1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Supervisor Mode Access Prevention support
4 *
5 * Copyright (C) 2012 Intel Corporation
6 * Author: H. Peter Anvin <hpa@linux.intel.com>
7 */
8
9#ifndef _ASM_X86_SMAP_H
10#define _ASM_X86_SMAP_H
11
12#include <asm/nops.h>
13#include <asm/cpufeatures.h>
14#include <asm/alternative.h>
15
16/* "Raw" instruction opcodes */
17#define __ASM_CLAC ".byte 0x0f,0x01,0xca"
18#define __ASM_STAC ".byte 0x0f,0x01,0xcb"
19
20#ifdef __ASSEMBLY__
21
22#define ASM_CLAC \
23 ALTERNATIVE "", __ASM_CLAC, X86_FEATURE_SMAP
24
25#define ASM_STAC \
26 ALTERNATIVE "", __ASM_STAC, X86_FEATURE_SMAP
27
28#else /* __ASSEMBLY__ */
29
30static __always_inline void clac(void)
31{
32 /* Note: a barrier is implicit in alternative() */
33 alternative("", __ASM_CLAC, X86_FEATURE_SMAP);
34}
35
36static __always_inline void stac(void)
37{
38 /* Note: a barrier is implicit in alternative() */
39 alternative("", __ASM_STAC, X86_FEATURE_SMAP);
40}
41
42static __always_inline unsigned long smap_save(void)
43{
44 unsigned long flags;
45
46 asm volatile ("# smap_save\n\t"
47 ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC "\n\t",
48 X86_FEATURE_SMAP)
49 : "=rm" (flags) : : "memory", "cc");
50
51 return flags;
52}
53
54static __always_inline void smap_restore(unsigned long flags)
55{
56 asm volatile ("# smap_restore\n\t"
57 ALTERNATIVE("", "push %0; popf\n\t",
58 X86_FEATURE_SMAP)
59 : : "g" (flags) : "memory", "cc");
60}
61
62/* These macros can be used in asm() statements */
63#define ASM_CLAC \
64 ALTERNATIVE("", __ASM_CLAC, X86_FEATURE_SMAP)
65#define ASM_STAC \
66 ALTERNATIVE("", __ASM_STAC, X86_FEATURE_SMAP)
67
68#endif /* __ASSEMBLY__ */
69
70#endif /* _ASM_X86_SMAP_H */
71

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