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 __packed 53 # define __packed __attribute__((__packed__)) 54 #endif 55 56 #ifndef __force 57 # define __force 58 #endif 59 60 #ifndef __weak 61 # define __weak __attribute__((weak)) 62 #endif 63 64 #ifndef likely 65 # define likely(x) __builtin_expect(!!(x), 1) 66 #endif 67 68 #ifndef unlikely 69 # define unlikely(x) __builtin_expect(!!(x), 0) 70 #endif 71 72 #define uninitialized_var(x) x = *(&(x)) 73 74 #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x)) 75 76 #include <linux/types.h> 77 78 /* 79 * Following functions are taken from kernel sources and 80 * break aliasing rules in their original form. 81 * 82 * While kernel is compiled with -fno-strict-aliasing, 83 * perf uses -Wstrict-aliasing=3 which makes build fail 84 * under gcc 4.4. 85 * 86 * Using extra __may_alias__ type to allow aliasing 87 * in this case. 88 */ 89 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t; 90 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t; 91 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t; 92 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t; 93 94 static __always_inline void __read_once_size(const volatile void *p, void *res, int size) 95 { 96 switch (size) { 97 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break; 98 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break; 99 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break; 100 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break; 101 default: 102 barrier(); 103 __builtin_memcpy((void *)res, (const void *)p, size); 104 barrier(); 105 } 106 } 107 108 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 109 { 110 switch (size) { 111 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break; 112 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break; 113 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break; 114 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break; 115 default: 116 barrier(); 117 __builtin_memcpy((void *)p, (const void *)res, size); 118 barrier(); 119 } 120 } 121 122 /* 123 * Prevent the compiler from merging or refetching reads or writes. The 124 * compiler is also forbidden from reordering successive instances of 125 * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the 126 * compiler is aware of some particular ordering. One way to make the 127 * compiler aware of ordering is to put the two invocations of READ_ONCE, 128 * WRITE_ONCE or ACCESS_ONCE() in different C statements. 129 * 130 * In contrast to ACCESS_ONCE these two macros will also work on aggregate 131 * data types like structs or unions. If the size of the accessed data 132 * type exceeds the word size of the machine (e.g., 32 bits or 64 bits) 133 * READ_ONCE() and WRITE_ONCE() will fall back to memcpy and print a 134 * compile-time warning. 135 * 136 * Their two major use cases are: (1) Mediating communication between 137 * process-level code and irq/NMI handlers, all running on the same CPU, 138 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 139 * mutilate accesses that either do not require ordering or that interact 140 * with an explicit memory barrier or atomic instruction that provides the 141 * required ordering. 142 */ 143 144 #define READ_ONCE(x) \ 145 ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; }) 146 147 #define WRITE_ONCE(x, val) \ 148 ({ union { typeof(x) __val; char __c[1]; } __u = { .__val = (val) }; __write_once_size(&(x), __u.__c, sizeof(x)); __u.__val; }) 149 150 151 #ifndef __fallthrough 152 # define __fallthrough 153 #endif 154 155 #endif /* _TOOLS_LINUX_COMPILER_H */ 156