diff options
| author | Catalin Marinas <catalin.marinas@arm.com> | 2017-07-05 12:59:42 +0300 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2017-08-21 13:13:00 +0300 |
| commit | 64c26841b34957ef8f33f7a9e8663aeee59c3ded (patch) | |
| tree | fe899931712ae0637bfc7b6eead18e7881d02e7e /arch/arm64/include | |
| parent | 73e86cb03cf2ec0aa3789dc8621c6d53619cac5e (diff) | |
| download | linux-64c26841b34957ef8f33f7a9e8663aeee59c3ded.tar.xz | |
arm64: Ignore hardware dirty bit updates in ptep_set_wrprotect()
ptep_set_wrprotect() is only called on CoW mappings which are private
(!VM_SHARED) with the pte either read-only (!PTE_WRITE && PTE_RDONLY) or
writable and software-dirty (PTE_WRITE && !PTE_RDONLY && PTE_DIRTY).
There is no race with the hardware update of the dirty state: clearing
of PTE_RDONLY when PTE_WRITE (a.k.a. PTE_DBM) is set. This patch removes
the code setting the software PTE_DIRTY bit in ptep_set_wrprotect() as
superfluous. A VM_WARN_ONCE is introduced in case the above logic is
wrong or the core mm code changes its use of ptep_set_wrprotect().
Reviewed-by: Will Deacon <will.deacon@arm.com>
Acked-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/include')
| -rw-r--r-- | arch/arm64/include/asm/pgtable.h | 21 |
1 files changed, 13 insertions, 8 deletions
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index a04bfb869a80..0117cbcd62d4 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -634,23 +634,28 @@ static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ /* - * ptep_set_wrprotect - mark read-only while trasferring potential hardware - * dirty status (PTE_DBM && !PTE_RDONLY) to the software PTE_DIRTY bit. + * ptep_set_wrprotect - mark read-only while preserving the hardware update of + * the Access Flag. */ #define __HAVE_ARCH_PTEP_SET_WRPROTECT static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long address, pte_t *ptep) { pte_t old_pte, pte; + /* + * ptep_set_wrprotect() is only called on CoW mappings which are + * private (!VM_SHARED) with the pte either read-only (!PTE_WRITE && + * PTE_RDONLY) or writable and software-dirty (PTE_WRITE && + * !PTE_RDONLY && PTE_DIRTY); see is_cow_mapping() and + * protection_map[]. There is no race with the hardware update of the + * dirty state: clearing of PTE_RDONLY when PTE_WRITE (a.k.a. PTE_DBM) + * is set. + */ + VM_WARN_ONCE(pte_write(*ptep) && !pte_dirty(*ptep), + "%s: potential race with hardware DBM", __func__); 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)); |