Deploying trusted services in S-EL0 Secure Partitions under OP-TEE
==================================================================

Trusted services built for the *opteesp* environment may be deployed to run within S-EL0 secure
partitions, managed by OP-TEE.  Secure partitions are loaded and run by OP-TEE using the early-TA
feature where a set of TAs or SPs are loaded during OP-TEE initialization.  This feature relies on
SP images being incorporated into the *OP-TEE OS* image at build time.  It is therefore necessary to
have access to the OP-TEE build environment and tools in order to deploy SP images.

Tool prerequisites and general build instruction for OP-TEE are described here:
`<https://optee.readthedocs.io/en/latest/building/gits/build.html>`_

Download page for Arm Fixed Virtual Platforms (FVP):
`<https://developer.arm.com/tools-and-software/simulation-models/fixed-virtual-platforms>`_

Incorporating SP images into the *OP-TEE OS* image
--------------------------------------------------

The set of SP images to include in the built *OP-TEE OS* image are specified to the *OP-TEE OS*
build by the EARLY_TA_PATHS make variable.  The EARLY_TA_PATHS variable should be assigned a string
containing a space separated list of file paths for each SP image file to include.  SP images
that need to be deployed from the Trusted Services project will be located in the install directory,
specified when the SP images where built i.e.::

    <CMAKE_INSTALL_PREFIX>/bin

The following example illustrates a setting of the EARLY_TA_PATHS variable to deploy the Secure Storage
SP and Crypto SP::

    EARLY_TA_PATHS="ts-install-dir/bin/dc1eef48-b17a-4ccf-ac8b-dfcff7711b14.stripped.elf \
        ts-install-dir/bin/d9df52d5-16a2-4bb2-9aa4-d26d3b84e8c0.stripped.elf"

To help with integration with the OP-TEE build system, the installation step for a deployment to the
*opteesp* environment includes the generation of a simple makefile that extends the EARLY_TA_PATHS
variable for the particular deployment.  For example, the generated makefile for the crypto SP
contains::

    OPTEE_OS_COMMON_EXTRA_FLAGS+=EARLY_TA_PATHS+=${TS_INSTALL_PREFIX}/bin/d9df52d5-16a2-4bb2-9aa4-d26d3b84e8c0.stripped.elf

The generated makefile is installed to::

    <CMAKE_INSTALL_PREFIX>/lib/make

Reference OP-TEE build with PSA RoT Services
--------------------------------------------
To provide an example integration of OP-TEE with a set of trusted services, a makefile called *fvp_ffa.mk*
is included in the OP-TEE build repository that builds OP-TEE OS with a set of SP images that provide PSA
RoT services.  SP images are built using the standard trusted services build flow and are automatically
injected into the *optee_os* build using the early TA feature described above.

A bootable Linux image is created that is intended to run on the Arm FVP virtual platform.  The built image
includes user space programs that may be used to test and demonstrate the deployed trusted services.

Setting up the OP-TEE build environment
'''''''''''''''''''''''''''''''''''''''
To help setup the OP-TEE build environment, a manifest file called *psa-sp-fvp.xml* is included in OP-TEE
manifests repository.  This may be used with the *repo* tool to manage the set of git repositories.  Note
that this manifest relies on SSH access to *github.com* so ensure that you have installed a suitable public
key into your *github* account.

Having created a new directory for the OP-TEE build environment, the required set of git repositories can
be cloned and fetched using::

    repo init -u https://git.trustedfirmware.org/OP-TEE/manifest.git -b psa-development -m psa-sp-fvp.xml
    repo sync

Building the reference OP-TEE image
'''''''''''''''''''''''''''''''''''
To build the bootable image that includes OP-TEE and the set of secure partition images that hold the
PSA RoT services, use the following (from your OP-TEE root directory)::

    cd build
    make -f fvp_ffa.mk all

This will take many tens of minutes to complete.

Running the reference OP-TEE image on FVP
'''''''''''''''''''''''''''''''''''''''''
The fvp makefile includes a *run* and *run-only* target which can be used to start the FVP model and
boot the built image.  The example assumes that the FVP model has been installed in the following
directory relative to the OP-TEE build directory::

    ../Foundation_Platformpkg/models/Linux64_GCC-6.4/

To boot the built image on FVP without building, use::

    make run-only FVP_PATH=../Foundation_Platformpkg/models/Linux64_GCC-6.4/

For information on running user space programs on FVP, see:

:ref:`Deploying Programs on FVP`

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

*Copyright (c) 2020-2021, Arm Limited and Contributors. All rights reserved.*

SPDX-License-Identifier: BSD-3-Clause