From: Will Deacon <will.deacon@arm.com>
Date: Sat, 1 Sep 2012 04:22:12 +0000 (+0100)
Subject: ARM: mm: introduce present, faulting entries for PAGE_NONE
X-Git-Tag: v3.2.58~72
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=960bd8ae3e6402a0409b11ed18a7ba9aaf69c3c5;p=pandora-kernel.git

ARM: mm: introduce present, faulting entries for PAGE_NONE

commit 26ffd0d43b186b0d5186354da8714a1c2d360df0 upstream.

PROT_NONE mappings apply the page protection attributes defined by _P000
which translate to PAGE_NONE for ARM. These attributes specify an XN,
RDONLY pte that is inaccessible to userspace. However, on kernels
configured without support for domains, such a pte *is* accessible to
the kernel and can be read via get_user, allowing tasks to read
PROT_NONE pages via syscalls such as read/write over a pipe.

This patch introduces a new software pte flag, L_PTE_NONE, that is set
to identify faulting, present entries.

Signed-off-by: Will Deacon <will.deacon@arm.com>
[bwh: Backported to 3.2 as dependency of commit b6ccb9803e90
 ('ARM: 7954/1: mm: remove remaining domain support from ARMv6'):
 - Drop 3-level changes
 - Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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