maintainer-feedback requested: [Bug 296052] x11/sddm: Wayland session login bounces with exit 125 on FreeBSD 15.1-RELEASE (ConsoleKit2)

Bugzilla Automation <[email protected]> has asked freebsd-kde (group)
<[email protected]> for maintainer-feedback:
Bug 296052: x11/sddm: Wayland session login bounces with exit 125 on FreeBSD
15.1-RELEASE (ConsoleKit2)
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=296052



--- Description ---
Summary

SDDM 0.21.0.36_2 fails to launch Wayland sessions on FreeBSD 15.1-RELEASE,
immediately returning to the greeter with sddm-helper exit code 125.
Authentication succeeds, sddm-helper starts the session, and it dies within
~40ms. This affects all Wayland sessions (Plasma 6.6.5 and LXQt both fail
identically). X11 sessions work correctly. Only Wayland sessions are affected.
Launching Plasma Wayland from a TTY via .zlogin works without issue.

Environment

FreeBSD 15.1-RELEASE (pkgbase)
SDDM 0.21.0.36_2 (pkg binary)
plasma6-plasma-workspace-6.6.5
ConsoleKit2 (not elogind)
Intel i7-8650U / UHD 620, drm-kmod
ThinkPad T480s
User shell: zsh

Steps to Reproduce

Enable sddm in rc.conf
Boot to SDDM greeter (runs on X11, vt9)
Select Plasma (Wayland) or any Wayland session
Enter valid credentials
Session bounces back to greeter within ~40ms

Observed Behavior

From /var/log/sddm.log (trimmed):

[20:56:22.345] (II) DAEMON: Greeter stopped. SDDM::Auth::HELPER_SUCCESS
[20:56:22.361] (II) HELPER: Starting Wayland user session:
  "/usr/local/share/sddm/scripts/wayland-session"
  "/usr/local/lib/libexec/plasma-dbus-run-session-if-needed
   /usr/local/bin/ck-launch-session /usr/local/bin/startplasma-wayland"
[20:56:22.410] (II) DAEMON: Session started true
[20:56:22.413] (II) HELPER: [PAM] Closing session
[20:56:22.414] (II) HELPER: [PAM] Ended.
[20:56:22.414] (WW) DAEMON: Auth: sddm-helper exited with 125

The session starts at .361, PAM closes at .413, 52ms total. No session log is
ever written to ~/.local/share/sddm/wayland-session.log or anywhere else.

The same exit 125 occurs with LXQt Wayland (startlxqtwayland), confirming this
is not Plasma-specific.

Debugging Performed

ConsoleKit2 session is active=TRUE, seat=seat0
/dev/dri/card0 and renderD128 exist with correct permissions
XDG_RUNTIME_DIR (/var/run/user/1003) exists, owned by user, mode 0700
polkit rules for operator group are in place
User is in wheel, operator, video, network groups
All binaries in the session command chain exist and are executable:

/usr/local/lib/libexec/plasma-dbus-run-session-if-needed (shell script)
/usr/local/bin/ck-launch-session
/usr/local/bin/startplasma-wayland
/usr/local/bin/dbus-run-session


plasma-dbus-run-session-if-needed was patched to use full path for
dbus-run-session. No change in behavior.
Attempted to capture session output by:
(a) Creating a debug .desktop file with /bin/sh -c wrapper redirecting
stdout/stderr to /tmp/plasma-session.log
(b) Patching wayland-session script with debug logging before exec
Neither produced any log file. The wayland-session script's zsh re-exec path
(exec $SHELL --login $0 "$@") appears to die before reaching the exec "$@" line
that runs the actual session command.
Confirmed no conflicting .zlogin exec (ttyv0 guard prevents it from firing on
SDDM's vt10)
No existing Plasma session was running during clean test attempts (wayland-0
socket cleared)
Every login attempt emits the following warning in the SDDM log: "Detected
locale C with character encoding US-ASCII, which is not UTF-8. Qt depends on a
UTF-8 locale, and has switched to C.UTF-8 instead." I do not know whether this
is related to the failure.


Expected Behavior

Wayland session should start on vt10. Executing the same command manually as
the affected user (mcapella) from ttyv0 successfully starts a Plasma Wayland
session:

/usr/local/lib/libexec/plasma-dbus-run-session-if-needed \
  ck-launch-session startplasma-wayland

Analysis

The wayland-session script re-execs itself under the user's login shell (zsh)
before launching the requested session. The 52ms lifetime and complete absence
of session log output suggest the failure may be occurring before the final
session command is executed, although I was unable to determine the exact
failure point.

The KDE Community Wiki documents SDDM Wayland on FreeBSD as bugged:
https://community.kde.org/FreeBSD/Setup

Workaround

Launch Plasma Wayland from .zlogin on ttyv0 instead of using SDDM:

shif [ "$(tty)" = "/dev/ttyv0" ] && [ -z "$DISPLAY" ] && \
   [ -z "$WAYLAND_DISPLAY" ]; then
    exec /usr/local/lib/libexec/plasma-dbus-run-session-if-needed \
      ck-launch-session startplasma-wayland
fi