Assorted tools of varying usefulness exist to debug the kernel.  By far
the best debugging tool is the human brain.  As Linus has said:

	...
	I'm afraid that I've seen too many people fix bugs
	by looking at debugger output, and that almost
	inevitably leads to fixing the symptoms rather than
	the underlying problems. 
	...
	"Use the Source, Luke, use the Source.  Be one with
	the code.".  Think of Luke Skywalker discarding the
	automatic firing system when closing on the deathstar,
	and firing the proton torpedo (or whatever) manually.
	_Then_ do you have the right mindset for fixing kernel
	bugs.
	...

Having said that, sometimes reading the source is not enough.  The
following tools exist in the IKD patch:

  Debug kernel stack overflows
  Detect software lockups
  Kernel tracer (show logic flow through procedures)
  Memleak detector

      Written by Ingo Molnar <mingo@pc7537.hil.siemens.at>.  Currently
      maintained by Mike Galbraith <mikeg@weiden.de>.

  Print-EIP on video ram

      Improved by Andrea Arcangeli.

  Kernel stack meter
  Kernel real profiling
  Semaphore deadlock detector

      Developed by Andrea Arcangeli.

  NMI oopser

      Written by Ingo Molnar.
      Integration into IKD and fixes for newer kernels
      by Andrea Arcangeli.

  kdb
      Written by Scott Lurndal (SGI)
      Integration into IKD by Andrea Arcangeli.

The original merge of debugging tools into a single patch set (IKD)
is been done by Keith Owens <kaos@ocs.com.au>.
PGP 917/C817FEC9.
Fingerprint 2B 25 0A 31 02 AE CA F7  73 0C 28 69 4A 7B 65 27

Currently the IKD patch is maintained by Andrea Arcangeli <andrea@suse.de>
and is dowloadable at:

	ftp://ftp.*.kernel.org/pub/linux/kernel/people/andrea/ikd/