1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _TOOLS_LINUX_COMPILER_H_
3 #define _TOOLS_LINUX_COMPILER_H_
4
5 #ifndef __ASSEMBLY__
6
7 #include <linux/compiler_types.h>
8
9 #ifndef __compiletime_error
10 # define __compiletime_error(message)
11 #endif
12
13 #ifdef __OPTIMIZE__
14 # define __compiletime_assert(condition, msg, prefix, suffix) \
15 do { \
16 extern void prefix ## suffix(void) __compiletime_error(msg); \
17 if (!(condition)) \
18 prefix ## suffix(); \
19 } while (0)
20 #else
21 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
22 #endif
23
24 #define _compiletime_assert(condition, msg, prefix, suffix) \
25 __compiletime_assert(condition, msg, prefix, suffix)
26
27 /**
28 * compiletime_assert - break build and emit msg if condition is false
29 * @condition: a compile-time constant condition to check
30 * @msg: a message to emit if condition is false
31 *
32 * In tradition of POSIX assert, this macro will break the build if the
33 * supplied condition is *false*, emitting the supplied error message if the
34 * compiler has support to do so.
35 */
36 #define compiletime_assert(condition, msg) \
37 _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
38
39 /* Optimization barrier */
40 /* The "volatile" is due to gcc bugs */
41 #define barrier() __asm__ __volatile__("": : :"memory")
42
43 #ifndef __always_inline
44 # define __always_inline inline __attribute__((always_inline))
45 #endif
46
47 #ifndef __always_unused
48 #define __always_unused __attribute__((__unused__))
49 #endif
50
51 #ifndef __noreturn
52 #define __noreturn __attribute__((__noreturn__))
53 #endif
54
55 #ifndef unreachable
56 #define unreachable() __builtin_unreachable()
57 #endif
58
59 #ifndef noinline
60 #define noinline
61 #endif
62
63 #ifndef __nocf_check
64 #define __nocf_check __attribute__((nocf_check))
65 #endif
66
67 #ifndef __naked
68 #define __naked __attribute__((__naked__))
69 #endif
70
71 /* Are two types/vars the same type (ignoring qualifiers)? */
72 #ifndef __same_type
73 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
74 #endif
75
76 /*
77 * This returns a constant expression while determining if an argument is
78 * a constant expression, most importantly without evaluating the argument.
79 * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
80 */
81 #define __is_constexpr(x) \
82 (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
83
84 /*
85 * Similar to statically_true() but produces a constant expression
86 *
87 * To be used in conjunction with macros, such as BUILD_BUG_ON_ZERO(),
88 * which require their input to be a constant expression and for which
89 * statically_true() would otherwise fail.
90 *
91 * This is a trade-off: const_true() requires all its operands to be
92 * compile time constants. Else, it would always returns false even on
93 * the most trivial cases like:
94 *
95 * true || non_const_var
96 *
97 * On the opposite, statically_true() is able to fold more complex
98 * tautologies and will return true on expressions such as:
99 *
100 * !(non_const_var * 8 % 4)
101 *
102 * For the general case, statically_true() is better.
103 */
104 #define const_true(x) __builtin_choose_expr(__is_constexpr(x), x, false)
105
106 #ifdef __ANDROID__
107 /*
108 * FIXME: Big hammer to get rid of tons of:
109 * "warning: always_inline function might not be inlinable"
110 *
111 * At least on android-ndk-r12/platforms/android-24/arch-arm
112 */
113 #undef __always_inline
114 #define __always_inline inline
115 #endif
116
117 #define __user
118 #define __rcu
119 #define __read_mostly
120
121 #ifndef __attribute_const__
122 # define __attribute_const__
123 #endif
124
125 #ifndef __maybe_unused
126 # define __maybe_unused __attribute__((unused))
127 #endif
128
129 #ifndef __used
130 # define __used __attribute__((__unused__))
131 #endif
132
133 #ifndef __packed
134 # define __packed __attribute__((__packed__))
135 #endif
136
137 #ifndef __force
138 # define __force
139 #endif
140
141 #ifndef __weak
142 # define __weak __attribute__((weak))
143 #endif
144
145 #ifndef likely
146 # define likely(x) __builtin_expect(!!(x), 1)
147 #endif
148
149 #ifndef unlikely
150 # define unlikely(x) __builtin_expect(!!(x), 0)
151 #endif
152
153 #include <linux/types.h>
154
155 /*
156 * Following functions are taken from kernel sources and
157 * break aliasing rules in their original form.
158 *
159 * While kernel is compiled with -fno-strict-aliasing,
160 * perf uses -Wstrict-aliasing=3 which makes build fail
161 * under gcc 4.4.
162 *
163 * Using extra __may_alias__ type to allow aliasing
164 * in this case.
165 */
166 typedef __u8 __attribute__((__may_alias__)) __u8_alias_t;
167 typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
168 typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
169 typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
170
__read_once_size(const volatile void * p,void * res,int size)171 static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
172 {
173 switch (size) {
174 case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break;
175 case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
176 case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
177 case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
178 default:
179 barrier();
180 __builtin_memcpy((void *)res, (const void *)p, size);
181 barrier();
182 }
183 }
184
__write_once_size(volatile void * p,void * res,int size)185 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
186 {
187 switch (size) {
188 case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break;
189 case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
190 case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
191 case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
192 default:
193 barrier();
194 __builtin_memcpy((void *)p, (const void *)res, size);
195 barrier();
196 }
197 }
198
199 /*
200 * Prevent the compiler from merging or refetching reads or writes. The
201 * compiler is also forbidden from reordering successive instances of
202 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
203 * particular ordering. One way to make the compiler aware of ordering is to
204 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
205 * statements.
206 *
207 * These two macros will also work on aggregate data types like structs or
208 * unions. If the size of the accessed data type exceeds the word size of
209 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
210 * fall back to memcpy and print a compile-time warning.
211 *
212 * Their two major use cases are: (1) Mediating communication between
213 * process-level code and irq/NMI handlers, all running on the same CPU,
214 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
215 * mutilate accesses that either do not require ordering or that interact
216 * with an explicit memory barrier or atomic instruction that provides the
217 * required ordering.
218 */
219
220 #define READ_ONCE(x) \
221 ({ \
222 union { typeof(x) __val; char __c[1]; } __u = \
223 { .__c = { 0 } }; \
224 __read_once_size(&(x), __u.__c, sizeof(x)); \
225 __u.__val; \
226 })
227
228 #define WRITE_ONCE(x, val) \
229 ({ \
230 union { typeof(x) __val; char __c[1]; } __u = \
231 { .__val = (val) }; \
232 __write_once_size(&(x), __u.__c, sizeof(x)); \
233 __u.__val; \
234 })
235
236
237 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
238 #define ___PASTE(a, b) a##b
239 #define __PASTE(a, b) ___PASTE(a, b)
240
241 #ifndef OPTIMIZER_HIDE_VAR
242 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
243 #define OPTIMIZER_HIDE_VAR(var) \
244 __asm__ ("" : "=r" (var) : "0" (var))
245 #endif
246
247 #ifndef __BUILD_BUG_ON_ZERO_MSG
248 #if defined(__clang__)
249 #define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) ((int)(sizeof(struct { int:(-!!(e)); })))
250 #else
251 #define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) ((int)sizeof(struct {_Static_assert(!(e), msg);}))
252 #endif
253 #endif
254
255 #endif /* __ASSEMBLY__ */
256
257 #endif /* _TOOLS_LINUX_COMPILER_H */
258