TF-M PSA Firmware

Overview

This TF-M integration example demonstrates how to use the PSA Firmware API to retrieve information about the current firmware, or implement a custom firmware update process.

Trusted Firmware (TF-M) Platform Security Architecture (PSA) APIs are used for the secure processing environment, with Zephyr running in the non-secure processing environment.

It uses IPC Mode for communication, where an IPC mechanism is inserted to handle secure TF-M API calls and responses. The OS-specific code to handle the IPC calls is in tfm_ipc.c.

TF-M supports three types of firmware upgrade mechanisms: https://tf-m-user-guide.trustedfirmware.org/docs/technical_references/design_docs/tfm_secure_boot.html#firmware-upgrade-operation

This example uses the overwrite firmware upgrade mechanism, in particular, it showcases upgrading the non-secure image which can be built from any other sample in the zephyr/samples directory.

The sample prints test info to the console either as a single-thread or multi-thread application.

Building and Running

This project needs another firmware as the update payload. It must use another example’s hex file, and should be specified on the command line as CONFIG_APP_FIRMWARE_UPDATE_IMAGE.

To use the tfm_integration/tfm_ipc sample as the NS firmware update payload, follow the instructions below:

This sample will only build on a Linux or macOS development system (not Windows), and has been tested on the following setups:

  • macOS Big Sur using QEMU 6.0.0 with gcc-arm-none-eabi-9-2020-q2-update

  • Linux (NixOS) using QEMU 6.2.0 with gcc from Zephyr SDK 0.14.1

  • Targets MPS3 AN547 and NXP LPCXPRESSO55S69

On MPS3 AN547:

Build:

1. Build the tfm_ipc sample with the non-secure board configuration, which will generate the firmware image we’ll use in psa_firmware during the update:

west build -b mps3_an547_ns -d build/build/tfm_ipc samples/tfm_integration/tfm_ipc

  1. Build psa_firmware

west build -b mps3_an547_ns -d build/build/psa_firmware samples/tfm_integration/psa_firmware -- -DCONFIG_APP_FIRMWARE_UPDATE_IMAGE=\"full/path/to/zephyr/build/tfm_ipc/zephyr/zephyr.hex\"

Note: This sample includes a pre-built firmware image (hello-an547.hex) in the boards directory. If you don’t pass the CONFIG_APP_FIRMWARE_UPDATE_IMAGE command line argument during step 2 (-- -DCONFIG_APP_FIRMWARE_UPDATE_IMAGE=...), this sample will automatically uses the pre-built hex file.

Run in real target:

  1. Copy application binary files (mcuboot.bin and tfm_sign.bin) to <MPS3 device name>/SOFTWARE/.

  2. Edit (e.g., with vim) the <MPS3 device name>/MB/HBI0263C/AN547/images.txt file, and update it as shown below:

    TITLE: Versatile Express Images Configuration File

[IMAGES]
TOTALIMAGES: 2 ;Number of Images (Max: 32)

IMAGE0ADDRESS: 0x10000000
IMAGE0FILE: \SOFTWARE\mcuboot.bin  ; BL2 bootloader

IMAGE1ADDRESS: 0x10080000
IMAGE1FILE: \SOFTWARE\tfm_sign.bin ; TF-M with application binary blob

  3. Save the file, exit the editor, and reset the MPS3 board.

Run in QEMU:

west build -b mps3_an547_ns -d build/build/psa_firmware samples/tfm_integration/psa_firmware -- -DCONFIG_APP_FIRMWARE_UPDATE_IMAGE=\"full/path/to/zephyr/build/tfm_ipc/zephyr/zephyr.hex\"
west build -t run -d build/build/psa_firmware

On LPCxpresso55S69:

1. Build the tfm_ipc sample with the non-secure board configuration, which will generate the firmware image we’ll use in psa_firmware during the update:

west build -b lpcxpresso55s69_ns -d build/build/tfm_ipc samples/tfm_integration/tfm_ipc

  1. Build psa_firmware:

west build -b lpcxpresso55s69_ns -d build/build/psa_firmware samples/tfm_integration/psa_firmware -- -DCONFIG_APP_FIRMWARE_UPDATE_IMAGE=\"full/path/to/zephyr/build/tfm_ipc/zephyr/zephyr.hex\"

Make sure your board is set up with LPC-Link2 J-Link Onboard Debug Probe, since this isn’t the debug interface boards ship with from the factory;

Next we need to manually flash the resulting image (tfm_merged.bin) with a J-Link as follows:

JLinkExe -device lpc55s69 -if swd -speed 2000 -autoconnect 1
J-Link>r
J-Link>erase
J-Link>loadfile build/tfm_merged.bin

Resetting the board and erasing it will unlock the board, this is useful in case it’s in an unknown state and can’t be flashed.

We need to reset the board manually after flashing the image to run this code.

Sample Output

[INF] Beginning TF-M provisioning
[WRN] TFM_DUMMY_PROVISIONING is not suitable for production! This device is NOT SECURE
[Sec Thread] Secure image initializing!
Booting TF-M v1.6.0+8cffe127
Creating an empty ITS flash layout.
Creating an empty PS flash layout.
*** Booting Zephyr OS build zephyr-v3.1.0-3851-g2bef8051b2fc  ***
PSA Firmware API test
Active S image version: 0.0.3-0
Active NS image version: 0.0.1-0
Starting FWU; Writing Firmware from 21000000 size 17802 bytes
Wrote Firmware; Writing Header from 2100458a size    16 bytes
Wrote Header; Installing Image
Installed New Firmware; Reboot Needed; Rebooting
[WRN] This device was provisioned with dummy keys. This device is NOT SECURE
[Sec Thread] Secure image initializing!
Booting TF-M v1.6.0+8cffe127
*** Booting Zephyr OS build zephyr-v3.1.0-3851-g2bef8051b2fc  ***
The version of the PSA Framework API is 257.
The minor version is 1.
Connect success!
TF-M IPC on mps3_an547

Common Problems

Compilation fails with Error: Header padding was not requested...

This error occurs when passing a signed image to CONFIG_APP_FIRMWARE_UPDATE_IMAGE on the command line, ex: zephyr_ns_signed.hex. Make sure you pass an unsigned, non-secure image (ex. zephyr.hex) to CONFIG_APP_FIRMWARE_UPDATE_IMAGE.