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ARM: mm: introduce L_PTE_VALID for page table entries

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For long-descriptor translation table formats, the ARMv7 architecture
defines the last two bits of the second- and third-level descriptors to
be:

	x0b	- Invalid
	01b	- Block (second-level), Reserved (third-level)
	11b	- Table (second-level), Page (third-level)

This allows us to define L_PTE_PRESENT as (3 << 0) and use this value to
create ptes directly. However, when determining whether a given pte
value is present in the low-level page table accessors, we only need to
check the least significant bit of the descriptor, allowing us to write
faulting, present entries which are required for PROT_NONE mappings.

This patch introduces L_PTE_VALID, which can be used to test whether a
pte should fault, and updates the low-level page table accessors
accordingly.

Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Will Deacon
2012-07-19 11:51:05 +01:00
parent 0cbbbad631
commit dbf62d5006
5 changed files with 6 additions and 6 deletions
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3
arch/arm/include/asm/pgtable-3level.h
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@@ -67,7 +67,8 @@
* These bits overlap with the hardware bits but the naming is preserved for
* consistency with the classic page table format.
*/
#define L_PTE_PRESENT (_AT(pteval_t, 3) << 0) /* Valid */
#define L_PTE_VALID (_AT(pteval_t, 1) << 0) /* Valid */
#define L_PTE_PRESENT (_AT(pteval_t, 3) << 0) /* Present */
#define L_PTE_FILE (_AT(pteval_t, 1) << 2) /* only when !PRESENT */
#define L_PTE_USER (_AT(pteval_t, 1) << 6) /* AP[1] */
#define L_PTE_RDONLY (_AT(pteval_t, 1) << 7) /* AP[2] */