package that contains kernel source?

[D. R. Evans]

I'm probably going blind, but I can't see which package contains the
kernel source for my system.

uname -a:
Linux homebrew 2.6.15-28-amd64-generic #1 SMP PREEMPT Thu Feb 1
15:53:41 UTC 2007 x86_64 GNU/Linux

Where do I get the source for this kernel build?