tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
61static __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
67static __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
81static inline void clac(void) { }
82static 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 */