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
15 /* "Raw" instruction opcodes */
16 #define __ASM_CLAC ".byte 0x0f,0x01,0xca"
17 #define __ASM_STAC ".byte 0x0f,0x01,0xcb"
18
19 #ifdef __ASSEMBLY__
20
21 #include <asm/alternative-asm.h>
22
23 #ifdef CONFIG_X86_SMAP
24
25 #define ASM_CLAC \
26 ALTERNATIVE "", __ASM_CLAC, X86_FEATURE_SMAP
27
28 #define ASM_STAC \
29 ALTERNATIVE "", __ASM_STAC, X86_FEATURE_SMAP
30
31 #else /* CONFIG_X86_SMAP */
32
33 #define ASM_CLAC
34 #define ASM_STAC
35
36 #endif /* CONFIG_X86_SMAP */
37
38 #else /* __ASSEMBLY__ */
39
40 #include <asm/alternative.h>
41
42 #ifdef CONFIG_X86_SMAP
43
clac(void)44 static __always_inline void clac(void)
45 {
46 /* Note: a barrier is implicit in alternative() */
47 alternative("", __ASM_CLAC, X86_FEATURE_SMAP);
48 }
49
stac(void)50 static __always_inline void stac(void)
51 {
52 /* Note: a barrier is implicit in alternative() */
53 alternative("", __ASM_STAC, X86_FEATURE_SMAP);
54 }
55
smap_save(void)56 static __always_inline unsigned long smap_save(void)
57 {
58 unsigned long flags;
59
60 asm volatile (ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC,
61 X86_FEATURE_SMAP)
62 : "=rm" (flags) : : "memory", "cc");
63
64 return flags;
65 }
66
smap_restore(unsigned long flags)67 static __always_inline void smap_restore(unsigned long flags)
68 {
69 asm volatile (ALTERNATIVE("", "push %0; popf", X86_FEATURE_SMAP)
70 : : "g" (flags) : "memory", "cc");
71 }
72
73 /* These macros can be used in asm() statements */
74 #define ASM_CLAC \
75 ALTERNATIVE("", __ASM_CLAC, X86_FEATURE_SMAP)
76 #define ASM_STAC \
77 ALTERNATIVE("", __ASM_STAC, X86_FEATURE_SMAP)
78
79 #else /* CONFIG_X86_SMAP */
80
clac(void)81 static inline void clac(void) { }
stac(void)82 static inline void stac(void) { }
83
smap_save(void)84 static inline unsigned long smap_save(void) { return 0; }
smap_restore(unsigned long flags)85 static inline void smap_restore(unsigned long flags) { }
86
87 #define ASM_CLAC
88 #define ASM_STAC
89
90 #endif /* CONFIG_X86_SMAP */
91
92 #endif /* __ASSEMBLY__ */
93
94 #endif /* _ASM_X86_SMAP_H */
95
