freebsd-src/tools/debugscripts

This directory contains gdb macros for kernel debugging.  When you
build a debug kernel, the target "gdbinit" in the kernel Makefile will
create the correct .gdbinit files in the kernel build directory.  To
perform kernel debugging, you would do:

  # cd /usr/obj/usr/src/sys/GENERIC  (or name of kernel config)
  # make gdbinit
  # gdb kernel.debug
  This GDB was configured as "i386-undermydesk-freebsd"...
  Ready to go.  Enter 'tr' to connect to remote target
  and 'getsyms' after connection to load kld symbols.
  (kgdb) 


This directory also contains a kgdb script that, given a crash dump number,
automatically extracts the path to the kernel source, runs gdb to extract
information about kernel modules loaded, and then reruns gdb loading the
necessary symbols for the modules.  You need to make sure you build the
modules w/ debugging symbols separately to get things to work.