aboutsummaryrefslogtreecommitdiff
path: root/tools/include/linux/compiler.h
blob: 04e32f965ad7f038beb2d8db9dc2119e07628744 (plain)
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
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _TOOLS_LINUX_COMPILER_H_
#define _TOOLS_LINUX_COMPILER_H_

#ifdef __GNUC__
#include <linux/compiler-gcc.h>
#endif

#ifndef __compiletime_error
# define __compiletime_error(message)
#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

#ifndef noinline
#define noinline
#endif

/* Are two types/vars the same type (ignoring qualifiers)? */
#ifndef __same_type
# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
#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
#define __rcu
#define __read_mostly

#ifndef __attribute_const__
# define __attribute_const__
#endif

#ifndef __maybe_unused
# define __maybe_unused		__attribute__((unused))
#endif

#ifndef __used
# define __used		__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

#ifndef __init
# define __init
#endif

#ifndef noinline
# define noinline
#endif

#define uninitialized_var(x) 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 and WRITE_ONCE, 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 or WRITE_ONCE in different C
 * statements.
 *
 * 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 */