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 */
16static 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. */
22static inline u64 protnone_mask(u64 val)
23{
24 return __pte_needs_invert(val) ? ~0ull : 0;
25}
26
27static 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
42