Building ChromeOS kernel without chroot

config.txt

earlyprintk=ttyS0,115200n8
console=tty1
console=ttyS0,115200n8
loglevel=7
init=/sbin/init
cros_secure
oops=panic
panic=-1
root=PARTUUID=%U/PARTNROFF=1
rootwait
rw
dm_verity.error_behavior=3
dm_verity.max_bios=-1
dm_verity.dev_wait=0
dm="1 vroot none ro 1,0 2506752 verity payload=ROOT_DEV
hashtree=HASH_DEV hashstart=2506752 alg=sha1
root_hexdigest=ab4ff111dcebd3e623dc4c0f86e96926f809553c
salt=2ce301bbe1e7067e2e00cdf707e7ad4028d2e64695829e33499f3667513dff01"
noinitrd cros_debug
vt.global_cursor_default=0
kern_guid=%U

kernel.its

/dts-v1/;

/ {
	description = "Chrome OS kernel image with one or more FDT blobs";
	#address-cells = <1>;

	images {
		kernel@1 {
			data = /incbin/("linux/arch/arm64/boot/Image");
			type = "kernel_noload";
			arch = "arm64";
			os = "linux";
			compression = "none";
			load = <0>;
			entry = <0>;
		};
		fdt@1 {
			description = "tegra132-ryu-p1.dtb";
			data = /incbin/("linux/arch/arm64/boot/dts/tegra132-ryu-p1.dtb");
			type = "flat_dt";
			arch = "arm64";
			compression = "none";
			hash@1 {
				algo = "sha1";
			};
		};
	};
	configurations {
		default = "conf@1";
		conf@1 {
			kernel = "kernel@1";
			fdt = "fdt@1";
		};
	};
};

update_kernel.sh

#!/bin/sh

set -e

ARCH_FLAGS='ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-'
REMOTE_ADDR=${1:-ryu}
ROOT=$(dirname $(readlink -f "$0"))

cd $ROOT

if [ ! -f work/lib/firmware/nvidia/tegra124/xusb.bin ]; then
	pushd work
	USB_FW_VER=2014.10.10.00.00
	wget http://commondatastorage.googleapis.com/chromeos-localmirror/distfiles/xhci-firmware-$USB_FW_VER.tbz2 -O xusb.tbz2
	tar -jxf xusb.tbz2
	popd
fi

mkdir -p work/root/boot

pushd linux
if [ chromeos/config/arm64/chromiumos-arm64.flavour.config -nt .config ]; then
	chromeos/scripts/prepareconfig chromiumos-arm64

	echo "CONFIG_EXTRA_FIRMWARE=\"nvidia/tegra124/xusb.bin\"" >> .config
	echo "CONFIG_EXTRA_FIRMWARE_DIR=\"$ROOT/work/lib/firmware\"" >> .config

	yes '' | make $ARCH_FLAGS oldconfig
fi

make $ARCH_FLAGS -j$(nproc)
make $ARCH_FLAGS INSTALL_MOD_PATH=../work/root --silent -j$(nproc) modules_install firmware_install
popd

if [ ! -e work/bootloader.bin ]; then
	# arm does not need a bootloader in kernel partition
	# creating fake bootloader image
	dd if=/dev/zero of=work/bootloader.bin bs=512 count=1 > /dev/null
fi

# Build kernel image (vmlinux + dtb)
# code comes from <chromeos>/chromeos/src/third_party/chromiumos-overlay/eclass/cros-kernel2.eclass
mkimage -D '-I dts -O dtb -p 1024 -i .' -f configs/kernel.its work/kernel.img > /dev/null
# TODO: generate *.its dynamically
# Is it possible to use dtb file from kernel compilation?


# kernel sign keys
# https://chromium.googlesource.com/chromiumos/platform/vboot_reference/+/master/tests/devkeys/kernel.keyblock
# https://chromium.googlesource.com/chromiumos/platform/vboot_reference/+/master/tests/devkeys/kernel_data_key.vbprivk

# sign the kernel. output is kernel.img -> kernel.bin
futility vbutil_kernel --pack work/kernel.bin \
	--keyblock configs/kernel.keyblock \
	--signprivate configs/kernel_data_key.vbprivk \
	--version 1 \
	--config configs/config.txt \
	--bootloader work/bootloader.bin \
	--vmlinuz work/kernel.img \
	--arch aarch64

cp -u linux/System.map work/root/boot/


# KERN-B partition 4
# ROOT-B partition 5

device=/dev/mmcblk0
kern_part_idx=4
root_part_idx=5
new_kernel_part=${device}p${kern_part_idx}
new_root_part=${device}p${root_part_idx}

function remote_sh() {
	REMOTE_OUT=$(ssh $REMOTE_ADDR "$@")
	return ${PIPESTATUS[0]}
}

# args: from, to
function remote_copy {
	REMOTE_OUT=$(scp $1 $REMOTE_ADDR:$2)
	return ${PIPESTATUS[0]}
}

# args remote root
function remote_sync_root {
	srcs=(boot lib/modules lib/firmware)
	for src in "${srcs[@]}"; do
		rsync -carq --safe-links --delete work/root/$src/ $REMOTE_ADDR:$1/$src/
	done
}

# copy and flash kernel
remote_copy work/kernel.bin /tmp/kernel.bin
remote_sh dd of=$new_kernel_part if=/tmp/kernel.bin bs=4K

# check if ROOT-B already mounted
remote_sh rootdev
current_root=$REMOTE_OUT
if [ "$current_root" == "$new_root_part" ]; then
	remote_sh mount -o remount,rw /
	remote_sync_root '/'
else
	remote_new_root='/tmp/new_root'
	remote_sh mkdir -p $remote_new_root
	remote_sh mount $new_root_part $remote_new_root
	remote_sync_root $remote_new_root
	remote_sh umount $new_root_part
fi

remote_sh cgpt add -i $kern_part_idx -S 0 -T 5 -P 15 $device

remote_sh uname -r -v
echo ' = Old kernel: ' $REMOTE_OUT

remote_sh sync
remote_sh reboot