1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_X86_BARRIER_H
3#define _ASM_X86_BARRIER_H
4
5#include <asm/alternative.h>
6#include <asm/nops.h>
7
8/*
9 * Force strict CPU ordering.
10 * And yes, this might be required on UP too when we're talking
11 * to devices.
12 */
13
14#ifdef CONFIG_X86_32
15#define mb() asm volatile(ALTERNATIVE("lock addl $0,-4(%%esp)", "mfence", \
16 X86_FEATURE_XMM2) ::: "memory", "cc")
17#define rmb() asm volatile(ALTERNATIVE("lock addl $0,-4(%%esp)", "lfence", \
18 X86_FEATURE_XMM2) ::: "memory", "cc")
19#define wmb() asm volatile(ALTERNATIVE("lock addl $0,-4(%%esp)", "sfence", \
20 X86_FEATURE_XMM2) ::: "memory", "cc")
21#else
22#define __mb() asm volatile("mfence":::"memory")
23#define __rmb() asm volatile("lfence":::"memory")
24#define __wmb() asm volatile("sfence" ::: "memory")
25#endif
26
27/**
28 * array_index_mask_nospec() - generate a mask that is ~0UL when the
29 * bounds check succeeds and 0 otherwise
30 * @index: array element index
31 * @size: number of elements in array
32 *
33 * Returns:
34 * 0 - (index < size)
35 */
36#define array_index_mask_nospec(idx,sz) ({ \
37 typeof((idx)+(sz)) __idx = (idx); \
38 typeof(__idx) __sz = (sz); \
39 unsigned long __mask; \
40 asm volatile ("cmp %1,%2; sbb %0,%0" \
41 :"=r" (__mask) \
42 :ASM_INPUT_G (__sz), \
43 "r" (__idx) \
44 :"cc"); \
45 __mask; })
46
47/* Prevent speculative execution past this barrier. */
48#define barrier_nospec() alternative("", "lfence", X86_FEATURE_LFENCE_RDTSC)
49
50#define __dma_rmb() barrier()
51#define __dma_wmb() barrier()
52
53#define __smp_mb() asm volatile("lock addl $0,-4(%%" _ASM_SP ")" ::: "memory", "cc")
54
55#define __smp_rmb() dma_rmb()
56#define __smp_wmb() barrier()
57#define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)
58
59#define __smp_store_release(p, v) \
60do { \
61 compiletime_assert_atomic_type(*p); \
62 barrier(); \
63 WRITE_ONCE(*p, v); \
64} while (0)
65
66#define __smp_load_acquire(p) \
67({ \
68 typeof(*p) ___p1 = READ_ONCE(*p); \
69 compiletime_assert_atomic_type(*p); \
70 barrier(); \
71 ___p1; \
72})
73
74/* Atomic operations are already serializing on x86 */
75#define __smp_mb__before_atomic() do { } while (0)
76#define __smp_mb__after_atomic() do { } while (0)
77
78/* Writing to CR3 provides a full memory barrier in switch_mm(). */
79#define smp_mb__after_switch_mm() do { } while (0)
80
81#include <asm-generic/barrier.h>
82
83#endif /* _ASM_X86_BARRIER_H */
84

source code of linux/arch/x86/include/asm/barrier.h