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trusted-firmware-m/platform/ext/readme.md

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Details for the platform/ext folder

This folder has code that has been imported from other projects. This means the files in this folder and subfolders have Apache 2.0 license which is different to BSD 3.0 license applied to the parent TF-M project.

NOTE This folder is strictly Apache 2.0 with the exception of cmake files. Maintainers should be consulted if this needs to be revisited.

Sub-folders

cmsis

This folder contains core and compiler specific header files imported from the CMSIS_5 project.

common

This folder contains stdout redirection to UART, a temporary memory mapped flash implementation for the bootloader and tfm_mbedtls_config.h for all the targets.

drivers

This folder contains the headers with CMSIS compliant driver definitions that that TF-M project expects a target to provide.

target_cfg.h

This file is expected to define the following macros respectively.

  • TFM_DRIVER_STDIO This macro should expand to a structure of type ARM_DRIVER_USART. TFM redirects its standard input and output to this instance of USART.
  • NS_DRIVER_STDIO This macro should expand to a structure of type ARM_DRIVER_USART. Non-Secure application redirects its standard input and output to this instance of USART.

target

This folder contains the files for individual target.

Flash layout header file

Target must provide a header file, called flash_layout.h, which defines the information explained in the follow subsections. The defines must be named as they are in the subsections.

BL2 bootloader

The BL2 bootloader requires the following definitions:

  • FLASH_BASE_ADDRESS Defines the first valid address in the flash.
  • FLASH_AREA_BL2_OFFSET Defines the offset from the flash base address where the BL2 - MCUBOOT area starts.
  • FLASH_AREA_BL2_SIZE Defines the size of the BL2 area.
  • FLASH_AREA_IMAGE_0_OFFSET Defines the offset from the flash base address where the image 0 area starts, which hosts the active firmware image.
  • FLASH_AREA_IMAGE_0_SIZE Defines the size of the image 0 area.
  • FLASH_AREA_IMAGE_1_OFFSET Defines the offset from the flash base address where the image 1 area starts, which is a placeholder for new firmware images.
  • FLASH_AREA_IMAGE_1_SIZE Defines the size of the image 1 area.
  • FLASH_AREA_IMAGE_SCRATCH_OFFSET Defines the offset from the flash base address where the scratch area starts, which is used during image swapping.
  • FLASH_AREA_IMAGE_SCRATCH_SIZE Defines the size of the scratch area. The minimal size must be as the biggest sector size in the flash.
  • FLASH_DEV_NAME Specifies the flash device used by BL2.
Assemble tool

The assemble.py tools is used to concatenate secure and non-secure binary to a single binary blob. It requires the following definitions:

  • SECURE_IMAGE_OFFSET Defines the offset from the single binary blob base address, where the secure image starts.
  • SECURE_IMAGE_MAX_SIZE Defines the maximum size of the secure image area.
  • NON_SECURE_IMAGE_OFFSET Defines the offset from the single binary blob base address, where the non-secure image starts.
  • NON_SECURE_IMAGE_MAX_SIZE Defines the maximum size of the non-secure image area.
Secure Storage (SST) Service definitions

The SST service requires the following definitions:

  • SST_FLASH_AREA_ADDR Defines the flash area address where the secure store area starts.
  • SST_SECTOR_SIZE Defines the size of the flash sectors.
  • SST_NBR_OF_SECTORS Defines the number of sectors available for the secure area.
  • SST_FLASH_DEV_NAME Specifies the flash device used by SST to store the data.
  • SST_FLASH_PROGRAM_UNIT Defines the smallest flash programmable unit in bytes.
  • SST_MAX_ASSET_SIZE Defines the maximum asset size to be stored in the SST area.
  • SST_NUM_ASSETS Defines the maximum number of assets to be stored in the SST area.

Note: The sectors must be consecutive.

Expose target support for HW components

Services may require HW components to be supported by the target to enable some features (e.g. SST service with rollback protection, etc). The following definitions need to be set in the <TARGET_NAME>.cmake file if the target has the following HW components:

  • TARGET_NV_COUNTERS_ENABLE Specifies that the target has non-volatile (NV) counters.

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