units: add mount for tracefs

Kernel 4.1 separated the tracing system from the debugfs,
actual documentation already points to a different path
that needs this new mount to exist.

the old sysfs path will still be an automount in the debugfs,
created by the kernel (for now).

Signed-off-by: Norbert Lange <nolange79@gmail.com>

units/meson.build

@@ -78,6 +78,8 @@ units = [
          'sysinit.target.wants/'],
         ['sys-kernel-debug.mount',              '',
          'sysinit.target.wants/'],
+        ['sys-kernel-tracing.mount',            '',
+         'sysinit.target.wants/'],
         ['sysinit.target',                      ''],
         ['syslog.socket',                       ''],
         ['system-systemd\\x2dcryptsetup.slice', 'HAVE_LIBCRYPTSETUP'],

units/sys-kernel-tracing.mount

@@ -0,0 +1,23 @@
+#  SPDX-License-Identifier: LGPL-2.1+
+#
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+[Unit]
+Description=Kernel Trace File System
+Documentation=https://www.kernel.org/doc/Documentation/trace/ftrace.txt
+Documentation=https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
+DefaultDependencies=no
+ConditionPathExists=/sys/kernel/tracing
+ConditionCapability=CAP_SYS_RAWIO
+Before=sysinit.target
+
+[Mount]
+What=tracefs
+Where=/sys/kernel/tracing
+Type=tracefs
+Options=nosuid,nodev,noexec