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
30 static __always_inline void clac(void)
31 {
32 /* Note: a barrier is implicit in alternative() */
33 alternative("", __ASM_CLAC, X86_FEATURE_SMAP);
34 }
35
36 static __always_inline void stac(void)
37 {
38 /* Note: a barrier is implicit in alternative() */
39 alternative("", __ASM_STAC, X86_FEATURE_SMAP);
40 }
41
42 static __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
54 static __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
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