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
  15 /* "Raw" instruction opcodes */
  16 #define __ASM_CLAC      ".byte 0x0f,0x01,0xca"
  17 #define __ASM_STAC      ".byte 0x0f,0x01,0xcb"
  18
  19 #ifdef __ASSEMBLY__
  20
  21 #include <asm/alternative-asm.h>
  22
  23 #ifdef CONFIG_X86_SMAP
  24
  25 #define ASM_CLAC \
  26         ALTERNATIVE "", __ASM_CLAC, X86_FEATURE_SMAP
  27
  28 #define ASM_STAC \
  29         ALTERNATIVE "", __ASM_STAC, X86_FEATURE_SMAP
  30
  31 #else /* CONFIG_X86_SMAP */
  32
  33 #define ASM_CLAC
  34 #define ASM_STAC
  35
  36 #endif /* CONFIG_X86_SMAP */
  37
  38 #else /* __ASSEMBLY__ */
  39
  40 #include <asm/alternative.h>
  41
  42 #ifdef CONFIG_X86_SMAP
  43
  44 static __always_inline void clac(void)
  45 {
  46         /* Note: a barrier is implicit in alternative() */
  47         alternative("", __ASM_CLAC, X86_FEATURE_SMAP);
  48 }
  49
  50 static __always_inline void stac(void)
  51 {
  52         /* Note: a barrier is implicit in alternative() */
  53         alternative("", __ASM_STAC, X86_FEATURE_SMAP);
  54 }
  55
  56 static __always_inline unsigned long smap_save(void)
  57 {
  58         unsigned long flags;
  59
  60         asm volatile ("# smap_save\n\t"
  61                       ALTERNATIVE("jmp 1f", "", X86_FEATURE_SMAP)
  62                       "pushf; pop %0; " __ASM_CLAC "\n\t"
  63                       "1:"
  64                       : "=rm" (flags) : : "memory", "cc");
  65
  66         return flags;
  67 }
  68
  69 static __always_inline void smap_restore(unsigned long flags)
  70 {
  71         asm volatile ("# smap_restore\n\t"
  72                       ALTERNATIVE("jmp 1f", "", X86_FEATURE_SMAP)
  73                       "push %0; popf\n\t"
  74                       "1:"
  75                       : : "g" (flags) : "memory", "cc");
  76 }
  77
  78 /* These macros can be used in asm() statements */
  79 #define ASM_CLAC \
  80         ALTERNATIVE("", __ASM_CLAC, X86_FEATURE_SMAP)
  81 #define ASM_STAC \
  82         ALTERNATIVE("", __ASM_STAC, X86_FEATURE_SMAP)
  83
  84 #else /* CONFIG_X86_SMAP */
  85
  86 static inline void clac(void) { }
  87 static inline void stac(void) { }
  88
  89 static inline unsigned long smap_save(void) { return 0; }
  90 static inline void smap_restore(unsigned long flags) { }
  91
  92 #define ASM_CLAC
  93 #define ASM_STAC
  94
  95 #endif /* CONFIG_X86_SMAP */
  96
  97 #endif /* __ASSEMBLY__ */
  98
  99 #endif /* _ASM_X86_SMAP_H */