##################
Trusted Firmware M
##################

Trusted Firmware-M (TF-M) implements the Secure Processing Environment (SPE)
for Armv8-M, Armv8.1-M architectures (e.g. the `Cortex-M33`_, `Cortex-M23`_,
`Cortex-M55`_, `Cortex-M85`_ processors) and dual-core platforms.
It is the platform security architecture reference implementation aligning with
PSA Certified guidelines, enabling chips, Real Time Operating Systems and
devices to become PSA Certified.

TF-M relies on an isolation boundary between the Non-secure Processing
Environment (NSPE) and the Secure Processing Environment (SPE). It can but is
not limited to using the `Arm TrustZone technology`_ on Armv8-M and Armv8.1-M
architectures. In pre-Armv8-M architectures physical core isolation is required.

**TF-M consists of:**

- Secure Boot to authenticate NSPE and SPE images
- TF-M Core for controlling the isolation, communication
  and execution within SPE and with NSPE
- Crypto, Internal Trusted Storage (ITS), Protected Storage (PS),
  Firmware Update and Attestation secure services

TF-M implements `PSA-FF-M`_ defined IPC and SFN mechanisms to allow communication
between isolated firmware partitions. TF-M is highly configurable allowing users
to only include the required secure services and features. Project provides
:ref:`Base_configuration` build with just TF-M core and platform drivers and 4 predefined
configurations known as :ref:`tf-m_profiles`. TF-M Profiles or TF-M base can
be configured to include required services and features as described in the
:ref:`tf-m_configuration` section.

.. figure:: readme_tfm_v8.png
   :scale: 65 %
   :align: center

   FF-M compliant design with TF-M

Applications and Libraries in the Non-secure Processing Environment can
utilize these secure services with a standardized set of PSA Functional APIs.
Applications running on Cortex-M devices can leverage TF-M services to ensure
secure connection with edge gateways and IoT cloud services. It also protects
the critical security assets such as sensitive data, keys and certificates on
the platform. TF-M is supported on several Cortex-M based
:doc:`Microcontrollers </platform/index>` and Real Time Operating
Systems (RTOS).

Terms ``TFM`` and ``TF-M`` are commonly used in documents and code and both
refer to ``Trusted Firmware M.`` :doc:`Glossary </glossary>` has the list
of terms and abbreviations.

#######
License
#######
The software is provided under a BSD-3-Clause :doc:`License </contributing/lic>`.
Contributions to this project are accepted under the same license with developer
sign-off as described in the :doc:`Contributing Guidelines </contributing/contributing_process>`.

This project contains code from other projects as listed below. The code from
external projects is limited to ``bl2``, ``lib`` and ``platform``
folders. The original license text is included in those source files.

- The ``bl2`` folder contains files imported from MCUBoot project and the files
  have Apache 2.0 license.
- The ``lib/ext`` folder may contain 3rd party projects and files with
  diverse licenses. Here are some that are different from the BSD-3-Clause and
  may be a part of the runtime image. The source code for these projects is
  fetched from upstream at build time only.

   - ``CMSIS_5``    - Apache 2.0 license
   - ``mbedcrypto`` - `Apache 2.0 license MbedTLS
     <https://github.com/Mbed-TLS/mbedtls/blob/development/LICENSE>`_
   - ``mcuboot``    - `Apache 2.0 license MCUBoot
     <https://github.com/mcu-tools/mcuboot/blob/main/LICENSE>`_
   - ``qcbor``      - `Modified BSD-3-Clause license
     <https://github.com/laurencelundblade/QCBOR#copyright-and-license>`_
   - ``tf-m-extras`` - Set of additional components. Please check individually in
     `tf-m-extras repository <https://git.trustedfirmware.org/TF-M/tf-m-extras.git/tree/>`_

- The ``platform`` folder currently contains platforms support imported from
  the external project and the files may have different licenses.

.. include:: /platform/platform_introduction.rst

The document :doc:`Supported Platforms </platform/index>` lists the details.

#########################
Release Notes and Process
#########################
The :doc:`Release Cadence and Process </releases/release_process>` provides
release cadence and process information.

The :doc:`Releases </releases/index>` provides details of
major features of the release and platforms supported.

####################
Feedback and Support
####################
For this release, feedback is requested via email to
`tf-m@lists.trustedfirmware.org <tf-m@lists.trustedfirmware.org>`__.

A bi-weekly technical forum is available for discussion on any technical topics
online. Welcome to join `TF-M Forum <https://www.trustedfirmware.org/meetings/tf-m-technical-forum>`__.

.. _Cortex-M33: https://developer.arm.com/Processors/Cortex-M33
.. _Cortex-M23: https://developer.arm.com/Processors/Cortex-M23
.. _Cortex-M55: https://developer.arm.com/Processors/Cortex-M55
.. _Cortex-M85: https://developer.arm.com/Processors/Cortex-M85
.. _PSA Certified: https://www.psacertified.org/about/developing-psa-certified/
.. _Arm TrustZone technology: https://developer.arm.com/ip-products/security-ip/trustzone/trustzone-for-cortex-m
.. _PSA-FF-M: https://www.arm.com/architecture/security-features/platform-security

--------------

*Copyright (c) 2017-2022, Arm Limited. All rights reserved.*