unpack zImage

You can also use it for boot.img

Compressed format:

gzip

stock_kernel$ path_to/arm-linux-androideabi-objdump -EL -b binary -D -m armv5t ./zImage | grep 8b1f
    4a28: 00088b1f andeq r8, r8, pc, lsl fp

4a28 =  18984(10)

stock_kernel$ dd if=./zImage of=piggy.gz bs=1 skip=18984

stock_kernel$ gunzip piggy.gz 

Источник:

http://morgue.openinkpot.org/wiki/Documentation/ZImageFormat

xz

Spec
header   FD377A585A00
footer     595A

Find header and footer offsets in hex editor (example: 16172 and 3800782)
footer

count=3800782 - 16172 + 2

dd if=./kernel of=piggy.xz bs=1 skip=16172 count=3784612

unxz piggy.xz