Re: [Qemu-devel] [PATCH v3 35/45] windbg: debug exception subscribing

[Mihail Abakumov]

Ladi Prosek писал 2017-11-29 10:13:

On Tue, Nov 21, 2017 at 3:10 PM, Mihail Abakumov
<mikhail.abaku...@ispras.ru> wrote:

Added handler registration of gdb debug exception. Its exception also can be used for windbg.

Signed-off-by: Mihail Abakumov <mikhail.abaku...@ispras.ru>
Signed-off-by: Pavel Dovgalyuk <dovga...@ispras.ru>
Signed-off-by: Dmitriy Koltunov <koltu...@ispras.ru>
---
 cpus.c                  |   18 +++++++++++++++++-
 gdbstub.c               |    4 ++++
 include/sysemu/sysemu.h |    2 ++
 windbgstub.c            |   16 ++++++++++++----
 4 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/cpus.c b/cpus.c
index 9bed61eefc..212553b7e3 100644
--- a/cpus.c
+++ b/cpus.c
@@ -77,6 +77,8 @@ int64_t max_advance;
 static QEMUTimer *throttle_timer;
 static unsigned int throttle_percentage;

+static void (*excp_debug_handler)(CPUState *cpu);
+
 #define CPU_THROTTLE_PCT_MIN 1
 #define CPU_THROTTLE_PCT_MAX 99
 #define CPU_THROTTLE_TIMESLICE_NS 10000000
@@ -960,9 +962,23 @@ static bool cpu_can_run(CPUState *cpu)
     return true;
 }

+bool register_excp_debug_handler(void (*handler)(CPUState *cpu))
+{
+    if (excp_debug_handler == NULL) {
+        excp_debug_handler = handler;
+        return true;
+    } else {
+        error_report("ERROR: Something debugger already using");

So I take it that -windbg and -gdb cannot be used at the same time.
Should it be handled in a more explicit way with a more user-friendly
error?

Right now I get this error, which is more like an implementation
detail (could the debug handler be refactored into a multicast event
in the future?) and does not even make sense as a sentence.

Yes. I have added a more user-friendly error. "Something debugger is
already in use. '-gdb' and '-windbg' cannot be used at the same time".
Or what do you mean under the explicit way? How to do it better?

+        return false;
+    }
+}
+
 static void cpu_handle_guest_debug(CPUState *cpu)
 {
-    gdb_set_stop_cpu(cpu);
+    if (excp_debug_handler != NULL) {
+        excp_debug_handler(cpu);
+    }
+
     qemu_system_debug_request();
     cpu->stopped = true;
 }
diff --git a/gdbstub.c b/gdbstub.c
index 2a94030d3b..8c76f54117 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -2006,6 +2006,10 @@ int gdbserver_start(const char *device)
     s->mon_chr = mon_chr;
     s->current_syscall_cb = NULL;

+    if (!register_excp_debug_handler(gdb_set_stop_cpu)) {
+        exit(1);
+    }
+
     return 0;
 }

diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index b21369672a..34588c99b4 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -193,6 +193,8 @@ QemuOpts *qemu_get_machine_opts(void);

 bool defaults_enabled(void);

+bool register_excp_debug_handler(void (*handler)(CPUState *cpu));
+
 extern QemuOptsList qemu_legacy_drive_opts;
 extern QemuOptsList qemu_common_drive_opts;
 extern QemuOptsList qemu_drive_opts;
diff --git a/windbgstub.c b/windbgstub.c
index 489abe6d6c..b33f412659 100755
--- a/windbgstub.c
+++ b/windbgstub.c

@@ -115,16 +115,20 @@ static void windbg_send_control_packet(uint16_t type)

     windbg_state->ctrl_packet_id ^= 1;
 }

-static void windbg_vm_stop(void)
+static void windbg_bp_handler(CPUState *cpu)
 {
-    CPUState *cpu = qemu_get_cpu(0);
-    vm_stop(RUN_STATE_PAUSED);
-
     SizedBuf buf = kd_gen_exception_sc(cpu);

windbg_send_data_packet(buf.data, buf.size, PACKET_TYPE_KD_STATE_CHANGE64);

     SBUF_FREE(buf);
 }

+static void windbg_vm_stop(void)
+{
+    CPUState *cpu = qemu_get_cpu(0);
+    vm_stop(RUN_STATE_PAUSED);
+    windbg_bp_handler(cpu);
+}
+
 static void windbg_process_manipulate_packet(ParsingContext *ctx)
 {
     CPUState *cpu;
@@ -432,6 +436,10 @@ int windbg_server_start(const char *device)

     qemu_register_reset(windbg_handle_reset, NULL);

+    if (!register_excp_debug_handler(windbg_bp_handler)) {
+        exit(1);
+    }
+
     atexit(windbg_exit);
     return 0;
 }