Run in a kernel source tree to make a boot image from a mainline kernel (assume $HOME/pmos exists be default)

mkbootimg.sh

#!/bin/bash

OUT="$HOME/pmos/mainline-boot.img"
DTB="$PWD/.output/arch/arm64/boot/dts/qcom/sdm845-oneplus-enchilada.dtb"
IMAGE="$PWD/.output/arch/arm64/boot/Image.gz"

THIS="$(basename $0)"

die() {
    echo $1 1>&2
    exit
}

usage() {
    echo "$THIS [ -d DTB(=$DTB) ] [ -r RAMDISK] [ -o OUT(=$OUT) ] [ -k KERNEL_IMAGE ] " 1>&2
    exit 1
}

while getopts "r:o:d:" options; do
	case "${options}" in
		r)
			RAMDISK=${OPTARG}
			;;
		o)
			OUT=${OPTARG}
			;;
		d)
			DTB=${OPTARG}
			;;
		k)
			IMAGE=${OPTARG}
			;;
		:)
			die "-${OPTARG} requires an argument"
			;;
		*)
			usage
			;;
	esac
done

[[ -f "$IMAGE" ]] || die "Kernel image \"$IMAGE\" doesn't exist"
[[ -f "$DTB" ]] || die "Device Tree Blob \"$DTB\" doesn't exist"

echo -e "$THIS: Appending dtb \"$(basename $DTB)\" to image \"$IMAGE\""
cat $IMAGE $DTB > /tmp/kernel-dtb || die "Failed to append dtb"

CMD="mkbootimg \
	--base 0x0 \
	--kernel_offset 0x8000 \
	--ramdisk_offset 0x1000000 \
	--tags_offset 0x100 \
	--pagesize 4096 \
	--second_offset 0xf00000 \
--kernel /tmp/kernel-dtb -o $OUT"
if [ ! -z $RAMDISK ]; then
	CMD="$CMD --ramdisk $RAMDISK"
fi
$CMD || echo "Failed to make $OUT"
echo "$THIS: Boot image at $OUT"