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 __always_unused
46 #define __always_unused __attribute__((__unused__))
47 #endif
48
49 #ifndef __noreturn
50 #define __noreturn __attribute__((__noreturn__))
51 #endif
52
53 #ifndef unreachable
54 #define unreachable() __builtin_unreachable()
55 #endif
56
57 #ifndef noinline
58 #define noinline
59 #endif
60
61 /* Are two types/vars the same type (ignoring qualifiers)? */
62 #ifndef __same_type
63 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
64 #endif
65
66 #ifdef __ANDROID__
67 /*
68 * FIXME: Big hammer to get rid of tons of:
69 * "warning: always_inline function might not be inlinable"
70 *
71 * At least on android-ndk-r12/platforms/android-24/arch-arm
72 */
73 #undef __always_inline
74 #define __always_inline inline
75 #endif
76
77 #define __user
78 #define __rcu
79 #define __read_mostly
80
81 #ifndef __attribute_const__
82 # define __attribute_const__
83 #endif
84
85 #ifndef __maybe_unused
86 # define __maybe_unused __attribute__((unused))
87 #endif
88
89 #ifndef __used
90 # define __used __attribute__((__unused__))
91 #endif
92
93 #ifndef __packed
94 # define __packed __attribute__((__packed__))
95 #endif
96
97 #ifndef __force
98 # define __force
99 #endif
100
101 #ifndef __weak
102 # define __weak __attribute__((weak))
103 #endif
104
105 #ifndef likely
106 # define likely(x) __builtin_expect(!!(x), 1)
107 #endif
108
109 #ifndef unlikely
110 # define unlikely(x) __builtin_expect(!!(x), 0)
111 #endif
112
113 #ifndef __init
114 # define __init
115 #endif
116
117 #include <linux/types.h>
118
119 /*
120 * Following functions are taken from kernel sources and
121 * break aliasing rules in their original form.
122 *
123 * While kernel is compiled with -fno-strict-aliasing,
124 * perf uses -Wstrict-aliasing=3 which makes build fail
125 * under gcc 4.4.
126 *
127 * Using extra __may_alias__ type to allow aliasing
128 * in this case.
129 */
130 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t;
131 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
132 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
133 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
134
__read_once_size(const volatile void * p,void * res,int size)135 static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
136 {
137 switch (size) {
138 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break;
139 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
140 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
141 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
142 default:
143 barrier();
144 __builtin_memcpy((void *)res, (const void *)p, size);
145 barrier();
146 }
147 }
148
__write_once_size(volatile void * p,void * res,int size)149 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
150 {
151 switch (size) {
152 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break;
153 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
154 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
155 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
156 default:
157 barrier();
158 __builtin_memcpy((void *)p, (const void *)res, size);
159 barrier();
160 }
161 }
162
163 /*
164 * Prevent the compiler from merging or refetching reads or writes. The
165 * compiler is also forbidden from reordering successive instances of
166 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
167 * particular ordering. One way to make the compiler aware of ordering is to
168 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
169 * statements.
170 *
171 * These two macros will also work on aggregate data types like structs or
172 * unions. If the size of the accessed data type exceeds the word size of
173 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
174 * fall back to memcpy and print a compile-time warning.
175 *
176 * Their two major use cases are: (1) Mediating communication between
177 * process-level code and irq/NMI handlers, all running on the same CPU,
178 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
179 * mutilate accesses that either do not require ordering or that interact
180 * with an explicit memory barrier or atomic instruction that provides the
181 * required ordering.
182 */
183
184 #define READ_ONCE(x) \
185 ({ \
186 union { typeof(x) __val; char __c[1]; } __u = \
187 { .__c = { 0 } }; \
188 __read_once_size(&(x), __u.__c, sizeof(x)); \
189 __u.__val; \
190 })
191
192 #define WRITE_ONCE(x, val) \
193 ({ \
194 union { typeof(x) __val; char __c[1]; } __u = \
195 { .__val = (val) }; \
196 __write_once_size(&(x), __u.__c, sizeof(x)); \
197 __u.__val; \
198 })
199
200
201 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
202 #define ___PASTE(a, b) a##b
203 #define __PASTE(a, b) ___PASTE(a, b)
204
205 #ifndef OPTIMIZER_HIDE_VAR
206 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
207 #define OPTIMIZER_HIDE_VAR(var) \
208 __asm__ ("" : "=r" (var) : "0" (var))
209 #endif
210
211 #endif /* _TOOLS_LINUX_COMPILER_H */
212
