1 python生成一个sector数据
def get_oem_bootmode():
    # Header size
    SECTOR_SIZE_IN_BYTES = 512

    header = [0 for i in \
        range(SECTOR_SIZE_IN_BYTES)]

    # magic
    # The ord() built-in function in
    # Python converts a character
    # into an ordinal integer number.
    header[0:7] = [ord('p'), ord('i'), ord('d'),
        ord('9'), ord('0'), ord('9'), ord('1'), ord('0')]

    output = StringIO.StringIO()
    for i in header:
        output.write(struct.pack("B", i))
    content = output.getvalue()
    output.close()

    # only need 512 bytes
    return content[:512]

2 制作ext4分区镜像
文件名：make_ko_img.sh

#!/bin/sh

MY_PATH=${PWD}
TARGET_DIR=${MY_PATH}/out/target/product/${TARGET_PRODUCT}
KO_DIR=${TARGET_DIR}/ko/lib/modules
TOOL_DIR=${MY_PATH}/out/host/linux-x86/bin

rm ${TARGET_DIR}/ko* -rf
mkdir --parents ${KO_DIR}

cp ${TARGET_DIR}/vendor/lib/modules/my_driver.ko ${KO_DIR}

# fastboot只接受Android sparse image（稀疏镜像格式）
# Android 8
#${TOOL_DIR}/make_ext4fs -l 8M -s -a ko ${TARGET_DIR}/ko.img ${TARGET_DIR}/ko/
# Android 10
make_ext4fs -l 8M -s -a ko ${TARGET_DIR}/ko.img ${TARGET_DIR}/ko/
#${TOOL_DIR}/simg2img ${TARGET_DIR}/ko.img ${TARGET_DIR}/ko.ext4

-l 8M是分区大小，make_ext4fs最小分区大小是8M，小于该值会导致编译失败
-a ko是指这个img用于Android，挂载点是/ko

makefile中调用：
MK_KO_IMG_SCRIPT := $(LOCAL_PATH)/path/to/make_ko_img.sh

$(MK_KO_IMG_SCRIPT)

3 Abbreviations
FRP：Android Factory Reset Protection