From: James
Subject: Checksum calculation
All-Replies: 36

A few weeks ago I stumbled across a post by someone on the london
netbsd-regional list.  The message was an advertisment for some T1500s which
mentioned that they'd managed to get NetBSD running on them.

I chased up the people referenced and managed to get hold of the checksum
calculation utility.

http://www.manque.net/~james/t1500 contains tsum.c and t1500.mbox

Compile tsum.c and pipe the kernel in on stdin, the checksum will be printed on stdout.  This should be appended to the kernel which is provided to the T1500 bythe dhcp server.

This does seem to produce the correct checksum based on the compaq provided
vmlinux (I tested this by trimming 8bytes from the end of the file,
re-calculating the checksum, appending it and comparing md5 checksums).

t1500.mbox contains the e-mails I exchaged with the varions NetBSD people, the
message <4281034C.4060900@netbsd.org> contains my commentary on the summary of
what I've achieved using stock kernels and the checksum generator (in sort, not all that much).

Next on my list of things to try are an intermediate bootloader (etherboot or
maybe grub if I can get it small enough) and also examine the changes made by
compaq to the GPL source which we've received off them.

Anyway, I thought I'd post this here just to let other people have shot at
getting things working if they wanted.  Good luck!

----
If you've built a kernel, there'll be the ELF kernel in /usr/src/linux/vmlinux.
...
The T1500 kernel is ELF with the checksum bolted on the end. The T1500
bootloader appears to reject anything which isn't ELF.