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ARM64: mm: Move PTE_PROT_NONE bit.

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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>
This commit is contained in:
Steve Capper 2013-05-28 13:35:51 +01:00
parent 072b1b62a6
commit 59911ca432
1 changed files with 12 additions and 12 deletions
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24
arch/arm64/include/asm/pgtable.h
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@ -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);