arch/x86/include/asm/smap.h

   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 <[email protected]>
   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
  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
  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
  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
  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 */