xref: /linux/arch/x86/include/asm/smap.h (revision 4f2c0a4acffbec01079c28f839422e64ddeff004)
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 
clac(void)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 
stac(void)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 
smap_save(void)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 
smap_restore(unsigned long flags)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