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 */
122 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t;
123 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
124 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
125 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
126
__read_once_size(const volatile void * p,void * res,int size)127 static __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
__write_once_size(volatile void * p,void * res,int size)141 static __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 */
202
