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OP-TEE

This is the repository of OP-TEE (Open Portable Trusted Execution Environment), the open-source TEE maintained by Linaro, with initial contributions from STMicroelectronics, Ericsson and Linaro Limited.

What OP-TEE is

OP-TEE is a Trusted Execution Environment designed as companion to a non-secure Linux kernel running on ARM® Cortex-A cores using the TrustZone® technology. OP-TEE meets the TEE System Architecture and provides the TEE Internal Core API v1.1 to Trusted Applications and the TEE Client API v1.0, all as defined by the GlobalPlatform TEE specifications.

The non-secure OS is referred to as the Rich Execution Environment (REE) in TEE specifications. It is typically a Linux OS flavor as a GNU/Linux distribution or the AOSP.

OP-TEE is designed primarily to rely on the ARM TrustZone technology as the underlying hardware isolation mechanism. However, it has been structured to be compatible with any isolation technology suitable for the TEE concept and goals, such as running as a virtual machine or on a dedicated CPU.

The main design goals for OP-TEE are:

  • Isolation - the TEE provides isolation from the non-secure OS and protects the loaded Trusted Applications (TAs) from each other using underlying HW support,
  • Small footprint - the TEE should remain small enough to reside in a reasonable amount of on-chip memory as found on ARM based systems,
  • Portability - the TEE aims at being easily pluggable to different architectures and available HW and has to support various setups such as multiple client OSes or multiple TEEs.

Repository structure

OP-TEE comes with several components:

  • a secure privileged layer, executing at ARM secure PL-1 level,
  • a set of secure userland libraries designed for Trusted Applications needs,
  • a Linux kernel driver merged since v4.12,
  • a Linux userland library designed upon the GPD TEE Client API specifications
  • a Linux userland supplicant application for remote services expected by the TEE OS,
  • and some build scripts, debugging tools and examples to ease its integration and the development of trusted applications and secure services.

These components are available from several git repositories. The main ones are the optee_os, the optee_client and the Linux kernel since v4.12.

The optee_os git repository contains the source code for the TEE OS itself. It includes the secure privileged layer hosting the Trusted Applications and libraries complying with the TEE Internal Core API v1.1. It is distributed mostly under the BSD 2-Clause open-source license. It includes few external files under BSD 3-Clause license or other free software licenses.

The optee_client git repository contains the source code for the TEE client library in a Linux OS providing the TEE Client API v1.0. It is distributed under the BSD 2-Clause open-source license.

The Linux kernel contains the source code for the OP-TEE Linux driver. It is distributed under the GPLv2 open-source license.

There are other OP-TEE components one might be interested in. The OP-TEE release tag references several git repositories enabling OP-TEE build and test for various platforms. Refer to the build documentation for information. The optee_test git repository proposes test materials through the xtest tool and dedicated trusted applications. The optee_examples git repository contains examples of TEE client and trusted applications and some documentation to get hands on trusted application development.

Documentation

Documentation on design, implementation and tools can be found in optee_os/documentation.

Contributions

Contributions to OP-TEE are managed by the OP-TEE gatekeepers, whose contact email is op-tee[at]linaro[.]org.

Anyone can contribute to OP-TEE as long as it is understood that it will require a sign-off. The sign-off is a simple line at the end of the explanation for the patch, which certifies that you wrote it or otherwise have the right to pass it on as an open-source patch (see below). You thereby assure that you have read and are following the rules stated in the Developer Certificate of Origin as stated below.

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
660 York Street, Suite 102,
San Francisco, CA 94110 USA

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.


Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

We have borrowed this procedure from the Linux kernel project to improve tracking of who did what, and for legal reasons.

To sign-off a patch, just add a line saying:

    Signed-off-by: Random J Developer <random@developer.example.org>

using your real name (sorry, no pseudonyms or anonymous contributions.)

Refer also to github.md to setup a github accournt in order to contribute to the project through issues reporting and pull requests.