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 <hpa@linux.intel.com>
   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 #ifdef CONFIG_X86_SMAP
  23
  24 #define ASM_CLAC \
  25         ALTERNATIVE "", __ASM_CLAC, X86_FEATURE_SMAP
  26
  27 #define ASM_STAC \
  28         ALTERNATIVE "", __ASM_STAC, X86_FEATURE_SMAP
  29
  30 #else /* CONFIG_X86_SMAP */
  31
  32 #define ASM_CLAC
  33 #define ASM_STAC
  34
  35 #endif /* CONFIG_X86_SMAP */
  36
  37 #else /* __ASSEMBLY__ */
  38
  39 #ifdef CONFIG_X86_SMAP
  40
  41 static __always_inline void clac(void)
  42 {
  43         /* Note: a barrier is implicit in alternative() */
  44         alternative("", __ASM_CLAC, X86_FEATURE_SMAP);
  45 }
  46
  47 static __always_inline void stac(void)
  48 {
  49         /* Note: a barrier is implicit in alternative() */
  50         alternative("", __ASM_STAC, X86_FEATURE_SMAP);
  51 }
  52
  53 static __always_inline unsigned long smap_save(void)
  54 {
  55         unsigned long flags;
  56
  57         asm volatile ("# smap_save\n\t"
  58                       ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC "\n\t",
  59                                   X86_FEATURE_SMAP)
  60                       : "=rm" (flags) : : "memory", "cc");
  61
  62         return flags;
  63 }
  64
  65 static __always_inline void smap_restore(unsigned long flags)
  66 {
  67         asm volatile ("# smap_restore\n\t"
  68                       ALTERNATIVE("", "push %0; popf\n\t",
  69                                   X86_FEATURE_SMAP)
  70                       : : "g" (flags) : "memory", "cc");
  71 }
  72
  73 /* These macros can be used in asm() statements */
  74 #define ASM_CLAC \
  75         ALTERNATIVE("", __ASM_CLAC, X86_FEATURE_SMAP)
  76 #define ASM_STAC \
  77         ALTERNATIVE("", __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 static inline unsigned long smap_save(void) { return 0; }
  85 static inline void smap_restore(unsigned long flags) { }
  86
  87 #define ASM_CLAC
  88 #define ASM_STAC
  89
  90 #endif /* CONFIG_X86_SMAP */
  91
  92 #endif /* __ASSEMBLY__ */
  93
  94 #endif /* _ASM_X86_SMAP_H */