This is the code part 2 and 3 of how to make a debugger:
- http://eli.thegreenplace.net/2011/01/27/how-debuggers-work-part-2-breakpoints
- http://eli.thegreenplace.net/2011/02/07/how-debuggers-work-part-3-debugging-information
The main additions I've added is support for 64 bit and a nice Makefile that should get you up and running faster.
Check out the READMEs in the subdirectories for further information.