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-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](https://developer.arm.com/architectures/security-architectures/platform-security-architecture).
TF-M is an open source project. It provides a reference implementation of PSA
The implementation of APIs which are defined in ```\ns_interface\os_wrapper\mutex.h``` by tf-m-tests
(tag: TF-Mv1.5.0 & TF-Mv1.6.0). 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](https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git/) to get the source code. This port is supported by TF-M version **tag: TF-Mv1.5.0**&**tag: TF-Mv1.6.0**.
Please refer to this [link](https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/tfm/building/tfm_build_instruction.html) 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|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 ```\app\tfm_ns_interface.c``` by tf-m-tests
(tag: TF-Mv1.5.0 & TF-Mv1.6.0) 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](https://tf-m-user-guide.trustedfirmware.org/integration_guide/tfm_fpu_support.html) 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-M55 and Cortex-M85 support MVE.
Please refer to [TF-M documentation](https://tf-m-user-guide.trustedfirmware.org/integration_guide/tfm_fpu_support.html) 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\install\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\install\interface\include```
These files are the necessary header files to call TF-M services.
