| /* SPDX-License-Identifier: GPL-2.0 */ |
| #ifndef _ASM_PGTABLE_INVERT_H |
| #define _ASM_PGTABLE_INVERT_H 1 |
| |
| #ifndef __ASSEMBLY__ |
| |
| /* |
| * A clear pte value is special, and doesn't get inverted. |
| * |
| * Note that even users that only pass a pgprot_t (rather |
| * than a full pte) won't trigger the special zero case, |
| * because even PAGE_NONE has _PAGE_PROTNONE | _PAGE_ACCESSED |
| * set. So the all zero case really is limited to just the |
| * cleared page table entry case. |
| */ |
| static inline bool __pte_needs_invert(u64 val) |
| { |
| return val && !(val & _PAGE_PRESENT); |
| } |
| |
| /* Get a mask to xor with the page table entry to get the correct pfn. */ |
| static inline u64 protnone_mask(u64 val) |
| { |
| return __pte_needs_invert(val) ? ~0ull : 0; |
| } |
| |
| static inline u64 flip_protnone_guard(u64 oldval, u64 val, u64 mask) |
| { |
| /* |
| * When a PTE transitions from NONE to !NONE or vice-versa |
| * invert the PFN part to stop speculation. |
| * pte_pfn undoes this when needed. |
| */ |
| if (__pte_needs_invert(oldval) != __pte_needs_invert(val)) |
| val = (val & ~mask) | (~val & mask); |
| return val; |
| } |
| |
| #endif /* __ASSEMBLY__ */ |
| |
| #endif |
