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