MCUboot: warning: zephyr/zephyr_pre0.elf has a LOAD segment with RWX permissions

[Glenn Andrews]

Same problem as  nRF Connect SDK link error with GCC 12 , which was 3 years ago...

Our app builds fine until we enable MCUboot, when we get the above warning, and being good people we have CONFIG_COMPILER_WARNINGS_AS_ERRORS enabled, which means our application can't build.

For now I've added target_link_options(app PUBLIC "LINKER:--no-warn-rwx-segments") to my CMakeLists.txt, but this isn't exactly an optimal solution, especially given how long it took to find it, and I'll have to remember the fix for every other project going forward.

Is there a plan to fix the linker script so it doesn't generate the error?

[Vidar Berg]

Hello,

Thank you for reporting. I don’t recall seeing reports of this error before, and the issue discussed in the linked Q&A is for TF-M, which I think may be a bit different since it’s built as an external project in Zephyr. Could you please let me know which toolchain and toolchain version you’re using so I can try to reproduce the same here? Is it the NCS toolchain or one of the others listed here?: https://docs.nordicsemi.com/bundle/ncs-3.2.0-preview3/page/zephyr/develop/toolchains/index.html?

Best regards,

Vidar

[Glenn Andrews]

We're using gcc-arm-none-eabi 12.2-Rel1

Somewhere around GCC 12 they added this warning, before that it was ignored.

[Vidar Berg]

Thank you for confirming. I was able to reproduce the same now just by building "Hello World" without the bootloader. I will investigate further and check with the developers whether this may be a known issue. I was on GCC version 12.2.0 prior to this.

arm-zephyr-eabi-gcc --version
arm-zephyr-eabi-gcc (Zephyr SDK 0.17.0) 12.2.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 

[Vidar Berg]

I have asked around and it does not appear to be a known issue. Internally we are using GCC from the Zephyr SDK  which means we have limited or no test coverage with this toolchain. I also tried Zephyr SDK v1.0.0-beta1 which includes GCC 14.3.0 but that did not trigger in this warning either. Is using the Zephyr SDK with arm-zephyr-eabi-gcc an option for you? This is the recommended toolchain and it greatly reduces the build times when using picolib. 

It may also be worth adding that the MPU driver is configured to prevent execution from RAM by default.  

[Glenn Andrews]

I'll check with the Powers That Be.

[Glenn Andrews]

We found a workaround in the Zephyr source code:

in zephyr/include/zephyr/linker/iterable_sections.h:

#define ITERABLE_SECTION_ROM(struct_type, subalign) \
  SECTION_PROLOGUE(struct_type##_area, (READONLY),) \
  { \
    Z_LINK_ITERABLE(struct_type); \
  } GROUP_ROM_LINK_IN(RAMABLE_REGION, ROMABLE_REGION)

The difference is adding (READONLY) to the SECTION_PROLOGUE