# Arm® Kronos Reference Software Stack The Arm Kronos Reference Software Stack is made available as part of the Arm Kronos Reference Design and is composed of multiple Open Source components which together form the proposed solution, including: - The [Runtime Security Engine (RSE)][1] running an instance of Trusted Firmware-M, which offers boot, cryptography, and secure storage services. - The Safety Island subsystem, running three instances of the Zephyr real-time operating system (RTOS). - The firmware for the Primary Compute, using Trusted Firmware-A, U-Boot, OP-TEE and Trusted Services. These are configured to be aligned with [Arm SystemReady IR][2]. The remaining software in the Primary Compute subsystem, based on the [Cassini][3] distribution, is available in two main architectures: baremetal and virtualization. ## Arm Kronos Reference Software Stack Documentation The project's documentation can be browsed at . To build a local version of the documentation, you will need [Sphinx][4] installed in your work environment. The following commands should be executed on a Linux machine and have been tested on hosts running Ubuntu 20.04 LTS. These can be used to generate an HTML version of the documentation under `public/`: sudo apt-get install python3-pip pip3 install -U -r documentation/requirements.txt sphinx-build -b html -a -W documentation public To render and explore the documentation, simply open `public/index.html` in a web browser. [1]: https://tf-m-user-guide.trustedfirmware.org/platform/arm/rse/readme.html [2]: https://www.arm.com/architecture/system-architectures/systemready-certification-program/ir [3]: https://cassini.readthedocs.io/en/v1.1.0/ [4]: https://www.sphinx-doc.org/