xref: /linux/arch/x86/include/asm/smap.h (revision 027ea4f5f2c814b703adabdd42b779cd98e24411)
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 #ifdef __ASSEMBLY__
17 
18 #define ASM_CLAC \
19 	ALTERNATIVE "", "clac", X86_FEATURE_SMAP
20 
21 #define ASM_STAC \
22 	ALTERNATIVE "", "stac", X86_FEATURE_SMAP
23 
24 #else /* __ASSEMBLY__ */
25 
clac(void)26 static __always_inline void clac(void)
27 {
28 	/* Note: a barrier is implicit in alternative() */
29 	alternative("", "clac", X86_FEATURE_SMAP);
30 }
31 
stac(void)32 static __always_inline void stac(void)
33 {
34 	/* Note: a barrier is implicit in alternative() */
35 	alternative("", "stac", X86_FEATURE_SMAP);
36 }
37 
smap_save(void)38 static __always_inline unsigned long smap_save(void)
39 {
40 	unsigned long flags;
41 
42 	asm volatile ("# smap_save\n\t"
43 		      ALTERNATIVE("", "pushf; pop %0; " "clac" "\n\t",
44 				  X86_FEATURE_SMAP)
45 		      : "=rm" (flags) : : "memory", "cc");
46 
47 	return flags;
48 }
49 
smap_restore(unsigned long flags)50 static __always_inline void smap_restore(unsigned long flags)
51 {
52 	asm volatile ("# smap_restore\n\t"
53 		      ALTERNATIVE("", "push %0; popf\n\t",
54 				  X86_FEATURE_SMAP)
55 		      : : "g" (flags) : "memory", "cc");
56 }
57 
58 /* These macros can be used in asm() statements */
59 #define ASM_CLAC \
60 	ALTERNATIVE("", "clac", X86_FEATURE_SMAP)
61 #define ASM_STAC \
62 	ALTERNATIVE("", "stac", X86_FEATURE_SMAP)
63 
64 #endif /* __ASSEMBLY__ */
65 
66 #endif /* _ASM_X86_SMAP_H */
67