Messages in this thread Patch in this message | | | From | Jin Yao <> | Subject | [PATCH v1 2/2] perf Documentation: Introduce the sysctl perf_allow_sample_leakage | Date | Fri, 15 Jun 2018 18:03:23 +0800 |
| |
Introduce a new sysctl /sys/devices/cpu/perf_allow_sample_leakage, which turns on/off dropping leaked kernel samples.
Signed-off-by: Jin Yao <yao.jin@linux.intel.com> --- tools/perf/Documentation/perf-record.txt | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt index 04168da..97fb0f8 100644 --- a/tools/perf/Documentation/perf-record.txt +++ b/tools/perf/Documentation/perf-record.txt @@ -93,6 +93,20 @@ OPTIONS prevent the shell interpretation. You also need to use --group on "perf report" to view group events together. + Note that if workload does a lot of kernel entry/exit we may see + kernel samples even if :u is specified. That is due to skid existing. + This might be a security issue because it can leak kernel address even + though kernel sampling support is disabled. We have a sysctl to turn + on/off the dropping of leaked kernel samples. + + /sys/devices/cpu/perf_allow_sample_leakage + + 0 - drop the leaked kernel samples, default option. + 1 - don't drop the leaked kernel samples. + + For example, write 1 to perf_allow_sample_leakage + echo 1 > /sys/devices/cpu/perf_allow_sample_leakage + --filter=<filter>:: Event filter. This option should follow a event selector (-e) which selects either tracepoint event(s) or a hardware trace PMU -- 2.7.4
| |