[$] Dumping kernel data structures with BPF

For as long as operating systems have had kernels, there has been a need toextract information from data structures stored within those kernels. Overthe years, a wide range of approaches have been taken to make thatinformation available. In current times, it has become natural to reachfor BPF as the tool of choice for a variety of problems, and gettinginformation from kernel data structures is no exception. There are twopatches in circulation that take rather different approaches to using BPFto dump information from kernel data structures to user space.