tinyramfs/generate

#!/bin/sh
#
# tiny initramfs generation tool

panic() {
    printf "panic >> %s\n" "$@"
    exit 1
}

info() {
    printf "info >> %s\n" "$@"
}

remove_tmpdir() {
    # remove tmpdir
    rm -rf "$tmpdir"
}

check_requirements() {
    # check needed files
    for f in ./config ./init ./busybox; do
	[ -e "$f" ] || panic "$f doesn't exists"
    done

    # TODO handle busybox requirements ( busybox --list | grep ash )

    # source config
    . ./config
}

create_structure() {
    # create FHS directory structure
    for d in dev tmp var run etc usr/lib usr/bin mnt/root proc root sys; do
	mkdir -p "${tmpdir}/${d}"
    done
}

create_symlinks() {
    # some dynamically linked libraries and binaries compiled with hardcoded
    # dependencies path. to make it worked we need create symlinks for them.
    # also POSIX ln doesn't have --relative flag like in GNU ln. as workaround
    # we change directory to tmpdir and make needed symlinks.
    ( cd "$tmpdir" && {
	ln -s usr/lib lib
	ln -s usr/lib lib64
	ln -s usr/bin bin
	ln -s usr/bin sbin
	ln -s ../run var/run
	cd "$tmpdir/usr"
	ln -s bin sbin
	ln -s lib lib64
    } )
}

#parse_fstab() {
# TODO parse fstab
#while [ "$use_fstab" -eq 1 ] && read fs dir type opts; do thing; done < /etc/fstab
#}

#parse_crypttab() {
# TODO parse crypttab
#}

# handle device managers
use_mdev() {
    # install mdev
    install -m644 mdev.conf -t "$tmpdir/etc"
    install -Dm755 storage-device -t "$tmpdir/lib/mdev"
}

use_mdevd() {
    # install mdevd
    install_binaries mdevd mdevd-coldplug
    install -m644 mdev.conf -t "$tmpdir/etc"
    install -Dm755 storage-device -t "$tmpdir/lib/mdev"
}

use_udev() {
    # install udev
    install_binaries udevd udevadm dmsetup
    # FIXME rewrite this piece of crap
    find /usr/lib/udev -type f | grep -v "rc_keymaps\|hwdb.d" | cpio -pd "$tmpdir" >/dev/null 2>&1
}

# handle lvm
use_lvm() {
    install_binaries lvm
    # FIXME this code doesn't working with udev
    #mkdir "$tmpdir/etc/lvm"
    # use_lvmetad = 0 - avoid lvmetad missing warning message
    #cat <<EOF > "$tmpdir/etc/lvm/lvmlocal.conf"
    #local {
    #	issue_discards = ${lvm_discard:-0}
    #	use_lvmetad = 0
    #}
    #EOF
    # TODO implement use_lvmconf
}

# handle luks
use_luks() {
    install_binaries cryptsetup

    # avoid locking directory missing warning message
    mkdir "${tmpdir}/run/cryptsetup"

    # TODO get rid of this workaround
    # workaround for luks2
    install -s -m755 /usr/lib/libgcc_s.so.1 -t "${tmpdir}/usr/lib"

    [ "$luks_discard" = 1 ] && luks_args="--allow-discards $luks_args"

    # TODO detached header
    # TODO keyfile
}

# TODO implement hostonly mode
# install drivers
install_drivers() {
    modker="${moddir}${kernel}"
    find \
	"${modker}/kernel/drivers/virtio" \
	"${modker}/kernel/arch" \
	"${modker}/kernel/crypto" \
	"${modker}/kernel/fs" \
	"${modker}/kernel/lib" \
	"${modker}/kernel/drivers/block" \
	"${modker}/kernel/drivers/ata" \
	"${modker}/kernel/drivers/md" \
	"${modker}/kernel/drivers/scsi" \
	"${modker}/kernel/drivers/usb/storage" \
	"${modker}/kernel/drivers/usb/host" \
	-type f | cpio -pd "$tmpdir" >/dev/null 2>&1

    # install list of drivers
    cp "${modker}/modules.softdep" "${modker}/modules.builtin" "${modker}/modules.order" "${tmpdir}/${modker}"

