Immutable bootloader + MCUBoot. External Flash. Update fails into bootloop.

RE: Immutable bootloader + MCUBoot. External Flash. Update fails into bootloop.

Carl Richard — Tue, 27 Apr 2021 14:03:28 GMT

Glad that you figured it out! While I'm not entirely sure of your intended behavior I suggest reading up on the Secure bootloader chain documentation which has some information about upgradable bootloaders. Including that you should enable the CONFIG_BUILD_S1_VARIANT Kconfig to a variant of the image for both slots, as upgrading the bootloader requires an image that is placed in a partition that's not in use.

Best regards,
Carl Richard

RE: Immutable bootloader + MCUBoot. Update fails into bootloop.

optical — Tue, 27 Apr 2021 13:16:52 GMT

I can confirm that the image indeed started to be swapped to correct location after i changed the direct memory access to flash_area_read.

RE: Immutable bootloader + MCUBoot. Update fails into bootloop.

optical — Tue, 27 Apr 2021 12:32:34 GMT

Is it possible that mcuboot nrf-noup commit does not take into account mcuboot_secondary inside external flash. I believe that the issue is in these lines inside mcuboot:

    const struct flash_area *secondary_fa =
        BOOT_IMG_AREA(state, BOOT_SECONDARY_SLOT);
    struct image_header *hdr = (struct image_header *)secondary_fa->fa_off;

These lines are using the fa_off set directly as pointer to image_header which is of course not there of the secondary_fa is located in external memory.

RE: Immutable bootloader + MCUBoot. Update fails into bootloop.

optical — Tue, 27 Apr 2021 12:13:56 GMT

My most worrying concern is that how is it possible to upload image inside the secondary partition which then corrupts the primary even when mcuboot does the revert operation making the device essentially bricked.

RE: Immutable bootloader + MCUBoot. Update fails into bootloop.

optical — Tue, 27 Apr 2021 11:06:10 GMT

I have added logging inside the mcuboot to show me where the application is beeing swapped. The s1 image is beeing swapped to the mcuboot_primary partition which corrupts the mcuboot_pad. Which then leads to mcuboot crasing with BUS FAULT.
Am i missing some KConfig option so the MCUBoot detects correctly the place where the S1 image should be swapped ?

RE: Immutable bootloader + MCUBoot. Update fails into bootloop.

optical — Tue, 27 Apr 2021 10:21:54 GMT

Note that the same behavior is present when the signed_by_mcuboot_and_b0_s1_image_update.bin image is uploaded directly using mcumgr img subsystem.
Which points to issue inside the MCUBoot swaping functionality it self not the dfu_target.