[$] More flexible memory access for BPF programs

All memory accesses in a BPF program arestatically checked for safety using the verifier, which analyzes the program in itsentirety before allowing it to run. While this allows BPF programs tosafely run in kernel space, it restricts how that program is able to usepointers. Until recently, one such constraint was that the size of a memoryregion referenced by a pointer in a BPF program must be statically knownwhen a BPF program is loaded. A recentpatch set by Joanne Koong enhances BPF to support loading programs withpointers to dynamically sized memory regions.