Re: [PATCH bpf-next] bpf: Add bpf_read_raw_record() helper

[Namhyung Kim]

On Fri, Aug 26, 2022 at 11:45 AM Song Liu <songliubraving@xxxxxx> wrote:

> > And actually, we can just read ctx->data and get the raw record,
> > right..?
>
> Played with this for a little bit. ctx->data appears to be not
> reliable sometimes. I guess (not 100% sure) this is because we
> call bpf program before event->orig_overflow_handler. We can
> probably add a flag to specify we want to call orig_overflow_handler
> first.

I'm not sure.  The sample_data should be provided by the caller
of perf_event_overflow.  So I guess the bpf program should see
a valid ctx->data.

Also I want to control calling the orig_overflow_handler based
on the return value of the BPF program.  So calling the orig
handler before BPF won't work for me. :)

Thanks,
Namhyung