From 59911ca4325dc7bd95e05c988fef3593b694e62c Mon Sep 17 00:00:00 2001 From: Steve Capper Date: Tue, 28 May 2013 13:35:51 +0100 Subject: [PATCH] ARM64: mm: Move PTE_PROT_NONE bit. Under ARM64, PTEs can be broadly categorised as follows: - Present and valid: Bit #0 is set. The PTE is valid and memory access to the region may fault. - Present and invalid: Bit #0 is clear and bit #1 is set. Represents present memory with PROT_NONE protection. The PTE is an invalid entry, and the user fault handler will raise a SIGSEGV. - Not present (file or swap): Bits #0 and #1 are clear. Memory represented has been paged out. The PTE is an invalid entry, and the fault handler will try and re-populate the memory where necessary. Huge PTEs are block descriptors that have bit #1 clear. If we wish to represent PROT_NONE huge PTEs we then run into a problem as there is no way to distinguish between regular and huge PTEs if we set bit #1. To resolve this ambiguity this patch moves PTE_PROT_NONE from bit #1 to bit #2 and moves PTE_FILE from bit #2 to bit #3. The number of swap/file bits is reduced by 1 as a consequence, leaving 60 bits for file and swap entries. Signed-off-by: Steve Capper Acked-by: Catalin Marinas --- arch/arm64/include/asm/pgtable.h | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 77b09d6fee23..2291de0258ed 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -25,8 +25,8 @@ * Software defined PTE bits definition. */ #define PTE_VALID (_AT(pteval_t, 1) << 0) -#define PTE_PROT_NONE (_AT(pteval_t, 1) << 1) /* only when !PTE_VALID */ -#define PTE_FILE (_AT(pteval_t, 1) << 2) /* only when !pte_present() */ +#define PTE_PROT_NONE (_AT(pteval_t, 1) << 2) /* only when !PTE_VALID */ +#define PTE_FILE (_AT(pteval_t, 1) << 3) /* only when !pte_present() */ #define PTE_DIRTY (_AT(pteval_t, 1) << 55) #define PTE_SPECIAL (_AT(pteval_t, 1) << 56) @@ -281,12 +281,12 @@ extern pgd_t idmap_pg_dir[PTRS_PER_PGD]; /* * Encode and decode a swap entry: - * bits 0-1: present (must be zero) - * bit 2: PTE_FILE - * bits 3-8: swap type + * bits 0, 2: present (must both be zero) + * bit 3: PTE_FILE + * bits 4-8: swap type * bits 9-63: swap offset */ -#define __SWP_TYPE_SHIFT 3 +#define __SWP_TYPE_SHIFT 4 #define __SWP_TYPE_BITS 6 #define __SWP_TYPE_MASK ((1 << __SWP_TYPE_BITS) - 1) #define __SWP_OFFSET_SHIFT (__SWP_TYPE_BITS + __SWP_TYPE_SHIFT) @@ -306,15 +306,15 @@ extern pgd_t idmap_pg_dir[PTRS_PER_PGD]; /* * Encode and decode a file entry: - * bits 0-1: present (must be zero) - * bit 2: PTE_FILE - * bits 3-63: file offset / PAGE_SIZE + * bits 0, 2: present (must both be zero) + * bit 3: PTE_FILE + * bits 4-63: file offset / PAGE_SIZE */ #define pte_file(pte) (pte_val(pte) & PTE_FILE) -#define pte_to_pgoff(x) (pte_val(x) >> 3) -#define pgoff_to_pte(x) __pte(((x) << 3) | PTE_FILE) +#define pte_to_pgoff(x) (pte_val(x) >> 4) +#define pgoff_to_pte(x) __pte(((x) << 4) | PTE_FILE) -#define PTE_FILE_MAX_BITS 61 +#define PTE_FILE_MAX_BITS 60 extern int kern_addr_valid(unsigned long addr); -- 2.34.1