From 1971188aa19651d8f447211c6535fb68661d77c5 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 21 Feb 2014 17:01:48 +0100 Subject: [PATCH] ARM: 7985/1: mm: implement pte_accessible for faulting mappings The pte_accessible macro can be used to identify page table entries capable of being cached by a TLB. In principle, this differs from pte_present, since PROT_NONE mappings are mapped using invalid entries identified as present and ptes designated as `old' can use either invalid entries or those with the access flag cleared (guaranteed not to be in the TLB). However, there is a race to take care of, as described in 20841405940e ("mm: fix TLB flush race between migration, and change_protection_range"), between a page being migrated and mprotected at the same time. In this case, we can check whether a TLB invalidation is pending for the mm and if so, temporarily consider PROT_NONE mappings as valid. This patch implements a quick pte_accessible macro for ARM by simply checking if the pte is valid/present depending on the mm. For classic MMU, these checks are identical and will generate some false positives for PROT_NONE mappings, but this is better than the current asm-generic definition of ((void)(pte),1). Finally, pte_present_user is moved to use pte_valid (and renamed appropriately) since we don't care about cache flushing for faulting mappings. Acked-by: Steve Capper Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/include/asm/pgtable.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h index 7d59b524f2af..5478e5d6ad89 100644 --- a/arch/arm/include/asm/pgtable.h +++ b/arch/arm/include/asm/pgtable.h @@ -216,13 +216,16 @@ static inline pte_t *pmd_page_vaddr(pmd_t pmd) #define pte_none(pte) (!pte_val(pte)) #define pte_present(pte) (pte_val(pte) & L_PTE_PRESENT) +#define pte_valid(pte) (pte_val(pte) & L_PTE_VALID) +#define pte_accessible(mm, pte) (mm_tlb_flush_pending(mm) ? pte_present(pte) : pte_valid(pte)) #define pte_write(pte) (!(pte_val(pte) & L_PTE_RDONLY)) #define pte_dirty(pte) (pte_val(pte) & L_PTE_DIRTY) #define pte_young(pte) (pte_val(pte) & L_PTE_YOUNG) #define pte_exec(pte) (!(pte_val(pte) & L_PTE_XN)) #define pte_special(pte) (0) -#define pte_present_user(pte) (pte_present(pte) && (pte_val(pte) & L_PTE_USER)) +#define pte_valid_user(pte) \ + (pte_valid(pte) && (pte_val(pte) & L_PTE_USER) && pte_young(pte)) #if __LINUX_ARM_ARCH__ < 6 static inline void __sync_icache_dcache(pte_t pteval) @@ -237,7 +240,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, { unsigned long ext = 0; - if (addr < TASK_SIZE && pte_present_user(pteval)) { + if (addr < TASK_SIZE && pte_valid_user(pteval)) { __sync_icache_dcache(pteval); ext |= PTE_EXT_NG; } -- 2.30.2