Grub for low-latency (Ubuntu Studio 20.04)

#! /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/>.
#
# Ubuntustudio customization that keeps the latest lowlatency kernel
# as the first menu item and default boot even if there is a newer
# generic or other kernel. Often the updated generic kernel is
# released a few days earlier than the lowlatency kernel

prefix="/usr"
exec_prefix="/usr"
datarootdir="/usr/share"
ubuntu_recovery="1"
quiet_boot="1"
quick_boot="1"
gfxpayload_dynamic="1"
vt_handoff="1"

. "$pkgdatadir/grub-mkconfig_lib"

export TEXTDOMAIN=grub
export TEXTDOMAINDIR="${datarootdir}/locale"

# only 09_lowlatency or 10_linux should run, since we got this far
# 10_linux should not run next
if [ -x /etc/grub.d/10_linux ]; then
  chmod -x /etc/grub.d/10_linux
fi

CLASS="--class gnu-linux --class gnu --class os"
SUPPORTED_INITS="sysvinit:/lib/sysvinit/init systemd:/lib/systemd/systemd upstart:/sbin/upstart"

if [ "x${GRUB_DISTRIBUTOR}" = "x" ] ; then
  OS=GNU/Linux
else
  case ${GRUB_DISTRIBUTOR} in
    Ubuntu|Kubuntu)
      OS="${GRUB_DISTRIBUTOR}"
      ;;
    *)
      OS="${GRUB_DISTRIBUTOR} GNU/Linux"
      ;;
  esac
  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/"`
    # We can't cope with devices loop-mounted from files here.
    case ${GRUB_DEVICE} in
      /dev/*) ;;
      *) exit 0 ;;
    esac
  ;;
esac

# 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_DISABLE_LINUX_UUID}" = "xtrue" ] \
    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
    || ( test -e "${GRUB_DEVICE}" && uses_abstraction "${GRUB_DEVICE}" lvm ); then
  LINUX_ROOT_DEVICE=${GRUB_DEVICE}
else
  LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
fi

case x"$GRUB_FS" in
    xbtrfs)
	rootsubvol="`make_system_path_relative_to_its_root /`"
	rootsubvol="${rootsubvol#/}"
	if [ "x${rootsubvol}" != x ]; then
	    GRUB_CMDLINE_LINUX="rootflags=subvol=${rootsubvol} ${GRUB_CMDLINE_LINUX}"
	fi;;
    xzfs)
	rpool=`${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

title_correction_code=

if [ -x /lib/recovery-mode/recovery-menu ]; then
    GRUB_CMDLINE_LINUX_RECOVERY=recovery
else
    GRUB_CMDLINE_LINUX_RECOVERY=single
fi
if [ "$ubuntu_recovery" = 1 ]; then
    GRUB_CMDLINE_LINUX_RECOVERY="$GRUB_CMDLINE_LINUX_RECOVERY nomodeset"
fi

if [ "$vt_handoff" = 1 ]; then
  for word in $GRUB_CMDLINE_LINUX_DEFAULT; do
    if [ "$word" = splash ]; then
      GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT \$vt_handoff"
    fi
  done
fi

if [ x"$GRUB_FORCE_PARTUUID" != x ]; then
   echo "set partuuid=${GRUB_FORCE_PARTUUID}"
fi

linux_entry ()
{
  os="$1"
  version="$2"
  type="$3"
  args="$4"

  if [ -z "$boot_device_id" ]; then
      boot_device_id="$(grub_get_device_id "${GRUB_DEVICE}")"
  fi
  if [ x$type != xsimple ] ; then
      case $type in
	  recovery)
	      title="$(gettext_printf "%s, with Linux %s (%s)" "${os}" "${version}" "$(gettext "${GRUB_RECOVERY_TITLE}")")" ;;
	  init-*)
	      title="$(gettext_printf "%s, with Linux %s (%s)" "${os}" "${version}" "${type#init-}")" ;;
	  *)
	      title="$(gettext_printf "%s, with Linux %s" "${os}" "${version}")" ;;
      esac
      if [ x"$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 "$replacement_title" | grub_quote)'; fi;"
	  grub_warn "$(gettext_printf "Please don't use old title \`%s' for GRUB_DEFAULT, use \`%s' (for versions before 2.00) or \`%s' (for 2.00 or later)" "$GRUB_ACTUAL_DEFAULT" "$replacement_title" "gnulinux-advanced-$boot_device_id>gnulinux-$version-$type-$boot_device_id")"
      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/^/$submenu_indentation/"
  fi
  if [ "$quick_boot" = 1 ]; then
      echo "	recordfail" | 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/"
  else
      if [ "x$GRUB_GFXPAYLOAD_LINUX" != xtext ]; then
	  echo "	load_video" | sed "s/^/$submenu_indentation/"
      fi
  fi
  if ([ "$ubuntu_recovery" = 0 ] || [ x$type != xrecovery ]) && \
     ([ "x$GRUB_GFXPAYLOAD_LINUX" != x ] || [ "$gfxpayload_dynamic" = 1 ]); then
      echo "	gfxmode \$linux_gfx_mode" | sed "s/^/$submenu_indentation/"
  fi

