42 lines
1.1 KiB
C
42 lines
1.1 KiB
C
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/* 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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