[Bug server/31554] gdbserver --once --multi mishandles run & attach failures

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31554

--- Comment #3 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Pedro Alves <palves@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=f1fc8dc2dccb4a224cdd1c3973c7a09a752aa95b

commit f1fc8dc2dccb4a224cdd1c3973c7a09a752aa95b
Author: Pedro Alves <pedro@palves.net>
Date:   Wed Apr 17 19:26:32 2024 +0100

    Fix "attach" failure handling with GDBserver

    This fixes the same issue as the previous patch, but for "attach"
    instead of "run".

    If attaching to a process with "attach" (vAttach packet) fails,
    GDBserver throws an error that escapes all the way to the top level.
    When an error escapes all the way like that, GDBserver interprets it
    as a disconnection, and either goes back to waiting for a new GDB
    connection, or exits, if --once was specified.

    Here's an example:

    On the GDB side:

     ...
     (gdb) tar extended-remote :9999
     ...
     Remote debugging using :9999
     (gdb) attach 1
     Attaching to process 1
     Attaching to process 1 failed
     (gdb)

    On the GDBserver side:

     $ gdbserver --once --multi :9999
     Listening on port 9999
     Remote debugging from host 127.0.0.1, port 37464
     gdbserver: Cannot attach to process 1: Operation not permitted (1)
     $   # gdbserver exited

    This is wrong, as we've connected with extended-remote/--multi.
    GDBserver should just report an error to vAttach, and continue
    connected to GDB, waiting for other commands.

    This commit fixes GDBserver by catching the error locally in
    handle_v_attach.

    Note we now let pid == 0 pass down to attach_inferior.  That is so we
    get a useful textual error message to report to GDB.

    This fixes a couple KFAILs in gdb.base/attach.exp.  Still, I thought
    it would be useful to add a new testcase specifically for this
    scenario, in case gdb.base/attach.exp is ever split and stops trying
    to attach again after a failed attach, with the same GDB session.

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=19558
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31554

    Change-Id: I25314c7e5f1435eff69cb84d57ecac13d8de3393
    Approved-By: Tom Tromey <tom@tromey.com>

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