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 */
100 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t;
101 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
102 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
103 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
104
__read_once_size(const volatile void * p,void * res,int size)105 static __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
__write_once_size(volatile void * p,void * res,int size)119 static __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 */
176
