1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _TOOLS_LINUX_COMPILER_H_ 3 #define _TOOLS_LINUX_COMPILER_H_ 4 5 #include <linux/compiler_types.h> 6 7 #ifndef __compiletime_error 8 # define __compiletime_error(message) 9 #endif 10 11 #ifdef __OPTIMIZE__ 12 # define __compiletime_assert(condition, msg, prefix, suffix) \ 13 do { \ 14 extern void prefix ## suffix(void) __compiletime_error(msg); \ 15 if (!(condition)) \ 16 prefix ## suffix(); \ 17 } while (0) 18 #else 19 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0) 20 #endif 21 22 #define _compiletime_assert(condition, msg, prefix, suffix) \ 23 __compiletime_assert(condition, msg, prefix, suffix) 24 25 /** 26 * compiletime_assert - break build and emit msg if condition is false 27 * @condition: a compile-time constant condition to check 28 * @msg: a message to emit if condition is false 29 * 30 * In tradition of POSIX assert, this macro will break the build if the 31 * supplied condition is *false*, emitting the supplied error message if the 32 * compiler has support to do so. 33 */ 34 #define compiletime_assert(condition, msg) \ 35 _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) 36 37 /* Optimization barrier */ 38 /* The "volatile" is due to gcc bugs */ 39 #define barrier() __asm__ __volatile__("": : :"memory") 40 41 #ifndef __always_inline 42 # define __always_inline inline __attribute__((always_inline)) 43 #endif 44 45 #ifndef __always_unused 46 #define __always_unused __attribute__((__unused__)) 47 #endif 48 49 #ifndef __noreturn 50 #define __noreturn __attribute__((__noreturn__)) 51 #endif 52 53 #ifndef unreachable 54 #define unreachable() __builtin_unreachable() 55 #endif 56 57 #ifndef noinline 58 #define noinline 59 #endif 60 61 /* Are two types/vars the same type (ignoring qualifiers)? */ 62 #ifndef __same_type 63 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) 64 #endif 65 66 #ifdef __ANDROID__ 67 /* 68 * FIXME: Big hammer to get rid of tons of: 69 * "warning: always_inline function might not be inlinable" 70 * 71 * At least on android-ndk-r12/platforms/android-24/arch-arm 72 */ 73 #undef __always_inline 74 #define __always_inline inline 75 #endif 76 77 #define __user 78 #define __rcu 79 #define __read_mostly 80 81 #ifndef __attribute_const__ 82 # define __attribute_const__ 83 #endif 84 85 #ifndef __maybe_unused 86 # define __maybe_unused __attribute__((unused)) 87 #endif 88 89 #ifndef __used 90 # define __used __attribute__((__unused__)) 91 #endif 92 93 #ifndef __packed 94 # define __packed __attribute__((__packed__)) 95 #endif 96 97 #ifndef __force 98 # define __force 99 #endif 100 101 #ifndef __weak 102 # define __weak __attribute__((weak)) 103 #endif 104 105 #ifndef likely 106 # define likely(x) __builtin_expect(!!(x), 1) 107 #endif 108 109 #ifndef unlikely 110 # define unlikely(x) __builtin_expect(!!(x), 0) 111 #endif 112 113 #ifndef __init 114 # define __init 115 #endif 116 117 #include <linux/types.h> 118 119 /* 120 * Following functions are taken from kernel sources and 121 * break aliasing rules in their original form. 122 * 123 * While kernel is compiled with -fno-strict-aliasing, 124 * perf uses -Wstrict-aliasing=3 which makes build fail 125 * under gcc 4.4. 126 * 127 * Using extra __may_alias__ type to allow aliasing 128 * in this case. 129 */ 130 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t; 131 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t; 132 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t; 133 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t; 134 135 static __always_inline void __read_once_size(const volatile void *p, void *res, int size) 136 { 137 switch (size) { 138 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break; 139 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break; 140 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break; 141 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break; 142 default: 143 barrier(); 144 __builtin_memcpy((void *)res, (const void *)p, size); 145 barrier(); 146 } 147 } 148 149 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 150 { 151 switch (size) { 152 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break; 153 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break; 154 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break; 155 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break; 156 default: 157 barrier(); 158 __builtin_memcpy((void *)p, (const void *)res, size); 159 barrier(); 160 } 161 } 162 163 /* 164 * Prevent the compiler from merging or refetching reads or writes. The 165 * compiler is also forbidden from reordering successive instances of 166 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some 167 * particular ordering. One way to make the compiler aware of ordering is to 168 * put the two invocations of READ_ONCE or WRITE_ONCE in different C 169 * statements. 170 * 171 * These two macros will also work on aggregate data types like structs or 172 * unions. If the size of the accessed data type exceeds the word size of 173 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will 174 * fall back to memcpy and print a compile-time warning. 175 * 176 * Their two major use cases are: (1) Mediating communication between 177 * process-level code and irq/NMI handlers, all running on the same CPU, 178 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 179 * mutilate accesses that either do not require ordering or that interact 180 * with an explicit memory barrier or atomic instruction that provides the 181 * required ordering. 182 */ 183 184 #define READ_ONCE(x) \ 185 ({ \ 186 union { typeof(x) __val; char __c[1]; } __u = \ 187 { .__c = { 0 } }; \ 188 __read_once_size(&(x), __u.__c, sizeof(x)); \ 189 __u.__val; \ 190 }) 191 192 #define WRITE_ONCE(x, val) \ 193 ({ \ 194 union { typeof(x) __val; char __c[1]; } __u = \ 195 { .__val = (val) }; \ 196 __write_once_size(&(x), __u.__c, sizeof(x)); \ 197 __u.__val; \ 198 }) 199 200 201 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */ 202 #define ___PASTE(a, b) a##b 203 #define __PASTE(a, b) ___PASTE(a, b) 204 205 #ifndef OPTIMIZER_HIDE_VAR 206 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 207 #define OPTIMIZER_HIDE_VAR(var) \ 208 __asm__ ("" : "=r" (var) : "0" (var)) 209 #endif 210 211 #endif /* _TOOLS_LINUX_COMPILER_H */ 212