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