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 #include <linux/types.h> 106 107 /* 108 * Following functions are taken from kernel sources and 109 * break aliasing rules in their original form. 110 * 111 * While kernel is compiled with -fno-strict-aliasing, 112 * perf uses -Wstrict-aliasing=3 which makes build fail 113 * under gcc 4.4. 114 * 115 * Using extra __may_alias__ type to allow aliasing 116 * in this case. 117 */ 118 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t; 119 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t; 120 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t; 121 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t; 122 123 static __always_inline void __read_once_size(const volatile void *p, void *res, int size) 124 { 125 switch (size) { 126 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break; 127 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break; 128 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break; 129 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break; 130 default: 131 barrier(); 132 __builtin_memcpy((void *)res, (const void *)p, size); 133 barrier(); 134 } 135 } 136 137 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 138 { 139 switch (size) { 140 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break; 141 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break; 142 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break; 143 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break; 144 default: 145 barrier(); 146 __builtin_memcpy((void *)p, (const void *)res, size); 147 barrier(); 148 } 149 } 150 151 /* 152 * Prevent the compiler from merging or refetching reads or writes. The 153 * compiler is also forbidden from reordering successive instances of 154 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some 155 * particular ordering. One way to make the compiler aware of ordering is to 156 * put the two invocations of READ_ONCE or WRITE_ONCE in different C 157 * statements. 158 * 159 * These two macros will also work on aggregate data types like structs or 160 * unions. If the size of the accessed data type exceeds the word size of 161 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will 162 * fall back to memcpy and print a compile-time warning. 163 * 164 * Their two major use cases are: (1) Mediating communication between 165 * process-level code and irq/NMI handlers, all running on the same CPU, 166 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 167 * mutilate accesses that either do not require ordering or that interact 168 * with an explicit memory barrier or atomic instruction that provides the 169 * required ordering. 170 */ 171 172 #define READ_ONCE(x) \ 173 ({ \ 174 union { typeof(x) __val; char __c[1]; } __u = \ 175 { .__c = { 0 } }; \ 176 __read_once_size(&(x), __u.__c, sizeof(x)); \ 177 __u.__val; \ 178 }) 179 180 #define WRITE_ONCE(x, val) \ 181 ({ \ 182 union { typeof(x) __val; char __c[1]; } __u = \ 183 { .__val = (val) }; \ 184 __write_once_size(&(x), __u.__c, sizeof(x)); \ 185 __u.__val; \ 186 }) 187 188 189 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */ 190 #define ___PASTE(a, b) a##b 191 #define __PASTE(a, b) ___PASTE(a, b) 192 193 #endif /* _TOOLS_LINUX_COMPILER_H */ 194