Re: [PATCH 18/31] Implement GDB_THREAD_OPTION_EXIT support for Linux GDBserver

Andrew Burgess via Gdb-patches
2023-06-08T14:15:31Z

Pedro Alves <pedro@palves.net> writes:

> This implements support for the new GDB_THREAD_OPTION_EXIT thread
> option for Linux GDBserver.

LGTM.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew

>
> Change-Id: I96b719fdf7fee94709e98bb3a90751d8134f3a38
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=27338
> ---
> gdbserver/linux-low.cc | 38 +++++++++++++++++++++++++-------------
> gdbserver/linux-low.h | 9 +++++----
> 2 files changed, 30 insertions(+), 17 deletions(-)
>
> diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
> index 8c0d3103398..ebc3bf34127 100644
> --- a/gdbserver/linux-low.cc
> +++ b/gdbserver/linux-low.cc
> @@ -144,6 +144,18 @@ is_leader (thread_info *thread)
> return ptid.pid () == ptid.lwp ();
> }
>
> +/* Return true if we should report thread exit events to GDB, for
> + THR. */
> +
> +static bool
> +report_exit_events_for (thread_info *thr)
> +{
> + client_state &cs = get_client_state ();
> +
> + return (cs.report_thread_events
> + || (thr->thread_options & GDB_THREAD_OPTION_EXIT) != 0);
> +}
> +
> /* LWP accessors. */
>
> /* See nat/linux-nat.h. */
> @@ -2230,7 +2242,6 @@ linux_low_ptrace_options (int attached)
> void
> linux_process_target::filter_event (int lwpid, int wstat)
> {
> - client_state &cs = get_client_state ();
> struct lwp_info *child;
> struct thread_info *thread;
> int have_stop_pc = 0;
> @@ -2317,7 +2328,7 @@ linux_process_target::filter_event (int lwpid, int wstat)
> /* If this is not the leader LWP, then the exit signal was not
> the end of the debugged application and should be ignored,
> unless GDB wants to hear about thread exits. */
> - if (cs.report_thread_events || is_leader (thread))
> + if (report_exit_events_for (thread) || is_leader (thread))
> {
> /* Since events are serialized to GDB core, and we can't
> report this one right now. Leave the status pending for
> @@ -2879,13 +2890,20 @@ ptid_t
> linux_process_target::filter_exit_event (lwp_info *event_child,
> target_waitstatus *ourstatus)
> {
> - client_state &cs = get_client_state ();
> struct thread_info *thread = get_lwp_thread (event_child);
> ptid_t ptid = ptid_of (thread);
>
> + /* Note we must filter TARGET_WAITKIND_SIGNALLED as well, otherwise
> + if a non-leader thread exits with a signal, we'd report it to the
> + core which would interpret it as the whole-process exiting.
> + There is no TARGET_WAITKIND_THREAD_SIGNALLED event kind. */
> + if (ourstatus->kind () != TARGET_WAITKIND_EXITED
> + && ourstatus->kind () != TARGET_WAITKIND_SIGNALLED)
> + return ptid;
> +
> if (!is_leader (thread))
> {
> - if (cs.report_thread_events)
> + if (report_exit_events_for (thread))
> ourstatus->set_thread_exited (0);
> else
> ourstatus->set_ignore ();
> @@ -3028,10 +3046,7 @@ linux_process_target::wait_1 (ptid_t ptid, target_waitstatus *ourstatus,
> WTERMSIG (w));
> }
>
> - if (ourstatus->kind () == TARGET_WAITKIND_EXITED)
> - return filter_exit_event (event_child, ourstatus);
> -
> - return ptid_of (current_thread);
> + return filter_exit_event (event_child, ourstatus);
> }
>
> /* If step-over executes a breakpoint instruction, in the case of a
> @@ -3600,10 +3615,7 @@ linux_process_target::wait_1 (ptid_t ptid, target_waitstatus *ourstatus,
> target_pid_to_str (ptid_of (current_thread)).c_str (),
> ourstatus->to_string ().c_str ());
>
> - if (ourstatus->kind () == TARGET_WAITKIND_EXITED)
> - return filter_exit_event (event_child, ourstatus);
> -
> - return ptid_of (current_thread);
> + return filter_exit_event (event_child, ourstatus);
> }
>
> /* Get rid of any pending event in the pipe. */
> @@ -5909,7 +5921,7 @@ linux_process_target::supports_vfork_events ()
> gdb_thread_options
> linux_process_target::supported_thread_options ()
> {
> - return GDB_THREAD_OPTION_CLONE;
> + return GDB_THREAD_OPTION_CLONE | GDB_THREAD_OPTION_EXIT;
> }
>
> /* Check if exec events are supported. */
> diff --git a/gdbserver/linux-low.h b/gdbserver/linux-low.h
> index c9f9db71e09..1c1754d2b59 100644
> --- a/gdbserver/linux-low.h
> +++ b/gdbserver/linux-low.h
> @@ -575,10 +575,11 @@ class linux_process_target : public process_stratum_target
> exited. */
> void check_zombie_leaders ();
>
> - /* Convenience function that is called when the kernel reports an exit
> - event. This decides whether to report the event to GDB as a
> - process exit event, a thread exit event, or to suppress the
> - event. */
> + /* Convenience function that is called when we're about to return an
> + event to the core. If the event is an exit or signalled event,
> + then this decides whether to report it as process-wide event, as
> + a thread exit event, or to suppress it. All other event kinds
> + are passed through unmodified. */
> ptid_t filter_exit_event (lwp_info *event_child,
> target_waitstatus *ourstatus);
>
> --
> 2.36.0