init: add a minimalist init program

This patch adds a minimalist init program.  It is somewhat lacking in
features, but is able to bring up a Hurd system with the runsystem and
rc scripts.  In fact, it roughly does what the former /hurd/init did,
modulo all the very early bootstrapping stuff and the startup
protocol.  It is started when all the essential servers are up and
running, so it can make use of most of the POSIX goodies, making its
implementation much simpler.

* Makefile (prog-subdirs): Add init.
* daemons/runsystem.sh: Generalize runsystem so that it can start any
init as specified on the kernel command line.  By default, it starts
/hurd/init.
* daemons/runsystem.hurd: This is a verbatim copy of runsystem.sh.  It
is started by /hurd/init.
* daemons/rc.sh: Do not start /hurd/mach-defpager as it is already
started in runsystem.sh.
* daemons/Makefile (SRCS): Add runsystem.hurd.
* init/Makefile: New file.
* init/init.c: Likewise.

1 files changed, 26 insertions, 54 deletions

diff --git a/daemons/runsystem.sh b/daemons/runsystem.sh
index f4f27711..ae25a7d6 100644
--- a/daemons/runsystem.sh
+++ b/daemons/runsystem.sh
@@ -1,9 +1,9 @@
 #!/bin/bash
 #
 # This program is run by /hurd/init at boot time after the essential
-# servers are up, and is responsible for running the "userland" parts of a
-# normal system.  This includes running the single-user shell as well as a
-# multi-user system.  This program is expected never to exit.
+# servers are up.  It does some initialization of its own and then
+# execs /hurd/init or any other roughly SysV init-compatible program
+# to bring up the "userland" parts of a normal system.
 #
 
 
@@ -22,11 +22,10 @@ fallback_shells='/bin/sh /bin/bash /bin/csh /bin/ash /bin/shd'
 # Shell used for normal single-user startup.
 SHELL=/bin/sh
 
-# Programs that do multi-user startup.
-RUNCOM=/libexec/rc
-RUNTTYS=/libexec/runttys
-# Signals that we should pass down to runttys.
-runttys_sigs='TERM INT HUP TSTP'
+# The init program to call.
+#
+# Can be overridden using init=something in the kernel command line.
+init=/hurd/init
 
 ###
 
@@ -44,7 +43,7 @@ trap 'reopen_console' SIGLOST
 # startup entirely.  We exec a single-user shell, so we will not come back
 # here.  The only way to get to multi-user from that shell will be
 # explicitly exec this script or something like that.
-function singleuser ()
+function singleuser()
 {
   test $# -eq 0 || echo "$0: $*"
   for try in ${fallback_shells}; do
@@ -54,6 +53,8 @@ function singleuser ()
   exit 127
 }
 
+# Print a newline.
+echo
 
 # See whether pflocal is set up already, and do so if not (install case)
 #
@@ -85,20 +86,23 @@ fi
 # The first argument is the kernel file name; skip that.
 shift
 flags=
+single=
 while [ $# -gt 0 ]; do
   arg="$1"
   shift
   case "$arg" in
   --*) ;;
+  init=*)
+    eval "${arg}"
+    ;;
   *=*) ;;
   -*)
     flags="${flags}${arg#-}"
     ;;
-  'single'|'emergency') # Linux compat
-    flags="${flags}s"
+  'single')
+    single="-s"
     ;;
-  'fastboot')
-    flags="${flags}f"
+  'fastboot'|'emergency')
     ;;
   esac
 done
@@ -106,50 +110,18 @@ done
 # Check boot flags.
 case "$flags" in
 *s*)
-  rc=false			# force single-user
-  ;;
-*f*)
-  rc="${RUNCOM}"		# fastboot
-  ;;
-*)
-  rc="${RUNCOM} autoboot"	# multi-user default
+  single="-s"			# force single-user
   ;;
 esac
 
-# Large infinite loop.  If this script ever exits, init considers that
-# a serious bogosity and punts to a fallback single-user shell.
-# We handle here the normal transitions between single-user and multi-user.
-while : ; do
-
-  # Run the rc script.  As long as it exits nonzero, punt to single-user.
-  # After the single-user shell exits, we will start over attempting to
-  # run rc; but later invocations strip the `autoboot' argument.
-  until $rc; do
-    rc=${RUNCOM}
-
-    # Run single-user shell and repeat as long as it dies with a signal.
-    until ${SHELL} || test $? -lt 128; do
-      :
-    done
-  done
-
-  # Now we are officially ready for normal multi-user operation.
-
-  # Trap certain signals and send them on to runttys.  For this to work, we
-  # must run it asynchronously and wait for it with the `wait' built-in.
-  runttys_pid=0
-  for sig in $runttys_sigs; do
-    trap "kill -$sig \${runttys_pid}" $sig
-  done
+# Start the default pager.  It will bail if there is already one running.
+/hurd/mach-defpager
 
-  # This program reads /etc/ttys and starts the programs it says to.
-  ${RUNTTYS} &
-  runttys_pid=$!
+# This is necessary to make stat / return the correct device ids.
+# Work around a race condition (probably in the root translator).
+for i in `seq 1 100000` ; do : ; done # XXX
 
-  # Wait for runttys to die, meanwhile handling trapped signals.
-  wait
+fsysopts / --update --readonly
 
-  # Go back to the top of the infinite loop, as if booting single-user.
-  rc=false
-
-done
+# Finally, start the actual init.
+exec ${init} ${single} -a