Has anybody messed about with kernel debugging?

I am just curious about it, if anybody has tried it. What did you try it for, how did you find it, have you had much experience with regular software debugging first?

Which operating system were you using, which tools did you try?

Is there anything I should know about it?

Just any information basically from your own experiences which you can share.

yes I did it, once.
Had to figure out how to control some of the control panel applets without pulling them onto the screen.
The company had a strict (IMO overly paranoid but there you have it) policy and wouldn't allow the control panel to their users (in fact it wasn't even accessible readonly).
So we started a kernel debugger to intercept the function calls generated when accessing the function we wanted to control, which were the options to reverse the left and right mouse buttons and set the mouse speed.

This was under OS/2 Warp, using the tools provided by IBM for that platform. Didn't work alone, but together with a very experienced guy who had some 20 years of experience programming OS/2 including kernel debugging (which allowed him to find and patch a bug in Lotus a few months later and send the patch to IBM, must have made some people over there blush to get a binary patch for a memory leak sent to them by a customer).

Kernel debugging isn't all that similar to regular debugging. You will need a good understanding of C and Assembler both.