[tip:perf/urgent] tools lib traceevent: Fix kbuffer_read_at_offset()

[tip-bot for Namhyung Kim]

Commit-ID:  a130347973c408c0e0017a52c74cbc3226c1f0ef
Gitweb:     http://git.kernel.org/tip/a130347973c408c0e0017a52c74cbc3226c1f0ef
Author:     Namhyung Kim <namhyung@xxxxxxxxxx>
AuthorDate: Sat, 1 Oct 2016 19:17:00 +0900
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Wed, 5 Oct 2016 11:36:22 -0300

tools lib traceevent: Fix kbuffer_read_at_offset()

When it's called with an offset less than or equal to the first event,
it'll return a garbage value since the data is not initialized.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20161001101700.29146-1-namhyung@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/lib/traceevent/kbuffer-parse.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/lib/traceevent/kbuffer-parse.c b/tools/lib/traceevent/kbuffer-parse.c
index 3bcada3..65984f1 100644
--- a/tools/lib/traceevent/kbuffer-parse.c
+++ b/tools/lib/traceevent/kbuffer-parse.c
@@ -622,6 +622,7 @@ void *kbuffer_read_at_offset(struct kbuffer *kbuf, int offset,
 
 	/* Reset the buffer */
 	kbuffer_load_subbuffer(kbuf, kbuf->subbuffer);
+	data = kbuffer_read_event(kbuf, ts);
 
 	while (kbuf->curr < offset) {
 		data = kbuffer_next_event(kbuf, ts);