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

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Date:   Fri, 22 Mar 2019 12:16:51 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 4.19 258/280] perf intel-pt: Fix divide by zero when TSC is not available

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

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

From: Adrian Hunter <adrian.hunter@...el.com>

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@...el.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: stable@...r.kernel.org # v4.9+
Link: https://lkml.kernel.org/n/tip-1i4j0wqoc8vlbkcizqqxpsf4@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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;