Last edited 6 days ago

OP-TEE remoteproc framework overview

Applicable for STM32MP15x lines, STM32MP21x lines, STM32MP23x lines, STM32MP25x lines
Info white.png Trusted domain applicability
This article is not applicable to M33-TD flavor More info green.png of STM32MP2 series

1. Framework purpose[edit | edit source]

The OP-TEE remote processor (RPROC) framework allows different platforms/architectures to control (power on, load firmware, power off) remote processors in the secure context. In addition, it offers services to authenticate the firmware image and isolate the associated memories to ensure the integrity of the firmware running on the remote processor. See also the wiki article How to protect the Cortex-M coprocessor firmware.

2. System overview[edit | edit source]

Remoteproc overview.png

2.1. Component description[edit | edit source]

  • remoteproc trusted application (TA): The remote processor framework generic part. Its role is to provide an interface to the Linux remoteproc framework to:
    • Load and authenticate a firmware image in the remote processor memory.
    • Provide the resource table address.
    • Control the remote processor execution (start, stop, etc.).
  • remoteproc pseudo trusted application (PTA): This component is the STM32MPU platform implementation of the services associated with the management of the Cortex®-M remote processor. Its role is to provide atomic services to the remoteproc TA:
    • Load and authenticate the image segment in the remote processor memory.
    • Manage the memory regions isolation.
  • stm32_remoteproc driver: Configuration of the Cortex®-M remote processor and associated memory based on the OP-TEE device tree. Its role is to determine if the Cortex®-M firmware image is managed by:
    • The OP-TEE remoteproc framework (signed firmware images): In this configuration, the remoteproc driver lists the memory regions declared in the device tree for the Cortex®-M usage and manages the Cortex®-M configuration (reset, boot address, TrustZone®, etc.).
    • The Linux remoteproc framework (ELF firmware image): In this configuration, the remoteproc driver disables the TrustZone® and provides access rights to the Linux remoteproc framework, in the nonsecure context, to manage the Cortex®-M (reset and nonsecure boot address).
Info white.png Information
In the STM32MPU embedded software distribution, the OP-TEE remoteproc framework requires that the remoteproc firmware is signed to use the Cortex®-M TrustZone®.

2.2. API description[edit | edit source]

3. Configuration[edit | edit source]

3.1. Build configuration[edit | edit source]

  • CFG_DRIVERS_REMOTEPROC and CFG_STM32MP_REMOTEPROC enable support for the stm32_remoteproc drivers.
  • CFG_REMOTEPROC_PTA enables support for the remoteproc PTA and the remoteproc TA.
  • CFG_IN_TREE_EARLY_TAS += remoteproc/80a4c275-0a47-4905-8285-1486a9771a08 specifies that the remoteproc TA is embedded in the OP-TEE OS firmware and accessible during the boot stage (refer to How to start the Cortex-M coprocessor from U-Boot for details).
  • RPROC_SIGN_KEY specifies the key used for the firmware image signature (default key is keys/default.pem ).
  • CFG_REMOTEPROC_TA_HEAP_SIZE specifies the size of the HEAP used by the remoteproc TA (default is 4kBytes).

3.2. Device tree configuration[edit | edit source]

3.2.1. STM32MP15x lines More info.png[edit | edit source]

The memory-region property defines the RETRAM and MCU SRAM base addresses and sizes in RETRAM and MCU SRAMs reserved for the Cortex®-M firmware and for inter-processor communication.

The memory regions are defined at board level:

  • On the STM32MP157Fx-ED1 evaluation board: The memory-regions are declared and referenced in stm32mp157f-ed1.dts[1].
  • On the STM32MP157Fx-DK discovery board: The memory-regions are declared and referenced in stm32mp15xx-dkx.dtsi[2].

Device tree deltas between signed and non-signed firmware support:

Non-signed (ELF) firmware
image support		 Signed firmware
image support 
&m4_rproc {
	/* no remoteproc device management needed in OP-TEE */
	compatible = "st,stm32mp1-m4";
	status = "disabled";
};

&m4_rproc {
	compatible = "st,stm32mp1-m4-tee";
	status = "okay";
	/*
	 * Declare memories used to run the CM4 firmware and shared memory
	 * used for inter-processors communication (including the resource table)
	 */
	memory-region = <&retram>, <&mcusram1>, <&mcusram2>, <&mcusram3>;

	/* The resets are managed by the OP-TEE remoteproc driver */
	resets = <&rcc MCU_R>, <&rcc MCU_HOLD_BOOT_R>;
	reset-names = "mcu_rst", "hold_boot";
};
Info white.png Information
The firmware memory mapping must be set according to these values in the STM32Cube firmware linker script.

