You can always work with pintos (http://web.stanford.edu/class/cs140/projects/pintos/pintos.html http://web.stanford.edu/class/cs140/projects/pintos/pintos.h...

You can always work with pintos (http://web.stanford.edu/class/cs140/projects/pintos/pintos.html http://web.stanford.edu/class/cs140/projects/pintos/pintos.h...) or some other relatively simple 32-bit operating system if you want to get a feel for how to do this stuff from scratch. There's not a lot of point in it with Linux and all. Mostly it's a lot of tricky multi-threaded C programming.