How the BPF Verifier Works
In a previous post we followed BPF code from C source all the way to a fully-resolved bytecode stream handed to the kernel. But the kernel does not just run that bytecode. First it has to be convinced the program is safe. That job belongs to the verifier, and it is the reason you can load your own code into the kernel’s hottest paths — every network packet, every system call — without the risk of crashing the machine. ...