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 __always_unused 46 #define __always_unused __attribute__((__unused__)) 47 #endif 48 49 #ifndef __noreturn 50 #define __noreturn __attribute__((__noreturn__)) 51 #endif 52 53 #ifndef unreachable 54 #define unreachable() __builtin_unreachable() 55 #endif 56 57 #ifndef noinline 58 #define noinline 59 #endif 60 61 /* Are two types/vars the same type (ignoring qualifiers)? */ 62 #ifndef __same_type 63 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) 64 #endif 65 66 /* 67 * This returns a constant expression while determining if an argument is 68 * a constant expression, most importantly without evaluating the argument. 69 * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> 70 */ 71 #define __is_constexpr(x) \ 72 (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) 73 74 #ifdef __ANDROID__ 75 /* 76 * FIXME: Big hammer to get rid of tons of: 77 * "warning: always_inline function might not be inlinable" 78 * 79 * At least on android-ndk-r12/platforms/android-24/arch-arm 80 */ 81 #undef __always_inline 82 #define __always_inline inline 83 #endif 84 85 #define __user 86 #define __rcu 87 #define __read_mostly 88 89 #ifndef __attribute_const__ 90 # define __attribute_const__ 91 #endif 92 93 #ifndef __maybe_unused 94 # define __maybe_unused __attribute__((unused)) 95 #endif 96 97 #ifndef __used 98 # define __used __attribute__((__unused__)) 99 #endif 100 101 #ifndef __packed 102 # define __packed __attribute__((__packed__)) 103 #endif 104 105 #ifndef __force 106 # define __force 107 #endif 108 109 #ifndef __weak 110 # define __weak __attribute__((weak)) 111 #endif 112 113 #ifndef likely 114 # define likely(x) __builtin_expect(!!(x), 1) 115 #endif 116 117 #ifndef unlikely 118 # define unlikely(x) __builtin_expect(!!(x), 0) 119 #endif 120 121 #ifndef __init 122 # define __init 123 #endif 124 125 #include <linux/types.h> 126 127 /* 128 * Following functions are taken from kernel sources and 129 * break aliasing rules in their original form. 130 * 131 * While kernel is compiled with -fno-strict-aliasing, 132 * perf uses -Wstrict-aliasing=3 which makes build fail 133 * under gcc 4.4. 134 * 135 * Using extra __may_alias__ type to allow aliasing 136 * in this case. 137 */ 138 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t; 139 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t; 140 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t; 141 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t; 142 143 static __always_inline void __read_once_size(const volatile void *p, void *res, int size) 144 { 145 switch (size) { 146 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break; 147 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break; 148 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break; 149 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break; 150 default: 151 barrier(); 152 __builtin_memcpy((void *)res, (const void *)p, size); 153 barrier(); 154 } 155 } 156 157 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 158 { 159 switch (size) { 160 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break; 161 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break; 162 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break; 163 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break; 164 default: 165 barrier(); 166 __builtin_memcpy((void *)p, (const void *)res, size); 167 barrier(); 168 } 169 } 170 171 /* 172 * Prevent the compiler from merging or refetching reads or writes. The 173 * compiler is also forbidden from reordering successive instances of 174 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some 175 * particular ordering. One way to make the compiler aware of ordering is to 176 * put the two invocations of READ_ONCE or WRITE_ONCE in different C 177 * statements. 178 * 179 * These two macros will also work on aggregate data types like structs or 180 * unions. If the size of the accessed data type exceeds the word size of 181 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will 182 * fall back to memcpy and print a compile-time warning. 183 * 184 * Their two major use cases are: (1) Mediating communication between 185 * process-level code and irq/NMI handlers, all running on the same CPU, 186 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 187 * mutilate accesses that either do not require ordering or that interact 188 * with an explicit memory barrier or atomic instruction that provides the 189 * required ordering. 190 */ 191 192 #define READ_ONCE(x) \ 193 ({ \ 194 union { typeof(x) __val; char __c[1]; } __u = \ 195 { .__c = { 0 } }; \ 196 __read_once_size(&(x), __u.__c, sizeof(x)); \ 197 __u.__val; \ 198 }) 199 200 #define WRITE_ONCE(x, val) \ 201 ({ \ 202 union { typeof(x) __val; char __c[1]; } __u = \ 203 { .__val = (val) }; \ 204 __write_once_size(&(x), __u.__c, sizeof(x)); \ 205 __u.__val; \ 206 }) 207 208 209 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */ 210 #define ___PASTE(a, b) a##b 211 #define __PASTE(a, b) ___PASTE(a, b) 212 213 #ifndef OPTIMIZER_HIDE_VAR 214 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 215 #define OPTIMIZER_HIDE_VAR(var) \ 216 __asm__ ("" : "=r" (var) : "0" (var)) 217 #endif 218 219 #endif /* _TOOLS_LINUX_COMPILER_H */ 220