diff options
| author | T.J. Purtell <tj@mobisocial.us> | 2013-11-06 18:38:05 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2013-11-07 00:19:06 +0000 |
| commit | 6ecf830e5029598732e04067e325d946097519cb (patch) | |
| tree | b174b452cca9b7c9aa44a79cfa963b7c03539628 /arch/arm/kernel/signal.c | |
| parent | e16b31bf47738f4498d7ce632e12d7d2a6a2492a (diff) | |
ARM: 7880/1: Clear the IT state independent of the Thumb-2 mode
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 <tj@mobisocial.us>
[rmk+kernel@arm.linux.org.uk: fixed whitespace formatting in patch]
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/signal.c')
| -rw-r--r-- | arch/arm/kernel/signal.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index ab3304225272..1aa5ecdd1b3d 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -375,12 +375,18 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig, */ 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; } |