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