Re: [PATCH bpf-next v1 3/7] bpf: Consolidate RCU and preempt locks in bpf_func_state

[Eduard Zingerman <eddyz87@gmail.com>]

On Wed, 2024-11-20 at 16:53 -0800, Kumar Kartikeya Dwivedi wrote:
> To ensure consistency in resource handling, move RCU and preemption
> state counters to bpf_func_state, and convert all users to access them
> through cur_func(env).
> 
> For the sake of consistency, also compare active_locks in ressafe as a
> quick way to eliminate iteration and entry matching if the number of
> locks are not the same.
> 
> OTOH, the comparison of active_preempt_locks and active_rcu_lock is
> needed for correctness, as state exploration cannot be avoided if these
> counters do not match, and not comparing them will lead to problems
> since they lack an actual entry in the acquired_res array.
> 
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

This change is a bit confusing to me.
The following is done currently:
- in setup_func_entry() called from check_func_call():
  copy_resource_state(callee, caller);
- in prepare_func_exit():
  copy_resource_state(caller, callee);

So it seems that it is logical to track resources in the
bpf_verifier_state and avoid copying.
There is probably something I don't understand.

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