> There are inherent security and stability risks with allowing user-space code to run inside the kernel. So, a number of checks are performed on every eBPF program before it is loaded. The first test ensures that the eBPF program terminates and does not contain any loops that could cause the kernel to lock up. This is checked by doing a depth-first search of the program's control flow graph (CFG). Unreachable instructions are strictly prohibited; any program that contains unreachable instructions will fail to load.