zephyr/cmake/linker/xt-ld/target.cmake
Torsten Rasmussen 2e3873adde cmake: improve Zephyr link phase
Zephyr is a bare metal build where standard libs are disabled.

This means that c and runtime libraries must manually be linked in.

This has generally been handled by using CMake's link libraries handling
but the issue with that is both de-duplication but also library link
order.

Standard libraries must be linked at last location to ensure symbols
are always available, however this is not optimal with
target_link_libraries() because this would ultimately require every
library to know the c library to link with, which is not desired.

Therefore, setup standard C and runtime library linking in linker
CMake files for toolchains where this is required.

This commit expands the principle introduced with toolchain abstraction,
see PR#24851.

This means that a toolchain implementation may specify standard C,
runtime, C++, etc libraries, as well as their link order.
Because a property approach is used, then Zephyr modules, such as the
Picolibc module can adjust such properties.

An optional `zephyr_linker_finalize()` macro is called at the end of
Zephyr's CMakeList process and can be used by the toolchain
implementation to define the final linker invocation.

This aligns the linker handling flow to the principle introduced in
PR#24851 and improves the flexibility and robustness of Zephyr build
system.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
2024-10-04 16:34:35 +01:00

163 lines
6.4 KiB
CMake

# SPDX-License-Identifier: Apache-2.0
set_property(TARGET linker PROPERTY devices_start_symbol "_device_list_start")
if(DEFINED TOOLCHAIN_HOME)
# When Toolchain home is defined, then we are cross-compiling, so only look
# for linker in that path, else we are using host tools.
set(LD_SEARCH_PATH PATHS ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
endif()
find_program(CMAKE_LINKER xt-ld ${LD_SEARCH_PATH})
set_ifndef(LINKERFLAGPREFIX -Wl)
if(CONFIG_CPP_EXCEPTIONS)
# When building with C++ Exceptions, it is important that crtbegin and crtend
# are linked at specific locations.
# The location is so important that we cannot let this be controlled by normal
# link libraries, instead we must control the link command specifically as
# part of toolchain.
set(CMAKE_CXX_LINK_EXECUTABLE
"<CMAKE_CXX_COMPILER> <FLAGS> <CMAKE_CXX_LINK_FLAGS> <LINK_FLAGS> ${LIBGCC_DIR}/crtbegin.o <OBJECTS> -o <TARGET> <LINK_LIBRARIES> ${LIBGCC_DIR}/crtend.o")
endif()
# Run $LINKER_SCRIPT file through the C preprocessor, producing ${linker_script_gen}
# NOTE: ${linker_script_gen} will be produced at build-time; not at configure-time
macro(configure_linker_script linker_script_gen linker_pass_define)
set(extra_dependencies ${ARGN})
if(CONFIG_CMAKE_LINKER_GENERATOR)
add_custom_command(
OUTPUT ${linker_script_gen}
COMMAND ${CMAKE_COMMAND}
-DPASS="${linker_pass_define}"
-DFORMAT="$<TARGET_PROPERTY:linker,FORMAT>"
-DENTRY="$<TARGET_PROPERTY:linker,ENTRY>"
-DMEMORY_REGIONS="$<TARGET_PROPERTY:linker,MEMORY_REGIONS>"
-DGROUPS="$<TARGET_PROPERTY:linker,GROUPS>"
-DSECTIONS="$<TARGET_PROPERTY:linker,SECTIONS>"
-DSECTION_SETTINGS="$<TARGET_PROPERTY:linker,SECTION_SETTINGS>"
-DSYMBOLS="$<TARGET_PROPERTY:linker,SYMBOLS>"
-DOUT_FILE=${CMAKE_CURRENT_BINARY_DIR}/${linker_script_gen}
-P ${ZEPHYR_BASE}/cmake/linker/ld/ld_script.cmake
)
else()
set(template_script_defines ${linker_pass_define})
list(TRANSFORM template_script_defines PREPEND "-D")
# Only Ninja and Makefile generators support DEPFILE.
if((CMAKE_GENERATOR STREQUAL "Ninja")
OR (CMAKE_GENERATOR MATCHES "Makefiles")
)
set(linker_script_dep DEPFILE ${PROJECT_BINARY_DIR}/${linker_script_gen}.dep)
else()
