add custom linker script (ARMmbed#103)

* add custom linker script
a custom linker script can be applied by adding the .ld filepath
as 2nd argument to mbed_set_post_build

* more detailed comment

* add if is_standalone for text cases

* replace COMMENT in add_custom_command by echo
COMMENT is not reliable printed

tools/cmake/mbed_set_linker_script.cmake

@@ -56,6 +56,8 @@ function(mbed_setup_linker_script mbed_os_target mbed_baremetal_target target_de
  OUTPUT
  ${LINKER_SCRIPT_PATH}
  PRE_LINK
+ COMMAND 
+ ${CMAKE_COMMAND} -E echo "Preprocess linker script: ${RAW_LINKER_SCRIPT_NAME} -> ${LINKER_SCRIPT_NAME}"
  COMMAND
  ${CMAKE_C_COMPILER} @${linker_defs_response_file}
  -E -x assembler-with-cpp
@@ -68,23 +70,80 @@ function(mbed_setup_linker_script mbed_os_target mbed_baremetal_target target_de
  ${target_defines_header}
  WORKING_DIRECTORY
  ${CMAKE_CURRENT_SOURCE_DIR}
- COMMENT
- "Preprocess linker script: ${RAW_LINKER_SCRIPT_NAME} -> ${LINKER_SCRIPT_NAME}"
  VERBATIM
  )
 
+
  # The job to create the linker script gets attached to the mbed-linker-script target,
  # which is then added as a dependency of the MCU target. This ensures the linker script will exist
  # by the time we need it.
  add_custom_target(mbed-linker-script DEPENDS ${LINKER_SCRIPT_PATH} VERBATIM)
  foreach(TARGET ${mbed_baremetal_target} ${mbed_os_target})
  add_dependencies(${TARGET} mbed-linker-script)
 
- # Add linker flags to the MCU target to pick up the preprocessed linker script
- target_link_options(${TARGET}
+ # When building the Mbed internal tests, the tests get created before the mbed-os target does. So, the normal logic 
+ # in mbed_set_post_build() to set the linker script does not work. So, we need to instead attach the linker script to 
+ # the mbed-os and mbed-baremetal libraries themselves, so it will get picked up automatically.
+ # This prevents a custom linker script from being used in STANDALONE mode, but we don't need to do that.
+ set_target_properties(${TARGET} PROPERTIES LINKER_SCRIPT_PATH ${LINKER_SCRIPT_PATH})
+
+ # add linker script only for tests
+ if(MBED_IS_STANDALONE)
+ target_link_options(${TARGET}
  INTERFACE
  "-T" "${LINKER_SCRIPT_PATH}"
- )
+ )
+ endif()
  endforeach()
 
 endfunction(mbed_setup_linker_script)
+
+
+#
+# Change the linker script to a custom supplied script instead of the built in.
+# this function is called by mbed_set_post_build(target linker_script)
+#
+# target: CMake target for Mbed OS
+# new_linker_script_path: raw linker script
+#
+function(mbed_set_custom_linker_script target new_linker_script_path)
+
+ set(RAW_LINKER_SCRIPT_PATHS ${CMAKE_CURRENT_SOURCE_DIR}/${new_linker_script_path})
+ set(CUSTOM_LINKER_SCRIPT_PATH ${CMAKE_CURRENT_BINARY_DIR}/${target}.link_spript.ld)
+
+ # To avoid path limits on Windows, we create a "response file" and set the path to it as a
+ # global property. We need this solely to pass the compile definitions to GCC's preprocessor,
+ # so it can expand any macro definitions in the linker script.
+ get_property(linker_defs_response_file GLOBAL PROPERTY COMPILE_DEFS_RESPONSE_FILE)
+
+ get_filename_component(RAW_LINKER_SCRIPT_NAME ${RAW_LINKER_SCRIPT_PATHS} NAME)
+ get_filename_component(LINKER_SCRIPT_NAME ${CUSTOM_LINKER_SCRIPT_PATH} NAME)
+
+ add_custom_command(
+ TARGET
+ ${target}
+ PRE_LINK
+ COMMAND 
+ ${CMAKE_COMMAND} -E echo "Preprocess custom linker script: ${RAW_LINKER_SCRIPT_NAME} -> ${LINKER_SCRIPT_NAME}"
+ COMMAND
+ ${CMAKE_C_COMPILER} @${linker_defs_response_file}
+ -E -x assembler-with-cpp
+ -include ${CMAKE_BINARY_DIR}/mbed-os/mbed-target-config.h
+ -P ${RAW_LINKER_SCRIPT_PATHS}
+ -o ${CUSTOM_LINKER_SCRIPT_PATH}
+ DEPENDS
+ ${RAW_LINKER_SCRIPT_PATHS}
+ ${linker_defs_response_file}
+ ${target_defines_header}
+ WORKING_DIRECTORY
+ ${CMAKE_CURRENT_SOURCE_DIR}
+ VERBATIM
+ )
+
+ # Add linker flags to the target to pick up the preprocessed linker script
+ target_link_options(${target}
+ PRIVATE
+ "-T" "${CUSTOM_LINKER_SCRIPT_PATH}"
+ )
+
+endfunction(mbed_set_custom_linker_script)

tools/cmake/mbed_target_functions.cmake

@@ -126,7 +126,32 @@ endfunction()
 #
 # Set post build operations
 #
+# target: the affected target
+# 2nd arg: optional, linker script path 
+#
 function(mbed_set_post_build target)
+ # add linker script. Skip for greentea test code, there the linker script is set in mbed_setup_linker_script()
+ if (NOT MBED_IS_STANDALONE)
+ if("${ARGN}" STREQUAL "")
+ if(TARGET mbed-os)
+ get_target_property(LINKER_SCRIPT_PATH mbed-os LINKER_SCRIPT_PATH)
+ target_link_options(${target}
+ PRIVATE
+ "-T" "${LINKER_SCRIPT_PATH}"
+ )
+ elseif(TARGET mbed-baremetal)
+ get_target_property(LINKER_SCRIPT_PATH mbed-baremetal LINKER_SCRIPT_PATH)
+ target_link_options(${target}
+ PRIVATE
+ "-T" "${LINKER_SCRIPT_PATH}"
+ )
+ endif()
+ else()
+ message(STATUS "${target} uses custom linker script ${ARGV2}")
+ mbed_set_custom_linker_script(${target} ${ARGV2})
+ endif()
+ endif()
+
  # The mapfile name includes the top-level target name and the
  # executable suffix for all toolchains as CMake hardcodes the name of the
  # diagnostic output file for some toolchains.