undefined reference to 'end' with nRF Connect SDK v2.4.0

[ske]

Hello,

Earlier, we developed a library using nordic sdk v2.3.0 on nRF5340 TF-M secure environment. Now we planned to switch from nordic sdk v2.3.0 to v2.4.0.

While trying to compile our source code using nordic sdk v2.4.0, we observed the linker error (undefined reference to end) while calling the malloc() api but this error is not observed in nordic sdk v2.3.0.

Linker error:
c:/nordic/toolchains/31f4403e35/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.exe: c:/nordic/toolchains/31f4403e35/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/lib/thumb/v8-m.main/nofp\libnosys.a(sbrk.o): in function `_sbrk':
sbrk.c:(.text._sbrk+0x1c): undefined reference to `end'
collect2.exe: error: ld returned 1 exit status

We could able to reproduce the same error with sample program (tfm_secure_peripheral). Here, we attached the compilation log and below is the code snippet for your reference. What are the changes we need to consider while compare between nordic sdk v2.4.0 and v2.3.0? Could you please point out if we missed anything? 

NOTE:
I observed the below CMake warning especially with nordic sdk v2.4.0.

CMake Warning at C:/nordic/v2.4.0/zephyr/CMakeLists.txt:838 (message):
No SOURCES given to Zephyr library: lib__libc__common

Excluding target from build.

[Øivind]

Hi,

Could you try to add CONFIG_MINIMAL_LIBC=y to prj.conf? If that doesn't work, can you try with CONFIG_NEWLIB_LIBC=y instead?

[ske]

Hello,

As you mentioned, we added the CONFIG_MINIMAL_LIBC=y in prj.conf and observed the same linker error. Then, we tried with CONFIG_NEWLIB_LIBC=y. This also providing the same linker error.

Could you please tell if any configuration needs to be enabled along with this?

[Øivind]

I looked a bit more into it, and in order to use malloc heap must be enabled, and it is by default disabled in TF-M. In TF-M the heap is hardcoded to a small size of 0x200 and is only meant for debug builds.

CONFIG_DEBUG=y enables the heap and will likely remove the error, but I suggest managing the memory in some other way instead.

[ske]

Hello,

We enabled the CONFIG_DEBUG=y in prj.conf and linker error is resolved with nRF connect sdk v2.4.0.

We surprised with this and want to understand about this dynamic memory allocation support removed in nRF Connect SDK v2.4.0. Could you tell the reason behind ?

In our library, we have some requirements to use dynamic memory allocation instead of static allocation where will get the dynamic data in TF-M secure environment. Do you have any reference or any other way on this?