[3.8.y.z extended stable] Patch "ARM: 7876/1: clear Thumb-2 IT state on exception handling" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ARM: 7876/1: clear Thumb-2 IT state on exception handling

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.14.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 6944129b707da075db064d15d27d757c82be3b9a Mon Sep 17 00:00:00 2001
From: Marc Zyngier <Marc.Zyngier at arm.com>
Date: Mon, 4 Nov 2013 11:42:29 +0100
Subject: ARM: 7876/1: clear Thumb-2 IT state on exception handling

commit e16b31bf47738f4498d7ce632e12d7d2a6a2492a upstream.

The exception handling code fails to clear the IT state, potentially
leading to incorrect execution of the fixup if the size of the IT
block is more than one.

Let fixup_exception do the IT sanitizing if a fixup has been found,
and restore CPSR from the stack when returning from a data abort.

Cc: Will Deacon <will.deacon at arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/arm/kernel/entry-armv.S | 1 +
 arch/arm/mm/extable.c        | 7 ++++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index a7de792..130ed1f 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -192,6 +192,7 @@ __dabt_svc:
 	svc_entry
 	mov	r2, sp
 	dabt_helper
+ THUMB(	ldr	r5, [sp, #S_PSR]	)	@ potentially updated CPSR
 	svc_exit r5				@ return from exception
  UNWIND(.fnend		)
 ENDPROC(__dabt_svc)
diff --git a/arch/arm/mm/extable.c b/arch/arm/mm/extable.c
index 9d28562..312e15e 100644
--- a/arch/arm/mm/extable.c
+++ b/arch/arm/mm/extable.c
@@ -9,8 +9,13 @@ int fixup_exception(struct pt_regs *regs)
 	const struct exception_table_entry *fixup;

 	fixup = search_exception_tables(instruction_pointer(regs));
-	if (fixup)
+	if (fixup) {
 		regs->ARM_pc = fixup->fixup;
+#ifdef CONFIG_THUMB2_KERNEL
+		/* Clear the IT state to avoid nasty surprises in the fixup */
+		regs->ARM_cpsr &= ~PSR_IT_MASK;
+#endif
+	}

 	return fixup != NULL;
 }
--
1.8.3.2