[$] A different approach to BPF loops

One of the key features of the extended BPF virtual machine is the verifier
built into the kernel that ensures that all BPF programs are safe to run.
BPF developers often see the verifier as a bit of a mixed blessing, though;
while it can catch a lot of problems before they happen, it can also be
hard to please. Comparisons with a well-meaning but rule-bound and picky
bureaucracy would not be entirely misplaced. The bpf_loop()
proposal from Joanne Koong is an attempt to make pleasing the BPF
bureaucrats a bit easier for one type of loop construct.