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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Peter Jones <pjones@redhat.com>
Date: Fri, 9 Dec 2016 15:40:29 -0500
Subject: [PATCH] Add BLS support to grub-mkconfig

GRUB now has BootLoaderSpec support, the user can choose to use this by
setting GRUB_ENABLE_BLSCFG to true in /etc/default/grub. On this setup,
the boot menu entries are not added to the grub.cfg, instead BLS config
files are parsed by blscfg command and the entries created dynamically.

A 10_linux_bls grub.d snippet to generate menu entries from BLS files
is also added that can be used on platforms where the bootloader doesn't
have BLS support and only can parse a normal grub configuration file.

Portions of the 10_linux_bls were taken from the ostree-grub-generator
script that's included in the OSTree project.

Fixes to support multi-devices and generate a BLS section even if no
kernels are found in the boot directory were proposed by Yclept Nemo
and Tom Gundersen respectively.

Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---
 Makefile.util.def           |   7 +
 util/grub-mkconfig.8        |   4 +
 util/grub-mkconfig.in       |   9 +-
 util/grub-mkconfig_lib.in   |  20 +-
 util/grub.d/10_linux.in     |  67 ++++++-
 util/grub.d/10_linux_bls.in | 478 ++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 580 insertions(+), 5 deletions(-)
 create mode 100644 util/grub.d/10_linux_bls.in

diff --git a/Makefile.util.def b/Makefile.util.def
index 2215cc759c0..a61613656d1 100644
--- a/Makefile.util.def
+++ b/Makefile.util.def
@@ -499,6 +499,13 @@ script = {
   condition = COND_HOST_LINUX;
 };
 
+script = {
+  name = '10_linux_bls';
+  common = util/grub.d/10_linux_bls.in;
+  installdir = grubconf;
+  condition = COND_HOST_LINUX;
+};
+
 script = {
   name = '10_xnu';
   common = util/grub.d/10_xnu.in;
diff --git a/util/grub-mkconfig.8 b/util/grub-mkconfig.8
index a2d1f577b9b..434fa4deda4 100644
--- a/util/grub-mkconfig.8
+++ b/util/grub-mkconfig.8
@@ -13,5 +13,9 @@
 \fB--output\fR=\fIFILE\fR
 Write generated output to \fIFILE\fR.
 
+.TP
+\fB--no-grubenv-update\fR
+Do not update variables in the grubenv file.
+
 .SH SEE ALSO
 .BR "info grub"
diff --git a/util/grub-mkconfig.in b/util/grub-mkconfig.in
index 4649e92eb0f..2601bdc0711 100644
--- a/util/grub-mkconfig.in
+++ b/util/grub-mkconfig.in
@@ -50,6 +50,8 @@ grub_get_kernel_settings="${sbindir}/@grub_get_kernel_settings@"
 export TEXTDOMAIN=@PACKAGE@
 export TEXTDOMAINDIR="@localedir@"
 
+export GRUB_GRUBENV_UPDATE="yes"
+
 . "${pkgdatadir}/grub-mkconfig_lib"
 
 # Usage: usage
@@ -59,6 +61,7 @@ usage () {
     gettext "Generate a grub config file"; echo
     echo
     print_option_help "-o, --output=$(gettext FILE)" "$(gettext "output generated config to FILE [default=stdout]")"
+    print_option_help "--no-grubenv-update" "$(gettext "do not update variables in the grubenv file")"
     print_option_help "-h, --help" "$(gettext "print this message and exit")"
