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 #ifndef __nocf_check
62 #define __nocf_check __attribute__((nocf_check))
63 #endif
64
65 #ifndef __naked
66 #define __naked __attribute__((__naked__))
67 #endif
68
69 /* Are two types/vars the same type (ignoring qualifiers)? */
70 #ifndef __same_type
71 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
72 #endif
73
74 /*
75 * This returns a constant expression while determining if an argument is
76 * a constant expression, most importantly without evaluating the argument.
77 * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
78 */
79 #define __is_constexpr(x) \
80 (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
81
82 #ifdef __ANDROID__
83 /*
84 * FIXME: Big hammer to get rid of tons of:
85 * "warning: always_inline function might not be inlinable"
86 *
87 * At least on android-ndk-r12/platforms/android-24/arch-arm
88 */
89 #undef __always_inline
90 #define __always_inline inline
91 #endif
92
93 #define __user
94 #define __rcu
95 #define __read_mostly
96
97 #ifndef __attribute_const__
98 # define __attribute_const__
99 #endif
100
101 #ifndef __maybe_unused
102 # define __maybe_unused __attribute__((unused))
103 #endif
104
105 #ifndef __used
106 # define __used __attribute__((__unused__))
107 #endif
108
109 #ifndef __packed
110 # define __packed __attribute__((__packed__))
111 #endif
112
113 #ifndef __force
114 # define __force
115 #endif
116
117 #ifndef __weak
118 # define __weak __attribute__((weak))
119 #endif
120
121 #ifndef likely
122 # define likely(x) __builtin_expect(!!(x), 1)
123 #endif
124
125 #ifndef unlikely
126 # define unlikely(x) __builtin_expect(!!(x), 0)
127 #endif
128
129 #ifndef __init
130 # define __init
131 #endif
132
133 #include <linux/types.h>
134
135 /*
136 * Following functions are taken from kernel sources and
137 * break aliasing rules in their original form.
138 *
139 * While kernel is compiled with -fno-strict-aliasing,
140 * perf uses -Wstrict-aliasing=3 which makes build fail
141 * under gcc 4.4.
142 *
143 * Using extra __may_alias__ type to allow aliasing
144 * in this case.
145 */
146 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t;
147 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
148 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
149 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
150
151 static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
152 {
153 switch (size) {
154 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break;
155 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
156 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
157 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
158 default:
159 barrier();
160 __builtin_memcpy((void *)res, (const void *)p, size);
161 barrier();
162 }
163 }
164
165 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
166 {
167 switch (size) {
168 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break;
169 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
170 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
171 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
172 default:
173 barrier();
174 __builtin_memcpy((void *)p, (const void *)res, size);
175 barrier();
176 }
177 }
178
179 /*
180 * Prevent the compiler from merging or refetching reads or writes. The
181 * compiler is also forbidden from reordering successive instances of
182 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
183 * particular ordering. One way to make the compiler aware of ordering is to
184 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
185 * statements.
186 *
187 * These two macros will also work on aggregate data types like structs or
188 * unions. If the size of the accessed data type exceeds the word size of
189 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
190 * fall back to memcpy and print a compile-time warning.
191 *
192 * Their two major use cases are: (1) Mediating communication between
193 * process-level code and irq/NMI handlers, all running on the same CPU,
194 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
195 * mutilate accesses that either do not require ordering or that interact
196 * with an explicit memory barrier or atomic instruction that provides the
197 * required ordering.
198 */
199
200 #define READ_ONCE(x) \
201 ({ \
202 union { typeof(x) __val; char __c[1]; } __u = \
203 { .__c = { 0 } }; \
204 __read_once_size(&(x), __u.__c, sizeof(x)); \
205 __u.__val; \
206 })
207
208 #define WRITE_ONCE(x, val) \
209 ({ \
210 union { typeof(x) __val; char __c[1]; } __u = \
211 { .__val = (val) }; \
212 __write_once_size(&(x), __u.__c, sizeof(x)); \
213 __u.__val; \
214 })
215
216
217 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
218 #define ___PASTE(a, b) a##b
219 #define __PASTE(a, b) ___PASTE(a, b)
220
221 #ifndef OPTIMIZER_HIDE_VAR
222 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
223 #define OPTIMIZER_HIDE_VAR(var) \
224 __asm__ ("" : "=r" (var) : "" (var))
225 #endif
226
227 #endif /* _TOOLS_LINUX_COMPILER_H */
228
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