Hardware requirements

  • Micro USB cable

  • EVK-MIMXRT595 board

  • Personal Computer

Board settings

No special settings are required.

Prepare the Demo

  1. Connect a micro USB cable between the PC host and the CMSIS DAP USB port on the board

  2. Open a serial terminal with the following settings:

    • 115200 baud rate

    • 8 data bits

    • No parity

    • One stop bit

    • No flow control

  3. Use secure project to download the program to target board. Please refer to “TrustZone application debugging” below for details.

  4. Launch the debugger in your IDE to begin running the demo. Note: Refering to the “Getting started with MCUXpresso SDK for EVK-MIMXRT595” documentation for more information on how to build and run the TrustZone examples in various IDEs.

Running the demo

The log below shows the output of the secure_faults demo in the terminal window:

Hello from secure world!
Entering normal world.
Welcome in normal world!
This is a text printed from normal world!
Comparing two string as a callback to normal world
String 1: Test1
String 2: Test2
Both strings are not equal!

Change testCaseNumber value in secure_faults_s(in secure_faults_s.c “main” function) project to trigger different secure error. The available testCaseNumber values are defined in veneer_table.h as macro, #define FAULT_NONE 0 #define FAULT_INV_S_TO_NS_TRANS 1 #define FAULT_INV_S_ENTRY 2 #define FAULT_INV_NS_DATA_ACCESS 3 #define FAULT_INV_INPUT_PARAMS 4 #define FAULT_INV_NS_DATA2_ACCESS 5 In case some secure error is raised, the information about error will be printed in the terminal window.

With testCaseNumber = FAULT_INV_S_TO_NS_TRANS, the below log will be shown in the terminal:

Hello from secure world!
Entering normal world.

Entering HardFault interrupt!
SAU->SFSR:INVTRAN fault: Invalid transition from secure to normal world.

With testCaseNumber = FAULT_INV_S_ENTRY, the below log will be shown in the terminal:

Hello from secure world!
Entering normal world.
Welcome in normal world!

Entering HardFault interrupt!
SAU->SFSR:INVEP fault: Invalid entry point to secure world.

With testCaseNumber = FAULT_INV_NS_DATA_ACCESS, the below log will be shown in the terminal:

Hello from secure world!
Entering normal world.
Welcome in normal world!

Entering HardFault interrupt!
SAU->SFSR:AUVIOL fault: SAU violation. Access to secure memory from normal world.
Address that caused SAU violation is 0x30000000.

With testCaseNumber = FAULT_INV_INPUT_PARAMS, the below log will be shown in the terminal:

Hello from secure world!
Entering normal world.
Welcome in normal world!
Input data error: String is not located in normal world!

With testCaseNumber = FAULT_INV_NS_DATA2_ACCESS, the below log will be shown in the terminal:

Hello from secure world!
Entering normal world.
Welcome in normal world!

Entering HardFault interrupt!
SCB->BFSR:PRECISERR fault: Precise data access error.
Address that caused secure bus violation is 0x330000.

Additional AHB secure controller error information:
Secure error at AHB layer 9.
Address that caused secure violation is 0x20330000.
Secure error caused by bus master number 0.
Security level of master 1.
Secure error happened during read data access.

TrustZone Application Development in SDK

Every TrustZone based application consists of two independent parts - secure part/project and non-secure part/project.

The secure project is stored in <application_name><application_name>_s directory. The non-secure project is stored in <application_name><application_name>_ns directory.

The secure projects always contains TrustZone configuration and it is executed after device RESET. The secure project usually ends by jump to non-secure application/project. If IDE allows the two projects in single workspace, the user can also find the project with <application_name>. This project contains both secure and non-secure projects in one workspace (Keil MDK, IAR) and it allows to user easy transition from one to another project.

Project Structure

The all TrustZone files related to TrustZone are located in trustzone virtual directory. The files are:

  • tzm_config.c

  • tzm_config.h

  • veneer_table.c

  • veneer_table.h

File tzm_config.c, tzm_config.h

This file is used by secure project only. It contains one function BOARD_InitTrustZone(), which configures complete TrustZone environment. It includes SAU, MPU’s, AHB secure controller and some TrustZone related registers from System Control Block. This function is called from SystemInitHook() function, it means during system initialization.

File veneer_table.c, veneer_table.h

This file defines all secure functions (secure entry functions) exported to normal world. This file is located in secure project only. While header file is used by both secure and non-secure projects. The secure entry functions usually contain validation of all input parameters in order to avoid any data leak from secure world.

The files veneer_table.h and <application_name>_s_import_lib.o or <application_name>_s_CMSE_lib.o create the connection between secure and non-secure projects. The library file is generated by linker during compilation of secure project and it is linked to the non-secure project as any other library.

TrustZone application compilation

Please compile secure project firstly since CMSE library is needed for compilation of non-secure project. After successful compilation of secure project, compile non-secure project.

TrustZone application debugging

  • Download both output file into device memory

  • Start execution of secure project since secure project is going to be executed after device RESET.

If IDE (Keil MDK, IAR) allows to manage download both output files as single download, the secure project is configured to download both secure and non-secure output files so debugging can be fully managed from secure project.

For IAR, please don’t choose Use flash loader option when download ram target output files.

If want to download secure and non-secure binary file into QSPI flash, should the following rules: Flash target: 1. secure binary download into 0x8000400 address. 2. non-secure binary download into 0x8100000 address. RAM target: 1. secure binary download into 0x8000400 address for IAR, download into 0x80000000 for other toolchains. 2. non-secure binary download into 0x8041000 address.

Device header file and secure/non-secure access to the peripherals

Both secure and non-secure project uses identical device header file. The access to secure and non-secure aliases for all peripherals is managed using compiler macro __ARM_FEATURE_CMSE.

For secure project using <PERIPH_BASE> means access through secure alias (address bit A28=1), using <PERIPH_BASE>_NS means access through non-secure alias(address bit A28=0) For non-secure project using <PERIPH_BASE> means access through non-secure alias (address bit A28=0). The non-secure project doesn’t have access to secure memory or peripherals regions so the secure access is not defined.