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 (ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC,
  61                                   X86_FEATURE_SMAP)
  62                       : "=rm" (flags) : : "memory", "cc");
  63
  64         return flags;
  65 }
  66
  67 static __always_inline void smap_restore(unsigned long flags)
  68 {
  69         asm volatile (ALTERNATIVE("", "push %0; popf", 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 */