     print_option_help "-v, --version" "$(gettext "print the version information and exit")"
     echo
@@ -94,6 +97,9 @@ do
     --output=*)
 	grub_cfg=`echo "$option" | sed 's/--output=//'`
 	;;
+    --no-grubenv-update)
+	GRUB_GRUBENV_UPDATE="no"
+	;;
     -*)
 	gettext_printf "Unrecognized option \`%s'\n" "$option" 1>&2
 	usage
@@ -259,7 +265,8 @@ export GRUB_DEFAULT \
   GRUB_OS_PROBER_SKIP_LIST \
   GRUB_DISABLE_SUBMENU \
   GRUB_DEFAULT_DTB \
-  SUSE_BTRFS_SNAPSHOT_BOOTING
+  SUSE_BTRFS_SNAPSHOT_BOOTING \
+  GRUB_ENABLE_BLSCFG
 
 if test "x${grub_cfg}" != "x"; then
   rm -f "${grub_cfg}.new"
diff --git a/util/grub-mkconfig_lib.in b/util/grub-mkconfig_lib.in
index b3aae534ddc..bc11df2bd84 100644
--- a/util/grub-mkconfig_lib.in
+++ b/util/grub-mkconfig_lib.in
@@ -30,6 +30,9 @@ fi
 if test "x$grub_file" = x; then
   grub_file="${bindir}/@grub_file@"
 fi
+if test "x$grub_editenv" = x; then
+  grub_editenv="${bindir}/@grub_editenv@"
+fi
 if test "x$grub_mkrelpath" = x; then
   grub_mkrelpath="${bindir}/@grub_mkrelpath@"
 fi
@@ -125,8 +128,19 @@ EOF
   fi
 }
 
+prepare_grub_to_access_device_with_variable ()
+{
+  device_variable="$1"
+  shift
+  prepare_grub_to_access_device "$@"
+  unset "device_variable"
+}
+
 prepare_grub_to_access_device ()
 {
+  if [ -z "$device_variable" ]; then
+    device_variable="root"
+  fi
   old_ifs="$IFS"
   IFS='
 '
@@ -161,14 +175,14 @@ prepare_grub_to_access_device ()
   # otherwise set root as per value in device.map.
   fs_hint="`"${grub_probe}" --device $@ --target=compatibility_hint`"
   if [ "x$fs_hint" != x ]; then
-    echo "set root='$fs_hint'"
+    echo "set ${device_variable}='$fs_hint'"
   fi
   if [ "x$GRUB_DISABLE_UUID" != "xtrue" ] && fs_uuid="`"${grub_probe}" --device $@ --target=fs_uuid 2> /dev/null`" ; then
     hints="`"${grub_probe}" --device $@ --target=hints_string 2> /dev/null`" || hints=
     echo "if [ x\$feature_platform_search_hint = xy ]; then"
-    echo "  search --no-floppy --fs-uuid --set=root ${hints} ${fs_uuid}"
+    echo "  search --no-floppy --fs-uuid --set=${device_variable} ${hints} ${fs_uuid}"
     echo "else"
-    echo "  search --no-floppy --fs-uuid --set=root ${fs_uuid}"
+    echo "  search --no-floppy --fs-uuid --set=${device_variable} ${fs_uuid}"
     echo "fi"
   fi
   IFS="$old_ifs"
diff --git a/util/grub.d/10_linux.in b/util/grub.d/10_linux.in
index 5cab299dc08..301594a0c9e 100644
--- a/util/grub.d/10_linux.in
+++ b/util/grub.d/10_linux.in
@@ -82,6 +82,67 @@ case x"$GRUB_FS" in
 	;;
 esac
 
+populate_header_warn()
+{
+cat <<EOF
+
+# This section was generated by a script. Do not modify the generated file - all changes
+# will be lost the next time file is regenerated. Instead edit the BootLoaderSpec files.
+#
+# The blscfg command parses the BootLoaderSpec files stored in /boot/loader/entries and
+# populates the boot menu. Please refer to the Boot Loader Specification documentation
+# for the files format: https://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/.
