Source Structure

TF-M is designed to provide a user-friendly source structure to ease integration and service development. This document introduces the source structure and its design intention of TF-M. Additionally, the folders below are important for TF-M integration and descibed in a separate documents:

/ (TF-M root)

This table describes the structure under the root folder with part of possible folders.

Folder name	Description
bl1	The 1st stage immutable bootloader
bl2	MCUBoot based 2nd stage bootloader
cmake	Cmake files of the build system
config	Configuration system files
docs	The documentation
interface	RoT service API for client calls
lib	The 3rd party libraries
platform	Platform intermedia files
secure_fw	The secure firmware
tools	Tools in scripts for building

platform

The platform folder contains SW ports of all supported platforms and the files necessary for adding a new platform. Please refer to platform folder document for more information.

Folder name	Description
include	HAL and platform public headers
ext	Platform ports and related files

platform/ext

This folder can include imported files licensed differently from TF-M’s BSD-3 license. More details are in the dedicated document Details for the platform/ext folder.

Folder name	Description
accelerator	Supported Crypto HW accelerators
cmsis	A copy of essential CMSIS headers
common	Common HAL implementation
driver	Driver headers for porting
target/<vendor>	Vendor specific folders with ported platforms

Each vendor is assigned one folder for usage under target/. A vendor contributes platform’s ports and manages the structure inside it.

secure_fw

This folder contains components needed by secure firmware and the exported interfaces for application, service development and HAL integration.

Folder name	Description
include	Public headers of secure_fw
partitions	Default services and SPRTL
spm	PSA FF-M SPM implementation
shared	Sources shared out of SPRTL

The shared sources can be referenced by the building system out of SPRTL. Generally, they are runtime and PSA APIs.

secure_fw/include

This folder holds public headers for external references by clients, services and platforms. Avoid putting private headers, not referenced by other modules in this include folder.

secure_fw/partitions

This folder contains default services implemented as partitions and runtime utilities used and provided by TF-M.

Folder name	Description
lib/runtime	The SPRTL sources and intermedia files
<partition_x>	Sources of partition_x
<partition_x>/include	RoT Service API headers of partition_x
<partition_y>	Sources of partition_y
<partition_y>/include	RoT Service API headers of partition_y

Here partition_x and partition_y are examples of RoT services without detailed structure of them.

secure_fw/spm

The SPM is the core component to provide a mechanism for providing secure services complied with PSA FF-M.

Folder name	Description
include	SPM public headers.
ffm	SPM logic complies with PSA FF-M specification
cmsis_psa	CMSIS implementation for PSA FF-M SPM