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 #ifndef __no_tail_call 51 #define __no_tail_call 52 #endif 53 54 /* Are two types/vars the same type (ignoring qualifiers)? */ 55 #ifndef __same_type 56 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) 57 #endif 58 59 #ifdef __ANDROID__ 60 /* 61 * FIXME: Big hammer to get rid of tons of: 62 * "warning: always_inline function might not be inlinable" 63 * 64 * At least on android-ndk-r12/platforms/android-24/arch-arm 65 */ 66 #undef __always_inline 67 #define __always_inline inline 68 #endif 69 70 #define __user 71 #define __rcu 72 #define __read_mostly 73 74 #ifndef __attribute_const__ 75 # define __attribute_const__ 76 #endif 77 78 #ifndef __maybe_unused 79 # define __maybe_unused __attribute__((unused)) 80 #endif 81 82 #ifndef __used 83 # define __used __attribute__((__unused__)) 84 #endif 85 86 #ifndef __packed 87 # define __packed __attribute__((__packed__)) 88 #endif 89 90 #ifndef __force 91 # define __force 92 #endif 93 94 #ifndef __weak 95 # define __weak __attribute__((weak)) 96 #endif 97 98 #ifndef likely 99 # define likely(x) __builtin_expect(!!(x), 1) 100 #endif 101 102 #ifndef unlikely 103 # define unlikely(x) __builtin_expect(!!(x), 0) 104 #endif 105 106 #ifndef __init 107 # define __init 108 #endif 109 110 #ifndef noinline 111 # define noinline 112 #endif 113 114 #define uninitialized_var(x) x = *(&(x)) 115 116 #include <linux/types.h> 117 118 /* 119 * Following functions are taken from kernel sources and 120 * break aliasing rules in their original form. 121 * 122 * While kernel is compiled with -fno-strict-aliasing, 123 * perf uses -Wstrict-aliasing=3 which makes build fail 124 * under gcc 4.4. 125 * 126 * Using extra __may_alias__ type to allow aliasing 127 * in this case. 128 */ 129 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t; 130 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t; 131 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t; 132 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t; 133 134 static __always_inline void __read_once_size(const volatile void *p, void *res, int size) 135 { 136 switch (size) { 137 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break; 138 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break; 139 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break; 140 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break; 141 default: 142 barrier(); 143 __builtin_memcpy((void *)res, (const void *)p, size); 144 barrier(); 145 } 146 } 147 148 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 149 { 150 switch (size) { 151 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break; 152 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break; 153 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break; 154 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break; 155 default: 156 barrier(); 157 __builtin_memcpy((void *)p, (const void *)res, size); 158 barrier(); 159 } 160 } 161 162 /* 163 * Prevent the compiler from merging or refetching reads or writes. The 164 * compiler is also forbidden from reordering successive instances of 165 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some 166 * particular ordering. One way to make the compiler aware of ordering is to 167 * put the two invocations of READ_ONCE or WRITE_ONCE in different C 168 * statements. 169 * 170 * These two macros will also work on aggregate data types like structs or 171 * unions. If the size of the accessed data type exceeds the word size of 172 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will 173 * fall back to memcpy and print a compile-time warning. 174 * 175 * Their two major use cases are: (1) Mediating communication between 176 * process-level code and irq/NMI handlers, all running on the same CPU, 177 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 178 * mutilate accesses that either do not require ordering or that interact 179 * with an explicit memory barrier or atomic instruction that provides the 180 * required ordering. 181 */ 182 183 #define READ_ONCE(x) \ 184 ({ \ 185 union { typeof(x) __val; char __c[1]; } __u = \ 186 { .__c = { 0 } }; \ 187 __read_once_size(&(x), __u.__c, sizeof(x)); \ 188 __u.__val; \ 189 }) 190 191 #define WRITE_ONCE(x, val) \ 192 ({ \ 193 union { typeof(x) __val; char __c[1]; } __u = \ 194 { .__val = (val) }; \ 195 __write_once_size(&(x), __u.__c, sizeof(x)); \ 196 __u.__val; \ 197 }) 198 199 200 #ifndef __fallthrough 201 # define __fallthrough 202 #endif 203 204 #endif /* _TOOLS_LINUX_COMPILER_H */ 205