target-arm: reject switching to monitor mode

Reject switching to monitor mode from non-secure state.
Signed-off-by: NSergey Fedorov <s.fedorov@samsung.com>
Signed-off-by: NFabian Aggeler <aggelerf@ethz.ch>
Signed-off-by: NGreg Bellows <greg.bellows@linaro.org>
Reviewed-by: NEdgar E. Iglesias <edgar.iglesias@xilinx.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 1413910544-20150-4-git-send-email-greg.bellows@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target-arm/helper.c

@@ -3531,6 +3531,8 @@ static int bad_mode_switch(CPUARMState *env, int mode)
     case ARM_CPU_MODE_IRQ:
     case ARM_CPU_MODE_FIQ:
         return 0;
+    case ARM_CPU_MODE_MON:
+        return !arm_is_secure(env);
     default:
         return 1;
     }