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The device /dev/hwctr was introduced to access complete CPU Measurement facility counter sets via an ioctl system call. The access the to device is limited to privileged processes running as root or superuser. The capability CAP_SYS_ADMIN is required. The device permissions are read/write for the device owner root. There is no need for this restriction. Make the device access permission read/write for all and reduce the capabilities to CAP_PERFMON. Any user space program with the CAP_PERFMON capability assigned to it can now read and display the CPU Measurement facility counter sets. For more details on perf tool usage and security, see linux documentation in Documentation/admin-guide/perf-security.rst. Signed-off-by: Thomas Richter <tmricht@linux.ibm.com> Acked-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
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.