LXR linux/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/cpufeature.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        661: ASM_NOP3 ;                                                 \
  32        .pushsection .altinstr_replacement, "ax" ;                      \
  33        662: __ASM_CLAC ;                                               \
  34        .popsection ;                                                   \
  35        .pushsection .altinstructions, "a" ;                            \
  36        altinstruction_entry 661b, 662b, X86_FEATURE_SMAP, 3, 3 ;       \
  37        .popsection
  38
  39#define ASM_STAC                                                        \
  40        661: ASM_NOP3 ;                                                 \
  41        .pushsection .altinstr_replacement, "ax" ;                      \
  42        662: __ASM_STAC ;                                               \
  43        .popsection ;                                                   \
  44        .pushsection .altinstructions, "a" ;                            \
  45        altinstruction_entry 661b, 662b, X86_FEATURE_SMAP, 3, 3 ;       \
  46        .popsection
  47
  48#else /* CONFIG_X86_SMAP */
  49
  50#define ASM_CLAC
  51#define ASM_STAC
  52
  53#endif /* CONFIG_X86_SMAP */
  54
  55#else /* __ASSEMBLY__ */
  56
  57#include <asm/alternative.h>
  58
  59#ifdef CONFIG_X86_SMAP
  60
  61static __always_inline void clac(void)
  62{
  63        /* Note: a barrier is implicit in alternative() */
  64        alternative(ASM_NOP3, __stringify(__ASM_CLAC), X86_FEATURE_SMAP);
  65}
  66
  67static __always_inline void stac(void)
  68{
  69        /* Note: a barrier is implicit in alternative() */
  70        alternative(ASM_NOP3, __stringify(__ASM_STAC), X86_FEATURE_SMAP);
  71}
  72
  73/* These macros can be used in asm() statements */
  74#define ASM_CLAC \
  75        ALTERNATIVE(ASM_NOP3, __stringify(__ASM_CLAC), X86_FEATURE_SMAP)
  76#define ASM_STAC \
  77        ALTERNATIVE(ASM_NOP3, __stringify(__ASM_STAC), X86_FEATURE_SMAP)
  78
  79#else /* CONFIG_X86_SMAP */
  80
  81static inline void clac(void) { }
  82static inline void stac(void) { }
  83
  84#define ASM_CLAC
  85#define ASM_STAC
  86
  87#endif /* CONFIG_X86_SMAP */
  88
  89#endif /* __ASSEMBLY__ */
  90
  91#endif /* _ASM_X86_SMAP_H */
  92