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
42