nRF53 Custom b0n Build

[AntonD]

I am trying to compile a custom bootloader for nRF5340 net core (b0n) that is part of a multi-image build.

I have created two separate applications, one based on b0n (nrf/samples/nrf5340/netboot) and one based on nrf/samples/bluetooth/peripheral_lbs. These both build without issue when used as single image applications and I can debug them (using hello_world on the app core) and they appear to work.

I have tried adding the b0n as a child image of the application by adding the following code to CMakeLists.txt

if (CONFIG_SECURE_BOOT)
  add_child_image(
    NAME b0n
    SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/../boot_stage1
  )
endif()

If I then build the net app, the application builds, but b0n is neither built nor linked.

I have tried adding CONFIG_SECURE_BOOT=y to the prj.conf file. If I have the above CMakeLists.txt change, I get the following compilation error:

=== child image b0n -  begin ===

loading initial cache file C:/Users/anton/src/bootloader-test/netapp/build/b0n/child_image_preload.cmake

CMake Error: The source "C:/Users/anton/src/bootloader-test/boot_stage1/CMakeLists.txt" does not match the source "C:/Users/anton/ncs/v1.9.1/nrf/samples/nrf5340/netboot/CMakeLists.txt" used to generate cache.  Re-run cmake with a different source directory.

CMake Error at C:\Users\anton\ncs\v1.9.1\nrf\cmake\multi_image.cmake:409 (message):

  CMake generation for b0n failed, aborting.  Command: 1

Call Stack (most recent call first):

  C:\Users\anton\ncs\v1.9.1\nrf\cmake\multi_image.cmake:150 (add_child_image_from_source)

  c:\Users\anton\src\bootloader-test\netapp\build\CMakeLists.txt:21 (add_child_image)

This confuses me in the following ways

• I don't know why the netboot sample should be used to generate the cache.
• The CMakeLists.txt are identical in both the sample and in my local build.
• I don't know why they need to match anyway.

What is going wrong here?

p.s. Most of the documnetation about multi-image bootloader builds suggest using CONFIG_B0_BUILD_STRATEGY_FROM_SOURCE=y. There doesn't appear to be an equivalent CONFIG_B0N_BUILD_STRATEGY_FROM_SOURCE.

[Sigurd Hellesvik]

Hi Anton

Since b0n and b0 is easily mixed, I will from now on refer to them as follows:

Network core bootloader: b0n

Application core nRF Secure Immutable Bootloader: NSIB

AntonD said:

I assume when you say that you are building a custom b0n for the cpuapp you mean that you are building a custom b0 for the cpuapp.

Your assumption is wrong. I am talking about custom b0n.

AntonD said:

So for some reason the partition manager script must not be running and must not be generating the "pm_config.h" header, or it is not in the correct include path. How do I rectify that?

I think that the reason it does not work for you is that the "application design"  we intent to be used for child images is different from the one you use.

I suggest that you take a step back and look at the overall design.
Am you making two different projects: One for the APP core and one for the NET core?

Or are you making one project for the whole nRF5340, like this?

The second solution is the one I described in my previous post, and the one recommended for nRF5340.

Regards,
Sigurd Hellesvik

[AntonD]

I have no problem creating the minimal example you talk about based on hello_world with unmodified b0 and b0n. The real problem is that I need to have custom bootloaders on both cores. I am not fussed about which of the two above architectures make more sense. However, they will need to be custom bootloaders, and that is where the problems come in.

The issues I have in the original email occur whether it is b0n on the cpunet or b0 on the cpuapp. I have tracked the problem to the block starting at "v1.9.1/nrf/samples/CMakeLists.txt:57" that is included in both the net core app and the app core app. If you enable "CONFIG_SECURE_BOOT" then this file will automatically include b0 or b0n into the application. If I add a custom b0 or b0n using the instructions here https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/ug_multi_image.html then it includes b0/b0n twice. This is why I get the error message above (the CMakeCache.txt is created once by the nrf samples b0/b0n code and once by my b0/b0n code ... and it gets quite confused). I have attempted to fix this by (temporarily) modifying the above CMakeLists.txt in the samples folder to not include b0 or b0n when CONFIG_B0_BUILD_STRATEGY_FROM_SOURCE is enabled. This returns me to the infamous "pm_config.h" not found error.

Following the above link, I have tried to add a custom netcore app too. I have created one using the hello_world example and as advised I have added the following line to the CMakeLists.txt of the appcore app:

add_child_image(
  NAME netapp
  SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/netapp
  DOMAIN CPUNET
  )

where "netapp" was the name and subdirectory of the hello_world application code for the cpunet core.

