target-arm: Implement checking of fired watchpoint

ARM stops before access to a location covered by watchpoint. Also, QEMU
watchpoint fire is not necessarily an architectural watchpoint match.
Unfortunately, that is hardly possible to ignore a fired watchpoint in
debug exception handler. So move watchpoint check from debug exception
handler to the dedicated watchpoint checking callback.

Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1454256948-10485-3-git-send-email-serge.fdrv@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target-arm/cpu.c

@@ -1483,6 +1483,7 @@ static void arm_cpu_class_init(ObjectClass *oc, void *data)
     cc->gdb_arch_name = arm_gdb_arch_name;
     cc->gdb_stop_before_watchpoint = true;
     cc->debug_excp_handler = arm_debug_excp_handler;
+    cc->debug_check_watchpoint = arm_debug_check_watchpoint;
 
     cc->disas_set_info = arm_disas_set_info;
 

target-arm/internals.h

@@ -409,6 +409,9 @@ void hw_breakpoint_update(ARMCPU *cpu, int n);
  */
 void hw_breakpoint_update_all(ARMCPU *cpu);
 
+/* Callback function for checking if a watchpoint should trigger. */
+bool arm_debug_check_watchpoint(CPUState *cs, CPUWatchpoint *wp);
+
 /* Callback function for when a watchpoint or breakpoint triggers. */
 void arm_debug_excp_handler(CPUState *cs);
 

target-arm/op_helper.c

@@ -976,6 +976,16 @@ void HELPER(check_breakpoints)(CPUARMState *env)
     }
 }
 
+bool arm_debug_check_watchpoint(CPUState *cs, CPUWatchpoint *wp)
+{
+    /* Called by core code when a CPU watchpoint fires; need to check if this
+     * is also an architectural watchpoint match.
+     */
+    ARMCPU *cpu = ARM_CPU(cs);
+
+    return check_watchpoints(cpu);
+}
+
 void arm_debug_excp_handler(CPUState *cs)
 {
     /* Called by core code when a watchpoint or breakpoint fires;
@@ -987,23 +997,20 @@ void arm_debug_excp_handler(CPUState *cs)
 
     if (wp_hit) {
         if (wp_hit->flags & BP_CPU) {
+            bool wnr = (wp_hit->flags & BP_WATCHPOINT_HIT_WRITE) != 0;
+            bool same_el = arm_debug_target_el(env) == arm_current_el(env);
+
             cs->watchpoint_hit = NULL;
-            if (check_watchpoints(cpu)) {
-                bool wnr = (wp_hit->flags & BP_WATCHPOINT_HIT_WRITE) != 0;
-                bool same_el = arm_debug_target_el(env) == arm_current_el(env);
-
-                if (extended_addresses_enabled(env)) {
-                    env->exception.fsr = (1 << 9) | 0x22;
-                } else {
-                    env->exception.fsr = 0x2;
-                }
-                env->exception.vaddress = wp_hit->hitaddr;
-                raise_exception(env, EXCP_DATA_ABORT,
-                                syn_watchpoint(same_el, 0, wnr),
-                                arm_debug_target_el(env));
+
+            if (extended_addresses_enabled(env)) {
+                env->exception.fsr = (1 << 9) | 0x22;
             } else {
-                cpu_resume_from_signal(cs, NULL);
+                env->exception.fsr = 0x2;
             }
+            env->exception.vaddress = wp_hit->hitaddr;
+            raise_exception(env, EXCP_DATA_ABORT,
+                    syn_watchpoint(same_el, 0, wnr),
+                    arm_debug_target_el(env));
         }
     } else {
         uint64_t pc = is_a64(env) ? env->pc : env->regs[15];