Support EROFS

EROFS, like Squashfs, is a read-only file system. It can be used to store airootfs in an image file.
Its advantage is the support for POSIX ACLs. EROFS downside is that currently it only supports LZ4 compression (LZMA support is not yet fully implemented).

A difference from Squashfs is that, EROFS stores change time (ctime) not modification time (mtime). The reverse is true for Squashfs.

Implements https://gitlab.archlinux.org/archlinux/archiso/-/issues/59

3 files changed, 78 insertions, 9 deletions

diff --git a/archiso/initcpio/hooks/archiso b/archiso/initcpio/hooks/archiso
index bf98332..1b848ce 100644
--- a/archiso/initcpio/hooks/archiso
+++ b/archiso/initcpio/hooks/archiso
@@ -81,12 +81,36 @@ _mnt_sfs() {
     _mnt_dev "${sfs_dev}" "${mnt}" "-r" "defaults"
 }
 
+# args: /path/to/image_file, mountpoint
+_mnt_erofs() {
+    local img="${1}"
+    local mnt="${2}"
+    local img_fullname="${img##*/}"
+    local erofs_dev
+
+    # shellcheck disable=SC2154
+    # defined via initcpio's parse_cmdline()
+    if [ "${copytoram}" = "y" ]; then
+        msg -n ":: Copying EROFS 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/${img_fullname}"
+        msg "done."
+    fi
+    erofs_dev="$(losetup --find --show --read-only -- "${img}")"
+    echo "${erofs_dev}" >> /run/archiso/used_block_devices
+    _mnt_dev "${erofs_dev}" "${mnt}" "-r" "defaults" "erofs"
+}
+
 # args: device, mountpoint, flags, opts
 _mnt_dev() {
     local dev="${1}"
     local mnt="${2}"
     local flg="${3}"
     local opts="${4}"
+    local fstype="${5:-auto}"
 
     mkdir -p "${mnt}"
 
@@ -99,7 +123,7 @@ _mnt_dev() {
         launch_interactive_shell
     done
 
-    if mount -o "${opts}" "${flg}" "${dev}" "${mnt}"; then
+    if mount -t "${fstype}" -o "${opts}" "${flg}" "${dev}" "${mnt}"; then
         msg ":: Device '${dev}' mounted successfully."
     else
         echo "ERROR; Failed to mount '${dev}'"
@@ -120,8 +144,9 @@ _verify_checksum() {
 
 _verify_signature() {
     local _status
+    local sigfile="${1}"
     cd "/run/archiso/bootmnt/${archisobasedir}/${arch}" || exit 1
-    gpg --homedir /gpg --status-fd 1 --verify airootfs.sfs.sig 2>/dev/null | grep -qE '^\[GNUPG:\] GOODSIG'
+    gpg --homedir /gpg --status-fd 1 --verify "${sigfile}" 2>/dev/null | grep -qE '^\[GNUPG:\] GOODSIG'
     _status=$?
     cd -- "${OLDPWD}" || exit 1
     return ${_status}
@@ -160,6 +185,7 @@ run_hook() {
 # args: /path/to/newroot
 archiso_mount_handler() {
     local newroot="${1}"
+    local sigfile
 
     if ! mountpoint -q "/run/archiso/bootmnt"; then
         _mnt_dev "${archisodevice}" "/run/archiso/bootmnt" "-r" "defaults"
@@ -190,15 +216,20 @@ archiso_mount_handler() {
     # defined via initcpio's parse_cmdline()
     if [ "${verify}" = "y" ]; then
         if [ -f "/run/archiso/bootmnt/${archisobasedir}/${arch}/airootfs.sfs.sig" ]; then
+            sigfile="airootfs.sfs.sig"
+        elif [ -f "/run/archiso/bootmnt/${archisobasedir}/${arch}/airootfs.erofs.sig" ]; then
+            sigfile="airootfs.erofs.sig"
+        fi
+        if [ -n "${sigfile}" ]; then
             msg -n ":: Signature verification requested, please wait..."
-            if _verify_signature; then
+            if _verify_signature "${sigfile}"; 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"
+            echo "ERROR: verify=y option specified but GPG signature not found in ${archisobasedir}/${arch}/"
             launch_interactive_shell
         fi
     fi
@@ -221,7 +252,11 @@ archiso_mount_handler() {
     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/bootmnt/${archisobasedir}/${arch}/airootfs.sfs" ]; then
+        _mnt_sfs "/run/archiso/bootmnt/${archisobasedir}/${arch}/airootfs.sfs" "/run/archiso/airootfs"
+    elif [ -f "/run/archiso/bootmnt/${archisobasedir}/${arch}/airootfs.erofs" ]; then
+        _mnt_erofs "/run/archiso/bootmnt/${archisobasedir}/${arch}/airootfs.erofs" "/run/archiso/airootfs"
+    fi
     if [ -f "/run/archiso/airootfs/airootfs.img" ]; then
         _mnt_dmsnapshot "/run/archiso/airootfs/airootfs.img" "${newroot}" "/"
     else
diff --git a/archiso/initcpio/hooks/archiso_pxe_http b/archiso/initcpio/hooks/archiso_pxe_http
index efae923..43b8b4b 100644
--- a/archiso/initcpio/hooks/archiso_pxe_http
+++ b/archiso/initcpio/hooks/archiso_pxe_http
@@ -39,6 +39,7 @@ _curl_get() {
 
 archiso_pxe_http_mount_handler () {
     newroot="${1}"
+    local img_type="sfs"
 
     msg ":: Mounting /run/archiso/httpspace (tmpfs) filesystem, size='${archiso_http_spc}'"
     mkdir -p "/run/archiso/httpspace"
@@ -46,7 +47,12 @@ archiso_pxe_http_mount_handler () {
 
