From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Mon, 3 Feb 2014 16:37:15 +0000 (+0100)
Subject: s390: fix kernel crash due to linkage stack instructions
X-Git-Tag: v3.2.57~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1664028240024d96721a5328c93ff206661cd9e1;p=pandora-kernel.git

s390: fix kernel crash due to linkage stack instructions

commit 8d7f6690cedb83456edd41c9bd583783f0703bf0 upstream.

The kernel currently crashes with a low-address-protection exception
if a user space process executes an instruction that tries to use the
linkage stack. Set the base-ASTE origin and the subspace-ASTE origin
of the dispatchable-unit-control-table to point to a dummy ASTE.
Set up control register 15 to point to an empty linkage stack with no
room left.

A user space process with a linkage stack instruction will still crash
but with a different exception which is correctly translated to a
segmentation fault instead of a kernel oops.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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