For additional details, refer to the wiki article STM32MP15 RAM mapping.

3.2.2. STM32MP25x lines More info.png[edit | edit source]

The memory-region property defines the DDR, RETRAM and/or MCU SRAMs base addresses and sizes reserved for the Cortex®-M secure firmware (TF-M) and nonsecure firmware (STM32Cube firmware), and reserved for inter-processor communication.

The memory regions are defined at board level:

  • On the STM32MP257x-EV1 evaluation board:
    • The memory-regions are declared in stm32mp257f-ev1-ca35tdcid-resmem.dtsi[3].
    • The memory-regions are referenced in the m33_rproc node in stm32mp257f-ev1.dts[4].
  • On the STM32MP257x-DK discovery board:
    • The memory-regions are declared in stm32mp257f-dk-ca35tdcid-resmem.dtsi[5].
    • The memory-regions are referenced in the m33_rproc node in stm32mp257f-dk.dts[6].

Device tree deltas between signed and non-signed firmware support:

Non-signed (ELF) firmware
image support		 Signed firmware
image support 
&m33_rproc {
	compatible = "st,stm32mp2-m33";
	status = "okay";
};

&m33_rproc {
	compatible = "st,stm32mp2-m33-tee";
	status = "okay";
	/*
	 * Declare memories used to run the CM33 firmware and shared memory
	 * used for inter-processors communication (including the resource table)
	 */
	memory-region = <&cm33_cube_fw>, <&cm33_cube_data>,
			<&ipc_shmem>, <&tfm_code>, <&tfm_data>,
			<&cm33_sram2>;
	/* The resets are managed by the OP-TEE remoteproc driver */
	resets = <&rcc C2_R>, <&rcc C2_HOLDBOOT_R>;
	reset-names = "mcu_rst", "hold_boot";
};
Info white.png Information
The firmware memory mapping must be set according to these values in the:

For additional details, refer to the wiki article STM32MP2_memory_mapping

4. How to use the framework[edit | edit source]

Refer to the wiki article How to protect the Cortex-M coprocessor firmware.

5. How to debug[edit | edit source]

Refer to the wiki article How to debug OP-TEE.

6. Source code location[edit | edit source]

7. References[edit | edit source]

  1. ↑ STM32MP157Fx ED1 board device tree file
  2. ↑ STM32MP157Fx DK board device tree file
  3. ↑ STM32MP257F EV1 board reserved memory device tree configuration file
  4. ↑ STM32MP257F EV1 board device tree configuration file
  5. ↑ STM32MP257F DK board reserved memory device tree configuration file
  6. ↑ STM32MP257F DK board device tree configuration file


Arm® Cortex®-M33 trusted domain

Open portable trusted execution environment

Trusted application

Pseudo trusted application

Cortex®

TrustZone®
Arm® and TrustZone® are registered trademarks of Arm Limited (or its subsidiaries) in the US and/or elsewhere.

Linux® is a registered trademark of Linus Torvalds.

Executable and linkable file

Application programming interface

Operating system

Microcontroller unit (MCUs have internal flash memory and are intended to operate with a minimum amount of external support ICs. They commonly are a self-contained, system-on-chip (SoC) designs.)

Doubledata rate (memory domain)

Trusted firmware for Arm® Cortex®-M (see TF-M) - NEW

Resource isolation framework

Arm® Cortex®-M33 trusted domain

Open portable trusted execution environment

Trusted application

Pseudo trusted application

Cortex®

TrustZone®
Arm® and TrustZone® are registered trademarks of Arm Limited (or its subsidiaries) in the US and/or elsewhere.

Linux® is a registered trademark of Linus Torvalds.

Executable and linkable file

Application programming interface

Operating system

Microcontroller unit (MCUs have internal flash memory and are intended to operate with a minimum amount of external support ICs. They commonly are a self-contained, system-on-chip (SoC) designs.)

Doubledata rate (memory domain)

Trusted firmware for Arm® Cortex®-M (see TF-M) - NEW

Resource isolation framework

Arm® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere. Arm logo.png

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