archiso

#!/bin/ash
#
# SPDX-License-Identifier: GPL-3.0-or-later

# args: source, newroot, mountpoint
_mnt_dmsnapshot() {
    local img="${1}"
    local newroot="${2}"
    local mnt="${3}"
    local img_fullname="${img##*/}";
    local img_name="${img_fullname%%.*}"
    local dm_snap_name="${dm_snap_prefix}_${img_name}"
    local ro_dev ro_dev_size rw_dev

    ro_dev="$(losetup --find --show --read-only -- "${img}")"
    echo "${ro_dev}" >> /run/archiso/used_block_devices
    ro_dev_size="$(blockdev --getsz "${ro_dev}")"

    if [ "${cow_persistent}" = "P" ]; then
        if [ -f "/run/archiso/cowspace/${cow_directory}/${img_name}.cow" ]; then
            msg ":: Found '/run/archiso/cowspace/${cow_directory}/${img_name}.cow', using as persistent."
        else
            msg ":: Creating '/run/archiso/cowspace/${cow_directory}/${img_name}.cow' as persistent."
            truncate -s "${cow_spacesize}" "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
        fi
    else
        if [ -f "/run/archiso/cowspace/${cow_directory}/${img_name}.cow" ]; then
            msg ":: Found '/run/archiso/cowspace/${cow_directory}/${img_name}.cow' but non-persistent requested, removing."
            rm -f "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
        fi
        msg ":: Creating '/run/archiso/cowspace/${cow_directory}/${img_name}.cow' as non-persistent."
        truncate -s "${cow_spacesize}" "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
    fi

    rw_dev="$(losetup --find --show "/run/archiso/cowspace/${cow_directory}/${img_name}.cow")"
    echo "${rw_dev}" >> /run/archiso/used_block_devices

    dmsetup create "${dm_snap_name}" --table \
        "0 ${ro_dev_size} snapshot ${ro_dev} ${rw_dev} ${cow_persistent} ${cow_chunksize}"

    if [ "${cow_persistent}" != "P" ]; then
        rm -f "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
    fi

    _mnt_dev "/dev/mapper/${dm_snap_name}" "${newroot}${mnt}" "-w" "defaults"
    readlink -f "/dev/mapper/${dm_snap_name}" >> /run/archiso/used_block_devices
}

# args: source, newroot, mountpoint
_mnt_overlayfs() {
    local src="${1}"
    local newroot="${2}"
    local mnt="${3}"
    mkdir -p "/run/archiso/cowspace/${cow_directory}/upperdir" "/run/archiso/cowspace/${cow_directory}/workdir"
    mount -t overlay -o \
    "lowerdir=${src},upperdir=/run/archiso/cowspace/${cow_directory}/upperdir,workdir=/run/archiso/cowspace/${cow_directory}/workdir" \
    airootfs "${newroot}${mnt}"
}


# args: /path/to/image_file, mountpoint
_mnt_sfs() {
    local img="${1}"
    local mnt="${2}"
    local img_fullname="${img##*/}"
    local sfs_dev

    # shellcheck disable=SC2154
    # defined via initcpio's parse_cmdline()
    if [ "${copytoram}" = "y" ]; then
        msg -n ":: Copying squashfs image to RAM..."
        if ! cp -- "${img}" "/run/archiso/copytoram/${img_fullname}" ; then
            echo "ERROR: while copy '${img}' to '/run/archiso/copytoram/${img_fullname}'"
            launch_interactive_shell
        fi
        img="/run/archiso/copytoram/${img_fullname}"
        msg "done."
    fi
    sfs_dev="$(losetup --find --show --read-only -- "${img}")"
    echo "${sfs_dev}" >> /run/archiso/used_block_devices
    _mnt_dev "${sfs_dev}" "${mnt}" "-r" "defaults"
}

# args: device, mountpoint, flags, opts
_mnt_dev() {
    local dev="${1}"
    local mnt="${2}"
    local flg="${3}"
    local opts="${4}"

    mkdir -p "${mnt}"

    msg ":: Mounting '${dev}' to '${mnt}'"

    while ! poll_device "${dev}" 30; do
        echo "ERROR: '${dev}' device did not show up after 30 seconds..."
        echo "   Falling back to interactive prompt"
        echo "   You can try to fix the problem manually, log out when you are finished"
        launch_interactive_shell
    done

    if mount -o "${opts}" "${flg}" "${dev}" "${mnt}"; then
        msg ":: Device '${dev}' mounted successfully."
    else
        echo "ERROR; Failed to mount '${dev}'"
        echo "   Falling back to interactive prompt"
        echo "   You can try to fix the problem manually, log out when you are finished"
        launch_interactive_shell
    fi
}

_verify_checksum() {
    local _status
    cd "/run/archiso/bootmnt/${archisobasedir}/${arch}" || exit 1
    sha512sum -c airootfs.sha512 > /tmp/checksum.log 2>&1
    _status=$?
    cd -- "${OLDPWD}" || exit 1
    return "${_status}"
}

