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3912b1f576
Add documentation for the Trusted Services TEE driver. Acked-by: Sumit Garg <sumit.garg@linaro.org> Signed-off-by: Balint Dobszay <balint.dobszay@arm.com> Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
72 lines
3.7 KiB
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72 lines
3.7 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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=================================
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TS-TEE (Trusted Services project)
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=================================
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This driver provides access to secure services implemented by Trusted Services.
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Trusted Services [1] is a TrustedFirmware.org project that provides a framework
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for developing and deploying device Root of Trust services in FF-A [2] S-EL0
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Secure Partitions. The project hosts the reference implementation of the Arm
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Platform Security Architecture [3] for Arm A-profile devices.
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The FF-A Secure Partitions (SP) are accessible through the FF-A driver [4] which
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provides the low level communication for this driver. On top of that the Trusted
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Services RPC protocol is used [5]. To use the driver from user space a reference
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implementation is provided at [6], which is part of the Trusted Services client
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library called libts [7].
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All Trusted Services (TS) SPs have the same FF-A UUID; it identifies the TS RPC
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protocol. A TS SP can host one or more services (e.g. PSA Crypto, PSA ITS, etc).
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A service is identified by its service UUID; the same type of service cannot be
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present twice in the same SP. During SP boot each service in the SP is assigned
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an "interface ID". This is just a short ID to simplify message addressing.
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The generic TEE design is to share memory at once with the Trusted OS, which can
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then be reused to communicate with multiple applications running on the Trusted
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OS. However, in case of FF-A, memory sharing works on an endpoint level, i.e.
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memory is shared with a specific SP. User space has to be able to separately
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share memory with each SP based on its endpoint ID; therefore a separate TEE
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device is registered for each discovered TS SP. Opening the SP corresponds to
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opening the TEE device and creating a TEE context. A TS SP hosts one or more
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services. Opening a service corresponds to opening a session in the given
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tee_context.
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Overview of a system with Trusted Services components::
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User space Kernel space Secure world
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~~~~~~~~~~ ~~~~~~~~~~~~ ~~~~~~~~~~~~
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+--------+ +-------------+
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| Client | | Trusted |
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+--------+ | Services SP |
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/\ +-------------+
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|| /\
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|| ||
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|| ||
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\/ \/
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+-------+ +----------+--------+ +-------------+
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| libts | | TEE | TS-TEE | | FF-A SPMC |
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| | | subsys | driver | | + SPMD |
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+-------+----------------+----+-----+--------+-----------+-------------+
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| Generic TEE API | | FF-A | TS RPC protocol |
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| IOCTL (TEE_IOC_*) | | driver | over FF-A |
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+-----------------------------+ +--------+-------------------------+
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References
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==========
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[1] https://www.trustedfirmware.org/projects/trusted-services/
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[2] https://developer.arm.com/documentation/den0077/
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[3] https://www.arm.com/architecture/security-features/platform-security
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[4] drivers/firmware/arm_ffa/
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[5] https://trusted-services.readthedocs.io/en/v1.0.0/developer/service-access-protocols.html#abi
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[6] https://git.trustedfirmware.org/TS/trusted-services.git/tree/components/rpc/ts_rpc/caller/linux/ts_rpc_caller_linux.c?h=v1.0.0
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[7] https://git.trustedfirmware.org/TS/trusted-services.git/tree/deployments/libts/arm-linux/CMakeLists.txt?h=v1.0.0
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