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