On Tue, Jan 21, 2020 at 04:03:23PM -0800, Alexei Starovoitov wrote:
> On Tue, Jan 21, 2020 at 01:05:08PM +0100, Jiri Olsa wrote:
> > Adding support to use perf_event_output in
> > BPF_TRACE_FENTRY/BPF_TRACE_FEXIT programs.
> >
> > Using nesting regs array from raw tracepoint helpers.
> >
> > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > ---
> > kernel/trace/bpf_trace.c | 41 ++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 41 insertions(+)
> >
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index 19e793aa441a..6a18e2ae6e30 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -1172,6 +1172,43 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > }
> > }
> >
> > +BPF_CALL_5(bpf_perf_event_output_kfunc, void *, ctx, struct bpf_map *, map,
> > + u64, flags, void *, data, u64, size)
> > +{
> > + struct pt_regs *regs = get_bpf_raw_tp_regs();
> > + int ret;
> > +
> > + if (IS_ERR(regs))
> > + return PTR_ERR(regs);
> > +
> > + perf_fetch_caller_regs(regs);
> > + ret = ____bpf_perf_event_output(regs, map, flags, data, size);
> > + put_bpf_raw_tp_regs();
> > + return ret;
> > +}
>
> I'm not sure why copy paste bpf_perf_event_output_raw_tp() into new function.
>
> > @@ -1181,6 +1218,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > return &bpf_skb_output_proto;
> > #endif
> > default:
> > + if (prog->expected_attach_type == BPF_TRACE_FENTRY ||
> > + prog->expected_attach_type == BPF_TRACE_FEXIT)
> > + return kfunc_prog_func_proto(func_id, prog);
> > +
> > return raw_tp_prog_func_proto(func_id, prog);
>
> Are you saying bpf_perf_event_output_raw_tp() for some reason
> didn't work for fentry/fexit?
> But above is exact copy-paste and it somehow worked?
>
> Ditto for patches 3,4.
ugh right.. did not realize that after switching to the rawtp
regs nest arrays it's identical and we don't need that
jirka
