1.1. Feature Overview

This page provides an overview of the current TF-A feature set. For a full description of these features and their implementation details, please see the documents that are part of the Components and System Design chapters.

The Change Log & Release Notes provides details of changes made since the last release.

1.1.1. Current features

  • Initialization of the secure world, for example exception vectors, control registers and interrupts for the platform.

  • Library support for CPU specific reset and power down sequences. This includes support for errata workarounds and the latest Arm DynamIQ CPUs.

  • Drivers to enable standard initialization of Arm System IP, for example Generic Interrupt Controller (GIC), Cache Coherent Interconnect (CCI), Cache Coherent Network (CCN), Network Interconnect (NIC) and TrustZone Controller (TZC).

  • Secure Monitor library code such as world switching, EL2/EL1 context management and interrupt routing.

  • SMC (Secure Monitor Call) handling, conforming to the SMC Calling Convention using an EL3 runtime services framework.

  • PSCI library support for CPU, cluster and system power management use-cases. This library is pre-integrated with the AArch64 EL3 Runtime Software, and is also suitable for integration with other AArch32 EL3 Runtime Software, for example an AArch32 Secure OS.

  • A generic SCMI driver to interface with conforming power controllers, for example the Arm System Control Processor (SCP).

  • A minimal AArch32 Secure Payload (SP_MIN) to demonstrate PSCI library integration with AArch32 EL3 Runtime Software.

  • Secure partition manager dispatcher(SPMD) with following two configurations:

    • S-EL2 SPMC implementation, widely compliant with FF-A v1.1 EAC0 and initial support of FF-A v1.2.

    • EL3 SPMC implementation, compliant with a subset of FF-A v1.1 EAC0.

  • Support for Arm CCA based on FEAT_RME which supports authenticated boot and execution of RMM with the necessary routing of RMI commands as specified in RMM Beta 0 Specification.

  • A Test SP and SPD to demonstrate AArch64 Secure Monitor functionality and SP interaction with PSCI.

  • SPDs for the OP-TEE Secure OS, NVIDIA Trusted Little Kernel, Trusty Secure OS and ProvenCore Secure OS.

  • A Trusted Board Boot implementation, conforming to all mandatory TBBR requirements. This includes image authentication, Firmware recovery, Firmware encryption and packaging of the various firmware images into a Firmware Image Package (FIP).

  • Measured boot support with PoC to showcase its interaction with firmware TPM (fTPM) service implemneted on top of OP-TEE.

  • Support for Dynamic Root of Trust for Measurement (DRTM).

  • Following firmware update mechanisms available:

    • PSA Firmware Update (PSA FWU)

    • TBBR Firmware Update (TBBR FWU)

  • Reliability, Availability, and Serviceability (RAS) functionality, including

    • A Secure Partition Manager (SPM) to manage Secure Partitions in Secure-EL0, which can be used to implement simple management and security services.

    • An SDEI dispatcher to route interrupt-based SDEI events.

    • An Exception Handling Framework (EHF) that allows dispatching of EL3 interrupts to their registered handlers, to facilitate firmware-first error handling.

  • A dynamic configuration framework that enables each of the firmware images to be configured at runtime if required by the platform. It also enables loading of a hardware configuration (for example, a kernel device tree) as part of the FIP, to be passed through the firmware stages. This feature is now incorporated inside the firmware configuration framework (fconf).

  • Support for alternative boot flows, for example to support platforms where the EL3 Runtime Software is loaded using other firmware or a separate secure system processor, or where a non-TF-A ROM expects BL2 to be loaded at EL3.

  • Support for Errata management firmware interface.

  • Support for the GCC, LLVM and Arm Compiler 6 toolchains.

  • Support for combining several libraries into a “romlib” image that may be shared across images to reduce memory footprint. The romlib image is stored in ROM but is accessed through a jump-table that may be stored in read-write memory, allowing for the library code to be patched.

  • Position-Independent Executable (PIE) support.

1.1.2. Experimental features

A feature is considered experimental when still in development or isn’t known to the TF-A team as widely deployed or proven on end products. It is generally advised such options aren’t pulled into real deployments, or done with the appropriate level of supplementary integration testing.

A feature is no longer considered experimental when it is generally agreed the said feature has reached a level of maturity and quality comparable to other features that have been integrated into products.

Experimental build options are found in following section Experimental build options. Their use through the build emits a warning message.

Additionally the following libraries are marked experimental when included in a platform:

  • MPU translation library lib/xlat_mpu

  • RSS comms driver drivers/arm/rss

1.1.3. Still to come

  • Support for additional platforms.

  • Documentation enhancements.

  • Ongoing support for new architectural features, CPUs and System IP.

  • Ongoing support for new Arm system architecture specifications.

  • Ongoing security hardening, optimization and quality improvements.

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