build boot & recovery without android tree (android 4.2.2 )
cd Rockchip-mkbootimg
cc -O2 -Wall -Wextra -o mkbootimg mkbootimg.c -lcrypto
cc -O2 -Wall -Wextra -o unpackbootimg unpackbootimg.c
unpackbootimg -i recovery.img mkbootimg --kernel recovery.img-zImage --ramdisk recovery.img-ramdisk.gz -o recovery_new.img
openssl sha1 recovery.img recovery_new.img
#ramdisk image can be modified like as,
mkdir ramdisk
gzip -cd recovery.img-ramdisk.gz | (cd ramdisk && cpio -i)
# modify files under ramdisk/
(cd ramdisk && find * | sort | cpio -o -H newc) | gzip > ramdisk_new.gz
thanks to fun
http://www.armtvtech.com/armtvtechforum/viewtopic.php?t=212&p=2551#p2554