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