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@arm.com>
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index d43c7e54ec6cafd568eb48c337d96c5bc4afa714..32640ae7750f78ce294cba0b22d6e2ad3168927c 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;
 }