Commit 6ecf830e authored Nov 06, 2013 by T.J. Purtell Committed by Russell King Nov 07, 2013

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>

parent e16b31bf

arch/arm/kernel/signal.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -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 */
		/*
		* 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;
		}