+
+EOF
+}
+
+if [ "x${GRUB_ENABLE_BLSCFG}" = "xtrue" ]; then
+  if [ x$dirname = x/ ]; then
+    if [ -z "${prepare_root_cache}" ]; then
+      prepare_grub_to_access_device ${GRUB_DEVICE}
+    fi
+  else
+    if [ -z "${prepare_boot_cache}" ]; then
+      prepare_grub_to_access_device ${GRUB_DEVICE_BOOT}
+    fi
+  fi
+
+  if [ -d /sys/firmware/efi ]; then
+      bootefi_device="`${grub_probe} --target=device /boot/efi/`"
+      prepare_grub_to_access_device_with_variable boot ${bootefi_device}
+  else
+      boot_device="`${grub_probe} --target=device /boot/`"
+      prepare_grub_to_access_device_with_variable boot ${boot_device}
+  fi
+
+  populate_header_warn
+
+  cat << EOF
+set default_kernelopts="root=${LINUX_ROOT_DEVICE} ro ${GRUB_CMDLINE_LINUX}"
+
+insmod blscfg
+blscfg
+EOF
+
+  if [ "x${GRUB_GRUBENV_UPDATE}" = "xyes" ]; then
+      blsdir="/boot/loader/entries"
+      [ -d "${blsdir}" ] && GRUB_BLS_FS="$(${grub_probe} --target=fs ${blsdir})"
+      if [ "x${GRUB_BLS_FS}" = "xbtrfs" ] || [ "x${GRUB_BLS_FS}" = "xzfs" ]; then
+          blsdir=$(make_system_path_relative_to_its_root "${blsdir}")
+          if [ "x${blsdir}" != "x/loader/entries" ] && [ "x${blsdir}" != "x/boot/loader/entries" ]; then
+              ${grub_editenv} - set blsdir="${blsdir}"
+          fi
+      fi
+
+      ${grub_editenv} - set kernelopts="root=${LINUX_ROOT_DEVICE} ro ${GRUB_CMDLINE_LINUX}"
+      if [ -n "${GRUB_EARLY_INITRD_LINUX_CUSTOM}" ]; then
+          ${grub_editenv} - set early_initrd="${GRUB_EARLY_INITRD_LINUX_CUSTOM}"
+      fi
+  fi
+
+  exit 0
+fi
+
 mktitle ()
 {
   local title_type
@@ -121,6 +182,7 @@ linux_entry ()
   if [ -z "$boot_device_id" ]; then
       boot_device_id="$(grub_get_device_id "${GRUB_DEVICE}")"
   fi
+
   if [ x$type != xsimple ] ; then
       title=$(mktitle "$type" "$version")
       if [ x"$title" = x"$GRUB_ACTUAL_DEFAULT" ] || [ x"Previous Linux versions>$title" = x"$GRUB_ACTUAL_DEFAULT" ]; then
@@ -224,6 +286,7 @@ is_top_level=true
 while [ "x$list" != "x" ] ; do
   linux=`version_find_latest $list`
   gettext_printf "Found linux image: %s\n" "$linux" >&2
+
   basename=`basename $linux`
   dirname=`dirname $linux`
   rel_dirname=`make_system_path_relative_to_its_root $dirname`
@@ -262,7 +325,9 @@ while [ "x$list" != "x" ] ; do
     for i in ${initrd}; do
       initrd_display="${initrd_display} ${dirname}/${i}"
     done
-    gettext_printf "Found initrd image: %s\n" "$(echo $initrd_display)" >&2
+    if [ "x${GRUB_ENABLE_BLSCFG}" != "xtrue" ]; then
+      gettext_printf "Found initrd image: %s\n" "$(echo $initrd_display)" >&2
+    fi
   fi
 
   fdt=
diff --git a/util/grub.d/10_linux_bls.in b/util/grub.d/10_linux_bls.in
new file mode 100644
index 00000000000..1b7536435f1
--- /dev/null
+++ b/util/grub.d/10_linux_bls.in
@@ -0,0 +1,478 @@
+#! /bin/sh
+set -e
+
+# grub-mkconfig helper script.
+# Copyright (C) 2006,2007,2008,2009,2010  Free Software Foundation, Inc.