# TODO: How would the linker script dependencies work for non-linker
# script generators.
message(STATUS "Warning; this generator is not well supported. The
Linker script may not be regenerated when it should.")
set(linker_script_dep "")
endif()
zephyr_get_include_directories_for_lang(C current_includes)
add_custom_command(
OUTPUT ${linker_script_gen}
DEPENDS
${LINKER_SCRIPT}
${AUTOCONF_H}
${extra_dependencies}
# NB: 'linker_script_dep' will use a keyword that ends 'DEPENDS'
${linker_script_dep}
COMMAND ${CMAKE_C_COMPILER}
-x assembler-with-cpp
${NOSYSDEF_CFLAG}
-MD -MF ${linker_script_gen}.dep -MT ${linker_script_gen}
-D_LINKER
-D_ASMLANGUAGE
-D__GCC_LINKER_CMD__
-imacros ${AUTOCONF_H}
${current_includes}
${template_script_defines}
-E ${LINKER_SCRIPT}
-P # Prevent generation of debug `#line' directives.
-o ${linker_script_gen}
VERBATIM
WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
COMMAND_EXPAND_LISTS
)
endif()
endmacro()
# Force symbols to be entered in the output file as undefined symbols
function(toolchain_ld_force_undefined_symbols)
foreach(symbol ${ARGN})
zephyr_link_libraries(${LINKERFLAGPREFIX},-u,${symbol})
endforeach()
endfunction()
# Link a target to given libraries with toolchain-specific argument order
#
# Usage:
# toolchain_ld_link_elf(
# TARGET_ELF <target_elf>
# OUTPUT_MAP <output_map_file_of_target>
# LIBRARIES_PRE_SCRIPT [libraries_pre_script]
# LINKER_SCRIPT <linker_script>
# LIBRARIES_POST_SCRIPT [libraries_post_script]
# DEPENDENCIES [dependencies]
# )
function(toolchain_ld_link_elf)
cmake_parse_arguments(
TOOLCHAIN_LD_LINK_ELF # prefix of output variables
"" # list of names of the boolean arguments
"TARGET_ELF;OUTPUT_MAP;LINKER_SCRIPT" # list of names of scalar arguments
"LIBRARIES_PRE_SCRIPT;LIBRARIES_POST_SCRIPT;DEPENDENCIES" # list of names of list arguments
${ARGN} # input args to parse
)
target_link_libraries(
${TOOLCHAIN_LD_LINK_ELF_TARGET_ELF}
${TOOLCHAIN_LD_LINK_ELF_LIBRARIES_PRE_SCRIPT}
${use_linker}
${TOPT}
${TOOLCHAIN_LD_LINK_ELF_LINKER_SCRIPT}
${TOOLCHAIN_LD_LINK_ELF_LIBRARIES_POST_SCRIPT}
${LINKERFLAGPREFIX},-Map=${TOOLCHAIN_LD_LINK_ELF_OUTPUT_MAP}
${LINKERFLAGPREFIX},--whole-archive
${WHOLE_ARCHIVE_LIBS}
${LINKERFLAGPREFIX},--no-whole-archive
${NO_WHOLE_ARCHIVE_LIBS}
$<TARGET_OBJECTS:${OFFSETS_LIB}>
-L${PROJECT_BINARY_DIR}
${TOOLCHAIN_LIBS}
${TOOLCHAIN_LD_LINK_ELF_DEPENDENCIES}
)
endfunction(toolchain_ld_link_elf)
# Function for finalizing link setup after Zephyr configuration has completed.
#
# This function will generate the correct CMAKE_C_LINK_EXECUTABLE / CMAKE_CXX_LINK_EXECUTABLE
# rule to ensure that standard c and runtime libraries are correctly placed
# and the end of link invocation and doesn't appear in the middle of the link
# command invocation.
macro(toolchain_linker_finalize)
get_property(zephyr_std_libs TARGET linker PROPERTY lib_include_dir)
get_property(link_order TARGET linker PROPERTY link_order_library)
foreach(lib ${link_order})
get_property(link_flag TARGET linker PROPERTY ${lib}_library)
list(APPEND zephyr_std_libs "${link_flag}")
endforeach()
string(REPLACE ";" " " zephyr_std_libs "${zephyr_std_libs}")
set(common_link "<LINK_FLAGS> <OBJECTS> -o <TARGET> <LINK_LIBRARIES> ${zephyr_std_libs}")
set(CMAKE_ASM_LINK_EXECUTABLE "<CMAKE_ASM_COMPILER> <FLAGS> <CMAKE_ASM_LINK_FLAGS> ${common_link}")
set(CMAKE_C_LINK_EXECUTABLE "<CMAKE_C_COMPILER> <FLAGS> <CMAKE_C_LINK_FLAGS> ${common_link}")
set(CMAKE_CXX_LINK_EXECUTABLE "<CMAKE_CXX_COMPILER> <FLAGS> <CMAKE_CXX_LINK_FLAGS> ${common_link}")
endmacro()
# xt-ld is Xtensa's own version of binutils' ld.
# So we can reuse most of the ld configurations.
include(${ZEPHYR_BASE}/cmake/linker/ld/target_relocation.cmake)
include(${ZEPHYR_BASE}/cmake/linker/ld/target_configure.cmake)