If you want something more hands on you can try "FreeBSD Device Drivers: A Guide for the Intrepid" by Joseph Kong. It is much easier to read, and my guess is yo

If you want something more hands on you can try "FreeBSD Device Drivers: A Guide for the Intrepid" by Joseph Kong. It is much easier to read, and my guess is you ran into it while making those BSD patches. He also has a short book on building rootkits for BSD, which is a very fun read and demonstrates how things like system calls work. If you want a guide to reading actual kernel code, here is a great resource explaining where some of the foundational pieces are. With a tool like cscope, reading the FreeBSD kernel is actually pretty easy. http://www.watson.org/~robert/freebsd/reading/ http://www.watson.org/~robert/freebsd/reading/ Hope that helps!