arch/x86/include/asm/pkru.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_X86_PKRU_H
   3 #define _ASM_X86_PKRU_H
   4
   5 #include <asm/fpu/xstate.h>
   6
   7 #define PKRU_AD_BIT 0x1u
   8 #define PKRU_WD_BIT 0x2u
   9 #define PKRU_BITS_PER_PKEY 2
  10
  11 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
  12 extern u32 init_pkru_value;
  13 #define pkru_get_init_value()   READ_ONCE(init_pkru_value)
  14 #else
  15 #define init_pkru_value 0
  16 #define pkru_get_init_value()   0
  17 #endif
  18
  19 static inline bool __pkru_allows_read(u32 pkru, u16 pkey)
  20 {
  21         int pkru_pkey_bits = pkey * PKRU_BITS_PER_PKEY;
  22         return !(pkru & (PKRU_AD_BIT << pkru_pkey_bits));
  23 }
  24
  25 static inline bool __pkru_allows_write(u32 pkru, u16 pkey)
  26 {
  27         int pkru_pkey_bits = pkey * PKRU_BITS_PER_PKEY;
  28         /*
  29          * Access-disable disables writes too so we need to check
  30          * both bits here.
  31          */
  32         return !(pkru & ((PKRU_AD_BIT|PKRU_WD_BIT) << pkru_pkey_bits));
  33 }
  34
  35 static inline u32 read_pkru(void)
  36 {
  37         if (cpu_feature_enabled(X86_FEATURE_OSPKE))
  38                 return rdpkru();
  39         return 0;
  40 }
  41
  42 static inline void write_pkru(u32 pkru)
  43 {
  44         if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
  45                 return;
  46         /*
  47          * WRPKRU is relatively expensive compared to RDPKRU.
  48          * Avoid WRPKRU when it would not change the value.
  49          */
  50         if (pkru != rdpkru())
  51                 wrpkru(pkru);
  52 }
  53
  54 static inline void pkru_write_default(void)
  55 {
  56         if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
  57                 return;
  58
  59         wrpkru(pkru_get_init_value());
  60 }
  61
  62 #endif