hvf: add guest debugging handlers for Apple Silicon hosts

Guests can now be debugged through the gdbstub. Support is added for
single-stepping, software breakpoints, hardware breakpoints and
watchpoints. The code has been structured like the KVM counterpart.

While guest debugging is enabled, the guest can still read and write the
DBG*_EL1 registers but they don't have any effect.

Signed-off-by: Francesco Cagnin <fcagnin@quarkslab.com>
Message-id: 20230601153107.81955-5-fcagnin@quarkslab.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

accel/hvf/hvf-accel-ops.c

@@ -343,12 +343,18 @@ static int hvf_accel_init(MachineState *ms)
     return hvf_arch_init();
 }
 
+static inline int hvf_gdbstub_sstep_flags(void)
+{
+    return SSTEP_ENABLE | SSTEP_NOIRQ;
+}
+
 static void hvf_accel_class_init(ObjectClass *oc, void *data)
 {
     AccelClass *ac = ACCEL_CLASS(oc);
     ac->name = "HVF";
     ac->init_machine = hvf_accel_init;
     ac->allowed = &hvf_allowed;
+    ac->gdbstub_supported_sstep_flags = hvf_gdbstub_sstep_flags;
 }
 
 static const TypeInfo hvf_accel_type = {
@@ -398,6 +404,8 @@ static int hvf_init_vcpu(CPUState *cpu)
     cpu->vcpu_dirty = 1;
     assert_hvf_ok(r);
 
+    cpu->hvf->guest_debug_enabled = false;
+
     return hvf_arch_init_vcpu(cpu);
 }
 
@@ -582,6 +590,8 @@ static void hvf_accel_ops_class_init(ObjectClass *oc, void *data)
     ops->insert_breakpoint = hvf_insert_breakpoint;
     ops->remove_breakpoint = hvf_remove_breakpoint;
     ops->remove_all_breakpoints = hvf_remove_all_breakpoints;
+    ops->update_guest_debug = hvf_update_guest_debug;
+    ops->supports_guest_debug = hvf_arch_supports_guest_debug;
 };
 static const TypeInfo hvf_accel_ops_type = {
     .name = ACCEL_OPS_NAME("hvf"),

accel/hvf/hvf-all.c

@@ -61,3 +61,9 @@ int hvf_sw_breakpoints_active(CPUState *cpu)
 {
     return !QTAILQ_EMPTY(&hvf_state->hvf_sw_breakpoints);
 }
+
+int hvf_update_guest_debug(CPUState *cpu)
+{
+    hvf_arch_update_guest_debug(cpu);
+    return 0;
+}

include/sysemu/hvf.h

@@ -56,6 +56,21 @@ int hvf_arch_insert_hw_breakpoint(target_ulong addr, target_ulong len,
 int hvf_arch_remove_hw_breakpoint(target_ulong addr, target_ulong len,
                                   int type);
 void hvf_arch_remove_all_hw_breakpoints(void);
+
+/*
+ * hvf_update_guest_debug:
+ * @cs: CPUState for the CPU to update
+ *
+ * Update guest to enable or disable debugging. Per-arch specifics will be
+ * handled by calling down to hvf_arch_update_guest_debug.
+ */
+int hvf_update_guest_debug(CPUState *cpu);
+void hvf_arch_update_guest_debug(CPUState *cpu);
+
+/*
+ * Return whether the guest supports debugging.
+ */
+bool hvf_arch_supports_guest_debug(void);
 #endif /* NEED_CPU_H */
 
 #endif

include/sysemu/hvf_int.h

@@ -54,6 +54,7 @@ struct hvf_vcpu_state {
     void *exit;
     bool vtimer_masked;
     sigset_t unblock_ipi_mask;
+    bool guest_debug_enabled;
 };
 
 void assert_hvf_ok(hv_return_t ret);

target/arm/hvf_arm.h

@@ -13,6 +13,13 @@
 
 #include "cpu.h"
 
+/**
+ * hvf_arm_init_debug() - initialize guest debug capabilities
+ *
+ * Should be called only once before using guest debug capabilities.
+ */
+void hvf_arm_init_debug(void);
+
 void hvf_arm_set_cpu_features_from_host(ARMCPU *cpu);
 
 #endif

target/i386/hvf/hvf.c

@@ -703,3 +703,12 @@ int hvf_arch_remove_hw_breakpoint(target_ulong addr, target_ulong len, int type)
 void hvf_arch_remove_all_hw_breakpoints(void)
 {
 }
+
+void hvf_arch_update_guest_debug(CPUState *cpu)
+{
+}
+
+inline bool hvf_arch_supports_guest_debug(void)
+{
+    return false;
+}