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.
