[klibc] run-init warning

[Alexander E. Patrakov]

H. Peter Anvin wrote:
> Please be aware that I HAVE NOT TESTED THIS PROGRAM... please try it in 
> a "safe" environment since for all I know it could nuke your "real root" 
> by mistake.

A fixed and tested version of the run-init program is attached. To see 
its real use example, put the attached "build.sh" script in the same 
directory as udev-026.tar.bz2 and 
klibc-0.129-with-fixed-run-init.tar.bz2 and run the build.sh script as 
root (root is needed because of mknod commands). The result is a copy of 
my working initramfs.

The check for not wiping out the real root filesystem is based on the 
presence of the /init file. Rationale: it is impossible to distinguish 
between initramfs and a chrooted environment based on the result of the 
statfs call.

KNOWN BUG: my previous /init script left really nothing in initramfs. 
Now /root is left there for some reason.

My initramfs does the following:

1) Disables hotplug in the kernel. It has been determined that the 
assumption "userspace is always ready to handle hotplug events" is 
inherently unsafe.
2) Interprets root=..., rootfstype=..., rootflags=..., init=..., ro and 
rw kernel command line options
3) Mounts the root filesystem (no NFS yet, sorry)
4) Mounts a ramfs on top of the real root's /dev directory (like in 
"mount devfs on boot") and creates /dev/null and /dev/console there
5) Wipes out initramfs contents and runs init from the root filesystem

Assumptions made upon initscripts (currently met in LFS CVS HEAD):

1) initscripts should be able to create all device nodes in /dev with 
the correct permissions, perhaps with the help of udevstart
2) initscripts should handle the situation when ramfs is already mounted 
on /dev
3) initscripts should echo /sbin/hotplug >/proc/sys/kernel/hotplug when 
the system is ready to handle hotplug events

-- 
Alexander E. Patrakov
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#!/bin/sh

if [ ! -d klibc-*/ ]
then
tar jxf klibc-*.tar.bz2
(
cd klibc-*/
ln -s /lib/modules/`uname -r`/build linux
#cp ../nuke.c utils
#sed -i 's,true false sleep ln,& nuke,' utils/Makefile
sed -i 's,^REGPARM_OPT.*$,# &,' klibc/arch/i386/MCONFIG
make
)
fi
if [ ! -d udev-*/ ]
then
tar jxf udev-*.tar.bz2
(
cd udev-*/
make USE_KLIBC=true USE_LOG=false # KLIBC_BASE=`echo $PWD/../klibc-*/`
)
fi
mkdir -p image/{dev,etc/udev,proc,root,sbin,sys}
ln -nsf sbin image/bin
mknod image/dev/console c 5 1
mknod image/dev/null c 1 3
cp klibc-*/ash/sh image/sbin
cp klibc-*/utils/static/{dd,fstype,run-init,mount,umount} image/sbin
cp udev-*/{udev,udevstart} image/sbin
cat >image/init <<"EOF"
#!/bin/sh

mount -t proc proc /proc
mount -t sysfs sysfs /sys

# Kernel is buggy by default
echo >/proc/sys/kernel/hotplug

echo "=================================="
echo "    This kernel uses initramfs    "
echo "=================================="

read cmdline </proc/cmdline
rw=0
init="/sbin/init"

for param in $cmdline
do
	case "$param" in
	root=*)
		root=`echo "$param" | dd bs=1 skip=5 2>/dev/null`
		if [ x"`echo "$root" | dd bs=1 count=5 2>/dev/null`" = x/dev/ ]
		then
			root=`echo "$root" | dd bs=1 skip=5 2>/dev/null`
		fi
		;;
	rootfstype=*|rootflags=*|init=*|kinit=*)
		eval "$param"
		;;
	ro)
		rw=0
		;;
	rw)
		rw=1
		;;
	esac
done

if [ ! -z "$kinit" ]
then
	exec "$kinit"
fi

if [ -z "$root" ]
then
	echo "No root parameter specified!"
	exit 1
fi

root="/dev/$root"

udevstart

if [ -z "$rootfstype" ]
then
	eval $( fstype <"$root" )
	rootfstype="$FSTYPE"
	if [ "$rootfstype" = "unknown" ]
	then
		echo "Unknown root filesystem type!"
		exit 1
	else
		echo "Guessed root filesystem type: $rootfstype"
	fi
fi

if [ ! -z "$rootflags" ]
then
	rootflags="$rootflags,"
fi

if [ "$rw" = 1 ]
then
	rootflags="$rootflags"rw
else
	rootflags="$rootflags"ro
fi

mount -t "$rootfstype" -o "$rootflags" "$root" /root
mount -t ramfs ramfs /root/dev

dd if=/etc/udev/udev.conf.host of=/etc/udev/udev.conf 2>/dev/null

ACTION=add DEVPATH=/class/mem/null udev class
ACTION=add DEVPATH=/class/tty/console udev class

exec </root/dev/console >/root/dev/console 2>&1

umount /sys
umount /proc

exec run-init /root "$init" "$@"
EOF
chmod 755 image/init
cat >image/etc/udev/udev.conf <<"EOF"
udev_root="/dev/"
udev_db="/dev/.udev.tdb"
udev_rules="/etc/udev/udev.rules"
default_mode="0600"
default_owner="root"
default_group="root"
udev_log="no"
EOF
cat >image/etc/udev/udev.conf.host <<"EOF"
udev_root="/root/dev/"
udev_db="/dev/.udev.tdb"
udev_rules="/etc/udev/udev.rules"
default_mode="0600"
default_owner="root"
default_group="root"
udev_log="no"
EOF
cp udev-*/etc/udev/udev.rules image/etc/udev
(
cd image
find . | cpio -o -H newc | gzip -9 >../initramfs_data.cpio.gz
)
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