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#ifdef __GNUC__
6#include <linux/compiler-gcc.h>
7#endif
8
9#ifndef __compiletime_error
10# define __compiletime_error(message)
11#endif
12
13#ifdef __OPTIMIZE__
14# define __compiletime_assert(condition, msg, prefix, suffix) \
15 do { \
16 extern void prefix ## suffix(void) __compiletime_error(msg); \
17 if (!(condition)) \
18 prefix ## suffix(); \
19 } while (0)
20#else
21# define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
22#endif
23
24#define _compiletime_assert(condition, msg, prefix, suffix) \
25 __compiletime_assert(condition, msg, prefix, suffix)
26
27/**
28 * compiletime_assert - break build and emit msg if condition is false
29 * @condition: a compile-time constant condition to check
30 * @msg: a message to emit if condition is false
31 *
32 * In tradition of POSIX assert, this macro will break the build if the
33 * supplied condition is *false*, emitting the supplied error message if the
34 * compiler has support to do so.
35 */
36#define compiletime_assert(condition, msg) \
37 _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
38
39/* Optimization barrier */
40/* The "volatile" is due to gcc bugs */
41#define barrier() __asm__ __volatile__("": : :"memory")
42
43#ifndef __always_inline
44# define __always_inline inline __attribute__((always_inline))
45#endif
46
47#ifndef noinline
48#define noinline
49#endif
50#ifndef __no_tail_call
51#define __no_tail_call
52#endif
53
54/* Are two types/vars the same type (ignoring qualifiers)? */
55#ifndef __same_type
56# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
57#endif
58
59#ifdef __ANDROID__
60/*
61 * FIXME: Big hammer to get rid of tons of:
62 * "warning: always_inline function might not be inlinable"
63 *
64 * At least on android-ndk-r12/platforms/android-24/arch-arm
65 */
66#undef __always_inline
67#define __always_inline inline
68#endif
69
70#define __user
71#define __rcu
72#define __read_mostly
73
74#ifndef __attribute_const__
75# define __attribute_const__
76#endif
77
78#ifndef __maybe_unused
79# define __maybe_unused __attribute__((unused))
80#endif
81
82#ifndef __used
83# define __used __attribute__((__unused__))
84#endif
85
86#ifndef __packed
87# define __packed __attribute__((__packed__))
88#endif
89
90#ifndef __force
91# define __force
92#endif
93
94#ifndef __weak
95# define __weak __attribute__((weak))
96#endif
97
98#ifndef likely
99# define likely(x) __builtin_expect(!!(x), 1)
100#endif
101
102#ifndef unlikely
103# define unlikely(x) __builtin_expect(!!(x), 0)
104#endif
105
106#ifndef __init
107# define __init
108#endif
109
110#ifndef noinline
111# define noinline
112#endif
113
114#include <linux/types.h>
115
116/*
117 * Following functions are taken from kernel sources and
118 * break aliasing rules in their original form.
119 *
120 * While kernel is compiled with -fno-strict-aliasing,
121 * perf uses -Wstrict-aliasing=3 which makes build fail
122 * under gcc 4.4.
123 *
124 * Using extra __may_alias__ type to allow aliasing
125 * in this case.
126 */
127typedef __u8 __attribute__((__may_alias__)) __u8_alias_t;
128typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
129typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
130typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
131
132static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
133{
134 switch (size) {
135 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break;
136 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
137 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
138 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
139 default:
140 barrier();
141 __builtin_memcpy((void *)res, (const void *)p, size);
142 barrier();
143 }
144}
145
146static __always_inline void __write_once_size(volatile void *p, void *res, int size)
147{
148 switch (size) {
149 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break;
150 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
151 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
152 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
153 default:
154 barrier();
155 __builtin_memcpy((void *)p, (const void *)res, size);
156 barrier();
157 }
158}
159
160/*
161 * Prevent the compiler from merging or refetching reads or writes. The
162 * compiler is also forbidden from reordering successive instances of
163 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
164 * particular ordering. One way to make the compiler aware of ordering is to
165 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
166 * statements.
167 *
168 * These two macros will also work on aggregate data types like structs or
169 * unions. If the size of the accessed data type exceeds the word size of
170 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
171 * fall back to memcpy and print a compile-time warning.
172 *
173 * Their two major use cases are: (1) Mediating communication between
174 * process-level code and irq/NMI handlers, all running on the same CPU,
175 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
176 * mutilate accesses that either do not require ordering or that interact
177 * with an explicit memory barrier or atomic instruction that provides the
178 * required ordering.
179 */
180
181#define READ_ONCE(x) \
182({ \
183 union { typeof(x) __val; char __c[1]; } __u = \
184 { .__c = { 0 } }; \
185 __read_once_size(&(x), __u.__c, sizeof(x)); \
186 __u.__val; \
187})
188
189#define WRITE_ONCE(x, val) \
190({ \
191 union { typeof(x) __val; char __c[1]; } __u = \
192 { .__val = (val) }; \
193 __write_once_size(&(x), __u.__c, sizeof(x)); \
194 __u.__val; \
195})
196
197
198#ifndef __fallthrough
199# define __fallthrough
200#endif
201
202/* Indirect macros required for expanded argument pasting, eg. __LINE__. */
203#define ___PASTE(a, b) a##b
204#define __PASTE(a, b) ___PASTE(a, b)
205
206#endif /* _TOOLS_LINUX_COMPILER_H */