166         case 1: *(volatile  __u8_alias_t *) p = *(__u8_alias_t  *) res; break;
 167         case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
 168         case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
 169         case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
 170         default:
 171                 barrier();
 172                 __builtin_memcpy((void *)p, (const void *)res, size);
 173                 barrier();
 174         }
 175 }
 176
 177 /*
 178  * Prevent the compiler from merging or refetching reads or writes. The
 179  * compiler is also forbidden from reordering successive instances of
 180  * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
 181  * particular ordering. One way to make the compiler aware of ordering is to
 182  * put the two invocations of READ_ONCE or WRITE_ONCE in different C
 183  * statements.
 184  *
 185  * These two macros will also work on aggregate data types like structs or
 186  * unions. If the size of the accessed data type exceeds the word size of
 187  * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
 188  * fall back to memcpy and print a compile-time warning.
 189  *
 190  * Their two major use cases are: (1) Mediating communication between
 191  * process-level code and irq/NMI handlers, all running on the same CPU,
 192  * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
 193  * mutilate accesses that either do not require ordering or that interact
 194  * with an explicit memory barrier or atomic instruction that provides the
 195  * required ordering.
 196  */
 197
 198 #define READ_ONCE(x)                                    \
 199 ({                                                      \
 200         union { typeof(x) __val; char __c[1]; } __u =   \
 201                 { .__c = { 0 } };                       \
 202         __read_once_size(&(x), __u.__c, sizeof(x));     \
 203         __u.__val;                                      \
 204 })
 205
 206 #define WRITE_ONCE(x, val)                              \
 207 ({                                                      \
 208         union { typeof(x) __val; char __c[1]; } __u =   \
 209                 { .__val = (val) };                     \
 210         __write_once_size(&(x), __u.__c, sizeof(x));    \
 211         __u.__val;                                      \
 212 })
 213
 214
 215 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
 216 #define ___PASTE(a, b) a##b
 217 #define __PASTE(a, b) ___PASTE(a, b)
 218
 219 #ifndef OPTIMIZER_HIDE_VAR
 220 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
 221 #define OPTIMIZER_HIDE_VAR(var)                                         \
 222         __asm__ ("" : "=r" (var) : "0" (var))
 223 #endif
 224
 225 #endif /* __ASSEMBLY__ */
 226
 227 #endif /* _TOOLS_LINUX_COMPILER_H */