1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_X86_PKRU_H
3#define _ASM_X86_PKRU_H
4
5#include <asm/cpufeature.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
12extern 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
19static 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
25static 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
35static inline u32 read_pkru(void)
36{
37 if (cpu_feature_enabled(X86_FEATURE_OSPKE))
38 return rdpkru();
39 return 0;
40}
41
42static 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
54static 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
63