FreeRTOS-Kernel/portable/ThirdParty/GCC/ARM_TFM/README.md

Target of this port

This port adds the support that FreeRTOS applications can call the secure services in Trusted Firmware M(TF-M) through Platform Security Architecture (PSA) API based on the ARM Cortex-M23, Cortex-M33, Cortex-M52, Cortex-M55 and Cortex-M85 platform.

The Platform Security Architecture (PSA) makes it quicker, easier and cheaper to design security into a device from the ground up. PSA is made up of four key stages: analyze, architect, implement, and certify. See PSA Resource Page.

TF-M is an open source project. It provides a reference implementation of PSA for Arm M-profile architecture. Please get the details from this link.

Derivation of the source code

• os_wrapper_freertos.c The implementation of APIs which are defined in /interface/include/os_wrapper/mutex.h in trusted-firmware-m (tag: TF-Mv2.0.0). The implementation is based on FreeRTOS mutex type semaphore.

Usage notes

To build a project based on this port:

• Step 1: build the secure image. Please follow the Build the Secure Side section for details.
• Step 2: build the nonsecure image. Please follow the Build the Non-Secure Side for details.

Build the Secure Side

Get the TF-M source code

See the link to get the source code. This port is supported by TF-M version tag: TF-Mv2.0.0.

Build TF-M

Please refer to this link to build the secure side. Note: TFM_NS_MANAGE_NSID must be configured as "OFF" when building TF-M.

Build the Non-Secure Side

Please copy all the files in freertos_kernel/portable/GCC/ARM_CM[23|33|52|55|85]_NTZ into the freertos_kernel/portable/ThirdParty/GCC/ARM_TFM folder before using this port. Note that TrustZone is enabled in this port. The TF-M runs in the Secure Side.

Please call the API tfm_ns_interface_init() which is defined in /interface/src/os_wrapper/tfm_ns_interface_rtos.c by trusted-firmware-m (tag: TF-Mv2.0.0) at the very beginning of your application. Otherwise, it will always fail when calling a TF-M service in the Nonsecure Side.

Configuration in FreeRTOS kernel

• configRUN_FREERTOS_SECURE_ONLY This macro should be configured as 0. In this port, TF-M runs in the Secure Side while FreeRTOS Kernel runs in the Non-Secure Side.

• configENABLE_FPU The setting of this macro is decided by the setting in Secure Side which is platform-specific. If the Secure Side enables Non-Secure access to FPU, then this macro can be configured as 0 or 1. Otherwise, this macro can only be configured as 0. Please note that Cortex-M23 does not support FPU. Please refer to TF-M documentation for FPU usage on the Non-Secure side.

• configENABLE_MVE The setting of this macro is decided by the setting in Secure Side which is platform-specific. If the Secure Side enables Non-Secure access to MVE, then this macro can be configured as 0 or 1. Otherwise, this macro can only be configured as 0. Please note that only Cortex-M52, Cortex-M55 and Cortex-M85 support MVE. Please refer to TF-M documentation for MVE usage on the Non-Secure side.

• configENABLE_TRUSTZONE This macro should be configured as 0 because TF-M doesn't use the secure context management function of FreeRTOS. New secure context management might be introduced when TF-M supports multiple secure context.

Integrate TF-M Non-Secure interface with FreeRTOS project

To enable calling TF-M services by the Non-Secure Side, the files below should be included in the FreeRTOS project and built together.

• files in trusted-firmware-m/build/api_ns/interface/src These files contain the implementation of PSA Functional Developer APIs which can be called by Non-Secure Side directly and PSA Firmware Framework APIs in the IPC model. These files should be taken as part of the Non-Secure source code.
• files in trusted-firmware-m/build/api_ns/interface/include These files are the necessary header files to call TF-M services.
• trusted-firmware-m/build/api_ns/interface/lib/s_veneers.o This object file contains all the Non-Secure callable functions exported by TF-M and it should be linked when generating the Non-Secure image.

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