plugins: hook-scripts: Add

Add a plugin that will allow the user to trigger the execution of
scripts from plugin hook points. This is particularly useful for early
boot debugging that needs to take place before regular services are
available.

For example, let's say that you want to enable some kernel tracing
before modules are loaded. With hook-scripts, you can just drop in a
shell script in /libexec/finit/hook/mount/all/ that will poke the
right control files in tracefs.

configure.ac

@@ -90,6 +90,7 @@ AC_PLUGIN([modprobe],      [yes], [Coldplug modules using modalias magic])
 AC_PLUGIN([resolvconf],    [no],  [Setup necessary files for resolvconf])
 AC_PLUGIN([x11-common],    [no],  [Console setup (for X)])
 AC_PLUGIN([netlink],       [yes], [Basic netlink plugin for IFUP/IFDN and GW events. Can be replaced with externally built plugin that links with libnl or similar.])
+AC_PLUGIN([hook-scripts],  [no],  [Trigger script execution from hook points])
 AC_PLUGIN([hotplug],       [yes], [Setup and start udev or mdev hotplug daemon])
 AC_PLUGIN([rtc],           [yes], [Save and restore RTC using hwclock])
 AC_PLUGIN([tty],           [yes], [Automatically activate new TTYs, e.g. USB-to-serial])
@@ -146,6 +147,11 @@ AC_ARG_WITH(watchdog,
         AS_HELP_STRING([--with-watchdog=[DEV]], [Enable built-in watchdog, default: /dev/watchdog]),
 	[watchdog=$withval], [with_watchdog=no watchdog=])
 
+AC_ARG_WITH(hook-scripts-path,
+        AS_HELP_STRING([--with-hook-scripts-path=DIR], [Base directory for hook scripts, default $libexecdir/finit/hook]),
+	[hook_scripts_path=$withval], [hook_scripts_path=yes])
+
+
 ### Enable features ###########################################################################
 
 # Create config.h from selected features and fallback defaults
@@ -240,6 +246,11 @@ AS_IF([test "x$with_watchdog" != "xno"], [
         AC_DEFINE_UNQUOTED(WDT_DEVNODE, "$watchdog", [Built-in watchdog device node])], [
 	watchdog=])
 
+AS_IF([test "x$enable_hook_scripts_plugin" = "xyes" -a "x$with_hook_scripts_path" != "xno"], [
+	AS_IF([test "x$hook_scripts_path" = "xyes"], [hook_scripts_path=$libexecdir/finit/hook])
+	AC_EXPAND_DIR(hook_scripts_path, "$hook_scripts_path")
+	AC_DEFINE_UNQUOTED(PLUGIN_HOOK_SCRIPTS_PATH, "$hook_scripts_path", [Built-in default: $libexecdir/finit])])
+
 # Control build with automake flags
 AM_CONDITIONAL(STATIC,    [test "x$enable_static" = "xyes"])
 AM_CONDITIONAL(KEVENTD,   [test "x$with_keventd"  != "xno"])

doc/plugins.md

@@ -34,6 +34,12 @@ For your convenience a set of *optional* plugins are available:
 * *dbus.so*: Setup and start system message bus, D-Bus, at boot.
   _Optional plugin._
 
+* *hook-scripts.so*: Trigger the execution of scripts from plugin hook
+  points (see [Hooks](#hooks)).  Scripts are located in
+  `/libexec/finit/hook` by default, this can be build-time customized
+  by using the `--with-hook-scripts-path=PATH` argument to
+  `configure`.  _Optional plugin._
+
 * *hotplug.so*: Setup and start either udev or mdev hotplug daemon, if
   available.  Enabled by default.
 

plugins/Makefile.am

@@ -64,6 +64,10 @@ if BUILD_DBUS_PLUGIN
 pkglib_LTLIBRARIES += dbus.la
 endif
 
+if BUILD_HOOK_SCRIPTS_PLUGIN
+pkglib_LTLIBRARIES += hook-scripts.la
+endif
+
 if BUILD_HOTPLUG_PLUGIN
 pkglib_LTLIBRARIES += hotplug.la
 endif

plugins/hook-scripts.c

@@ -0,0 +1,116 @@
+/* Trigger scripts to run from finit's hooks
+ *
+ * Copyright (c) 2022  Tobias Waldekranz <tobias@waldekranz.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "finit.h"
+#include "helpers.h"
+#include "plugin.h"
+#include "config.h"
+
+#define CHOOSE(x, y) y
+static const char *hscript_paths[] = HOOK_TYPES;
+#undef CHOOSE
+
+static void hscript_run_parts(hook_point_t hook)
+{
+	char path[CMD_SIZE] = "";
+
+	strlcat(path, PLUGIN_HOOK_SCRIPTS_PATH, sizeof(path));
+	strlcat(path, hscript_paths[hook] + 4, sizeof(path));
+
+	run_parts(path, NULL);
+}
+
+static void hscript_banner(void *arg)
+{
+	hscript_run_parts(HOOK_BANNER);
+}
+
+static void hscript_rootfs_up(void *arg)
+{
+	hscript_run_parts(HOOK_ROOTFS_UP);
+}
+
+static void hscript_mount_error(void *arg)
+{
+	hscript_run_parts(HOOK_MOUNT_ERROR);
+}
+
+static void hscript_mount_post(void *arg)
+{
+	hscript_run_parts(HOOK_MOUNT_POST);
+}
+
+static void hscript_basefs_up(void *arg)
+{
+	hscript_run_parts(HOOK_BASEFS_UP);
+}
+
+static void hscript_network_up(void *arg)
+{
+	hscript_run_parts(HOOK_NETWORK_UP);
+}
+
+static void hscript_svc_up(void *arg)
+{
+	hscript_run_parts(HOOK_SVC_UP);
+}
+
+static void hscript_system_up(void *arg)
+{
+	hscript_run_parts(HOOK_SYSTEM_UP);
+}
+
+static void hscript_shutdown(void *arg)
+{
+	hscript_run_parts(HOOK_SHUTDOWN);
+}
+
+static plugin_t plugin = {
+	.name = __FILE__,
+	.hook[HOOK_BANNER]      = { .cb  = hscript_banner      },
+	.hook[HOOK_ROOTFS_UP]   = { .cb  = hscript_rootfs_up   },
+	.hook[HOOK_MOUNT_ERROR] = { .cb  = hscript_mount_error },
+	.hook[HOOK_MOUNT_POST]  = { .cb  = hscript_mount_post  },
+	.hook[HOOK_BASEFS_UP]   = { .cb  = hscript_basefs_up   },
+	.hook[HOOK_NETWORK_UP]  = { .cb  = hscript_network_up  },
+	.hook[HOOK_SVC_UP]      = { .cb  = hscript_svc_up      },
+	.hook[HOOK_SYSTEM_UP]   = { .cb  = hscript_system_up   },
+	.hook[HOOK_SHUTDOWN]    = { .cb  = hscript_shutdown    },
+};
+
+PLUGIN_INIT(plugin_init)
+{
+	plugin_register(&plugin);
+}
+
+PLUGIN_EXIT(plugin_exit)
+{
+	plugin_unregister(&plugin);
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */