1 #ifndef _TOOLS_LINUX_COMPILER_H_ 2 #define _TOOLS_LINUX_COMPILER_H_ 3 4 #ifdef __GNUC__ 5 #include <linux/compiler-gcc.h> 6 #endif 7 8 #ifndef __compiletime_error 9 # define __compiletime_error(message) 10 #endif 11 12 /* Optimization barrier */ 13 /* The "volatile" is due to gcc bugs */ 14 #define barrier() __asm__ __volatile__("": : :"memory") 15 16 #ifndef __always_inline 17 # define __always_inline inline __attribute__((always_inline)) 18 #endif 19 20 #ifndef noinline 21 #define noinline 22 #endif 23 24 /* Are two types/vars the same type (ignoring qualifiers)? */ 25 #ifndef __same_type 26 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) 27 #endif 28 29 #ifdef __ANDROID__ 30 /* 31 * FIXME: Big hammer to get rid of tons of: 32 * "warning: always_inline function might not be inlinable" 33 * 34 * At least on android-ndk-r12/platforms/android-24/arch-arm 35 */ 36 #undef __always_inline 37 #define __always_inline inline 38 #endif 39 40 #define __user 41 #define __rcu 42 #define __read_mostly 43 44 #ifndef __attribute_const__ 45 # define __attribute_const__ 46 #endif 47 48 #ifndef __maybe_unused 49 # define __maybe_unused __attribute__((unused)) 50 #endif 51 52 #ifndef __used 53 # define __used __attribute__((__unused__)) 54 #endif 55 56 #ifndef __packed 57 # define __packed __attribute__((__packed__)) 58 #endif 59 60 #ifndef __force 61 # define __force 62 #endif 63 64 #ifndef __weak 65 # define __weak __attribute__((weak)) 66 #endif 67 68 #ifndef likely 69 # define likely(x) __builtin_expect(!!(x), 1) 70 #endif 71 72 #ifndef unlikely 73 # define unlikely(x) __builtin_expect(!!(x), 0) 74 #endif 75 76 #ifndef __init 77 # define __init 78 #endif 79 80 #ifndef noinline 81 # define noinline 82 #endif 83 84 #define uninitialized_var(x) x = *(&(x)) 85 86 #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x)) 87 88 #include <linux/types.h> 89 90 /* 91 * Following functions are taken from kernel sources and 92 * break aliasing rules in their original form. 93 * 94 * While kernel is compiled with -fno-strict-aliasing, 95 * perf uses -Wstrict-aliasing=3 which makes build fail 96 * under gcc 4.4. 97 * 98 * Using extra __may_alias__ type to allow aliasing 99 * in this case. 100 */ 101 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t; 102 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t; 103 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t; 104 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t; 105 106 static __always_inline void __read_once_size(const volatile void *p, void *res, int size) 107 { 108 switch (size) { 109 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break; 110 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break; 111 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break; 112 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break; 113 default: 114 barrier(); 115 __builtin_memcpy((void *)res, (const void *)p, size); 116 barrier(); 117 } 118 } 119 120 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 121 { 122 switch (size) { 123 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break; 124 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break; 125 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break; 126 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break; 127 default: 128 barrier(); 129 __builtin_memcpy((void *)p, (const void *)res, size); 130 barrier(); 131 } 132 } 133 134 /* 135 * Prevent the compiler from merging or refetching reads or writes. The 136 * compiler is also forbidden from reordering successive instances of 137 * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the 138 * compiler is aware of some particular ordering. One way to make the 139 * compiler aware of ordering is to put the two invocations of READ_ONCE, 140 * WRITE_ONCE or ACCESS_ONCE() in different C statements. 141 * 142 * In contrast to ACCESS_ONCE these two macros will also work on aggregate 143 * data types like structs or unions. If the size of the accessed data 144 * type exceeds the word size of the machine (e.g., 32 bits or 64 bits) 145 * READ_ONCE() and WRITE_ONCE() will fall back to memcpy and print a 146 * compile-time warning. 147 * 148 * Their two major use cases are: (1) Mediating communication between 149 * process-level code and irq/NMI handlers, all running on the same CPU, 150 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 151 * mutilate accesses that either do not require ordering or that interact 152 * with an explicit memory barrier or atomic instruction that provides the 153 * required ordering. 154 */ 155 156 #define READ_ONCE(x) \ 157 ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; }) 158 159 #define WRITE_ONCE(x, val) \ 160 ({ union { typeof(x) __val; char __c[1]; } __u = { .__val = (val) }; __write_once_size(&(x), __u.__c, sizeof(x)); __u.__val; }) 161 162 163 #ifndef __fallthrough 164 # define __fallthrough 165 #endif 166 167 #endif /* _TOOLS_LINUX_COMPILER_H */ 168