| From | kan.liang@intel ... | Subject | [PATCH V5 02/17] perf mmap: fix: recalculate size for overwrite mode. | Date | Thu, 18 Jan 2018 13:26:17 -0800 |
| |
From: Kan Liang <kan.liang@intel.com>
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 <kan.liang@intel.com> --- 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
|