arch/x86/include/asm/smap.h

   1 /*
   2  * Supervisor Mode Access Prevention support
   3  *
   4  * Copyright (C) 2012 Intel Corporation
   5  * Author: H. Peter Anvin <hpa@linux.intel.com>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; version 2
  10  * of the License.
  11  */
  12
  13 #ifndef _ASM_X86_SMAP_H
  14 #define _ASM_X86_SMAP_H
  15
  16 #include <linux/stringify.h>
  17 #include <asm/nops.h>
  18 #include <asm/cpufeatures.h>
  19
  20 /* "Raw" instruction opcodes */
  21 #define __ASM_CLAC      .byte 0x0f,0x01,0xca
  22 #define __ASM_STAC      .byte 0x0f,0x01,0xcb
  23
  24 #ifdef __ASSEMBLY__
  25
  26 #include <asm/alternative-asm.h>
  27
  28 #ifdef CONFIG_X86_SMAP
  29
  30 #define ASM_CLAC \
  31         ALTERNATIVE "", __stringify(__ASM_CLAC), X86_FEATURE_SMAP
  32
  33 #define ASM_STAC \
  34         ALTERNATIVE "", __stringify(__ASM_STAC), X86_FEATURE_SMAP
  35
  36 #else /* CONFIG_X86_SMAP */
  37
  38 #define ASM_CLAC
  39 #define ASM_STAC
  40
  41 #endif /* CONFIG_X86_SMAP */
  42
  43 #else /* __ASSEMBLY__ */
  44
  45 #include <asm/alternative.h>
  46
  47 #ifdef CONFIG_X86_SMAP
  48
  49 static __always_inline void clac(void)
  50 {
  51         /* Note: a barrier is implicit in alternative() */
  52         alternative("", __stringify(__ASM_CLAC), X86_FEATURE_SMAP);
  53 }
  54
  55 static __always_inline void stac(void)
  56 {
  57         /* Note: a barrier is implicit in alternative() */
  58         alternative("", __stringify(__ASM_STAC), X86_FEATURE_SMAP);
  59 }
  60
  61 /* These macros can be used in asm() statements */
  62 #define ASM_CLAC \
  63         ALTERNATIVE("", __stringify(__ASM_CLAC), X86_FEATURE_SMAP)
  64 #define ASM_STAC \
  65         ALTERNATIVE("", __stringify(__ASM_STAC), X86_FEATURE_SMAP)
  66
  67 #else /* CONFIG_X86_SMAP */
  68
  69 static inline void clac(void) { }
  70 static inline void stac(void) { }
  71
  72 #define ASM_CLAC
  73 #define ASM_STAC
  74
  75 #endif /* CONFIG_X86_SMAP */
  76
  77 #endif /* __ASSEMBLY__ */
  78
  79 #endif /* _ASM_X86_SMAP_H */