No board specified for domain 'CPUNET'. This configuration is typically defined in C:/Users/anton/ncs/v1.9.1/zephyr/boards/arm/nrf5340dk_nrf5340/Kconfig

So, to get back to the original question, how do I set up a build that has a custom b0 and a custom b0n?

I will need both. Minimal examples are fine.

[Sigurd Hellesvik]

Hi

nRF Connect SDK v1.9.1. nRF5340DK.

Here is a sample showcasing how to use custom NSIB and b0n with a hello world sample. The files I have added or changed will be listed below:

ncs/nrf/samples/CmakeLists.txt:

Fullscreen 8547.CMakeLists.txt Download

#
# Copyright (c) 2019 Nordic Semiconductor ASA
#
# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
#

if (CONFIG_SPM)
  get_cmake_property(VARIABLES              VARIABLES)
  get_cmake_property(VARIABLES_CACHED CACHE_VARIABLES)

  set(regex "^CONFIG_SPM_SERVICE.+")

  list(FILTER VARIABLES        INCLUDE REGEX ${regex})
  list(FILTER VARIABLES_CACHED INCLUDE REGEX ${regex})

  foreach(var_name ${VARIABLES} ${VARIABLES_CACHED})
    set(spm_${var_name} ${${var_name}})
  endforeach()

  set(spm_CONFIG_SPM_SECURE_SERVICES ${CONFIG_SPM_SECURE_SERVICES})

  if (CONFIG_SPM_SERVICE_NS_HANDLER_FROM_SPM_FAULT)
      add_overlay_config(
        spm
        ${NRF_DIR}/samples/spm/spm_ns_handler_from_spm_fault.conf
        )

      add_overlay_dts(
        mcuboot
        ${NRF_DIR}/samples/spm/spm_uart.overlay
      )
  endif()

  if (CONFIG_BOARD_ENABLE_CPUNET)
      add_overlay_config(
        spm
        ${NRF_DIR}/samples/spm/spm_enable_cpunet.conf
        )
  endif()

  add_child_image(
    NAME spm
    SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/spm
    )

  if (CONFIG_ARM_FIRMWARE_USES_SECURE_ENTRY_FUNCS AND
      NOT CONFIG_SPM_BUILD_STRATEGY_FROM_SOURCE AND
      NOT EXISTS ${CONFIG_ARM_ENTRY_VENEERS_LIB_NAME})
    message(WARNING "NOTE: SPM is not built from source, and the firmware use secure "
      "entry functions. However, the configured library file is not found.
      Ensure that the configuration 'ARM_ENTRY_VENEERS_LIB_NAME'
      points to the .a file (default 'spm/libspmsecureentries.a')
      generated alongside the flashed or merged SPM hex file")
  endif()
endif()

if (CONFIG_SECURE_BOOT)
  if (CONFIG_SOC_NRF5340_CPUNET)
    # Share some information which is used when generating the zip file
    # with the update binaries.
    set_shared(IMAGE net_core PROPERTY SOC ${CONFIG_SOC})
    set_shared(IMAGE net_core PROPERTY VERSION ${CONFIG_FW_INFO_FIRMWARE_VERSION})
    add_child_image(
      NAME b0n
      SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/custom_b0n
      )
  else()
    add_child_image(
      NAME b0
      SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/custom_nsib
      )
  endif()
  if (CONFIG_SOC_NRF5340_CPUAPP AND CONFIG_BOOTLOADER_MCUBOOT)
      add_overlay_config(
        mcuboot
        ${NRF_DIR}/subsys/bootloader/image/log_minimal.conf
        )
  endif()
  if (CONFIG_BUILD_S1_VARIANT AND "${CONFIG_S1_VARIANT_IMAGE_NAME}" STREQUAL "app")
    add_child_image(
      NAME s1_image
      PRELOAD_IMAGE app
      )
  endif()
endif()

if (CONFIG_NCS_SAMPLE_EMPTY_APP_CORE_CHILD_IMAGE)
  add_child_image(
    NAME "empty_app_core"
    SOURCE_DIR "${NRF_DIR}/samples/nrf5340/empty_app_core"
    DOMAIN "CPUAPP"
    BOARD ${CONFIG_DOMAIN_CPUAPP_BOARD}
    )
endif()

if (CONFIG_NCS_INCLUDE_RPMSG_CHILD_IMAGE)

