compiler.h

 1/* SPDX-License-Identifier: GPL-2.0 */
 2#ifndef LINUX_COMPILER_H
 3#define LINUX_COMPILER_H
 4
 5/* Avoid redefinition warnings */
 6#undef __user
 7#include "../../../include/linux/compiler_types.h"
 8#undef __user
 9#define __user
10
11#define WRITE_ONCE(var, val) \
12	(*((volatile typeof(val) *)(&(var))) = (val))
13
14#define READ_ONCE(var) (*((volatile typeof(var) *)(&(var))))
15
16#define __aligned(x) __attribute((__aligned__(x)))
17
18/**
19 * data_race - mark an expression as containing intentional data races
20 *
21 * This data_race() macro is useful for situations in which data races
22 * should be forgiven.  One example is diagnostic code that accesses
23 * shared variables but is not a part of the core synchronization design.
24 * For example, if accesses to a given variable are protected by a lock,
25 * except for diagnostic code, then the accesses under the lock should
26 * be plain C-language accesses and those in the diagnostic code should
27 * use data_race().  This way, KCSAN will complain if buggy lockless
28 * accesses to that variable are introduced, even if the buggy accesses
29 * are protected by READ_ONCE() or WRITE_ONCE().
30 *
31 * This macro *does not* affect normal code generation, but is a hint
32 * to tooling that data races here are to be ignored.  If the access must
33 * be atomic *and* KCSAN should ignore the access, use both data_race()
34 * and READ_ONCE(), for example, data_race(READ_ONCE(x)).
35 */
36#define data_race(expr)							\
37({									\
38	auto __v = (expr);						\
39	__v;								\
40})
41
42#define __must_check
43
44#endif