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

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@arm.com>
Cc: stable@vger.kernel.org
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 7 insertions, 1 deletions

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 9cbe70c8b0ef..ec3e5cf46308 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 9d285626bc7d..312e15e6d00b 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;
 }