linux-kernel - [tip:perf/core] perf intel-pt: Fix timestamp following overflow

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tip-91d29b288aed3406caf7c454bf2b898c96cfd177@git.kernel.org>
Date:   Fri, 9 Mar 2018 00:48:47 -0800
From:   tip-bot for Adrian Hunter <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     jolsa@...hat.com, adrian.hunter@...el.com, hpa@...or.com,
        tglx@...utronix.de, linux-kernel@...r.kernel.org, acme@...hat.com,
        mingo@...nel.org
Subject: [tip:perf/core] perf intel-pt: Fix timestamp following overflow

Commit-ID:  91d29b288aed3406caf7c454bf2b898c96cfd177
Gitweb:     https://git.kernel.org/tip/91d29b288aed3406caf7c454bf2b898c96cfd177
Author:     Adrian Hunter <adrian.hunter@...el.com>
AuthorDate: Wed, 7 Mar 2018 16:02:24 +0200
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Thu, 8 Mar 2018 10:05:56 -0300

perf intel-pt: Fix timestamp following overflow

timestamp_insn_cnt is used to estimate the timestamp based on the number of
instructions since the last known timestamp.

If the estimate is not accurate enough decoding might not be correctly
synchronized with side-band events causing more trace errors.

However there are always timestamps following an overflow, so the
estimate is not needed and can indeed result in more errors.

Suppress the estimate by setting timestamp_insn_cnt to zero.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: stable@...r.kernel.org
Link: http://lkml.kernel.org/r/1520431349-30689-5-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/intel-pt-decoder/intel-pt-decoder.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
index 5e4d0bbafc8b..f9157aed1289 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -1378,6 +1378,7 @@ static int intel_pt_overflow(struct intel_pt_decoder *decoder)
 	intel_pt_clear_tx_flags(decoder);
 	decoder->have_tma = false;
 	decoder->cbr = 0;
+	decoder->timestamp_insn_cnt = 0;
 	decoder->pkt_state = INTEL_PT_STATE_ERR_RESYNC;
 	decoder->overflow = true;
 	return -EOVERFLOW;