The bpf_map_defs are now wrapped with UnsafeCell, which also happens to
provide a cozy way to get a *mut pointer. An UnsafeCell isn't strictly
required as the struct fields are practically opaque to us, but using an
UnsafeCell follows the general best practices against miscompilation and
also prevents some obvious errors.
HashMap::get_mut was removed because the idea is completely unsound.
Previous users should wrap their data with UnsafeCell instead or use
atomics.
Closes: https://github.com/aya-rs/aya/issues/233
Map lookup and deletion can yield stale keys and values by virtue of
sharing a data structure with userspace programs and other BPF programs
which can modify it. However, all accesses remain perfectly safe and will
not cause memory corruption or data races.
Tatsuyuki Ishi
Thia Wyrod
Dave Tucker
Alessandro Decina