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llext: add support for building relocatable ELF files

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This commit adds support for building relocatable (partially linked)
ELF files as the binary object type for the llext subsystem.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>
This commit is contained in:
Luca Burelli 2024-04-09 10:36:00 +02:00 • committed by Maureen Helm
commit e24295f0f5
2 changed files with 43 additions and 0 deletions
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35
cmake/modules/extensions.cmake
View file

@ -5318,6 +5318,26 @@ function(add_llext_target target_name)
add_library(${llext_lib_target} OBJECT ${source_files})
set(llext_lib_output $<TARGET_OBJECTS:${llext_lib_target}>)
elseif(CONFIG_LLEXT_TYPE_ELF_RELOCATABLE)
# CMake does not directly support a "RELOCATABLE" library target.
# The "SHARED" target would be similar, but that unavoidably adds
# a "-shared" flag to the linker command line which does firmly
# conflict with "-r".
# A workaround is to use an executable target and make the linker
# output a relocatable file. The output file suffix is changed so
# the result looks like the object file it actually is.
add_executable(${llext_lib_target} EXCLUDE_FROM_ALL ${source_files})
target_link_options(${llext_lib_target} PRIVATE -r)
set_target_properties(${llext_lib_target} PROPERTIES
SUFFIX ${CMAKE_C_OUTPUT_EXTENSION})
set(llext_lib_output $<TARGET_FILE:${llext_lib_target}>)
# Add the llext flags to the linking step as well
target_link_options(${llext_lib_target} PRIVATE
${LLEXT_APPEND_FLAGS}
)
elseif(CONFIG_LLEXT_TYPE_ELF_SHAREDLIB)
# Create a shared library
@ -5380,6 +5400,21 @@ function(add_llext_target target_name)
DEPENDS ${llext_proc_target} ${llext_pkg_input}
)
elseif(CONFIG_LLEXT_TYPE_ELF_RELOCATABLE)
# Need to remove just some sections from the relocatable object
# (using strip in this case would remove _all_ symbols)
add_custom_command(
OUTPUT ${llext_pkg_output}
COMMAND $<TARGET_PROPERTY:bintools,elfconvert_command>
$<TARGET_PROPERTY:bintools,elfconvert_flag>
$<TARGET_PROPERTY:bintools,elfconvert_flag_section_remove>.xt.*
$<TARGET_PROPERTY:bintools,elfconvert_flag_infile>${llext_pkg_input}
$<TARGET_PROPERTY:bintools,elfconvert_flag_outfile>${llext_pkg_output}
$<TARGET_PROPERTY:bintools,elfconvert_flag_final>
DEPENDS ${llext_proc_target} ${llext_pkg_input}
)
elseif(CONFIG_LLEXT_TYPE_ELF_SHAREDLIB)
# Need to strip the shared library of some sections

8
subsys/llext/Kconfig
View file

@ -23,6 +23,14 @@ config LLEXT_TYPE_ELF_OBJECT
llext subsystem. A single compiler invocation is used to
generate the object file.
config LLEXT_TYPE_ELF_RELOCATABLE
bool "Relocatable ELF file"
help
Build and expect relocatable (partially linked )files as the
binary object type for the llext subsystem. These object files
are generated by the linker by combining multiple object files
into a single one.
config LLEXT_TYPE_ELF_SHAREDLIB
bool "Shared library ELF file"
help