Implement a hook-system that allows to add custom code to the initscripts at certain places

A function add_hook can be called from functions.d to register a hook function. The existing hooks
are based on suggestions from Michael Towers (larch) and on the implementation of initscripts-extras-fbsplash
which currently uses the strings passed to stat_busy and stat_done for this. More hooks can
be added if requested.

The implementation uses associative arrays and will thus only work with bash 4 or later

5 files changed, 78 insertions, 1 deletions

diff --git a/functions b/functions
index 8745a38..56b78be 100644
--- a/functions
+++ b/functions
@@ -229,8 +229,52 @@ ck_status() {
   fi		
 }
 
+###############################
+# Custom hooks in initscripts #
+###############################
+# Hooks can be used to include custom code in various places in the rc.* scripts
+#
+# Define a hook function in a functions.d file using:
+#  function_name() {
+#    ...
+#  }
+#  add_hook hook_name function_name
+# It's allowed to register several hook functions for the same hook
+#
+# The function takes the filename of the script that launched it as an argument
+#
+# Currently, the following hooks exist:
+# start: at the beginning of rc.{multi,shutdown,single,sysinit}
+# end: at the end of rc.{multi,single,sysinit}
+# udevlaunched: after udev has been launched in rc.sysinit and rc.single
+# udevsettled: after uevents have settled in rc.sysinit and rc.single
+# premount: before local filesystems are mounted, but after root is mounted read-write in rc.sysinit
+# prekillall: before all processes are being killed in rc.shutdown and rc.single
+# postkillall: after all processes have been killed in rc.shutdown and rc.single
+# poweroff: directly before powering off in rc.shutdown
+#
+# Make sure to never override the add_hook and run_hook functions via functions.d
+
+declare -A hook_funcs
+for hook in start end udevlaunched udevsettled premount prekillall postkillall poweroff; do
+	hook_funcs["${hook}"]=""
+done
+
+add_hook() {
+	[ -z "$1" -o -z "$2" ] && return 1
+	hook_funcs["$1"]="${hook_funcs["$1"]} $2"
+}
+
+run_hook() {
+	local func
+
+	[ -z "$1" ] && return 1
+	for func in ${hook_funcs["$1"]}; do
+		${func} "$2"
+	done
+}
 
-#Source additional functions at the end to allow overrides
+# Source additional functions at the end to allow overrides
 for f in /etc/rc.d/functions.d/*; do
   if [ -e $f ]; then
     . $f
diff --git a/rc.multi b/rc.multi
index 731e48e..0cddd1d 100755
--- a/rc.multi
+++ b/rc.multi
@@ -6,6 +6,8 @@
 . /etc/rc.conf
 . /etc/rc.d/functions
 
+run_hook start rc.multi
+
 # Load sysctl variables if sysctl.conf is present
 [ -r /etc/sysctl.conf ] && /sbin/sysctl -q -p &>/dev/null
 
@@ -24,4 +26,6 @@ if [ -x /etc/rc.local ]; then
 	/etc/rc.local
 fi
 
+run_hook end rc.multi
+
 # vim: set ts=2 noet:
diff --git a/rc.shutdown b/rc.shutdown
index e2a4a84..5921e1c 100755
--- a/rc.shutdown
+++ b/rc.shutdown
@@ -6,6 +6,8 @@
 . /etc/rc.conf
 . /etc/rc.d/functions
 
+run_hook start rc.shutdown
+
 # avoid staircase effect
 /bin/stty onlcr
 
@@ -41,6 +43,8 @@ if [ "$PREVLEVEL" = "3" -o "$PREVLEVEL" = "5" ]; then
 	done
 fi
 
+run_hook prekillall rc.shutdown
+
 # Terminate all processes
 stat_busy "Sending SIGTERM To Processes"
 /sbin/killall5 -15 &> /dev/null
@@ -52,6 +56,8 @@ stat_busy "Sending SIGKILL To Processes"
 /bin/sleep 1
 stat_done
 
+run_hook postkillall rc.shutdown
+
 stat_busy "Saving Random Seed"
 RANDOM_SEED=/var/lib/misc/random-seed
 [ -d $(dirname $RANDOM_SEED) ] || mkdir -p $(dirname $RANDOM_SEED)
@@ -132,6 +138,8 @@ stat_busy "Remounting Root Filesystem Read-only"
 /bin/mount -n -o remount,ro /
 stat_done
 
