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