From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932368AbeARV1o (ORCPT ); Thu, 18 Jan 2018 16:27:44 -0500 Received: from mga04.intel.com ([192.55.52.120]:47419 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752689AbeARV1d (ORCPT ); Thu, 18 Jan 2018 16:27:33 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,378,1511856000"; d="scan'208";a="11477204" From: kan.liang@intel.com To: acme@kernel.org, peterz@infradead.org, mingo@redhat.com, linux-kernel@vger.kernel.org Cc: wangnan0@huawei.com, jolsa@kernel.org, namhyung@kernel.org, ak@linux.intel.com, yao.jin@linux.intel.com, Kan Liang Subject: [PATCH V5 02/17] perf mmap: fix: recalculate size for overwrite mode. Date: Thu, 18 Jan 2018 13:26:17 -0800 Message-Id: <1516310792-208685-3-git-send-email-kan.liang@intel.com> X-Mailer: git-send-email 2.5.5 In-Reply-To: <1516310792-208685-1-git-send-email-kan.liang@intel.com> References: <1516310792-208685-1-git-send-email-kan.liang@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kan Liang In perf_mmap__push(), the 'size' need to be recalculated, otherwise the invalid data might be pushed to the record in overwrite mode. The issue is introduced by commit 7fb4b407a124 ("perf mmap: Don't discard prev in backward mode"). When the ringbuffer is full in overwrite mode, backward_rb_find_range will be called to recalculate the 'start' and 'end'. The 'size' needs to be recalculated accordingly. Unconditionally recalculate the 'size', not just for full ringbuffer in overwrite mode. Because, - There is no harmful to recalculate the 'size' for other cases. - The code of calculating 'start' and 'end' will be factored out later. The new function does not need to return 'size'. Signed-off-by: Kan Liang --- tools/perf/util/mmap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c index 05076e6..97cf4fa 100644 --- a/tools/perf/util/mmap.c +++ b/tools/perf/util/mmap.c @@ -302,6 +302,8 @@ int perf_mmap__push(struct perf_mmap *md, bool overwrite, return -1; } + size = end - start; + if ((start & md->mask) + size != (end & md->mask)) { buf = &data[start & md->mask]; size = md->mask + 1 - (start & md->mask); -- 2.5.5