If a profiling program runs in a non-root PID namespace, if CoreSight driver enables PID tracing (with contextID), it can lead to mismatching issue between the context ID traced in hardware (from the root namespace) and the PIDs gathered by profiling tool (e.g. perf) in its non-root namespace.
CoreSight driver has tried to address this issue for the contextID related interfaces under sysfs, but it misses to prevent user to set VMID (virtual contextID) for kernel runs in EL2 with VHE; furthermore, it misses to handle the case when the profiling tool runs in the non-root PID namespace.
For this reason, this patch series is to correct contextID tracing for non-root namespace. After applied this patchset, patch 02 doesn't permit users to access virtual contextID via sysfs nodes in the non-root PID namespace, patch 03 and 04 stop to trace PID packet for non-root PID namespace.
This patch is dependent on the patchset "pid: Introduce helper task_is_in_root_ns()" [1].
[1] https://lore.kernel.org/lkml/20211208083320.472503-1-leo.yan@linaro.org/
Leo Yan (4): coresight: etm4x: Add lock for reading virtual context ID comparator coresight: etm4x: Don't use virtual contextID for non-root PID namespace coresight: etm4x: Don't trace PID for non-root PID namespace coresight: etm3x: Don't trace PID for non-root PID namespace
.../coresight/coresight-etm3x-core.c | 4 +++ .../coresight/coresight-etm4x-core.c | 10 +++++-- .../coresight/coresight-etm4x-sysfs.c | 30 +++++++++++++++++++ 3 files changed, 42 insertions(+), 2 deletions(-)