Immutable bootloader minimal config does not fit

[maximevince]

I noticed the minimal b0 immutable bootloader build does not fit anymore.

I used the example here: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/bootloader/README.html

And the same one is here, btw: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/ug_bootloader.html

Firstly, overlay-minimal-size.conf does not seem to exist anymore, but it looks like it's called "prj_minimal.config" now.

When adjusting the example command to this:

west build -b nrf52840dk_nrf52840 zephyr/samples/hello_world -- -DCONFIG_SECURE_BOOT=y -Db0_OVERLAY_CONFIG=prj_minimal.conf

instead of:

west build -b nrf52840dk_nrf52840 zephyr/samples/hello_world -- -DCONFIG_SECURE_BOOT=y -Db0_OVERLAY_CONFIG=overlay-minimal-size.conf

This results in a b0 bootloader too big for the 12kB partition size:

/home/vinz/gnuarmemb/gcc-arm-none-eabi-10-2020-q4-major/bin/../lib/gcc/arm-none-eabi/10.2.1/../../../../arm-none-eabi/bin/ld: zephyr/zephyr_prebuilt.elf section `text' will not fit in region `FLASH'
/home/vinz/gnuarmemb/gcc-arm-none-eabi-10-2020-q4-major/bin/../lib/gcc/arm-none-eabi/10.2.1/../../../../arm-none-eabi/bin/ld: region `FLASH' overflowed by 2340 bytes
Memory region Used Size Region Size %age Used
FLASH: 14628 B 12 KB 119.04%
SRAM: 38560 B 256 KB 14.71%
IDT_LIST: 8 B 2 KB 0.39%
collect2: error: ld returned 1 exit status

I suspect that "prj_minimal.conf" is not meant as an overlay, and the original "overlay-minimal-size.conf" has disappeared.

What does work, however, is to go to the nrf/samples/bootloader directory,
and build it explicitly using "prj_minimal.conf", like this:

west build -p=always -b nrf52840dk_nrf52840 -- -DCONF_FILE=prj_minimal.conf

Can this be fixed? Or at least the documentation?

Thanks!

[Simon]

There seems to be some problems regarding the secure bootloader and the nrf52840 particurlarly, check out this commit: https://github.com/nrfconnect/sdk-nrf/commit/2c2d619e69ceeb5db52606df12215c5fcd48993f

I was able to bulid using this command however: west build -b nrf52840dk_nrf52840 zephyr/samples/hello_world -- -DCONFIG_SECURE_BOOT=y 

Best regards,

Simon

[maximevince]

Thanks,

That shrinks the bootloader using prj.conf a bit indeed, but when using prj_minimal.conf, (which my question is about)
the partition size is not 0x7000 at all, but 12kB (0x3000), since it sets CONFIG_B0_MIN_PARTITION_SIZE=y.
Also, CONFIG_TIMEOUT_64BIT=n is already configured that way when using prj_minimal.conf.

[Simon]

I've forwarded this internally. I'll keep you updated.

If CONFIG_B0_MIN_PARTITION_SIZE is set to 'n' in nrf/samples/bootloader/prj_minimal.conf the sample builds with the following command:

west build -b nrf52840dk_nrf52840 zephyr/samples/hello_world --  DCONFIG_SECURE_BOOT=y -Db0_CONF_FILE=prj_minimal.conf

If I set CONFIG_B0_MIN_PARTITION_SIZE back to 'y', the sample fails with the above command.

Best regards,

Simon

[maximevince]

Thanks, that is exactly the issue.

[Simon]

I got told that the solution was to give b0 more space. Hopefully a fix will get merged into NCS master soon.

[maximevince]

yes, that's what I did over here. But I though it would be nice if the example compiled as expected, which is why I reported the issue.