perf: Make perf_event_output() propagate the output() return

For the original mode of operation it isn't needed, since we report back
errors via PERF_RECORD_LOST records in the ring buffer, but for use in
bpf_perf_event_output() it is convenient to return the errors, basically
-ENOSPC.

Currently bpf_perf_event_output() returns an error indication, the last
thing it does, which is to push it to the ring buffer is that can fail
and if so, this failure won't be reported back to its users, fix it.

Reported-by: Jamal Hadi Salim <jhs@mojatatu.com>
Tested-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/r/20190118150938.GN5823@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index f8ec36197718..4eb88065a9b5 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -978,9 +978,9 @@ extern void perf_event_output_forward(struct perf_event *event,
 extern void perf_event_output_backward(struct perf_event *event,
 				       struct perf_sample_data *data,
 				       struct pt_regs *regs);
-extern void perf_event_output(struct perf_event *event,
-			      struct perf_sample_data *data,
-			      struct pt_regs *regs);
+extern int perf_event_output(struct perf_event *event,
+			     struct perf_sample_data *data,
+			     struct pt_regs *regs);
 
 static inline bool
 is_default_overflow_handler(struct perf_event *event)