+#
+# GRUB is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# GRUB is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+
+prefix="@prefix@"
+exec_prefix="@exec_prefix@"
+datarootdir="@datarootdir@"
+
+. "$pkgdatadir/grub-mkconfig_lib"
+
+export TEXTDOMAIN=@PACKAGE@
+export TEXTDOMAINDIR="@localedir@"
+
+CLASS="--class gnu-linux --class gnu --class os --unrestricted"
+
+if [ "x${GRUB_DISTRIBUTOR}" = "x" ] ; then
+  OS="$(eval $(grep PRETTY_NAME /etc/os-release) ; echo ${PRETTY_NAME})"
+  CLASS="--class $(eval $(grep '^ID_LIKE=\|^ID=' /etc/os-release) ; [ -n "${ID_LIKE}" ] && echo ${ID_LIKE} || echo ${ID}) ${CLASS}"
+else
+  OS="${GRUB_DISTRIBUTOR}"
+  CLASS="--class $(echo ${GRUB_DISTRIBUTOR} | tr 'A-Z' 'a-z' | cut -d' ' -f1|LC_ALL=C sed 's,[^[:alnum:]_],_,g') ${CLASS}"
+fi
+
+# loop-AES arranges things so that /dev/loop/X can be our root device, but
+# the initrds that Linux uses don't like that.
+case ${GRUB_DEVICE} in
+  /dev/loop/*|/dev/loop[0-9])
+    GRUB_DEVICE=`losetup ${GRUB_DEVICE} | sed -e "s/^[^(]*(\([^)]\+\)).*/\1/"`
+  ;;
+esac
+
+# Default to disabling partition uuid support to maintian compatibility with
+# older kernels.
+GRUB_DISABLE_LINUX_PARTUUID=${GRUB_DISABLE_LINUX_PARTUUID-true}
+
+# btrfs may reside on multiple devices. We cannot pass them as value of root= parameter
+# and mounting btrfs requires user space scanning, so force UUID in this case.
+if ( [ "x${GRUB_DEVICE_UUID}" = "x" ] && [ "x${GRUB_DEVICE_PARTUUID}" = "x" ] ) \
+    || ( [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
+	&& [ "x${GRUB_DISABLE_LINUX_PARTUUID}" = "xtrue" ] ) \
+    || ( ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
+	&& ! test -e "/dev/disk/by-partuuid/${GRUB_DEVICE_PARTUUID}" ) \
+    || ( test -e "${GRUB_DEVICE}" && uses_abstraction "${GRUB_DEVICE}" lvm ); then
+  LINUX_ROOT_DEVICE=${GRUB_DEVICE}
+elif [ "x${GRUB_DEVICE_UUID}" = "x" ] \
+    || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ]; then
+  LINUX_ROOT_DEVICE=PARTUUID=${GRUB_DEVICE_PARTUUID}
+else
+  LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
+fi
+
+case x"$GRUB_FS" in
+    xbtrfs)
+	if [ "x${SUSE_BTRFS_SNAPSHOT_BOOTING}" = "xtrue" ]; then
+	GRUB_CMDLINE_LINUX="${GRUB_CMDLINE_LINUX} \${extra_cmdline}"
+	else
+	rootsubvol="`make_system_path_relative_to_its_root /`"
+	rootsubvol="${rootsubvol#/}"
+	if [ "x${rootsubvol}" != x ]; then
+	    GRUB_CMDLINE_LINUX="rootflags=subvol=${rootsubvol} ${GRUB_CMDLINE_LINUX}"
+	fi
+	fi;;
+    xzfs)
+	rpool=`${grub_probe} --device ${GRUB_DEVICE} --target=fs_label 2>/dev/null || true`
+	bootfs="`make_system_path_relative_to_its_root / | sed -e "s,@$,,"`"
+	LINUX_ROOT_DEVICE="ZFS=${rpool}${bootfs}"
+	;;
+esac
+
+mktitle ()
+{
+  local title_type
+  local version
+  local OS_NAME
+  local OS_VERS
+
+  title_type=$1 && shift
+  version=$1 && shift
+
+  OS_NAME="$(eval $(grep ^NAME= /etc/os-release) ; echo ${NAME})"
+  OS_VERS="$(eval $(grep ^VERSION= /etc/os-release) ; echo ${VERSION})"
+
+  case $title_type in
+    recovery)
+      title=$(printf '%s (%s) %s (recovery mode)' \
+                     "${OS_NAME}" "${version}" "${OS_VERS}")
+      ;;
+    *)
+      title=$(printf '%s (%s) %s' \
+                     "${OS_NAME}" "${version}" "${OS_VERS}")
+      ;;
+  esac
+  echo -n ${title}
+}
+
+title_correction_code=
+
+populate_header_warn()
+{
+cat <<EOF
+
+# This section was generated by a script. Do not modify the generated file - all changes
+# will be lost the next time file is regenerated. Instead edit the BootLoaderSpec files.
