From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx114.postini.com [74.125.245.114]) by kanga.kvack.org (Postfix) with SMTP id 8271A6B0069 for ; Thu, 23 May 2013 13:08:30 -0400 (EDT) Received: by mail-we0-f169.google.com with SMTP id q55so2298565wes.14 for ; Thu, 23 May 2013 10:08:28 -0700 (PDT) From: Steve Capper Subject: [PATCH 08/11] ARM64: mm: Swap PTE_FILE and PTE_PROT_NONE bits. Date: Thu, 23 May 2013 18:07:55 +0100 Message-Id: <1369328878-11706-9-git-send-email-steve.capper@linaro.org> In-Reply-To: <1369328878-11706-1-git-send-email-steve.capper@linaro.org> References: <1369328878-11706-1-git-send-email-steve.capper@linaro.org> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Michal Hocko , Ken Chen , Mel Gorman , Catalin Marinas , Will Deacon , patches@linaro.org, Steve Capper 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): Bits #0 and #1 are clear, bit #2 is set. 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. As huge PTEs are always present, the meaning of bits #1 and #2 can be swapped for invalid PTEs. This patch swaps the PTE_FILE and PTE_PROT_NONE constants, allowing us to represent PROT_NONE huge PTEs. Signed-off-by: Steve Capper Acked-by: Catalin Marinas --- arch/arm64/include/asm/pgtable.h | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 77b09d6..8867282 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_FILE (_AT(pteval_t, 1) << 1) /* only when !pte_present() */ +#define PTE_PROT_NONE (_AT(pteval_t, 1) << 2) /* only when !PTE_VALID */ #define PTE_DIRTY (_AT(pteval_t, 1) << 55) #define PTE_SPECIAL (_AT(pteval_t, 1) << 56) @@ -281,8 +281,8 @@ 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 0, 2: present (must both be zero) + * bit 1: PTE_FILE * bits 3-8: swap type * bits 9-63: swap offset */ @@ -306,8 +306,8 @@ 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 0, 2: present (must both be zero) + * bit 1: PTE_FILE * bits 3-63: file offset / PAGE_SIZE */ #define pte_file(pte) (pte_val(pte) & PTE_FILE) -- 1.8.1.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org