1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _TOOLS_LINUX_COMPILER_H_ 3 #define _TOOLS_LINUX_COMPILER_H_ 4 5 #ifndef __ASSEMBLY__ 6 7 #include <linux/compiler_types.h> 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 __always_unused 48 #define __always_unused __attribute__((__unused__)) 49 #endif 50 51 #ifndef __noreturn 52 #define __noreturn __attribute__((__noreturn__)) 53 #endif 54 55 #ifndef unreachable 56 #define unreachable() __builtin_unreachable() 57 #endif 58 59 #ifndef noinline 60 #define noinline 61 #endif 62 63 #ifndef __nocf_check 64 #define __nocf_check __attribute__((nocf_check)) 65 #endif 66 67 #ifndef __naked 68 #define __naked __attribute__((__naked__)) 69 #endif 70 71 /* Are two types/vars the same type (ignoring qualifiers)? */ 72 #ifndef __same_type 73 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) 74 #endif 75 76 /* 77 * This returns a constant expression while determining if an argument is 78 * a constant expression, most importantly without evaluating the argument. 79 * Glory to Martin Uecker <[email protected]> 80 */ 81 #define __is_constexpr(x) \ 82 (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) 83 84 #ifdef __ANDROID__ 85 /* 86 * FIXME: Big hammer to get rid of tons of: 87 * "warning: always_inline function might not be inlinable" 88 * 89 * At least on android-ndk-r12/platforms/android-24/arch-arm 90 */ 91 #undef __always_inline 92 #define __always_inline inline 93 #endif 94 95 #define __user 96 #define __rcu 97 #define __read_mostly 98 99 #ifndef __attribute_const__ 100 # define __attribute_const__ 101 #endif 102 103 #ifndef __maybe_unused 104 # define __maybe_unused __attribute__((unused)) 105 #endif 106 107 #ifndef __used 108 # define __used __attribute__((__unused__)) 109 #endif 110 111 #ifndef __packed 112 # define __packed __attribute__((__packed__)) 113 #endif 114 115 #ifndef __force 116 # define __force 117 #endif 118 119 #ifndef __weak 120 # define __weak __attribute__((weak)) 121 #endif 122 123 #ifndef likely 124 # define likely(x) __builtin_expect(!!(x), 1) 125 #endif 126 127 #ifndef unlikely 128 # define unlikely(x) __builtin_expect(!!(x), 0) 129 #endif 130 131 #include <linux/types.h> 132 133 /* 134 * Following functions are taken from kernel sources and 135 * break aliasing rules in their original form. 136 * 137 * While kernel is compiled with -fno-strict-aliasing, 138 * perf uses -Wstrict-aliasing=3 which makes build fail 139 * under gcc 4.4. 140 * 141 * Using extra __may_alias__ type to allow aliasing 142 * in this case. 143 */ 144 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t; 145 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t; 146 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t; 147 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t; 148 149 static __always_inline void __read_once_size(const volatile void *p, void *res, int size) 150 { 151 switch (size) { 152 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break; 153 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break; 154 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break; 155 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break; 156 default: 157 barrier(); 158 __builtin_memcpy((void *)res, (const void *)p, size); 159 barrier(); 160 } 161 } 162 163 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 164 { 165 switch (size) { 166 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break; 167 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break; 168 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break; 169 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break; 170 default: 171 barrier(); 172 __builtin_memcpy((void *)p, (const void *)res, size); 173 barrier(); 174 } 175 } 176 177 /* 178 * Prevent the compiler from merging or refetching reads or writes. The 179 * compiler is also forbidden from reordering successive instances of 180 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some 181 * particular ordering. One way to make the compiler aware of ordering is to 182 * put the two invocations of READ_ONCE or WRITE_ONCE in different C 183 * statements. 184 * 185 * These two macros will also work on aggregate data types like structs or 186 * unions. If the size of the accessed data type exceeds the word size of 187 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will 188 * fall back to memcpy and print a compile-time warning. 189 * 190 * Their two major use cases are: (1) Mediating communication between 191 * process-level code and irq/NMI handlers, all running on the same CPU, 192 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 193 * mutilate accesses that either do not require ordering or that interact 194 * with an explicit memory barrier or atomic instruction that provides the 195 * required ordering. 196 */ 197 198 #define READ_ONCE(x) \ 199 ({ \ 200 union { typeof(x) __val; char __c[1]; } __u = \ 201 { .__c = { 0 } }; \ 202 __read_once_size(&(x), __u.__c, sizeof(x)); \ 203 __u.__val; \ 204 }) 205 206 #define WRITE_ONCE(x, val) \ 207 ({ \ 208 union { typeof(x) __val; char __c[1]; } __u = \ 209 { .__val = (val) }; \ 210 __write_once_size(&(x), __u.__c, sizeof(x)); \ 211 __u.__val; \ 212 }) 213 214 215 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */ 216 #define ___PASTE(a, b) a##b 217 #define __PASTE(a, b) ___PASTE(a, b) 218 219 #ifndef OPTIMIZER_HIDE_VAR 220 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 221 #define OPTIMIZER_HIDE_VAR(var) \ 222 __asm__ ("" : "=r" (var) : "0" (var)) 223 #endif 224 225 #endif /* __ASSEMBLY__ */ 226 227 #endif /* _TOOLS_LINUX_COMPILER_H */ 228