Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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kernel
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linux
1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _TOOLS_LINUX_COMPILER_H_
3#define _TOOLS_LINUX_COMPILER_H_
4
5#ifdef __GNUC__
6#include <linux/compiler-gcc.h>
7#endif
8
9#ifndef __compiletime_error
10# define __compiletime_error(message)
11#endif
12
13/* Optimization barrier */
14/* The "volatile" is due to gcc bugs */
15#define barrier() __asm__ __volatile__("": : :"memory")
16
17#ifndef __always_inline
18# define __always_inline inline __attribute__((always_inline))
19#endif
20
21#ifndef noinline
22#define noinline
23#endif
24
25/* Are two types/vars the same type (ignoring qualifiers)? */
26#ifndef __same_type
27# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
28#endif
29
30#ifdef __ANDROID__
31/*
32 * FIXME: Big hammer to get rid of tons of:
33 * "warning: always_inline function might not be inlinable"
34 *
35 * At least on android-ndk-r12/platforms/android-24/arch-arm
36 */
37#undef __always_inline
38#define __always_inline inline
39#endif
40
41#define __user
42#define __rcu
43#define __read_mostly
44
45#ifndef __attribute_const__
46# define __attribute_const__
47#endif
48
49#ifndef __maybe_unused
50# define __maybe_unused __attribute__((unused))
51#endif
52
53#ifndef __used
54# define __used __attribute__((__unused__))
55#endif
56
57#ifndef __packed
58# define __packed __attribute__((__packed__))
59#endif
60
61#ifndef __force
62# define __force
63#endif
64
65#ifndef __weak
66# define __weak __attribute__((weak))
67#endif
68
69#ifndef likely
70# define likely(x) __builtin_expect(!!(x), 1)
71#endif
72
73#ifndef unlikely
74# define unlikely(x) __builtin_expect(!!(x), 0)
75#endif
76
77#ifndef __init
78# define __init
79#endif
80
81#ifndef noinline
82# define noinline
83#endif
84
85#define uninitialized_var(x) x = *(&(x))
86
87#include <linux/types.h>
88
89/*
90 * Following functions are taken from kernel sources and
91 * break aliasing rules in their original form.
92 *
93 * While kernel is compiled with -fno-strict-aliasing,
94 * perf uses -Wstrict-aliasing=3 which makes build fail
95 * under gcc 4.4.
96 *
97 * Using extra __may_alias__ type to allow aliasing
98 * in this case.
99 */
100typedef __u8 __attribute__((__may_alias__)) __u8_alias_t;
101typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
102typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
103typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
104
105static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
106{
107 switch (size) {
108 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break;
109 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
110 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
111 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
112 default:
113 barrier();
114 __builtin_memcpy((void *)res, (const void *)p, size);
115 barrier();
116 }
117}
118
119static __always_inline void __write_once_size(volatile void *p, void *res, int size)
120{
121 switch (size) {
122 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break;
123 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
124 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
125 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
126 default:
127 barrier();
128 __builtin_memcpy((void *)p, (const void *)res, size);
129 barrier();
130 }
131}
132
133/*
134 * Prevent the compiler from merging or refetching reads or writes. The
135 * compiler is also forbidden from reordering successive instances of
136 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
137 * particular ordering. One way to make the compiler aware of ordering is to
138 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
139 * statements.
140 *
141 * These two macros will also work on aggregate data types like structs or
142 * unions. If the size of the accessed data type exceeds the word size of
143 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
144 * fall back to memcpy and print a compile-time warning.
145 *
146 * Their two major use cases are: (1) Mediating communication between
147 * process-level code and irq/NMI handlers, all running on the same CPU,
148 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
149 * mutilate accesses that either do not require ordering or that interact
150 * with an explicit memory barrier or atomic instruction that provides the
151 * required ordering.
152 */
153
154#define READ_ONCE(x) \
155({ \
156 union { typeof(x) __val; char __c[1]; } __u = \
157 { .__c = { 0 } }; \
158 __read_once_size(&(x), __u.__c, sizeof(x)); \
159 __u.__val; \
160})
161
162#define WRITE_ONCE(x, val) \
163({ \
164 union { typeof(x) __val; char __c[1]; } __u = \
165 { .__val = (val) }; \
166 __write_once_size(&(x), __u.__c, sizeof(x)); \
167 __u.__val; \
168})
169
170
171#ifndef __fallthrough
172# define __fallthrough
173#endif
174
175#endif /* _TOOLS_LINUX_COMPILER_H */