+run_hook poweroff rc.shutdown
+
 # Power off or reboot
 if [ "$RUNLEVEL" = "0" ]; then
 	printsep
diff --git a/rc.single b/rc.single
index 50b7cfb..d72e95b 100755
--- a/rc.single
+++ b/rc.single
@@ -6,6 +6,8 @@
 . /etc/rc.conf
 . /etc/rc.d/functions
 
+run_hook start rc.single
+
 if [ "$PREVLEVEL" = "3" -o "$PREVLEVEL" = "5" ]; then
 	# Find daemons NOT in the DAEMONS array. Shut these down first
 	if [ -d /var/run/daemons ]; then
@@ -26,6 +28,8 @@ if [ "$PREVLEVEL" = "3" -o "$PREVLEVEL" = "5" ]; then
 fi
 
 if [ "$PREVLEVEL" != "N" ]; then
+	run_hook prekillall rc.single
+
 	# Terminate all processes
 	stat_busy "Sending SIGTERM To Processes"
 	/sbin/killall5 -15 &> /dev/null
@@ -37,10 +41,14 @@ if [ "$PREVLEVEL" != "N" ]; then
 	/bin/sleep 1
 	stat_done
 
+	run_hook postkillall rc.single
+
 	stat_busy "Starting UDev Daemon"
 	/sbin/udevd --daemon
 	stat_done
 
+	run_hook udevlaunched rc.single
+
 	# Trigger udev uevents
 	if /bin/pidof -o %PPID /sbin/udevd >/dev/null; then
 	  stat_busy "Triggering UDev uevents"
@@ -55,6 +63,8 @@ if [ "$PREVLEVEL" != "N" ]; then
 		stat_done
 	fi
 
+	run_hook udevsettled rc.single
+
 	# try syslog-NG first, then fall back to good ol' syslogd
 	if [ -x /etc/rc.d/syslog-ng ]; then
 		/etc/rc.d/syslog-ng start
@@ -64,6 +74,8 @@ if [ "$PREVLEVEL" != "N" ]; then
 	fi
 fi
 
+run_hook end rc.single
+
 if [ "$RUNLEVEL" = "1" ]; then
 	printsep
 	printhl "Entering single-user mode..."
diff --git a/rc.sysinit b/rc.sysinit
index f6463cc..60dcbef 100755
--- a/rc.sysinit
+++ b/rc.sysinit
@@ -14,6 +14,8 @@ printhl "Copyright 2007-2009 Aaron Griffin"
 printhl "Distributed under the GNU General Public License (GPL)"
 printsep
 
+run_hook start rc.sysinit
+
 # mount /proc, /sys and our RAM /dev
 /bin/mount -n -t tmpfs udev /dev -o mode=0755,size=10M,nosuid
 /bin/mount -n -t proc none /proc
@@ -63,6 +65,8 @@ stat_busy "Starting UDev Daemon"
 /sbin/udevd --daemon
 stat_done
 
+run_hook udevlaunched rc.sysinit
+
 # Trigger udev uevents
 if /bin/pidof -o %PPID /sbin/udevd >/dev/null; then
   stat_busy "Triggering UDev uevents"
@@ -108,6 +112,8 @@ if /bin/pidof -o %PPID /sbin/udevd >/dev/null; then
 	stat_done
 fi
 
+run_hook udevsettled rc.sysinit
+
 # bring up the loopback interface
 if [ -d /sys/class/net/lo ]; then
 	stat_busy "Bringing up loopback interface"
@@ -282,6 +288,7 @@ stat_busy "Mounting Local Filesystems"
 if [ -e /proc/mounts ]; then
 	/bin/grep -e "/proc " -e "/sys " -e "/dev " /proc/mounts >> /etc/mtab
 fi
+run_hook premount rc.sysinit
 # now mount all the local filesystems
 /bin/mount -a -t $NETFS -O no_netdev
 stat_done
@@ -412,5 +419,7 @@ fi
 
 /bin/dmesg >| /var/log/dmesg.log
 
+run_hook end rc.sysinit
+
 # End of file
 # vim: set ts=2 noet: