[PATCH 4.9 111/118] perf intel-pt: Fix divide by zero when TSC is not available

From: Greg Kroah-Hartman
Date: Fri Mar 22 2019 - 08:59:36 EST


4.9-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
@@ -2259,6 +2259,8 @@ 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;