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-M33 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
for Arm M-profile architecture. Please get the details from this [link](https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git/about/).
# Derivation of the source code
* ```os_wrapper_freertos.c```
The implementation of APIs which are defined in ```os_wrapper\mutex.h``` by TF-M
See the [link](https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git/) to get the source code. This port is based on TF-M version **tag: TF-Mv1.2.0**.
Please refer to this [link](https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git/tree/docs/getting_started/tfm_build_instruction.rst) to build the secure side.
_**Note:** ```CONFIG_TFM_ENABLE_CTX_MGMT``` must be configured as "OFF" when building TF-M_.
Please copy all the files in ```freertos_kernel\portable\GCC\ARM_CM33_NTZ``` into the ```freertos_kernel\portable\ThirdParty\GCC\ARM_CM33_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 ```tfm_ns_interface.c``` at the very beginning of your application. Otherwise, it will always fail when calling a TF-M service in the Nonsecure Side.
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.
* ```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\export\tfm\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\export\tfm\include```
These files are the necessary header files to call TF-M services.
