mirror of
https://github.com/torvalds/linux.git
synced 2025-11-03 18:20:25 +02:00
002dff36ac
Now that 'smp_read_barrier_depends()' has gone the way of the Norwegian Blue, drop the inclusion of <asm/barrier.h> in 'asm-generic/rwonce.h'. This requires fixups to some architecture vdso headers which were previously relying on 'asm/barrier.h' coming in via 'linux/compiler.h'. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Will Deacon <will@kernel.org>
90 lines
2.9 KiB
C
90 lines
2.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* Prevent the compiler from merging or refetching reads or writes. The
|
|
* compiler is also forbidden from reordering successive instances of
|
|
* READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
|
|
* particular ordering. One way to make the compiler aware of ordering is to
|
|
* put the two invocations of READ_ONCE or WRITE_ONCE in different C
|
|
* statements.
|
|
*
|
|
* These two macros will also work on aggregate data types like structs or
|
|
* unions.
|
|
*
|
|
* Their two major use cases are: (1) Mediating communication between
|
|
* process-level code and irq/NMI handlers, all running on the same CPU,
|
|
* and (2) Ensuring that the compiler does not fold, spindle, or otherwise
|
|
* mutilate accesses that either do not require ordering or that interact
|
|
* with an explicit memory barrier or atomic instruction that provides the
|
|
* required ordering.
|
|
*/
|
|
#ifndef __ASM_GENERIC_RWONCE_H
|
|
#define __ASM_GENERIC_RWONCE_H
|
|
|
|
#ifndef __ASSEMBLY__
|
|
|
|
#include <linux/compiler_types.h>
|
|
#include <linux/kasan-checks.h>
|
|
#include <linux/kcsan-checks.h>
|
|
|
|
/*
|
|
* Yes, this permits 64-bit accesses on 32-bit architectures. These will
|
|
* actually be atomic in some cases (namely Armv7 + LPAE), but for others we
|
|
* rely on the access being split into 2x32-bit accesses for a 32-bit quantity
|
|
* (e.g. a virtual address) and a strong prevailing wind.
|
|
*/
|
|
#define compiletime_assert_rwonce_type(t) \
|
|
compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
|
|
"Unsupported access size for {READ,WRITE}_ONCE().")
|
|
|
|
/*
|
|
* Use __READ_ONCE() instead of READ_ONCE() if you do not require any
|
|
* atomicity. Note that this may result in tears!
|
|
*/
|
|
#ifndef __READ_ONCE
|
|
#define __READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x))
|
|
#endif
|
|
|
|
#define READ_ONCE(x) \
|
|
({ \
|
|
compiletime_assert_rwonce_type(x); \
|
|
__READ_ONCE(x); \
|
|
})
|
|
|
|
#define __WRITE_ONCE(x, val) \
|
|
do { \
|
|
*(volatile typeof(x) *)&(x) = (val); \
|
|
} while (0)
|
|
|
|
#define WRITE_ONCE(x, val) \
|
|
do { \
|
|
compiletime_assert_rwonce_type(x); \
|
|
__WRITE_ONCE(x, val); \
|
|
} while (0)
|
|
|
|
static __no_sanitize_or_inline
|
|
unsigned long __read_once_word_nocheck(const void *addr)
|
|
{
|
|
return __READ_ONCE(*(unsigned long *)addr);
|
|
}
|
|
|
|
/*
|
|
* Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need to load a
|
|
* word from memory atomically but without telling KASAN/KCSAN. This is
|
|
* usually used by unwinding code when walking the stack of a running process.
|
|
*/
|
|
#define READ_ONCE_NOCHECK(x) \
|
|
({ \
|
|
compiletime_assert(sizeof(x) == sizeof(unsigned long), \
|
|
"Unsupported access size for READ_ONCE_NOCHECK()."); \
|
|
(typeof(x))__read_once_word_nocheck(&(x)); \
|
|
})
|
|
|
|
static __no_kasan_or_inline
|
|
unsigned long read_word_at_a_time(const void *addr)
|
|
{
|
|
kasan_check_read(addr, 1);
|
|
return *(unsigned long *)addr;
|
|
}
|
|
|
|
#endif /* __ASSEMBLY__ */
|
|
#endif /* __ASM_GENERIC_RWONCE_H */
|