tinyramfs/tinyramfs

#!/bin/sh
#
# https://shellcheck.net/wiki/SC2154
# shellcheck disable=2154

# TODO add version
usage()
{
    cat >&2 << EOF
usage: ${0##*/} [option]... <output>
    -c <file>  set path to config
    -k <kern>  set kernel version
    -m <path>  set path to modules
    -l         enable local mode
    -d         enable debug mode
    -f         overwrite initramfs image
    -h         display this message
EOF

    exit "$1"
}

init_base()
{
    print 'creating ramfs structure'

    mkdir -p "${tmpdir:=${TMPDIR:-/tmp}/tinyramfs.$$}"

    # https://shellcheck.net/wiki/SC2015
    # shellcheck disable=2015
    [ "$debug" ] && set -x || trap 'rm -rf $tmpdir' EXIT INT

    (
        cd "$tmpdir"

        # https://wikipedia.org/wiki/Filesystem_Hierarchy_Standard
        mkdir -p \
            dev sys tmp run var proc root \
            usr/lib usr/bin mnt/root etc/tinyramfs

        ln -s usr/lib lib
        ln -s usr/bin bin
        ln -s usr/bin sbin
        ln -s ../run  var/run
        ln -s ../run/lock var/lock
        ln -s bin     usr/sbin

        ln -s lib/tinyramfs/init.sh   init
        ln -s ../lib/tinyramfs/helper.sh bin/helper
    )

    for _bin in \
        \[ sh ln env mkdir sleep \
        printf switch_root mount
    do
        copy_exec "$_bin"
    done

    if ! command -v ldd > /dev/null; then
        print 'unable to find ldd' '~>'
    fi

    if ! command -v blkid > /dev/null; then
        print 'unable to find blkid' '~>'
    else
        copy_exec blkid
    fi

    copy_file "$config" /etc/tinyramfs/config    0644
    copy_file "$init"   /lib/tinyramfs/init.sh   0755
    copy_file "$devh"   /lib/tinyramfs/helper.sh 0755
    copy_file "$shrd"   /lib/tinyramfs/common.sh 0755
}

copy_hooks()
{
    # https://shellcheck.net/wiki/SC2086
    # shellcheck disable=2086
    { IFS=,; set -- $hooks; unset IFS; }

    for _hook; do
        copy_hook "$_hook"
    done
}

copy_modules()
{
    # Skip this function if kernel
    # compiled with builtin modules.
    if [ "$monolith" ]; then
        return

    elif [ "$hostonly" ]; then
        print 'copying hostonly modules'

        # Perform autodetection of modules via /sys
        # https://wiki.archlinux.org/index.php/Modalias
        find /sys/devices -name modalias -exec sort -u {} + |

        while read -r _mod; do
            # Skip unneeded modules and skip modules which
            # depends on them as well.
            case $(modprobe -S "$kernel" -D "$_mod") in
                *wmi* | *gpu* | *net*) continue ;;
            esac 2> /dev/null

            copy_kmod "$_mod"
        done

        if [ "$root_type" ]; then
            copy_kmod "$root_type"
        else
            while read -r _ _dir _type _; do
                [ "$_dir" = / ] && break
            done < /proc/mounts || panic 'unable to detect rootfs module'

            copy_kmod "$_type"
        fi
    else
        print 'copying all modules'

        (
            cd "${moddir}/${kernel}/kernel"

            find \
                fs lib arch crypto drivers/md drivers/ata drivers/scsi \
                drivers/block drivers/virtio drivers/usb/host \
                drivers/usb/storage -type f 2> /dev/null |

            while read -r _mod; do
                copy_file "$_mod" "/lib/modules/${kernel}/${_mod}" 0644
            done
        )
    fi

    copy_exec modprobe

    copy_file "${moddir}/${kernel}/modules.order" \
              "/lib/modules/${kernel}/modules.order" 0644

    copy_file "${moddir}/${kernel}/modules.builtin" \
              "/lib/modules/${kernel}/modules.builtin" 0644

    depmod -b "$tmpdir" "$kernel"
}

create_image()
{
    print 'generating initramfs image'

    [ -z "$force" ] && [ -e "$output" ] &&
        panic 'initramfs image already exist'

    (cd "$tmpdir" && find . | cpio -oH newc 2> /dev/null) | ${compress:-cat} > "$output" ||
        panic 'failed to generate initramfs image'

    print "done: $output" '+>'
}

while getopts c:k:m:ldfh opt; do case $opt in
    c) config=$OPTARG ;;
    k) kernel=$OPTARG ;;
    m) moddir=$OPTARG ;;
    l) local=1 ;;
    d) debug=1 ;;
    f) force=1 ;;
    h) usage 0 ;;
    ?) usage 2 ;;
esac; done

shift "$((OPTIND - 1))"

# https://shellcheck.net/wiki/SC2015
# shellcheck disable=2015
[ "$1" ] && output=$1 || usage 2

[ "$local" ] && {
    init="${PWD}/lib/init.sh"
    shrd="${PWD}/lib/common.sh"
    devh="${PWD}/lib/helper.sh"
}

: "${kernel:=$(uname -r)}"
: "${moddir:=/lib/modules}"
: "${init:=/lib/tinyramfs/init.sh}"
: "${devh:=/lib/tinyramfs/helper.sh}"
: "${shrd:=/lib/tinyramfs/common.sh}"

# -e: Exit if command return status greater than 0
# -f: Disable globbing *?[]
set -ef

# https://shellcheck.net/wiki/SC1090
# shellcheck disable=1090
. "$shrd"

# https://shellcheck.net/wiki/SC1090
# shellcheck disable=1090
. "${config:=/etc/tinyramfs/config}"

init_base
copy_hooks
copy_modules
create_image