From 483a6c9d447f625b991fa04a1530493d893984db Mon Sep 17 00:00:00 2001 From: Rabin Vincent Date: Sat, 24 May 2014 17:38:01 +0100 Subject: [PATCH] ARM: 8064/1: fix v7-M signal return MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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") Cc: stable@kernel.org Acked-by: Uwe Kleine-König Signed-off-by: Rabin Vincent Signed-off-by: Russell King --- arch/arm/kernel/entry-header.S | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S index 1420725142ca..efb208de75ec 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}