[PATCH v1 3/4] coresight: etm4x: Don't trace contextID for non-root namespace in perf mode

[Leo Yan]

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.

Signed-off-by: Leo Yan <leo.yan at 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))
 		/* bit[6], Context ID tracing bit */
 		config->cfg |= BIT(ETM4_CFG_BIT_CTXTID);
 
@@ -629,7 +631,11 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
 			ret = -EINVAL;
 			goto out;
 		}
-		config->cfg |= BIT(ETM4_CFG_BIT_VMID) | BIT(ETM4_CFG_BIT_VMID_OPT);
+
+		/* Only trace virtual contextID when runs in root PID namespace */
+		if (task_active_pid_ns(current) == &init_pid_ns)
+			config->cfg |= BIT(ETM4_CFG_BIT_VMID) |
+				       BIT(ETM4_CFG_BIT_VMID_OPT);
 	}
 
 	/* return stack - enable if selected and supported */
-- 
2.25.1