BPF allows programs uploaded from user space to be run, safely, within the kernel. The io_uring subsystem, too, can be thought of as a way of loading programs in the kernel, though the programs in question are mostly a sequence of I/O-related system calls. It has sometimes seemed inevitable that io_uring would, like many other parts of the kernel, gain BPF capabilities as a way of providing more flexibility to user space. That has not yet happened, but there are currently two patches sets under consideration that take different approaches to the problem.