Build and update ChromeOS kernel

update_kernel.rb

#!/usr/bin/ruby

require 'fileutils'

REMOTE_ADDR = ARGV[0] || 'ryu'
SRC_DIR = File.expand_path(File.dirname(__FILE__))
WORK_DIR = SRC_DIR + '/work'

KERNEL_FLAGS = 'ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-'


# Build kernel
Dir.chdir(SRC_DIR + '/linux')
unless File.exists?('.config')
	system('./chromeos/scripts/prepareconfig chromiumos-arm64')
	system("yes '' | #{KERNEL_FLAGS} make oldconfig")
end

FileUtils.mkdir_p(WORK_DIR + '/root/boot')

system("#{KERNEL_FLAGS} make -j6")
system("#{KERNEL_FLAGS} INSTALL_PATH=#{WORK_DIR}/root/boot INSTALL_MOD_PATH=#{WORK_DIR}/root make --silent -j6 modules_install firmware_install")

unless File.exists?(WORK_DIR + '/bootloader.bin')
	# arm does not need/have a bootloader in kernel partition
	puts "Creating fake bootloader image"
	system("dd if=/dev/zero of=#{WORK_DIR}/bootloader.bin bs=512 count=1")
end

# Build kernel image (vmlinux + dtb)
`mkimage -D '-I dts -O dtb -p 1024' -f #{SRC_DIR}/configs/kernel.its #{WORK_DIR}/kernel.img`
# TODO: generate *.its dynamically


# 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
system("vbutil_kernel --pack #{WORK_DIR}/kernel.bin \
		--keyblock #{SRC_DIR}/configs/kernel.keyblock \
		--signprivate #{SRC_DIR}/configs/kernel_data_key.vbprivk \
		--version 1 \
		--config #{SRC_DIR}/configs/config.txt \
		--bootloader #{WORK_DIR}/bootloader.bin \
		--vmlinuz #{WORK_DIR}/kernel.img \
		--arch arm")

FileUtils.cp('System.map', WORK_DIR + '/root/boot')

# Deploy kernel to the board

def remote_sh(cmd)
	`ssh #{REMOTE_ADDR} "#{cmd}"`
end

def remote_copy(from, to)
	`rsync -a #{from} #{REMOTE_ADDR}:#{to}`
end

def remote_sync_root(to)
	for dir in %w(boot lib/modules lib/firmware)
		system("rsync -cr --safe-links --delete #{WORK_DIR}/root/#{dir}/ #{REMOTE_ADDR}:#{to}/#{dir}")
	end
end

# 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.to_s
new_root_part = device + 'p' + root_part_idx.to_s


# copy and flash kernel
remote_copy("#{WORK_DIR}/kernel.bin", '/tmp/kernel.bin')
remote_sh("dd of=#{new_kernel_part} if=/tmp/kernel.bin bs=4K")

# check if ROOT-B already mounted
current_root = remote_sh('rootdev').strip
# sync modules
if current_root == new_root_part
	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("mount #{new_root_part}")
end


# mark KERN-B partition boot once
remote_sh("cgpt add -i #{kern_part_idx} -S 0 -T 2 -P 15 #{device}")

old_kernel = remote_sh('uname -r -v')
remote_sh('sync')
#remote_sh('reboot')
puts " = Old kernel: #{old_kernel}"