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# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
# Helper script to generate GRUB bootloader configuration files for
# x86 platforms.
SCRIPT_ROOT=$(readlink -f $(dirname "$0")/..)
. "${SCRIPT_ROOT}/" || exit 1
# We're invoked only by build_image, which runs in the chroot
# Flags.
DEFINE_string arch "x86" \
"The boot architecture: arm or x86. (Default: x86)"
DEFINE_string to "/tmp/boot" \
"Path to populate with bootloader templates (Default: /tmp/boot)"
DEFINE_string usb_disk /dev/sdb3 \
"Path syslinux should use to do a usb boot. Default: /dev/sdb3"
DEFINE_string boot_args "" \
"Additional boot arguments to pass to the commandline (Default: '')"
DEFINE_boolean enable_bootcache ${FLAGS_FALSE} \
"Default all bootloaders to NOT use boot cache."
DEFINE_boolean enable_rootfs_verification ${FLAGS_FALSE} \
"Controls if verity is used for root filesystem checking (Default: false)"
DEFINE_integer verity_error_behavior 3 \
"Verified boot error behavior [0: I/O errors, 1: reboot, 2: nothing] \
(Default: 3)"
DEFINE_integer verity_max_ios -1 \
"Optional number of outstanding I/O operations. (Default: 1024)"
# Parse flags
FLAGS "$@" || exit 1
eval set -- "${FLAGS_ARGV}"
# Only let dm-verity block if rootfs verification is configured.
# Also, set which device mapper correspondes to verity
if [[ ${FLAGS_enable_rootfs_verification} -eq ${FLAGS_TRUE} ]]; then
if [[ ${FLAGS_enable_bootcache} -eq ${FLAGS_TRUE} ]]; then
# Common kernel command-line args
common_args="quiet console=tty2 init=/sbin/init boot=local rootwait ro noresume"
common_args="${common_args} noswap loglevel=1 ${FLAGS_boot_args}"
# Common verified boot command-line args
verity_common="${verity_common} dm_verity.max_bios=${FLAGS_verity_max_ios}"
# Ensure that dm-verity waits for its device.
# TODO(wad) should add a timeout that display a useful message
verity_common="${verity_common} dm_verity.dev_wait=${dev_wait}"
# Populate the x86 rootfs to support legacy and EFI bios config templates.
# The templates are used by the installer to populate partition 12 with
# the correct bootloader configuration.
if [[ "${FLAGS_arch}" = "x86" || "${FLAGS_arch}" = "amd64" ]]; then
# TODO: For some reason the /dev/disk/by-uuid is not being generated by udev
# in the initramfs. When we figure that out, switch to root=UUID=${UUID}.
sudo mkdir -p ${FLAGS_to}
# /boot/syslinux must be installed in partition 12 as /syslinux/.
sudo mkdir -p "${SYSLINUX_DIR}"
cat <<EOF | sudo dd of="${SYSLINUX_DIR}/syslinux.cfg" 2>/dev/null
# the actual target
include /syslinux/default.cfg
# chromeos-usb.A
include /syslinux/usb.A.cfg
# chromeos-hd.A / chromeos-vhd.A
include /syslinux/root.A.cfg
# chromeos-hd.B / chromeos-vhd.B
include /syslinux/root.B.cfg
info "Emitted ${SYSLINUX_DIR}/syslinux.cfg"
if [[ ${FLAGS_enable_rootfs_verification} -eq ${FLAGS_TRUE} ]]; then
# To change the active target, only this file needs to change.
cat <<EOF | sudo dd of="${SYSLINUX_DIR}/default.cfg" 2>/dev/null
DEFAULT chromeos-vusb.A
# To change the active target, only this file needs to change.
cat <<EOF | sudo dd of="${SYSLINUX_DIR}/default.cfg" 2>/dev/null
DEFAULT chromeos-usb.A
info "Emitted ${SYSLINUX_DIR}/default.cfg"
cat <<EOF | sudo dd of="${SYSLINUX_DIR}/usb.A.cfg" 2>/dev/null
label chromeos-usb.A
menu label chromeos-usb.A
kernel vmlinuz.A
append ${common_args} root=${FLAGS_usb_disk} i915.modeset=1 cros_legacy
label chromeos-vusb.A
menu label chromeos-vusb.A
kernel vmlinuz.A
append ${common_args} ${verity_common} root=${ROOTDEV} \
i915.modeset=1 cros_legacy dm="DMTABLEA"
info "Emitted ${SYSLINUX_DIR}/usb.A.cfg"
