[v5,0/8] gdbstub: Allow late attachment

Message

Ilya Leoshkevich Jan. 10, 2025, 2:09 p.m. UTC

v4: https://lore.kernel.org/qemu-devel/[e-mail]/
v4 -> v5: Fix the qemu-user-only build by adding qemu-sockets.c to it.
          Drop the qapi_bool_parse() changes (Daniel).

v3: https://lore.kernel.org/qemu-devel/[e-mail]/
v3 -> v4: Rebase.
          Add missing "\n"s to error messages.
          Use unix_listen() (Alex).
          Use qapi_bool_parse() and patch it to accept NULL (Alex).
          Remove a leftover include (Alex).
          Rename port_or_path to path, set it to NULL after freeing (Alex).

v2: https://lore.kernel.org/qemu-devel/[e-mail]/
v2 -> v3: Rebase.
          Patches that need review:
          - [PATCH 2/8] gdbstub: Try unlinking the unix socket before binding
          - [PATCH 4/8] user: Introduce host_interrupt_signal  # linux part
          - [PATCH 6/8] gdbstub: Allow late attachment
          - [PATCH 7/8] docs/user: Document the %d placeholder and suspend=n QEMU_GDB features
          - [PATCH 8/8] tests/tcg: Add late gdbstub attach test

v1: https://lore.kernel.org/qemu-devel/[e-mail]/
v1 -> v2: Rebase, fix conflicts with the QEMU_RTSIG_MAP patch.
          Use qemu_get_thread_id() for %d (Helge, Richard, Warner).
          Add R-bs, except for the Richard's one on 4/8, since
          conflict resolution caused a noticeable change.

Hi,

This series adds the ability to attach GDB to a running qemu-user
instance. This is useful for debugging multi-process apps.

Patches 1 and 2 implement a small related feature: the ability to
create individual UNIX sockets for each child process.

Patches 3-5 add the required infrastructure. In particular, we need
to reserve a host signal for waking up threads, as discussed in [1].
By the way, the problem with atomicity of checking for pending signals
and invoking syscalls that I'm describing in that thread seems to
have already been solved by the safe_syscall infrastructure, so the
changes are fairly simple.

If this series is accepted, I will rebase the all-stop series on top
of it.

Patch 6 is the implementation, patch 7 is a documentation update,
patch 8 is a test. I tested this series on Linux and only
compile-tested on the BSDs.

Best regards,
Ilya

Ilya Leoshkevich (8):
  gdbstub: Allow the %d placeholder in the socket path
  gdbstub: Try unlinking the unix socket before binding
  user: Introduce user/signal.h
  user: Introduce host_interrupt_signal
  osdep: Introduce qemu_kill_thread()
  gdbstub: Allow late attachment
  docs/user: Document the %d placeholder and suspend=n QEMU_GDB features
  tests/tcg: Add late gdbstub attach test

 bsd-user/main.c                            |   1 -
 bsd-user/signal-common.h                   |   1 -
 bsd-user/signal.c                          |  13 ++
 docs/user/main.rst                         |  16 ++-
 gdbstub/user.c                             | 154 +++++++++++++++++----
 include/qemu/osdep.h                       |   9 ++
 include/user/signal.h                      |  25 ++++
 linux-user/main.c                          |   1 -
 linux-user/signal-common.h                 |   1 -
 linux-user/signal.c                        |  26 +++-
 linux-user/syscall.c                       |   1 +
 stubs/meson.build                          |   2 +
 stubs/monitor-fd.c                         |   9 ++
 tests/guest-debug/run-test.py              |  15 +-
 tests/tcg/multiarch/Makefile.target        |   9 +-
 tests/tcg/multiarch/gdbstub/late-attach.py |  28 ++++
 tests/tcg/multiarch/late-attach.c          |  41 ++++++
 util/meson.build                           |   2 +
 util/oslib-posix.c                         |  15 ++
 19 files changed, 326 insertions(+), 43 deletions(-)
 create mode 100644 include/user/signal.h
 create mode 100644 stubs/monitor-fd.c
 create mode 100644 tests/tcg/multiarch/gdbstub/late-attach.py
 create mode 100644 tests/tcg/multiarch/late-attach.c