1 /*
2 * Supervisor Mode Access Prevention support
3 *
4 * Copyright (C) 2012 Intel Corporation
5 * Author: H. Peter Anvin <hpa@linux.intel.com>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; version 2
10 * of the License.
11 */
12
13 #ifndef _ASM_X86_SMAP_H
14 #define _ASM_X86_SMAP_H
15
16 #include <linux/stringify.h>
17 #include <asm/nops.h>
18 #include <asm/cpufeature.h>
19
20 /* "Raw" instruction opcodes */
21 #define __ASM_CLAC .byte 0x0f,0x01,0xca
22 #define __ASM_STAC .byte 0x0f,0x01,0xcb
23
24 #ifdef __ASSEMBLY__
25
26 #include <asm/alternative-asm.h>
27
28 #ifdef CONFIG_X86_SMAP
29
30 #define ASM_CLAC \
31 661: ASM_NOP3 ; \
32 .pushsection .altinstr_replacement, "ax" ; \
33 662: __ASM_CLAC ; \
34 .popsection ; \
35 .pushsection .altinstructions, "a" ; \
36 altinstruction_entry 661b, 662b, X86_FEATURE_SMAP, 3, 3 ; \
37 .popsection
38
39 #define ASM_STAC \
40 661: ASM_NOP3 ; \
41 .pushsection .altinstr_replacement, "ax" ; \
42 662: __ASM_STAC ; \
43 .popsection ; \
44 .pushsection .altinstructions, "a" ; \
45 altinstruction_entry 661b, 662b, X86_FEATURE_SMAP, 3, 3 ; \
46 .popsection
47
48 #else /* CONFIG_X86_SMAP */
49
50 #define ASM_CLAC
51 #define ASM_STAC
52
53 #endif /* CONFIG_X86_SMAP */
54
55 #else /* __ASSEMBLY__ */
56
57 #include <asm/alternative.h>
58
59 #ifdef CONFIG_X86_SMAP
60
clac(void)61 static __always_inline void clac(void)
62 {
63 /* Note: a barrier is implicit in alternative() */
64 alternative(ASM_NOP3, __stringify(__ASM_CLAC), X86_FEATURE_SMAP);
65 }
66
stac(void)67 static __always_inline void stac(void)
68 {
69 /* Note: a barrier is implicit in alternative() */
70 alternative(ASM_NOP3, __stringify(__ASM_STAC), X86_FEATURE_SMAP);
71 }
72
73 /* These macros can be used in asm() statements */
74 #define ASM_CLAC \
75 ALTERNATIVE(ASM_NOP3, __stringify(__ASM_CLAC), X86_FEATURE_SMAP)
76 #define ASM_STAC \
77 ALTERNATIVE(ASM_NOP3, __stringify(__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
84 #define ASM_CLAC
85 #define ASM_STAC
86
87 #endif /* CONFIG_X86_SMAP */
88
89 #endif /* __ASSEMBLY__ */
90
91 #endif /* _ASM_X86_SMAP_H */
92