[$] A helper library for BPF arenas

BPF arenas are areas of memory (potentially shared with user space) where programs have free reign to build their own data structures, unburdened by the verifier's bounds checks. Many of those data structures are potentially usable in multiple programs. Emil Tsalapatis brought his work on libarena, a library containing generic utilities for use in BPF arenas, to the 2026 Linux Storage, Filesystem, Memory-Management, and BPF Summit. Although the library is already available as part of the kernel, it is still in its early stages and he has more work planned.