From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnaldo Carvalho de Melo Subject: [PATCH 03/21] perf mmap: Recalculate size for overwrite mode Date: Tue, 6 Feb 2018 13:53:32 -0300 Message-ID: <20180206165350.2570-4-acme@kernel.org> References: <20180206165350.2570-1-acme@kernel.org> Return-path: In-Reply-To: <20180206165350.2570-1-acme@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Kan Liang , Andi Kleen , Jin Yao , Namhyung Kim , Peter Zijlstra , Wang Nan , Arnaldo Carvalho de Melo List-Id: linux-perf-users.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 ring buffer 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 ring buffer 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 Acked-by: Jiri Olsa Cc: Andi Kleen Cc: Jin Yao Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Wang Nan Fixes: 7fb4b407a124 ("perf mmap: Don't discard prev in backward mode") Link: http://lkml.kernel.org/r/1516310792-208685-3-git-send-email-kan.liang@intel.com Signed-off-by: Arnaldo Carvalho de Melo --- 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 05076e683938..97cf4fab564b 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); -- 2.14.3