Commit ff1712f9 authored by Will Deacon's avatar Will Deacon
Browse files

arm64: pgtable: Ensure dirty bit is preserved across pte_wrprotect() 



With hardware dirty bit management, calling pte_wrprotect() on a writable,
dirty PTE will lose the dirty state and return a read-only, clean entry.

Move the logic from ptep_set_wrprotect() into pte_wrprotect() to ensure that
the dirty bit is preserved for writable entries, as this is required for
soft-dirty bit management if we enable it in the future.

Cc: <stable@vger.kernel.org>
Fixes: 2f4b829c ("arm64: Add support for hardware updates of the access and dirty pte bits")
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20201120143557.6715-3-will@kernel.org


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 07509e10

arch/arm64/include/asm/pgtable.h

+14 −13
Original line number Diff line number Diff line
@@ -165,13 +165,6 @@ static inline pmd_t set_pmd_bit(pmd_t pmd, pgprot_t prot) 
	return pmd;

}



static inline pte_t pte_wrprotect(pte_t pte)

{

	pte = clear_pte_bit(pte, __pgprot(PTE_WRITE));

	pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));

	return pte;

}



static inline pte_t pte_mkwrite(pte_t pte)

{

	pte = set_pte_bit(pte, __pgprot(PTE_WRITE));
@@ -197,6 +190,20 @@ static inline pte_t pte_mkdirty(pte_t pte) 
	return pte;

}



static inline pte_t pte_wrprotect(pte_t pte)

{

	/*

	 * If hardware-dirty (PTE_WRITE/DBM bit set and PTE_RDONLY

	 * clear), set the PTE_DIRTY bit.

	 */

	if (pte_hw_dirty(pte))

		pte = pte_mkdirty(pte);



	pte = clear_pte_bit(pte, __pgprot(PTE_WRITE));

	pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));

	return pte;

}



static inline pte_t pte_mkold(pte_t pte)

{

	return clear_pte_bit(pte, __pgprot(PTE_AF));
@@ -846,12 +853,6 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres 
	pte = READ_ONCE(*ptep);

	do {

		old_pte = pte;

		/*

		 * If hardware-dirty (PTE_WRITE/DBM bit set and PTE_RDONLY

		 * clear), set the PTE_DIRTY bit.

		 */

		if (pte_hw_dirty(pte))

			pte = pte_mkdirty(pte);

		pte = pte_wrprotect(pte);

		pte_val(pte) = cmpxchg_relaxed(&pte_val(*ptep),

					       pte_val(old_pte), pte_val(pte));

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