Re: [Qemu-devel] [PATCH 2 30/39] windbg: debug exception subscribing

["Alex Bennée" <alex.bennee@linaro.org>]

Mikhail Abakumov <mikhail.abakumov@ispras.ru> writes:

> Add handler registration of gdb debug exception. Its exception also can be used
> for windbg.
>
> Signed-off-by: Mikhail Abakumov <mikhail.abakumov@ispras.ru>
> Signed-off-by: Pavel Dovgalyuk <dovgaluk@ispras.ru>
> ---
>  cpus.c                  |   19 ++++++++++++++++++-
>  gdbstub.c               |    4 ++++
>  include/sysemu/sysemu.h |    2 ++
>  windbgstub.c            |   14 ++++++++++++++
>  4 files changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/cpus.c b/cpus.c
> index a2b33ccb29..c8b05260b4 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -79,6 +79,8 @@ 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
> @@ -1103,9 +1105,24 @@ 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("Something debugger is already in use. '-gdb' and "
> +                     "'-windbg' cannot be used at the same time");
> +        return false;
> +    }
> +}
> +
>  static void cpu_handle_guest_debug(CPUState *cpu)
>  {
> -    gdb_set_stop_cpu(cpu);

If we are going to have a handler approach we can make gdb_set_stop_cpu
static and remove the gdbstub.h reference from cpus.c as well.

> +    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 c4e4f9f082..9ed4fe2e8e 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -2074,6 +2074,10 @@ 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 8d6095d98b..826b701bfa 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -203,6 +203,8 @@ 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 a1c013cd8c..0e4ad6d009 100644
> --- a/windbgstub.c
> +++ b/windbgstub.c
> @@ -129,9 +129,19 @@ static void windbg_send_control_packet(WindbgState *state, uint16_t type,
>      qemu_chr_fe_write(&state->chr, PTR(packet), sizeof(packet));
>  }
>
> +static void windbg_bp_handler(CPUState *cs)
> +{
> +    DBGKD_ANY_WAIT_STATE_CHANGE *sc = kd_state_change_exc(cs);
> +    windbg_send_data_packet(windbg_state, (uint8_t *) sc,
> +                            sizeof(DBGKD_ANY_WAIT_STATE_CHANGE),
> +                            PACKET_TYPE_KD_STATE_CHANGE64);
> +}
> +
>  static void windbg_vm_stop(void)
>  {
> +    CPUState *cs = qemu_get_cpu(0);

This can fail - although I guess it's unlikely someone has hotplugged cpu0.

>      vm_stop(RUN_STATE_PAUSED);
> +    windbg_bp_handler(cs);
>  }
>
>  static void windbg_process_manipulate_packet(WindbgState *state)
> @@ -481,6 +491,10 @@ 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;
>  }


--
Alex Bennée