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>

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 9cbe70c8b0ef7b8d16a806602608fba205966d31..ec3e5cf46308108616387013f0f86f124dcf114f 100644 (file)
--- 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 9d285626bc7da4fe3e2be2e952c38923c05f5204..312e15e6d00b8a6b909747305166e1bc7f581bf0 100644 (file)
--- 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;
 }