  if (CONFIG_NCS_SAMPLE_MULTIPROTOCOL_RPMSG_CHILD_IMAGE)
    set(CHILD_IMAGE_NAME "multiprotocol_rpmsg")
    set(CHILD_IMAGE_PATH "${NRF_DIR}/samples/nrf5340/multiprotocol_rpmsg")

  elseif (CONFIG_NCS_SAMPLE_HCI_RPMSG_CHILD_IMAGE)
    set(CHILD_IMAGE_NAME "hci_rpmsg")
    set(CHILD_IMAGE_PATH "${ZEPHYR_BASE}/samples/bluetooth/hci_rpmsg")

  elseif (CONFIG_NCS_SAMPLE_802154_RPMSG_CHILD_IMAGE)
    set(CHILD_IMAGE_NAME "802154_rpmsg")
    set(CHILD_IMAGE_PATH "${ZEPHYR_BASE}/samples/boards/nrf/ieee802154/802154_rpmsg")

  elseif (CONFIG_NCS_SAMPLE_RPC_HOST_CHILD_IMAGE)
    set(CHILD_IMAGE_NAME "rpc_host")
    set(CHILD_IMAGE_PATH "${NRF_DIR}/samples/bluetooth/rpc_host")

  else()
    # If we get here, something is wrong with the Kconfig resolution
    message(WARNING "CONFIG_NCS_INCLUDE_RPMSG_CHILD_IMAGE is set but "
      "couldn't resolve which RPMsg sample to add.")
  endif()

  # Only include a child image if both image name and path have been defined.
  # Prevents e.g. menuconfig from becoming inaccessible, among others.
  if(CHILD_IMAGE_NAME AND CHILD_IMAGE_PATH)

    if (CONFIG_NRF53_UPGRADE_NETWORK_CORE)
      # Inject this configuration from parent image to enable
      # secure bootloader on the network core. This enables firmware update
      # of the network core application.
      add_overlay_config(
        ${CHILD_IMAGE_NAME}
        "${NRF_DIR}/subsys/bootloader/image/secure_boot.conf"
      )

      # Inject this configuration from parent image mcuboot to enable
      # the PCD subsystem which is used to communicate the firmware update
      # to the network core bootloader.
      add_overlay_config(
        mcuboot
        "${NRF_DIR}/subsys/pcd/pcd.conf"
      )
    endif()

    add_child_image(
      NAME ${CHILD_IMAGE_NAME}
      SOURCE_DIR ${CHILD_IMAGE_PATH}
      DOMAIN "CPUNET"
      BOARD ${CONFIG_DOMAIN_CPUNET_BOARD}
      )
  endif()

endif()

Any location: hello_world:
2275.hello_world.zip

ncs/nrf/samples/custom_nsib:

custom_nsib.zip

ncs/nrf/samples/custom_b0n:

custom_b0n.zip

custom_nsib is a slightly changed copy of nrf/samples/bootloader and custom_b0n is a slightly changed sample of nrf/samples/nrf5340/netboot.
They both have a print function added to the top of main to verify the change.

Build this hello_world as such:

west build -b nrf5340dk_nrf5340_cpuapp

Is this what you needed?

Regards,
Sigurd Hellesvik

[AntonD]

No. This is not what I am looking for. Modifying the SDK in this way is a bad idea for several reasons but most notably:

• This will break any other project I am working on using the SDK supplanting the standard bootloader with a custom one.
• If I need to change SDK version it will revert any changes and if this file changes significantly may mean that I cannot replicate this behaviour.
• The source code for the bootloaders ends up in the SDK instead of a logical place for development/version control etc.

Also, this doesn't really answer the network core app problem.

[Sigurd Hellesvik]

Hi

Yea, I agree that it is far from ideal to make changes to the SDK.
I asked our developers about this, and here is my question and what they had to say:

"I want to make changes to the b0n child image for my application. So I copy nrf/samples/nrf5340/netboot to somewhere else(ex ~/custom_netboot).
How to I tell my application(ex. hello_world) to include custom_netboot instead of netboot? How to do this without making changes to the SDK?"

" You need to add new kconfig for selecting custom_netboot and then add some cmake code (typically in a ZEPHYR_EXTRA_MODULE which performs the conditional add_child_image. See the example: https://github.com/oivoii/rpmsg-simple-nrf5340/pull/2/files "

I will try this myself as well. Then I will have a look at your network core app problem after.

Regards,
Sigurd Hellesvik