    # generate dependencies list of drivers
    depmod -b "$tmpdir" "$kernel"
}

# TODO make strip optional
# handle binaries
install_binaries() {
    for b in $(printf "%s\n" "$@" | tr " " "\n"); do
	# check binary existence
	command -v "$b" >/dev/null 2>&1 || panic "$b doesn't exists"

	# install and strip binary
	install -s -m755 "$(command -v $b)" -t "${tmpdir}/usr/bin"

        # check statically linking
	ldd "$(command -v $b)" >/dev/null 2>&1 || continue

	# install libraries
	install_libraries $b
    done
}

# TODO make strip optional
# handle libraries
install_libraries() {
    for l in $(ldd "$(command -v $1)" | sed -nre 's,.* (/.*lib.*/.*.so.*) .*,\1,p' -e 's,.*(/lib.*/ld.*.so.*) .*,\1,p'); do
	# check symlink
	if [ -h "$l" ]; then
	    # check lib already existence
	    if [ ! -e "${tmpdir}/usr/lib/${l##*/}" ] && [ ! -e "${tmpdir}/$(readlink -f $l)" ]; then
		# regular
		install -s -m755 "$(readlink -f $l)" -t "${tmpdir}/usr/lib"

		# FIXME handle all symlinks
		# symlink may link to symlink
		[ -h "/usr/lib/$(readlink $l)" ] && cp -a "/usr/lib/$(readlink $l)" "${tmpdir}/usr/lib"

		# symlink
		cp -a "$l" "${tmpdir}/usr/lib"
	    fi
	else
	    if [ ! -e "${tmpdir}/usr/lib/${l##*/}" ]; then
		install -s -m755 "$l" -t "${tmpdir}/usr/lib"
	    fi
	fi
    done
}

install_files() {
# initialize config
cat <<EOF > "${tmpdir}/config"
root="$root"
root_type="$root_type"
root_args="$root_args"
devmgr="$devmgr"
use_mdev="1"
#drivers="$drivers"
use_lvm="$use_lvm"
use_luks="$use_luks"
luks_root="$luks_root"
luks_header="$luks_header"
luks_keyfile="$luks_keyfile"
luks_args="$luks_args"
EOF

# needed for devmgr
cat <<EOF > "${tmpdir}/etc/group"
root:x:0:
tty:x:5:
dialout:x:11:
uucp:x:14:
kmem:x:3:
input:x:25:
video:x:13:
audio:x:12:
lp:x:10:
disk:x:9:
cdrom:x:16:
tape:x:6:
kvm:x:24:
floppy:x:8:
EOF

# needed for devmgr
cat <<EOF > "${tmpdir}/etc/passwd"
root:x:0:0::/root:/bin/sh
nobody:x:99:99::/:/bin/false
EOF

    # install init script
    install -m755 ./init -t "$tmpdir"
}

# TODO add more compession tools
# create cpio archive and compress
create_initramfs() {
    {
	( cd "$tmpdir" && {
	    find . | cpio -oH newc | gzip -9
	} ) > "/root/initramfs-${kernel}.img.gz"
    } >/dev/null 2>&1

    [ "$?" = 0 ] || panic "failed to generate initramfs image"
}

# main function :)

[ "$(id -u)" = 0 ] || panic "must be run as root"

# remove tmpdir on exit or unexpected error
#trap remove_tmpdir EXIT INT
set -x

# handle debug mode
[ "$debug" = 1 ] && {
    set -x
    trap : EXIT INT
}

# variables
tmpdir="$(mktemp -d /tmp/initramfs.XXXXXXXX)" || panic "failed to create working directory"
kernel="$(uname -r)"
moddir="/lib/modules/"

check_requirements
create_structure
create_symlinks
#parse_fstab
#parse_crypttab
install_binaries $binaries
install_drivers
install_files

case "$devmgr" in
    mdev) use_mdev ;;
    mdevd) use_mdevd ;;
    udev) use_udev ;;
    *) panic "devmgr option broken" ;;
esac

[ "$use_luks" = 1 ] && use_luks
[ "$use_lvm" = 1 ] && use_lvm

create_initramfs

info "done! check out initramfs-${kernel}.img.gz"