aboutsummaryrefslogtreecommitdiff
path: root/arch/arm/kernel/entry-header.S
diff options
context:
space:
mode:
authorRabin Vincent <rabin@rab.in>2014-05-24 17:38:01 +0100
committerShow Liu <show.liu@linaro.org>2014-06-18 12:05:21 +0800
commit4b7a57d15b83f16e719a31e15e9a203acb198254 (patch)
tree0ed8912d613748246b635716b0924b82b9862dea /arch/arm/kernel/entry-header.S
parent2cbbfce93bbb6190113d65bb1848b103e7d805cc (diff)
downloadlinaro-lsk-4b7a57d15b83f16e719a31e15e9a203acb198254.tar.gz
ARM: 8064/1: fix v7-M signal return
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-K├Ânig <u.kleine-koenig@pengutronix.de> Signed-off-by: Rabin Vincent <rabin@rab.in> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/arm/kernel/entry-header.S')
-rw-r--r--arch/arm/kernel/entry-header.S4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S
index 39f89fbd511..88c6babeb0b 100644
--- 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}