Trusted Firmware-A

November 24, 2025 ยท View on GitHub

Trusted Firmware-A (TF-A) is a reference implementation of secure world software for Arm A-Profile architectures_ (Armv8-A and Armv7-A), including an Exception Level 3 (EL3) Secure Monitor_. It provides a suitable starting point for productization of secure world boot and runtime firmware, in either the AArch32 or AArch64 execution states.

TF-A implements Arm interface standards, including:

  • Power State Coordination Interface (PSCI)_
  • Trusted Board Boot Requirements CLIENT (TBBR-CLIENT)_
  • SMC Calling Convention_
  • System Control and Management Interface (SCMI)_
  • Software Delegated Exception Interface (SDEI)_

The code is designed to be portable and reusable across hardware platforms and software models that are based on the Armv8-A and Armv7-A architectures.

In collaboration with interested parties, we will continue to enhance TF-A with reference implementations of Arm standards to benefit developers working with Armv7-A and Armv8-A TrustZone technology.

Users are encouraged to do their own security validation, including penetration testing, on any secure world code derived from TF-A.

More Info and Documentation

To find out more about Trusted Firmware-A, please view the full documentation_ that is available through trustedfirmware.org_.

Copyright (c) 2013-2025, Arm Limited and Contributors. All rights reserved.

.. _Armv7-A and Armv8-A: https://developer.arm.com/products/architecture/a-profile .. _Secure Monitor: http://www.arm.com/products/processors/technologies/trustzone/tee-smc.php .. Power State Coordination Interface (PSCI): PSCI .. _PSCI: https://developer.arm.com/documentation/den0022/latest .. _Trusted Board Boot Requirements CLIENT (TBBR-CLIENT): https://developer.arm.com/docs/den0006/latest .. _SMC Calling Convention: https://developer.arm.com/documentation/den0028/latest .. System Control and Management Interface (SCMI): SCMI .. _SCMI: https://developer.arm.com/documentation/den0056/latest .. Software Delegated Exception Interface (SDEI): SDEI .. _SDEI: https://developer.arm.com/documentation/den0054/latest .. _Arm A-Profile architectures: https://developer.arm.com/architectures/cpu-architecture/a-profile .. _view the full documentation: https://www.trustedfirmware.org/docs/tf-a .. _trustedfirmware.org: http://www.trustedfirmware.org