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 #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
  26 static __always_inline void clac(void)
  27 {
  28         /* Note: a barrier is implicit in alternative() */
  29         alternative("", "clac", X86_FEATURE_SMAP);
  30 }
  31
  32 static __always_inline void stac(void)
  33 {
  34         /* Note: a barrier is implicit in alternative() */
  35         alternative("", "stac", X86_FEATURE_SMAP);
  36 }
  37
  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
  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 */