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As commented in the function ctxid_pid_store(), it can cause the PID values mismatching between context ID tracing and PID allocated in a non-root namespace. For this reason, when a process runs in non-root PID namespace, the driver doesn't allow PID tracing and returns failure when access contextID related sysfs nodes. VMID works for virtual contextID when the kernel runs in EL2 mode with VHE; on the other hand, the driver doesn't prevent users from accessing it when programs run in the non-root namespace. Thus this can lead to same issues with contextID described above. This patch imposes the checking on VMID related sysfs knobs and returns failure if current process runs in non-root PID namespace. Signed-off-by: Leo Yan <leo.yan@linaro.org> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Link: https://lore.kernel.org/r/20220204152403.71775-3-leo.yan@linaro.org
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.