+
+EOF
+}
+
+read_config()
+{
+    config_file=${1}
+    title=""
+    initrd=""
+    options=""
+    linux=""
+    grub_users=""
+    grub_arg=""
+    grub_class=""
+
+    while read -r line
+    do
+        record=$(echo ${line} | cut -f 1 -d ' ')
+        value=$(echo ${line} | cut -s -f2- -d ' ')
+        case "${record}" in
+            "title")
+                title=${value}
+                ;;
+            "initrd")
+                initrd=${value}
+                ;;
+            "linux")
+                linux=${value}
+                ;;
+            "options")
+                options=${value}
+                ;;
+            "grub_users")
+                grub_users=${value}
+                ;;
+            "grub_arg")
+                grub_arg=${value}
+                ;;
+            "grub_class")
+                grub_class=${value}
+                ;;
+        esac
+    done < ${config_file}
+}
+
+populate_menu()
+{
+    blsdir="/boot/loader/entries"
+    local -a files
+    local IFS=$'\n'
+    gettext_printf "Generating boot entries from BLS files...\n" >&2
+
+    files=($(for bls in ${blsdir}/*.conf ; do
+        if ! [[ -e "${bls}" ]] ; then
+            continue
+        fi
+        bls="${bls%.conf}"
+        bls="${bls##*/}"
+        echo "${bls}"
+    done | ${kernel_sort} | tac)) || :
+
+    for bls in "${files[@]}" ; do
+        read_config "${blsdir}/${bls}.conf"
+
+        menu="${menu}menuentry '${title}' --class ${grub_class} ${grub_arg} --id=${bls} {\n"
+        menu="${menu}\t linux ${linux} ${options}\n"
+        if [ -n "${initrd}" ] ; then
+            menu="${menu}\t initrd ${boot_prefix}${initrd}\n"
+        fi
+        menu="${menu}}\n\n"
+    done
+    # The printf command seems to be more reliable across shells for special character (\n, \t) evaluation
+    printf "$menu"
+}
+
+linux_entry ()
+{
+  os="$1"
+  version="$2"
+  type="$3"
+  isdebug="$4"
+  args="$5"
+
+  if [ -z "$boot_device_id" ]; then
+      boot_device_id="$(grub_get_device_id "${GRUB_DEVICE}")"
+  fi
+
+  if [ "x${GRUB_ENABLE_BLSCFG}" = "xtrue" ]; then
+    if [ x$dirname = x/ ]; then
+      if [ -z "${prepare_root_cache}" ]; then
+        prepare_grub_to_access_device ${GRUB_DEVICE}
+      fi
+    else
+      if [ -z "${prepare_boot_cache}" ]; then
+        prepare_grub_to_access_device ${GRUB_DEVICE_BOOT}
+      fi
+    fi
+
+    if [ -d /sys/firmware/efi ]; then
+        bootefi_device="`${grub_probe} --target=device /boot/efi/`"
+        prepare_grub_to_access_device_with_variable boot ${bootefi_device}
+    else
+        boot_device="`${grub_probe} --target=device /boot/`"
+        prepare_grub_to_access_device_with_variable boot ${boot_device}
+    fi
+
+    populate_header_warn
+    populate_menu
+
+    if [ "x${GRUB_GRUBENV_UPDATE}" = "xyes" ]; then
+        blsdir="/boot/loader/entries"
+        [ -d "${blsdir}" ] && GRUB_BLS_FS="$(${grub_probe} --target=fs ${blsdir})"
