The BPF in-kernel virtual machine has
brought a new set of capabilities to a number of functional areas in the
kernel, including, significantly, tracing.
Since BPF programs run in the kernel, much effort goes into ensuring that
they will not cause problems for the running system;
to that end, the BPF verifier checks every possible aspect of each BPF program’s
behavior to ensure that it is safe to run in the kernel — with one notable
exception. With a patch set titled “revolutionize
bpf tracing“, Alexei Starovoitov aims to close that loophole and
eliminate a set of potential problems in a widely used class of BPF
programs.

Source: LWN.net – [$] Type checking for BPF tracing