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