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1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #ifndef _ASM_PGTABLE_INVERT_H | |
3 | #define _ASM_PGTABLE_INVERT_H 1 | |
4 | ||
5 | #ifndef __ASSEMBLY__ | |
6 | ||
cb649fea SC |
7 | /* |
8 | * A clear pte value is special, and doesn't get inverted. | |
9 | * | |
10 | * Note that even users that only pass a pgprot_t (rather | |
11 | * than a full pte) won't trigger the special zero case, | |
12 | * because even PAGE_NONE has _PAGE_PROTNONE | _PAGE_ACCESSED | |
13 | * set. So the all zero case really is limited to just the | |
14 | * cleared page table entry case. | |
15 | */ | |
b1fb6302 AK |
16 | static inline bool __pte_needs_invert(u64 val) |
17 | { | |
cb649fea | 18 | return val && !(val & _PAGE_PRESENT); |
b1fb6302 AK |
19 | } |
20 | ||
21 | /* Get a mask to xor with the page table entry to get the correct pfn. */ | |
22 | static inline u64 protnone_mask(u64 val) | |
23 | { | |
24 | return __pte_needs_invert(val) ? ~0ull : 0; | |
25 | } | |
26 | ||
27 | static inline u64 flip_protnone_guard(u64 oldval, u64 val, u64 mask) | |
28 | { | |
29 | /* | |
30 | * When a PTE transitions from NONE to !NONE or vice-versa | |
31 | * invert the PFN part to stop speculation. | |
32 | * pte_pfn undoes this when needed. | |
33 | */ | |
34 | if (__pte_needs_invert(oldval) != __pte_needs_invert(val)) | |
35 | val = (val & ~mask) | (~val & mask); | |
36 | return val; | |
37 | } | |
38 | ||
39 | #endif /* __ASSEMBLY__ */ | |
40 | ||
41 | #endif |