target-arm: implement IRQ/FIQ routing to Monitor mode

SCR.{IRQ/FIQ} bits allow to route IRQ/FIQ exceptions to monitor CPU
mode. When taking IRQ exception to monitor mode FIQ exception is
additionally masked.
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: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 1416242878-876-10-git-send-email-greg.bellows@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target-arm/helper.c

@@ -4233,12 +4233,21 @@ void arm_cpu_do_interrupt(CPUState *cs)
         /* Disable IRQ and imprecise data aborts.  */
         mask = CPSR_A | CPSR_I;
         offset = 4;
+        if (env->cp15.scr_el3 & SCR_IRQ) {
+            /* IRQ routed to monitor mode */
+            new_mode = ARM_CPU_MODE_MON;
+            mask |= CPSR_F;
+        }
         break;
     case EXCP_FIQ:
         new_mode = ARM_CPU_MODE_FIQ;
         addr = 0x1c;
         /* Disable FIQ, IRQ and imprecise data aborts.  */
         mask = CPSR_A | CPSR_I | CPSR_F;
+        if (env->cp15.scr_el3 & SCR_FIQ) {
+            /* FIQ routed to monitor mode */
+            new_mode = ARM_CPU_MODE_MON;
+        }
         offset = 4;
         break;
     case EXCP_SMC: