Hi Leo,
On 31/10/2021 14:42, Leo Yan wrote:
When runs in perf mode, the driver always enables the contextID tracing. This can lead to confusion if the program runs in non-root PID namespace and potentially leak kernel information.
When programs running in perf mode, this patch changes to only enable contextID tracing for root PID namespace.
The only concern with the patch here is we silently ignore the CTXTID flag and the perf assumes the CTXTID is traced, when traced from a non-root namespace. Does the decoder handle this case gracefully ? We are fine if that is the case.
Either way, we don't want to enforce the policy in the perf tool, if we can transparently handle the missing CTXTID and allow the trace session and decode complete. That said, your approach is the safe bet here.
Signed-off-by: Leo Yan leo.yan@linaro.org
drivers/hwtracing/coresight/coresight-etm4x-core.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c index e24252eaf8e4..6e614bfb38c6 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c @@ -615,7 +615,9 @@ static int etm4_parse_event_config(struct coresight_device *csdev, config->cfg |= BIT(11); }
- if (attr->config & BIT(ETM_OPT_CTXTID))
- /* Only trace contextID when runs in root PID namespace */
- if ((attr->config & BIT(ETM_OPT_CTXTID)) &&
(task_active_pid_ns(current) == &init_pid_ns))
As mentioned in the previous comment, please add a helper here, than open coding the check.
Kind regards Suzuki