+        if [ "x${GRUB_BLS_FS}" = "xbtrfs" ] || [ "x${GRUB_BLS_FS}" = "xzfs" ]; then
+            blsdir=$(make_system_path_relative_to_its_root "${blsdir}")
+            if [ "x${blsdir}" != "x/loader/entries" ] && [ "x${blsdir}" != "x/boot/loader/entries" ]; then
+                ${grub_editenv} - set blsdir="${blsdir}"
+            fi
+        fi
+
+	${grub_editenv} - set kernelopts="root=${linux_root_device_thisversion} ro ${args}"
+	if [ -n "${GRUB_EARLY_INITRD_LINUX_CUSTOM}" ]; then
+	    ${grub_editenv} - set early_initrd="${GRUB_EARLY_INITRD_LINUX_CUSTOM}"
+	fi
+    fi
+
+    exit 0
+  fi
+
+  if [ x$type != xsimple ] ; then
+      title=$(mktitle "$type" "$version")
+      if [ x"$title" = x"$GRUB_ACTUAL_DEFAULT" ] || [ x"Previous Linux versions>$title" = x"$GRUB_ACTUAL_DEFAULT" ]; then
+	  replacement_title="$(echo "Advanced options for ${OS}" | sed 's,>,>>,g')>$(echo "$title" | sed 's,>,>>,g')"
+	  quoted="$(echo "$GRUB_ACTUAL_DEFAULT" | grub_quote)"
+	  title_correction_code="${title_correction_code}if [ \"x\$default\" = '$quoted' ]; then default='$(echo "$replacement_title" | grub_quote)'; fi;"
+      fi
+      if [ x$isdebug = xdebug ]; then
+	  title="$title${GRUB_LINUX_DEBUG_TITLE_POSTFIX}"
+      fi
+      echo "menuentry '$(echo "$title" | grub_quote)' ${CLASS} \$menuentry_id_option 'gnulinux-$version-$type-$boot_device_id' {" | sed "s/^/$submenu_indentation/"
+  else
+      echo "menuentry '$(echo "$os" | grub_quote)' ${CLASS} \$menuentry_id_option 'gnulinux-simple-$boot_device_id' {" | sed "s/^/$submenu_indentation/"
+  fi
+  if [ x$type != xrecovery ] ; then
+      save_default_entry | grub_add_tab
+  fi
+
+  # Use ELILO's generic "efifb" when it's known to be available.
+  # FIXME: We need an interface to select vesafb in case efifb can't be used.
+  if [ "x$GRUB_GFXPAYLOAD_LINUX" = x ]; then
+      echo "	load_video" | sed "s/^/$submenu_indentation/"
+      if grep -qx "CONFIG_FB_EFI=y" "${config}" 2> /dev/null \
+	  && grep -qx "CONFIG_VT_HW_CONSOLE_BINDING=y" "${config}" 2> /dev/null; then
+	  echo "	set gfxpayload=keep" | sed "s/^/$submenu_indentation/"
+      fi
+  else
+      if [ "x$GRUB_GFXPAYLOAD_LINUX" != xtext ]; then
+	  echo "	load_video" | sed "s/^/$submenu_indentation/"
+      fi
+      echo "	set gfxpayload=$GRUB_GFXPAYLOAD_LINUX" | sed "s/^/$submenu_indentation/"
+  fi
+
+  echo "	insmod gzio" | sed "s/^/$submenu_indentation/"
+
+  if [ x$dirname = x/ ]; then
+    if [ -z "${prepare_root_cache}" ]; then
+      prepare_root_cache="$(prepare_grub_to_access_device ${GRUB_DEVICE} | grub_add_tab)"
+    fi
+    printf '%s\n' "${prepare_root_cache}" | sed "s/^/$submenu_indentation/"
+  else
+    if [ -z "${prepare_boot_cache}" ]; then
+      prepare_boot_cache="$(prepare_grub_to_access_device ${GRUB_DEVICE_BOOT} | grub_add_tab)"
+    fi
+    printf '%s\n' "${prepare_boot_cache}" | sed "s/^/$submenu_indentation/"
+  fi
+  sed "s/^/$submenu_indentation/" << EOF
