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The CLKSCREW attack [0] exposed security vulnerabilities in energy management implementations where untrusted software had direct access to clock and voltage hardware controls. In this attack, the malicious software was able to place the platform into unsafe overclocked or undervolted configurations. Such configurations then enabled the injection of predictable faults to reveal secrets. Many Arm-based systems used to or still use voltage regulator and clock frameworks in the kernel. These frameworks allow callers to independently manipulate frequency and voltage settings. Such implementations can render systems susceptible to this form of attack. Attacks such as CLKSCREW are now being mitigated by not having direct and independent control of clock and voltage in the kernel and moving that control to a trusted entity, such as the SCP firmware or secure world firmware/software which are to perform sanity checking on the requested performance levels, thereby preventing any attempted malicious programming. With the advent of such an abstraction, there is a need to replace the generic clock and regulator bindings used by such devices with a generic performance domains bindings. [0] https://www.usenix.org/conference/usenixsecurity17/technical-sessions/presentation/tang Cc: Rob Herring <robh+dt@kernel.org> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Viresh Kumar <viresh.kumar@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.