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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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1
arch/arm/include/asm/pgtable-2level.h
View File

@ -115,6 +115,7 @@
* The PTE table pointer refers to the hardware entries; the "Linux"
* entries are stored 1024 bytes below.
*/
#define L_PTE_VALID (_AT(pteval_t, 1) << 0) /* Valid */
#define L_PTE_PRESENT (_AT(pteval_t, 1) << 0)
#define L_PTE_YOUNG (_AT(pteval_t, 1) << 1)
#define L_PTE_FILE (_AT(pteval_t, 1) << 2) /* only when !PRESENT */

3
arch/arm/include/asm/pgtable-3level.h
View File

@ -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] */

4
arch/arm/include/asm/pgtable.h
View File

@ -203,9 +203,7 @@ static inline pte_t *pmd_page_vaddr(pmd_t pmd)
#define pte_exec(pte) (!(pte_val(pte) & L_PTE_XN))
#define pte_special(pte) (0)
#define pte_present_user(pte) \
((pte_val(pte) & (L_PTE_PRESENT | L_PTE_USER)) == \
(L_PTE_PRESENT | L_PTE_USER))
#define pte_present_user(pte) (pte_present(pte) && (pte_val(pte) & L_PTE_USER))
#if __LINUX_ARM_ARCH__ < 6
static inline void __sync_icache_dcache(pte_t pteval)

2
arch/arm/mm/proc-v7-2level.S
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@ -100,7 +100,7 @@ ENTRY(cpu_v7_set_pte_ext)
orrne r3, r3, #PTE_EXT_XN
tst r1, #L_PTE_YOUNG
tstne r1, #L_PTE_PRESENT
tstne r1, #L_PTE_VALID
moveq r3, #0
ARM( str r3, [r0, #2048]! )

2
arch/arm/mm/proc-v7-3level.S
View File

@ -65,7 +65,7 @@ ENDPROC(cpu_v7_switch_mm)
*/
ENTRY(cpu_v7_set_pte_ext)
#ifdef CONFIG_MMU
tst r2, #L_PTE_PRESENT
tst r2, #L_PTE_VALID
beq 1f
tst r3, #1 << (55 - 32) @ L_PTE_DIRTY
orreq r2, #L_PTE_RDONLY