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