| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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| 2 | #ifndef _ASM_PGTABLE_INVERT_H |
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| 3 | #define _ASM_PGTABLE_INVERT_H 1 |
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| 4 | |
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| 5 | #ifndef __ASSEMBLY__ |
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| 6 | |
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| 7 | /* |
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| 8 | * A clear pte value is special, and doesn't get inverted. |
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| 9 | * |
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| 10 | * Note that even users that only pass a pgprot_t (rather |
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| 11 | * than a full pte) won't trigger the special zero case, |
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| 12 | * because even PAGE_NONE has _PAGE_PROTNONE | _PAGE_ACCESSED |
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| 13 | * set. So the all zero case really is limited to just the |
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| 14 | * cleared page table entry case. |
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| 15 | */ |
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| 16 | static inline bool __pte_needs_invert(u64 val) |
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| 17 | { |
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| 18 | return val && !(val & _PAGE_PRESENT); |
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| 19 | } |
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| 20 | |
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| 21 | /* Get a mask to xor with the page table entry to get the correct pfn. */ |
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| 22 | static inline u64 protnone_mask(u64 val) |
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| 23 | { |
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| 24 | return __pte_needs_invert(val) ? ~0ull : 0; |
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| 25 | } |
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| 26 | |
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| 27 | static inline u64 flip_protnone_guard(u64 oldval, u64 val, u64 mask) |
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| 28 | { |
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| 29 | /* |
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| 30 | * When a PTE transitions from NONE to !NONE or vice-versa |
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| 31 | * invert the PFN part to stop speculation. |
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| 32 | * pte_pfn undoes this when needed. |
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| 33 | */ |
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| 34 | if (__pte_needs_invert(val: oldval) != __pte_needs_invert(val)) |
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| 35 | val = (val & ~mask) | (~val & mask); |
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| 36 | return val; |
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| 37 | } |
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| 38 | |
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| 39 | #endif /* __ASSEMBLY__ */ |
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| 40 | |
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| 41 | #endif |
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| 42 | |
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