ARM: mm: introduce L_PTE_VALID for page table entries
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>
diff --git a/arch/arm/mm/proc-v7-2level.S b/arch/arm/mm/proc-v7-2level.S
index e37600b..e755e9f 100644
--- a/arch/arm/mm/proc-v7-2level.S
+++ b/arch/arm/mm/proc-v7-2level.S
@@ -100,7 +100,7 @@
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]! )