Re: [PATCH] tracing/user_events: Run BPF program if attached

On Mon, May 8, 2023 at 9:38 AM Beau Belgrave [off-list ref] wrote:

Programs that utilize user_events today only get the event payloads via
perf or ftrace when writing event data. When BPF programs are attached
to tracepoints created by user_events the BPF programs do not get run
even though the attach succeeds. This causes confusion by the users of
the programs, as they expect the data to be available via BPF programs
they write. We have several projects that have hit this and requested
BPF program support when publishing data via user_events from their
user processes in production.

Swap out perf_trace_buf_submit() for perf_trace_run_bpf_submit() to
ensure BPF programs that are attached are run in addition to writing to
perf or ftrace buffers. This requires no changes to the BPF infrastructure
and only utilizes the GPL exported function that modules and other
components may use for the same purpose. This keeps user_events consistent
with how other kernel, modules, and probes expose tracepoint data to allow
attachment of a BPF program.

Sorry, I have to keep my Nack here.

I see no practical use case for bpf progs to be connected to user events.

There must be a different way to solve your user needs
and this is not bpf.