Poking and Probing the System

As you gain experience in kernel debugging, you gain little tricks to help you poke and probe the kernel for answers. Because kernel debugging can prove rather challenging, every little tip and trick helps. Let's look at a couple.

Using UID as a Conditional

If the code you are developing is process-related, sometimes you can develop alternative implementations without breaking the existing code. This is helpful if you are rewriting an important system call and would like a fully functional system with which to debug it. For example, assume you are rewriting the fork() algorithm to take advantage of an exciting new feature. Unless you get everything right on the first try, it would not be easy to debug the system: A nonfunctioning fork() system call is certain to result in a nonfunctioning system. As always, there is hope.