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>
Git-commit: 6ecf830e5029598732e04067e325d946097519cb
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
Change-Id: I74275a3d98aef291d6f41b1905acc3aeecb50b47
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index d68d1b6..ffc0902 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -437,12 +437,18 @@
*/
thumb = handler & 1;
+#if __LINUX_ARM_ARCH__ >= 7
+ /*
+ * 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;
-#if __LINUX_ARM_ARCH__ >= 7
- /* clear the If-Then Thumb-2 execution state */
- cpsr &= ~PSR_IT_MASK;
-#endif
} else
cpsr &= ~PSR_T_BIT;
}