[Qemu-devel] [PATCH v2 2/2] target-arm: Implement checking of fired watchpoint

[Sergey Fedorov <serge.fdrv@gmail.com>]

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>
---
 target-arm/cpu.c       |  1 +
 target-arm/internals.h |  3 +++
 target-arm/op_helper.c | 35 +++++++++++++++++++++--------------
 3 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/target-arm/cpu.c b/target-arm/cpu.c
index 0e582c4..21ec18e 100644
--- a/target-arm/cpu.c
+++ b/target-arm/cpu.c
@@ -1474,6 +1474,7 @@ 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;
 
diff --git a/target-arm/internals.h b/target-arm/internals.h
index d226bbe..7e67eaa 100644
--- a/target-arm/internals.h
+++ b/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);
+
 /* Callback function for when a watchpoint or breakpoint triggers. */
 void arm_debug_excp_handler(CPUState *cs);
 
diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
index a5ee65f..859691a 100644
--- a/target-arm/op_helper.c
+++ b/target-arm/op_helper.c
@@ -975,6 +975,16 @@ void HELPER(check_breakpoints)(CPUARMState *env)
     }
 }
 
+bool arm_debug_check_watchpoint(CPUState *cs)
+{
+    /* 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;
@@ -986,23 +996,20 @@ 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];
-- 
1.9.1