+	linux	${rel_dirname}/${basename} root=${linux_root_device_thisversion} ro ${args}
+EOF
+  if test -n "${initrd}" ; then
+    initrd_path=
+    for i in ${initrd}; do
+      initrd_path="${initrd_path} ${rel_dirname}/${i}"
+    done
+    sed "s/^/$submenu_indentation/" << EOF
+	initrd	$(echo $initrd_path)
+EOF
+  fi
+  if test -n "${fdt}" ; then
+    sed "s/^/$submenu_indentation/" << EOF
+	devicetree	${rel_dirname}/${fdt}
+EOF
+  fi
+  sed "s/^/$submenu_indentation/" << EOF
+}
+EOF
+}
+
+machine=`uname -m`
+case "x$machine" in
+    xi?86 | xx86_64)
+	list=
+	for i in /boot/vmlinuz-* /vmlinuz-* /boot/kernel-* ; do
+	    if grub_file_is_not_garbage "$i" ; then list="$list $i" ; fi
+	done ;;
+    *)
+	list=
+	for i in /boot/vmlinuz-* /boot/vmlinux-* /vmlinuz-* /vmlinux-* /boot/kernel-* ; do
+                  if grub_file_is_not_garbage "$i" ; then list="$list $i" ; fi
+	done ;;
+esac
+
+if [ "x${GRUB_ENABLE_BLSCFG}" = "xtrue" ]; then
+    for i in /boot/ostree/*/vmlinuz-* ; do
+        if grub_file_is_not_garbage "$i" ; then list="$list $i" ; fi
+    done
+fi
+
+case "$machine" in
+    i?86) GENKERNEL_ARCH="x86" ;;
+    mips|mips64) GENKERNEL_ARCH="mips" ;;
+    mipsel|mips64el) GENKERNEL_ARCH="mipsel" ;;
+    arm*) GENKERNEL_ARCH="arm" ;;
+    *) GENKERNEL_ARCH="$machine" ;;
+esac
+
+prepare_boot_cache=
+prepare_root_cache=
+boot_device_id=
+title_correction_code=
+
+# Extra indentation to add to menu entries in a submenu. We're not in a submenu
+# yet, so it's empty. In a submenu it will be equal to '\t' (one tab).
+submenu_indentation=""
+
+is_top_level=true
+while [ "x$list" != "x" ] ; do
+  linux=`version_find_latest $list`
+  if [ "x${GRUB_ENABLE_BLSCFG}" != "xtrue" ]; then
+    gettext_printf "Found linux image: %s\n" "$linux" >&2
+  fi
+
+  basename=`basename $linux`
+  dirname=`dirname $linux`
+  rel_dirname=`make_system_path_relative_to_its_root $dirname`
+  version=`echo $basename | sed -e "s,^[^0-9]*-,,g"`
+  alt_version=`echo $version | sed -e "s,\.old$,,g"`
+  linux_root_device_thisversion="${LINUX_ROOT_DEVICE}"
+
+  initrd_early=
+  for i in ${GRUB_EARLY_INITRD_LINUX_STOCK} \
+	   ${GRUB_EARLY_INITRD_LINUX_CUSTOM}; do
+    if test -e "${dirname}/${i}" ; then
+      initrd_early="${initrd_early} ${i}"
+    fi
+  done
+
+  initrd_real=
+  for i in "initrd.img-${version}" "initrd-${version}.img" "initrd-${version}.gz" \
+	   "initrd-${version}" "initramfs-${version}.img" \
+	   "initrd.img-${alt_version}" "initrd-${alt_version}.img" \
+	   "initrd-${alt_version}" "initramfs-${alt_version}.img" \
+	   "initramfs-genkernel-${version}" \
+	   "initramfs-genkernel-${alt_version}" \
+	   "initramfs-genkernel-${GENKERNEL_ARCH}-${version}" \
+	   "initramfs-genkernel-${GENKERNEL_ARCH}-${alt_version}"; do
+    if test -e "${dirname}/${i}" ; then
+      initrd_real="${i}"
+      break
+    fi
+  done
+
+  initrd=
+  if test -n "${initrd_early}" || test -n "${initrd_real}"; then
+    initrd="${initrd_early} ${initrd_real}"
+
