Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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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#include <linux/compiler_types.h>
6
7#ifndef __compiletime_error
8# define __compiletime_error(message)
9#endif
10
11#ifdef __OPTIMIZE__
12# define __compiletime_assert(condition, msg, prefix, suffix) \
13 do { \
14 extern void prefix ## suffix(void) __compiletime_error(msg); \
15 if (!(condition)) \
16 prefix ## suffix(); \
17 } while (0)
18#else
19# define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
20#endif
21
22#define _compiletime_assert(condition, msg, prefix, suffix) \
23 __compiletime_assert(condition, msg, prefix, suffix)
24
25/**
26 * compiletime_assert - break build and emit msg if condition is false
27 * @condition: a compile-time constant condition to check
28 * @msg: a message to emit if condition is false
29 *
30 * In tradition of POSIX assert, this macro will break the build if the
31 * supplied condition is *false*, emitting the supplied error message if the
32 * compiler has support to do so.
33 */
34#define compiletime_assert(condition, msg) \
35 _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
36
37/* Optimization barrier */
38/* The "volatile" is due to gcc bugs */
39#define barrier() __asm__ __volatile__("": : :"memory")
40
41#ifndef __always_inline
42# define __always_inline inline __attribute__((always_inline))
43#endif
44
45#ifndef noinline
46#define noinline
47#endif
48
49/* Are two types/vars the same type (ignoring qualifiers)? */
50#ifndef __same_type
51# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
52#endif
53
54#ifdef __ANDROID__
55/*
56 * FIXME: Big hammer to get rid of tons of:
57 * "warning: always_inline function might not be inlinable"
58 *
59 * At least on android-ndk-r12/platforms/android-24/arch-arm
60 */
61#undef __always_inline
62#define __always_inline inline
63#endif
64
65#define __user
66#define __rcu
67#define __read_mostly
68
69#ifndef __attribute_const__
70# define __attribute_const__
71#endif
72
73#ifndef __maybe_unused
74# define __maybe_unused __attribute__((unused))
75#endif
76
77#ifndef __used
78# define __used __attribute__((__unused__))
79#endif
80
81#ifndef __packed
82# define __packed __attribute__((__packed__))
83#endif
84
85#ifndef __force
86# define __force
87#endif
88
89#ifndef __weak
90# define __weak __attribute__((weak))
91#endif
92
93#ifndef likely
94# define likely(x) __builtin_expect(!!(x), 1)
95#endif
96
97#ifndef unlikely
98# define unlikely(x) __builtin_expect(!!(x), 0)
99#endif
100
101#ifndef __init
102# define __init
103#endif
104
105#ifndef noinline
106# define noinline
107#endif
108
109#include <linux/types.h>
110
111/*
112 * Following functions are taken from kernel sources and
113 * break aliasing rules in their original form.
114 *
115 * While kernel is compiled with -fno-strict-aliasing,
116 * perf uses -Wstrict-aliasing=3 which makes build fail
117 * under gcc 4.4.
118 *
119 * Using extra __may_alias__ type to allow aliasing
120 * in this case.
121 */
122typedef __u8 __attribute__((__may_alias__)) __u8_alias_t;
123typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
124typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
125typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
126
127static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
128{
129 switch (size) {
130 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break;
131 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
132 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
133 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
134 default:
135 barrier();
136 __builtin_memcpy((void *)res, (const void *)p, size);
137 barrier();
138 }
139}
140
141static __always_inline void __write_once_size(volatile void *p, void *res, int size)
142{
143 switch (size) {
144 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break;
145 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
146 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
147 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
148 default:
149 barrier();
150 __builtin_memcpy((void *)p, (const void *)res, size);
151 barrier();
152 }
153}
154
155/*
156 * Prevent the compiler from merging or refetching reads or writes. The
157 * compiler is also forbidden from reordering successive instances of
158 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
159 * particular ordering. One way to make the compiler aware of ordering is to
160 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
161 * statements.
162 *
163 * These two macros will also work on aggregate data types like structs or
164 * unions. If the size of the accessed data type exceeds the word size of
165 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
166 * fall back to memcpy and print a compile-time warning.
167 *
168 * Their two major use cases are: (1) Mediating communication between
169 * process-level code and irq/NMI handlers, all running on the same CPU,
170 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
171 * mutilate accesses that either do not require ordering or that interact
172 * with an explicit memory barrier or atomic instruction that provides the
173 * required ordering.
174 */
175
176#define READ_ONCE(x) \
177({ \
178 union { typeof(x) __val; char __c[1]; } __u = \
179 { .__c = { 0 } }; \
180 __read_once_size(&(x), __u.__c, sizeof(x)); \
181 __u.__val; \
182})
183
184#define WRITE_ONCE(x, val) \
185({ \
186 union { typeof(x) __val; char __c[1]; } __u = \
187 { .__val = (val) }; \
188 __write_once_size(&(x), __u.__c, sizeof(x)); \
189 __u.__val; \
190})
191
192
193#ifndef __fallthrough
194# define __fallthrough
195#endif
196
197/* Indirect macros required for expanded argument pasting, eg. __LINE__. */
198#define ___PASTE(a, b) a##b
199#define __PASTE(a, b) ___PASTE(a, b)
200
201#endif /* _TOOLS_LINUX_COMPILER_H */