include/asm/smap.h

0001 /* SPDX-License-Identifier: GPL-2.0-only */
0002 /*
0003  * Supervisor Mode Access Prevention support
0004  *
0005  * Copyright (C) 2012 Intel Corporation
0006  * Author: H. Peter Anvin <hpa@linux.intel.com>
0007  */
0008
0009 #ifndef _ASM_X86_SMAP_H
0010 #define _ASM_X86_SMAP_H
0011
0012 #include <asm/nops.h>
0013 #include <asm/cpufeatures.h>
0014 #include <asm/alternative.h>
0015
0016 /* "Raw" instruction opcodes */
0017 #define __ASM_CLAC  ".byte 0x0f,0x01,0xca"
0018 #define __ASM_STAC  ".byte 0x0f,0x01,0xcb"
0019
0020 #ifdef __ASSEMBLY__
0021
0022 #define ASM_CLAC \
0023     ALTERNATIVE "", __ASM_CLAC, X86_FEATURE_SMAP
0024
0025 #define ASM_STAC \
0026     ALTERNATIVE "", __ASM_STAC, X86_FEATURE_SMAP
0027
0028 #else /* __ASSEMBLY__ */
0029
0030 static __always_inline void clac(void)
0031 {
0032     /* Note: a barrier is implicit in alternative() */
0033     alternative("", __ASM_CLAC, X86_FEATURE_SMAP);
0034 }
0035
0036 static __always_inline void stac(void)
0037 {
0038     /* Note: a barrier is implicit in alternative() */
0039     alternative("", __ASM_STAC, X86_FEATURE_SMAP);
0040 }
0041
0042 static __always_inline unsigned long smap_save(void)
0043 {
0044     unsigned long flags;
0045
0046     asm volatile ("# smap_save\n\t"
0047               ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC "\n\t",
0048                   X86_FEATURE_SMAP)
0049               : "=rm" (flags) : : "memory", "cc");
0050
0051     return flags;
0052 }
0053
0054 static __always_inline void smap_restore(unsigned long flags)
0055 {
0056     asm volatile ("# smap_restore\n\t"
0057               ALTERNATIVE("", "push %0; popf\n\t",
0058                   X86_FEATURE_SMAP)
0059               : : "g" (flags) : "memory", "cc");
0060 }
0061
0062 /* These macros can be used in asm() statements */
0063 #define ASM_CLAC \
0064     ALTERNATIVE("", __ASM_CLAC, X86_FEATURE_SMAP)
0065 #define ASM_STAC \
0066     ALTERNATIVE("", __ASM_STAC, X86_FEATURE_SMAP)
0067
0068 #endif /* __ASSEMBLY__ */
0069
0070 #endif /* _ASM_X86_SMAP_H */