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
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
63
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