On Tue, Mar 30, 2021 at 4:16 PM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Tue, Mar 30, 2021 at 3:54 PM Pedro Tammela <pctammela@xxxxxxxxx> wrote:
> >
> > BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
> > {
> > + if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
> > + return -EINVAL;
> > +
> > bpf_ringbuf_commit(sample, flags, false /* discard */);
> > +
> > return 0;
>
> I think ringbuf design was meant for bpf_ringbuf_submit to never fail.
> If we do flag validation it probably should be done at the verifier time.
Oops, replied on another version already. But yes, BPF verifier relies
on it succeeding. I don't think we can do flags validation at BPF
verification time, though, because it is defined as non-const integer
and we do have valid cases where we dynamically determine whether to
FORCE_WAKEUP or NO_WAKEUP, based on application-driven criteria (e.g.,
amount of enqueued data).