  echo "	insmod gzio" | sed "s/^/$submenu_indentation/"
  echo "	if [ x\$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi" | sed "s/^/$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/^/$submenu_indentation/"
  fi
  if [ x"$quiet_boot" = x0 ] || [ x"$type" != xsimple ]; then
    message="$(gettext_printf "Loading Linux %s ..." ${version})"
    sed "s/^/$submenu_indentation/" << EOF
	echo	'$(echo "$message" | grub_quote)'
EOF
  fi
  if test -d /sys/firmware/efi && test -e "${linux}.efi.signed"; then
    sed "s/^/$submenu_indentation/" << EOF
	linux	${rel_dirname}/${basename}.efi.signed root=${linux_root_device_thisversion} ro ${args}
EOF
  else
    # We have initrd and PARTUUID is set - we try to boot without initrd, and fallback to using it
    # if it fails.
    # "panic=-1" means "on panic reboot immediately". "panic=0" disables the reboot behavior.
    if [ x"$GRUB_FORCE_PARTUUID" != x ]; then
        linux_root_device_thisversion="PARTUUID=${GRUB_FORCE_PARTUUID}"
    fi
    message="$(gettext_printf "Loading initial ramdisk ...")"
    if test -n "${initrd}" && [ x"$GRUB_FORCE_PARTUUID" != x ]; then
        sed "s/^/$submenu_indentation/" << EOF
	if [ "\${initrdfail}" = 1 ]; then
	  linux	${rel_dirname}/${basename} root=${linux_root_device_thisversion} ro ${args}
EOF
        if [ x"$quiet_boot" = x0 ] || [ x"$type" != xsimple ]; then
          sed "s/^/$submenu_indentation/" << EOF
	  echo	'$(echo "$message" | grub_quote)'
EOF
        fi

        sed "s/^/$submenu_indentation/" << EOF
	  initrd	${rel_dirname}/${initrd}
	else
	  linux	${rel_dirname}/${basename} root=${linux_root_device_thisversion} ro ${args} panic=-1
	fi
	initrdfail
EOF
    else
    # We don't have initrd or we don't want to set PARTUUID. Don't try initrd-less boot with fallback.
        sed "s/^/$submenu_indentation/" << EOF
	linux	${rel_dirname}/${basename} root=${linux_root_device_thisversion} ro ${args}
EOF
        if test -n "${initrd}"; then
            # We do have initrd - let's use it at boot.
            # TRANSLATORS: ramdisk isn't identifier. Should be translated.
            if [ x"$quiet_boot" = x0 ] || [ x"$type" != xsimple ]; then
              sed "s/^/$submenu_indentation/" << EOF
	echo	'$(echo "$message" | grub_quote)'
EOF
            fi
            sed "s/^/$submenu_indentation/" << EOF
	initrd	${rel_dirname}/${initrd}
EOF
        fi
    fi
  fi
  sed "s/^/$submenu_indentation/" << EOF
}
EOF
}

machine=`uname -m`
case "x$machine" in
    xi?86 | xx86_64)
	list=
	for i in /boot/vmlinuz-*lowlatency /vmlinuz-*lowlatency /boot/kernel-*lowlatency ; do
	    if grub_file_is_not_garbage "$i" ; then list="$list $i" ; fi
	done
	list2=
	for i in /boot/vmlinuz-*generic /vmlinuz-*generic /boot/kernel-*generic ; do
	    if grub_file_is_not_garbage "$i" ; then list2="$list2 $i" ; fi
	done ;;
    *)
	list=
	for i in /boot/vmlinuz-*lowlatency /boot/vmlinux-*lowlatency /vmlinuz-*lowlatency /vmlinux-*lowlatency /boot/kernel-*lowlatency ; do
                  if grub_file_is_not_garbage "$i" ; then list="$list $i" ; fi
	done
	list2=
	for i in /boot/vmlinuz-*generic /boot/vmlinux-*generic /vmlinuz-*generic /vmlinux-*generic /boot/kernel-*generic ; do
                  if grub_file_is_not_garbage "$i" ; then list2="$list2 $i" ; fi
	done ;;
esac

