[$] A look at what's possible with BPF arenas

BPF arenas are areas of memory where the verifier can safely relax its checking of
pointers, allowing programmers to write arbitrary data structures in BPF. Emil
Tsalapatis reported on how his team has used arenas in writing

sched_ext schedulers at the 2025 Linux Storage, Filesystem,
Memory-Management, and BPF Summit. His biggest complaint was about the fact that
kernel pointers can't be stored in BPF arenas — something that the BPF
developers hope to address, although there are some implementation problems that
must be sorted out first.