[Aboriginal] elf header help

[wangji]

dear oldpal FirmwareLinux !

I have always been intrigued by the ELF header ,without never been able
to clarify myself for understanding !

To be concise : 
using mipsel_rootfs from 
1 openwrt (a.k.a kamikaze 7/8.x mipsel)
2 firmwareLinux_mipsel_rootfs (old one 2009,but I guess won't change
with more recent version)

I can only use qemu-mipsel-static from_ubuntu_nattty_10.04/10 to
recognise FirmwareLinux_busybox

But for openwrt_kamikaze_mipsel I need my own qemu-mipsel-static ,
-I don't remember how I got it (either I had compiled it or I had from 
google on some Portuguese site -people working on Nokia's embedded
stuffs )
Could you give me a guide line how to examine this problem 

Here how I tested different cases :
I just copy qemu-mipsel-static into mipsel_rootfs/usr/bin/
then from my ubuntu's_inside_that_mipsel_rootfs :

chroot . /bin/busybox 

to run mips_busybox locally.

(my ubuntu had binfmt-support + qemu_installed from synaptic_ubuntu by
default)
thanks