_verify_signature() {
    local _status
    cd "/run/archiso/bootmnt/${archisobasedir}/${arch}" || exit 1
    gpg --homedir /gpg --status-fd 1 --verify airootfs.sfs.sig 2>/dev/null | grep -qE '^\[GNUPG:\] GOODSIG'
    _status=$?
    cd -- "${OLDPWD}" || exit 1
    return ${_status}
}

run_hook() {
    [ -z "${arch}" ] && arch="$(uname -m)"
    [ -z "${copytoram_size}" ] && copytoram_size="75%"
    [ -z "${archisobasedir}" ] && archisobasedir="arch"
    [ -z "${dm_snap_prefix}" ] && dm_snap_prefix="arch"
    # shellcheck disable=SC2154
    # defined via initcpio's parse_cmdline()
    [ -z "${archisodevice}" ] && archisodevice="/dev/disk/by-label/${archisolabel}"
    [ -z "${cow_spacesize}" ] && cow_spacesize="256M"
    # shellcheck disable=SC2154
    # defined via initcpio's parse_cmdline()
    if [ -n "${cow_label}" ]; then
        cow_device="/dev/disk/by-label/${cow_label}"
        [ -z "${cow_persistent}" ] && cow_persistent="P"
    elif [ -n "${cow_device}" ]; then
        [ -z "${cow_persistent}" ] && cow_persistent="P"
    else
        cow_persistent="N"
    fi

    [ -z "${cow_flags}" ] && cow_flags="defaults"
    [ -z "${cow_directory}" ] && cow_directory="persistent_${archisolabel}/${arch}"
    [ -z "${cow_chunksize}" ] && cow_chunksize="8"

    # set mount handler for archiso
    export mount_handler="archiso_mount_handler"
}

# This function is called normally from init script, but it can be called
# as chain from other mount handlers.
# args: /path/to/newroot
archiso_mount_handler() {
    local newroot="${1}"

    if ! mountpoint -q "/run/archiso/bootmnt"; then
        _mnt_dev "${archisodevice}" "/run/archiso/bootmnt" "-r" "defaults"
        if [ "${copytoram}" != "y" ]; then
            readlink -f "${archisodevice}" >> /run/archiso/used_block_devices
        fi
    fi

    # shellcheck disable=SC2154
    # defined via initcpio's parse_cmdline()
    if [ "${checksum}" = "y" ]; then
        if [ -f "/run/archiso/bootmnt/${archisobasedir}/${arch}/airootfs.sha512" ]; then
            msg -n ":: Self-test requested, please wait..."
            if _verify_checksum; then
                msg "done. Checksum is OK, continue booting."
            else
                echo "ERROR: one or more files are corrupted"
                echo "see /tmp/checksum.log for details"
                launch_interactive_shell
            fi
        else
            echo "ERROR: checksum=y option specified but ${archisobasedir}/${arch}/airootfs.sha512 not found"
            launch_interactive_shell
        fi
    fi

    # shellcheck disable=SC2154
    # defined via initcpio's parse_cmdline()
    if [ "${verify}" = "y" ]; then
        if [ -f "/run/archiso/bootmnt/${archisobasedir}/${arch}/airootfs.sfs.sig" ]; then
            msg -n ":: Signature verification requested, please wait..."
            if _verify_signature; then
                msg "done. Signature is OK, continue booting."
            else
                echo "ERROR: one or more files are corrupted"
                launch_interactive_shell
            fi
        else
            echo "ERROR: verify=y option specified but ${archisobasedir}/${arch}/airootfs.sfs.sig not found"
            launch_interactive_shell
        fi
    fi

    if [ "${copytoram}" = "y" ]; then
        msg ":: Mounting /run/archiso/copytoram (tmpfs) filesystem, size=${copytoram_size}"
        mkdir -p /run/archiso/copytoram
        mount -t tmpfs -o "size=${copytoram_size}",mode=0755 copytoram /run/archiso/copytoram
    fi

    if [ -n "${cow_device}" ]; then
        _mnt_dev "${cow_device}" "/run/archiso/cowspace" "-r" "${cow_flags}"
        readlink -f "${cow_device}" >> /run/archiso/used_block_devices
        mount -o remount,rw "/run/archiso/cowspace"
    else
        msg ":: Mounting /run/archiso/cowspace (tmpfs) filesystem, size=${cow_spacesize}..."
        mkdir -p /run/archiso/cowspace
        mount -t tmpfs -o "size=${cow_spacesize}",mode=0755 cowspace /run/archiso/cowspace
    fi
    mkdir -p "/run/archiso/cowspace/${cow_directory}"
    chmod 0700 "/run/archiso/cowspace/${cow_directory}"

    _mnt_sfs "/run/archiso/bootmnt/${archisobasedir}/${arch}/airootfs.sfs" "/run/archiso/airootfs"
    if [ -f "/run/archiso/airootfs/airootfs.img" ]; then
        _mnt_dmsnapshot "/run/archiso/airootfs/airootfs.img" "${newroot}" "/"
    else
        _mnt_overlayfs "/run/archiso/airootfs" "${newroot}" "/"
    fi

    if [ "${copytoram}" = "y" ]; then
        umount -d /run/archiso/bootmnt
        rmdir /run/archiso/bootmnt
    fi
}

# vim: set ft=sh: