target-arm: Update arm_generate_debug_exceptions() to handle EL2/EL3

The arm_generate_debug_exceptions() function as originally implemented
assumes no EL2 or EL3. Since we now have much more of an implementation
of those now, fix this assumption.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NSergey Fedorov <serge.fdrv@gmail.com>
Message-id: 1454506721-11843-5-git-send-email-peter.maydell@linaro.org

target-arm/cpu.h

@@ -1742,9 +1742,7 @@ typedef enum ARMASIdx {
     ARMASIdx_S = 1,
 } ARMASIdx;
 
-/* Return the Exception Level targeted by debug exceptions;
- * currently always EL1 since we don't implement EL2 or EL3.
- */
+/* Return the Exception Level targeted by debug exceptions. */
 static inline int arm_debug_target_el(CPUARMState *env)
 {
     bool secure = arm_is_secure(env);
@@ -1767,6 +1765,14 @@ static inline int arm_debug_target_el(CPUARMState *env)
 
 static inline bool aa64_generate_debug_exceptions(CPUARMState *env)
 {
+    if (arm_is_secure(env)) {
+        /* MDCR_EL3.SDD disables debug events from Secure state */
+        if (extract32(env->cp15.mdcr_el3, 16, 1) != 0
+            || arm_current_el(env) == 3) {
+            return false;
+        }
+    }
+
     if (arm_current_el(env) == arm_debug_target_el(env)) {
         if ((extract32(env->cp15.mdscr_el1, 13, 1) == 0)
             || (env->daif & PSTATE_D)) {
@@ -1778,10 +1784,42 @@ static inline bool aa64_generate_debug_exceptions(CPUARMState *env)
 
 static inline bool aa32_generate_debug_exceptions(CPUARMState *env)
 {
-    if (arm_current_el(env) == 0 && arm_el_is_aa64(env, 1)) {
+    int el = arm_current_el(env);
+
+    if (el == 0 && arm_el_is_aa64(env, 1)) {
         return aa64_generate_debug_exceptions(env);
     }
-    return arm_current_el(env) != 2;
+
+    if (arm_is_secure(env)) {
+        int spd;
+
+        if (el == 0 && (env->cp15.sder & 1)) {
+            /* SDER.SUIDEN means debug exceptions from Secure EL0
+             * are always enabled. Otherwise they are controlled by
+             * SDCR.SPD like those from other Secure ELs.
+             */
+            return true;
+        }
+
+        spd = extract32(env->cp15.mdcr_el3, 14, 2);
+        switch (spd) {
+        case 1:
+            /* SPD == 0b01 is reserved, but behaves as 0b00. */
+        case 0:
+            /* For 0b00 we return true if external secure invasive debug
+             * is enabled. On real hardware this is controlled by external
+             * signals to the core. QEMU always permits debug, and behaves
+             * as if DBGEN, SPIDEN, NIDEN and SPNIDEN are all tied high.
+             */
+            return true;
+        case 2:
+            return false;
+        case 3:
+            return true;
+        }
+    }
+
+    return el != 2;
 }
 
 /* Return true if debugging exceptions are currently enabled.