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
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 */
16 static inline bool __pte_needs_invert(u64 val)
17 {
18 return val && !(val & _PAGE_PRESENT);
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