[PATCH 4.19 258/280] perf intel-pt: Fix divide by zero when TSC is not available

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Adrian Hunter <adrian.hunter@xxxxxxxxx>

commit 076333870c2f5bdd9b6d31e7ca1909cf0c84cbfa upstream.

When TSC is not available, "timeless" decoding is used but a divide by
zero occurs if perf_time_to_tsc() is called.

Ensure the divisor is not zero.

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v4.9+
Link: https://lkml.kernel.org/n/tip-1i4j0wqoc8vlbkcizqqxpsf4@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 tools/perf/util/intel-pt.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -2507,6 +2507,8 @@ int intel_pt_process_auxtrace_info(union
 	}
 
 	pt->timeless_decoding = intel_pt_timeless_decoding(pt);
+	if (pt->timeless_decoding && !pt->tc.time_mult)
+		pt->tc.time_mult = 1;
 	pt->have_tsc = intel_pt_have_tsc(pt);
 	pt->sampling_mode = false;
 	pt->est_tsc = !pt->timeless_decoding;