SGI's kernprof is a Linux kernel profiling tool that can generate call-graph information for the running Linux kernel. It doesn't profile kernel modules, though.
The latest patch on their website is version 0.13 for Linux 2.4.20. Applying it to 2.4.32 results in some rejects. I've resolved the rejects and am posting the patch for anyone to use it.
While at it, I also updated the userspace tools (v0.16) so that they compile cleanly.
kernprof userspace tools clean compile patch