     # shellcheck disable=SC2154
     # defined via initcpio's parse_cmdline()
-    _curl_get "${archiso_http_srv}${archisobasedir}/${arch}/airootfs.sfs" "/${arch}"
+    if ! curl -L -f -o /dev/null -s -r 0-0 "${archiso_http_srv}${archisobasedir}/${arch}/airootfs.sfs"; then
+        if curl -L -f -o /dev/null -s -r 0-0 "${archiso_http_srv}${archisobasedir}/${arch}/airootfs.erofs"; then
+            img_type="erofs"
+        fi
+    fi
+    _curl_get "${archiso_http_srv}${archisobasedir}/${arch}/airootfs.${img_type}" "/${arch}"
 
     # shellcheck disable=SC2154
     # defined via initcpio's parse_cmdline()
@@ -56,7 +62,7 @@ archiso_pxe_http_mount_handler () {
     # shellcheck disable=SC2154
     # defined via initcpio's parse_cmdline()
     if [ "${verify}" = "y" ]; then
-        _curl_get "${archiso_http_srv}${archisobasedir}/${arch}/airootfs.sfs.sig" "/${arch}"
+        _curl_get "${archiso_http_srv}${archisobasedir}/${arch}/airootfs.${img_type}.sig" "/${arch}"
     fi
 
     mkdir -p "/run/archiso/bootmnt"
diff --git a/archiso/mkarchiso b/archiso/mkarchiso
index 021bcfa..0d7c698 100755
--- a/archiso/mkarchiso
+++ b/archiso/mkarchiso
@@ -200,13 +200,30 @@ _mkairootfs_squashfs() {
     install -d -m 0755 -- "${isofs_dir}/${install_dir}/${arch}"
     _msg_info "Creating SquashFS image, this may take some time..."
     _run_mksquashfs "${airootfs_dir}"
+}
+
+# Makes an EROFS file system from a source directory.
+_mkairootfs_erofs() {
+    local fsuuid
+    [[ -e "${airootfs_dir}" ]] || _msg_error "The path '${airootfs_dir}' does not exist" 1
+
+    install -d -m 0755 -- "${isofs_dir}/${install_dir}/${arch}"
+    local image_path="${isofs_dir}/${install_dir}/${arch}/airootfs.erofs"
+    # Generate reproducible file system UUID from SOURCE_DATE_EPOCH
+    fsuuid="$(uuidgen --sha1 --namespace 93a870ff-8565-4cf3-a67b-f47299271a96 --name "${SOURCE_DATE_EPOCH}")"
+    _msg_info "Creating EROFS image, this may take some time..."
+    mkfs.erofs -U "${fsuuid}" "${airootfs_image_tool_options[@]}" -- "${image_path}" "${airootfs_dir}"
     _msg_info "Done!"
 }
 
 _mkchecksum() {
     _msg_info "Creating checksum file for self-test..."
     cd -- "${isofs_dir}/${install_dir}/${arch}"
-    sha512sum airootfs.sfs > airootfs.sha512
+    if [[ -e "${isofs_dir}/${install_dir}/${arch}/airootfs.sfs" ]]; then
+        sha512sum airootfs.sfs > airootfs.sha512
+    elif [[ -e "${isofs_dir}/${install_dir}/${arch}/airootfs.erofs" ]]; then
+        sha512sum airootfs.erofs > airootfs.sha512
+    fi
     cd -- "${OLDPWD}"
     _msg_info "Done!"
 }
@@ -214,7 +231,11 @@ _mkchecksum() {
 _mksignature() {
     _msg_info "Signing SquashFS image..."
     cd -- "${isofs_dir}/${install_dir}/${arch}"
-    gpg --detach-sign --default-key "${gpg_key}" airootfs.sfs
+    if [[ -e "${isofs_dir}/${install_dir}/${arch}/airootfs.sfs" ]]; then
+        gpg --detach-sign --default-key "${gpg_key}" airootfs.sfs
+    elif [[ -e "${isofs_dir}/${install_dir}/${arch}/airootfs.erofs" ]]; then
+        gpg --detach-sign --default-key "${gpg_key}" airootfs.erofs
+    fi
     cd -- "${OLDPWD}"
     _msg_info "Done!"
 }
@@ -634,6 +655,13 @@ _validate_requirements_airootfs_image_type_ext4+squashfs() {
     _validate_requirements_airootfs_image_type_squashfs
 }
 
+_validate_requirements_airootfs_image_type_erofs() {
+    if ! command -v mkfs.erofs; then
+        (( validation_error=validation_error+1 ))
+        _msg_error "Validating '${airootfs_image_type}': mkfs.erofs is not available on this host. Install 'erofs-utils'!" 0
+    fi
+}
+
 # SYSLINUX El Torito
 _add_xorrisofs_options_bios.syslinux.eltorito() {
     xorrisofs_options+=(