From b2e30785526c7e1b7bba74d5c50784cfcfe0bc21 Mon Sep 17 00:00:00 2001 From: "T.J. Purtell" Date: Wed, 6 Nov 2013 18:38:05 +0100 Subject: ARM: 7880/1: Clear the IT state independent of the Thumb-2 mode commit 6ecf830e5029598732e04067e325d946097519cb upstream. The ARM architecture reference specifies that the IT state bits in the PSR must be all zeros in ARM mode or behavior is unspecified. On the Qualcomm Snapdragon S4/Krait architecture CPUs the processor continues to consider the IT state bits while in ARM mode. This makes it so that some instructions are skipped by the CPU. Signed-off-by: T.J. Purtell [rmk+kernel@arm.linux.org.uk: fixed whitespace formatting in patch] Signed-off-by: Russell King Signed-off-by: Zefan Li --- arch/arm/kernel/signal.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index d68d1b694680..ffc090232389 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -437,12 +437,18 @@ setup_return(struct pt_regs *regs, struct k_sigaction *ka, */ thumb = handler & 1; - if (thumb) { - cpsr |= PSR_T_BIT; #if __LINUX_ARM_ARCH__ >= 7 - /* clear the If-Then Thumb-2 execution state */ - cpsr &= ~PSR_IT_MASK; + /* + * Clear the If-Then Thumb-2 execution state + * ARM spec requires this to be all 000s in ARM mode + * Snapdragon S4/Krait misbehaves on a Thumb=>ARM + * signal transition without this. + */ + cpsr &= ~PSR_IT_MASK; #endif + + if (thumb) { + cpsr |= PSR_T_BIT; } else cpsr &= ~PSR_T_BIT; } -- cgit v1.2.3