This is a note to let you know that I've just added the patch titled
ARM: 8064/1: fix v7-M signal return
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-8064-1-fix-v7-m-signal-return.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 483a6c9d447f625b991fa04a1530493d893984db Mon Sep 17 00:00:00 2001
From: Rabin Vincent <rabin@xxxxxx>
Date: Sat, 24 May 2014 17:38:01 +0100
Subject: ARM: 8064/1: fix v7-M signal return
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From: Rabin Vincent <rabin@xxxxxx>
commit 483a6c9d447f625b991fa04a1530493d893984db upstream.
According to the ARM ARM, the behaviour is UNPREDICTABLE if the PC read
from the exception return stack is not half word aligned. See the
pseudo code for ExceptionReturn() and PopStack().
The signal handler's address has the bit 0 set, and setup_return()
directly writes this to regs->ARM_pc. Current hardware happens to
discard this bit, but QEMU's emulation doesn't and this makes processes
crash. Mask out bit 0 before the exception return in order to get
predictable behaviour.
Fixes: 19c4d593f0b4 ("ARM: ARMv7-M: Add support for exception handling")
Acked-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Signed-off-by: Rabin Vincent <rabin@xxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/kernel/entry-header.S | 4 ++++
1 file changed, 4 insertions(+)
--- a/arch/arm/kernel/entry-header.S
+++ b/arch/arm/kernel/entry-header.S
@@ -132,6 +132,10 @@
orrne r5, V7M_xPSR_FRAMEPTRALIGN
biceq r5, V7M_xPSR_FRAMEPTRALIGN
+ @ ensure bit 0 is cleared in the PC, otherwise behaviour is
+ @ unpredictable
+ bic r4, #1
+
@ write basic exception frame
stmdb r2!, {r1, r3-r5}
ldmia sp, {r1, r3-r5}
Patches currently in stable-queue which might be from rabin@xxxxxx are
queue-3.14/arm-8064-1-fix-v7-m-signal-return.patch
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