coresight: etm4x: Use Trace Filtering controls dynamically

The Trace Filtering support (FEAT_TRF) ensures that the ETM
can be prohibited from generating any trace for a given EL.
This is much stricter knob, than the TRCVICTLR exception level
masks, which doesn't prevent the ETM from generating Context
packets for an "excluded" EL. At the moment, we do a onetime
enable trace at user and kernel and leave it untouched for the
kernel life time. This implies that the ETM could potentially
generate trace packets containing the kernel addresses, and
thus leaking the kernel virtual address in the trace.

This patch makes the switch dynamic, by honoring the filters
set by the user and enforcing them in the TRFCR controls.
We also rename the cpu_enable_tracing() appropriately to
cpu_detect_trace_filtering() and the drvdata member
trfc => trfcr to indicate the "value" of the TRFCR_EL1.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Al Grant <al.grant@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20210914102641.1852544-3-suzuki.poulose@arm.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
index 82cba16b73a6..3c4d69b096ca 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.h
+++ b/drivers/hwtracing/coresight/coresight-etm4x.h
@@ -919,7 +919,10 @@ struct etmv4_save_state {
  * @nooverflow:	Indicate if overflow prevention is supported.
  * @atbtrig:	If the implementation can support ATB triggers
  * @lpoverride:	If the implementation can support low-power state over.
- * @trfc:	If the implementation supports Arm v8.4 trace filter controls.
+ * @trfcr:	If the CPU supports FEAT_TRF, value of the TRFCR_ELx that
+ *		allows tracing at all ELs. We don't want to compute this
+ *		at runtime, due to the additional setting of TRFCR_CX when
+ *		in EL2. Otherwise, 0.
  * @config:	structure holding configuration parameters.
  * @save_trfcr:	Saved TRFCR_EL1 register during a CPU PM event.
  * @save_state:	State to be preserved across power loss
@@ -972,7 +975,7 @@ struct etmv4_drvdata {
 	bool				nooverflow;
 	bool				atbtrig;
 	bool				lpoverride;
-	bool				trfc;
+	u64				trfcr;
 	struct etmv4_config		config;
 	u64				save_trfcr;
 	struct etmv4_save_state		*save_state;