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