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linker: Include libkernel.a in the whole-archive when llext is enabled

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Differently from other libraries, which are included whole in the final
Zephyr ELF, libkernel.a itself isn't. Assuming this is intended to
enable optimisations (if it isn't, this patch will break things) - linker
can remove parts of the kernel that are not used by the application.

However, when considering Linkable Loadable Extensions (llext), this
optimisations can be counterproductive: for instance, syscalls that are
not used by the application won't be available for extensions. It won't
matter if someone "EXPORT_SYMBOL" for them, or even try to keep them
using LINKER_KEEP, they'll be gone.

To avoid that, this patches includes, when CONFIG_LLEXT=y, libkernel.a
inside the linker "whole-archive" block. This ends up making it consider
libkernel.a as a library whose all symbols should be kept. Note this
doesn't mean that all symbols will be there - things compiled out via
Kconfig will naturally still be out.

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>
This commit is contained in:
Ederson de Souza 2024-03-21 15:50:13 -07:00 • committed by Anas Nashif
commit 321e395a8f
6 changed files with 16 additions and 9 deletions
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7
CMakeLists.txt
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@ -876,6 +876,13 @@ foreach(zephyr_lib ${ZEPHYR_LIBS_PROPERTY})
add_dependencies(${zephyr_lib} zephyr_generated_headers)
endforeach()
if(CONFIG_LLEXT)
set(WHOLE_ARCHIVE_LIBS ${ZEPHYR_LIBS_PROPERTY} kernel)
else()
set(WHOLE_ARCHIVE_LIBS ${ZEPHYR_LIBS_PROPERTY})
set(NO_WHOLE_ARCHIVE_LIBS kernel)
endif()
get_property(OUTPUT_FORMAT GLOBAL PROPERTY PROPERTY_OUTPUT_FORMAT)
if (CONFIG_CODE_DATA_RELOCATION)