linker: section_tags: fix missing include

[Finomnis]

Fixes #76254.

Using section tags like __dtcm_noinit_section should resolve to:

__attribute__((section(".dtcm_noinit"), used))

However, due to a missing include, they resolve to:

__attribute__((section("_DTCM_NOINIT_SECTION_NAME"), used))

... failing to move the variable to the proper section and causing the following warning:

ld.bfd.exe: warning: orphan section `_DTCM_NOINIT_SECTION_NAME' from `app/libapp.a(main.c.obj)' being placed in section `_DTCM_NOINIT_SECTION_NAME'

[ycsin]

Is the build error reproducible with an upstream board & application?

[Finomnis]

Is the build error reproducible with an upstream board & application?

Sadly no. I thought this one would:

west build -b mimxrt1170_evk/mimxrt1176/cm7 zephyr/samples/boards/mimxrt1170_evk_cm7/magic_addr/

... but it seems that the header is in fact included there, through:

• #include <zephyr/kernel.h>
• #include <zephyr/kernel_includes.h>
• #include <zephyr/linker/sections.h>

If the official 'solution' is to include <zephyr/kernel.h> in user code, then we should at least add a compile time check for it somewhere. But IMO it would be better to force the include in linker_sections.h.

[ycsin]

<zephyr/linker/sections.h> includes section_tags.h at the bottom, but nothing suggests that section_tags.h is an internal/hidden header, in that sense this PR is a valid fix, since it is not including things that it required.

[Finomnis]

<zephyr/linker/sections.h> includes section_tags.h at the bottom, but nothing suggests that section_tags.h is an internal/hidden header, in that sense this PR is a valid fix, since it is not including things that it required.

If that is the case, then this change causes a circular header dependency :/

Would it be better to indicate that section_tags.h is an internal header and instead tell users to use sections.h instead?

Or remove section_tags.h from sections.h as well? Although that would be a breaking API change.

EDIT:
The more I think about it the more I am of the opinion that sections.h should not include section_tags.h. That's a dependency inversion; a thing should include its dependencies. But the current case is that the dependency includes its dependee.

[Finomnis]

@nashif @tomi-font Now that 3.7 is out, could this be added to 3.7.1?

[tomi-font]

Added the relevant backport tag. This PR should be picked up for merging at some point, I think.