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=

cat << 'EOF'
function gfxmode {
	set gfxpayload="${1}"
EOF
if [ "$vt_handoff" = 1 ]; then
  cat << 'EOF'
	if [ "${1}" = "keep" ]; then
		set vt_handoff=vt.handoff=1
	else
		set vt_handoff=
	fi
EOF
fi
cat << EOF
}
EOF

# 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$GRUB_GFXPAYLOAD_LINUX" != x ] || [ "$gfxpayload_dynamic" = 0 ]; then
  echo "set linux_gfx_mode=$GRUB_GFXPAYLOAD_LINUX"
else
  cat << EOF
if [ "\${recordfail}" != 1 ]; then
  if [ -e \${prefix}/gfxblacklist.txt ]; then
    if hwmatch \${prefix}/gfxblacklist.txt 3; then
      if [ \${match} = 0 ]; then
        set linux_gfx_mode=keep
      else
        set linux_gfx_mode=text
      fi
    else
      set linux_gfx_mode=text
    fi
  else
    set linux_gfx_mode=keep
  fi
else
  set linux_gfx_mode=text
fi
EOF
fi
cat << EOF
export linux_gfx_mode
EOF

# 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
is_generic_top=true
if  [ "x$list" = "x" ]; then
  is_top_level=false
  generic_is_default=true
fi
if  [ "x$list2" = "x" ]; then
  is_generic_top=false
fi
while [ "x$list $list2" != "x" ] ; do
  if [ "x$is_generic_top" = xtrue ] && [ "x$is_top_level" != xtrue ]; then
    linux=`version_find_latest $list2`
    case $linux in
      *.efi.signed)
        # We handle these in linux_entry.
        list2=`echo $list2 | tr ' ' '\n' | grep -vx $linux | tr '\n' ' '`
        continue
        ;;
    esac
  else
    linux=`version_find_latest $list`
    if [ "x$linux" = "x" ]; then
      break
    fi
    case $linux in
      *.efi.signed)
        # We handle these in linux_entry.
        list=`echo $list | tr ' ' '\n' | grep -vx $linux | tr '\n' ' '`
        continue
        ;;
    esac
  fi
  gettext_printf "Found linux image: %s\n" "$linux" >&2
  basename=`basename $linux`
  dirname=`dirname $linux`
  rel_dirname=`make_system_path_relative_to_its_root $dirname`
  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=
  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}/${i}" ; then
      initrd="$i"
      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 -n "${initrd}" ; then
    gettext_printf "Found initrd image: %s\n" "${dirname}/${initrd}" >&2
  elif test -z "${initramfs}" ; then
    # "UUID=" and "ZFS=" magic is parsed by initrd or initramfs.  Since there's
    # no initrd or builtin initramfs, it can't work here.
    linux_root_device_thisversion=${GRUB_DEVICE}
  fi

  if [ "x$is_top_level" = xtrue ] && [ "x${GRUB_DISABLE_SUBMENU}" != xy ]; then
    linux_entry "${OS} (lowlatency)" "${version}" simple \
    "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"

    if [ -z "$boot_device_id" ]; then
	boot_device_id="$(grub_get_device_id "${GRUB_DEVICE}")"
    fi
    if [ "x$is_generic_top" != xtrue ]; then
    submenu_indentation="$grub_tab"
    # TRANSLATORS: %s is replaced with an OS name
    echo "submenu '$(gettext_printf "Advanced options for %s" "${OS}" | grub_quote)' \$menuentry_id_option 'gnulinux-advanced-$boot_device_id' {"
    fi
    is_top_level=false
    continue
  fi

  if [ "x$is_generic_top" = xtrue ] && [ "x${GRUB_DISABLE_SUBMENU}" != xy ]; then
    linux_entry "${OS} (generic)" "${version}" simple \
    "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"

    submenu_indentation="$grub_tab"
    list="$list $list2"

    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_generic_top=false
    continue

  fi

  linux_entry "${OS}" "${version}" advanced \
              "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"
  for supported_init in ${SUPPORTED_INITS}; do
    init_path="${supported_init#*:}"
    if [ -x "${init_path}" ] && [ "$(readlink -f /sbin/init)" != "$(readlink -f "${init_path}")" ]; then
      linux_entry "${OS}" "${version}" "init-${supported_init%%:*}" \
		  "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT} init=${init_path}"
    fi
  done
  if [ "x${GRUB_DISABLE_RECOVERY}" != "xtrue" ]; then
    linux_entry "${OS}" "${version}" recovery \
                "${GRUB_CMDLINE_LINUX_RECOVERY} ${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"