This article by userdiscusses the methods used to extract information from the FreeBSD kernel, and offers a solution that provides a boost in performance for those looking to do kernel debugging.
We previously explored FreeBSD userspace coredumps. Backtrace’s debugging platform supports FreeBSD kernel coredumps too, and their traces share many features. They are constructed somewhat differently, and in the process of adding support for them, we found a way to improve performance for automated programs accessing them.
Generating kernel core files
A kernel core is typically only generated in exceptional circumstances. Unlike userspace processes, kernel routines cannot fault without sacrificing the machine’s availability. This means things like page faults and illegal instructions inside the kernel stop the machine, instead of just one process. At that point, in most cases, it is only usable enough to inspect its state in a debugger, or to generate a core file.