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
  61 static __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
  67 static __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
  81 static inline void clac(void) { }
  82 static 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 */