Re: [PATCH v2 0/4] coresight: etm: Correct PID tracing for non-root namespace

On 13/12/2021 12:13, Leo Yan wrote:

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/ (local)


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

For the series,

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

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