# Different files are used so that the updater can only touch the file it
# needs to for a given change. This will minimize any potential accidental
# updates issues, hopefully.
cat <<EOF | sudo dd of="${SYSLINUX_DIR}/root.A.cfg" 2>/dev/null
label chromeos-hd.A
menu label chromeos-hd.A
kernel vmlinuz.A
append ${common_args} root=HDROOTA i915.modeset=1 cros_legacy
label chromeos-vhd.A
menu label chromeos-vhd.A
kernel vmlinuz.A
append ${common_args} ${verity_common} root=${ROOTDEV} \
i915.modeset=1 cros_legacy dm="DMTABLEA"
info "Emitted ${SYSLINUX_DIR}/root.A.cfg"
cat <<EOF | sudo dd of="${SYSLINUX_DIR}/root.B.cfg" 2>/dev/null
label chromeos-hd.B
menu label chromeos-hd.B
kernel vmlinuz.B
append ${common_args} root=HDROOTB i915.modeset=1 cros_legacy
label chromeos-vhd.B
menu label chromeos-vhd.B
kernel vmlinuz.B
append ${common_args} ${verity_common} root=${ROOTDEV} \
i915.modeset=1 cros_legacy dm="DMTABLEB"
info "Emitted ${SYSLINUX_DIR}/root.B.cfg"
cat <<EOF | sudo dd of="${SYSLINUX_DIR}/README" 2>/dev/null
Partition 12 contains the active bootloader configuration when
booting from a non-Chrome OS BIOS. EFI BIOSes use /efi/*
and legacy BIOSes use this syslinux configuration.
info "Emitted ${SYSLINUX_DIR}/README"
# To cover all of our bases, now populate templated boot support for efi.
sudo mkdir -p "${FLAGS_to}"/efi/boot
if [[ -f /bin/grub2-mkimage ]];then
# Use the newer grub2 1.99+
-p /efi/boot
part_gpt fat ext2 hfs hfsplus normal boot chain configfile linux
sudo grub2-mkimage -O x86_64-efi \
-o "${FLAGS_to}/efi/boot/bootx64.efi" "${grub_args[@]}"
sudo i386-grub2-mkimage -O i386-efi \
-o "${FLAGS_to}/efi/boot/bootia32.efi" "${grub_args[@]}"
# Remove this else case after a few weeks (sometime in Dec 2011)
-p /efi/boot
part_gpt fat ext2 normal boot sh chain configfile linux
sudo grub-mkimage -o "${FLAGS_to}/efi/boot/bootx64.efi" "${grub_args[@]}"
sudo i386-grub-mkimage -o "${FLAGS_to}/efi/boot/bootia32.efi" \
# Templated variables:
# DMTABLEA, DMTABLEB -> '0 xxxx verity ... '
# This should be replaced during postinst when updating the ESP.
cat <<EOF | sudo dd of="${FLAGS_to}/efi/boot/grub.cfg" 2>/dev/null
set default=0
set timeout=2
# NOTE: These magic grub variables are a Chrome OS hack. They are not portable.
menuentry "local image A" {
linux \$grubpartA/boot/vmlinuz ${common_args} i915.modeset=1 cros_efi root=/dev/\$linuxpartA
menuentry "local image B" {
linux \$grubpartB/boot/vmlinuz ${common_args} i915.modeset=1 cros_efi root=/dev/\$linuxpartB
menuentry "verified image A" {
linux \$grubpartA/boot/vmlinuz ${common_args} ${verity_common} \
i915.modeset=1 cros_efi root=${ROOTDEV} dm=\\"DMTABLEA\\"
menuentry "verified image B" {
linux \$grubpartB/boot/vmlinuz ${common_args} ${verity_common} \
i915.modeset=1 cros_efi root=${ROOTDEV} dm=\\"DMTABLEB\\"
# FIXME: usb doesn't support verified boot for now
menuentry "Alternate USB Boot" {
linux (hd0,3)/boot/vmlinuz ${common_args} root=/dev/sdb3 i915.modeset=1 cros_efi
if [[ ${FLAGS_enable_rootfs_verification} -eq ${FLAGS_TRUE} ]]; then
sudo sed -i -e 's/^set default=.*/set default=2/' \
info "Emitted ${FLAGS_to}/efi/boot/grub.cfg"
exit 0
info "The target platform does not use bootloader templates."