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Sec proxy data buffer is 60 bytes with the last of the registers indicating transmission completion. This however poses a bit of a challenge. The backing memory for sec_proxy is regular memory, and all sec proxy does is to trigger a burst of all 60 bytes of data over to the target thread backing ring accelerator. It doesn't do a memory scrub when it moves data out in the burst. When we transmit multiple messages, remnants of previous message is also transmitted which results in some random data being set in TISCI fields of messages that have been expanded forward. The entire concept of backward compatibility hinges on the fact that the unused message fields remain 0x0 allowing for 0x0 value to be specially considered when backward compatibility of message extension is done. So, instead of just writing the completion register, we continue to fill the message buffer up with 0x0 (note: for partial message involving completion, we already do this). This allows us to scale and introduce ABI changes back into TF-A only as needed. Signed-off-by: Nishanth Menon <nm@ti.com> Change-Id: Ie22cb2a319f4aa80aef23ffc7e059207e5d4c640 |
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readme.rst
Trusted Firmware-A
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) 2013-2019, Arm Limited and Contributors. All rights reserved.