From 59911ca4325dc7bd95e05c988fef3593b694e62c Mon Sep 17 00:00:00 2001
From: Steve Capper <steve.capper@linaro.org>
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 <steve.capper@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
---
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);
--
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