+    initrd_display=
+    for i in ${initrd}; do
+      initrd_display="${initrd_display} ${dirname}/${i}"
+    done
+    if [ "x${GRUB_ENABLE_BLSCFG}" != "xtrue" ]; then
+      gettext_printf "Found initrd image: %s\n" "$(echo $initrd_display)" >&2
+    fi
+  fi
+
+  fdt=
+  for i in "dtb-${version}" "dtb-${alt_version}"; do
+    if test -f "${dirname}/${i}/${GRUB_DEFAULT_DTB}" ; then
+      fdt="${i}/${GRUB_DEFAULT_DTB}"
+      break
+    fi
+  done
+
+  config=
+  for i in "${dirname}/config-${version}" "${dirname}/config-${alt_version}" "/etc/kernels/kernel-config-${version}" ; do
+    if test -e "${i}" ; then
+      config="${i}"
+      break
+    fi
+  done
+
+  initramfs=
+  if test -n "${config}" ; then
+      initramfs=`grep CONFIG_INITRAMFS_SOURCE= "${config}" | cut -f2 -d= | tr -d \"`
+  fi
+
+  if test -z "${initramfs}" && test -z "${initrd_real}" ; then
+    # "UUID=" and "ZFS=" magic is parsed by initrd or initramfs.  Since there's
+    # no initrd or builtin initramfs, it can't work here.
+    if [ "x${GRUB_DEVICE_PARTUUID}" = "x" ] \
+	|| [ "x${GRUB_DISABLE_LINUX_PARTUUID}" = "xtrue" ]; then
+
+	linux_root_device_thisversion=${GRUB_DEVICE}
+    else
+	linux_root_device_thisversion=PARTUUID=${GRUB_DEVICE_PARTUUID}
+    fi
+  fi
+
+  if [ "x${GRUB_DISABLE_SUBMENU}" = "xyes" ] || [ "x${GRUB_DISABLE_SUBMENU}" = "xy" ]; then
+    GRUB_DISABLE_SUBMENU="true"
+  fi
+
+  if [ "x$is_top_level" = xtrue ] && [ "x${GRUB_DISABLE_SUBMENU}" != xtrue ]; then
+    linux_entry "${OS}" "${version}" simple standard \
+    "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"
+    if [ "x$GRUB_LINUX_MAKE_DEBUG" = "xtrue" ]; then
+      linux_entry "${OS}" "${version}" simple debug \
+        "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT} ${GRUB_CMDLINE_LINUX_DEBUG}"
+    fi
+
+    submenu_indentation="$grub_tab"
+
+    if [ -z "$boot_device_id" ]; then
+	boot_device_id="$(grub_get_device_id "${GRUB_DEVICE}")"
+    fi
+    # TRANSLATORS: %s is replaced with an OS name
+    echo "submenu '$(gettext_printf "Advanced options for %s" "${OS}" | grub_quote)' \$menuentry_id_option 'gnulinux-advanced-$boot_device_id' {"
+    is_top_level=false
+  fi
+
+  linux_entry "${OS}" "${version}" advanced standard \
+              "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"
+  if [ "x$GRUB_LINUX_MAKE_DEBUG" = "xtrue" ]; then
+    linux_entry "${OS}" "${version}" advanced debug \
+                "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT} ${GRUB_CMDLINE_LINUX_DEBUG}"
+  fi
+
+  if [ "x${GRUB_DISABLE_RECOVERY}" != "xtrue" ]; then
+    linux_entry "${OS}" "${version}" recovery standard \
+                "single ${GRUB_CMDLINE_LINUX}"
+  fi
+
+  list=`echo $list | tr ' ' '\n' | fgrep -vx "$linux" | tr '\n' ' '`
+done
+
+# If at least one kernel was found, then we need to
+# add a closing '}' for the submenu command.
+if [ x"$is_top_level" != xtrue ]; then
+  echo '}'
+fi
+
+echo "$title_correction_code"