From: Will Deacon <will.deacon@arm.com>
Date: Thu, 19 Jul 2012 10:51:05 +0000 (+0100)
Subject: ARM: mm: introduce L_PTE_VALID for page table entries
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5b9182ed0aa7cb46a397b291d3db8e402c474bca;p=pandora-kernel.git

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>
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