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 */ 202