kconfig: cmake: CMake linker script generator symbol added

A "Linker script" choice group has been added to the linker options
menu.

The existing HAVE_CUSTOM_LINKER_SCRIPT config has been relocated inside
the linker script menu.

Two new entries has been created:
- LD template, for using the old ld template files together with the C
  pre-processor to create the final linker script.
- CMake linker generator, used for ARMClang / armlink toolchain.
  The CMake linker generator is also supported for LD linker scripts
  for the ARM architecture.

In CMake, the file cmake/linker/ld/target.cmake has been updated to
support the CMake LD linker generator.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>

Kconfig.zephyr

@@ -132,8 +132,36 @@ config ROM_START_OFFSET
 	  alignment requirements on most ARM targets, although some targets
 	  may require smaller or larger values.
 
+config LD_LINKER_SCRIPT_SUPPORTED
+	bool
+	default y
+
+choice LINKER_SCRIPT
+	prompt "Linker script"
+	default LD_LINKER_TEMPLATE if LD_LINKER_SCRIPT_SUPPORTED
+
+config LD_LINKER_TEMPLATE
+	bool "LD template"
+	depends on LD_LINKER_SCRIPT_SUPPORTED
+	help
+	  Select this option to use the LD linker script templates.
+	  The templates are pre-processed by the C pre-processor to create the
+	  final LD linker script.
+
+config CMAKE_LINKER_GENERATOR
+	bool "CMake generator"
+	depends on ARM
+	help
+	  Select this option to use the Zephyr CMake linker script generator.
+	  The linker configuration is written in CMake and the final linker
+	  script will be generated by the toolchain specific linker generator.
+	  For LD based linkers, this will be the ld generator, for ARMClang /
+	  armlink based linkers it will be the scatter generator.
+
+endchoice
+
 config HAVE_CUSTOM_LINKER_SCRIPT
-	bool "Custom linker scripts provided"
+	bool "Custom linker script provided"
 	help
 	  Set this option if you have a custom linker script which needed to
 	  be define in CUSTOM_LINKER_SCRIPT.

cmake/linker/ld/target.cmake

@@ -31,6 +31,28 @@ endif()
 macro(configure_linker_script linker_script_gen linker_pass_define)
   set(extra_dependencies ${ARGN})
 
+  if(CONFIG_CMAKE_LINKER_GENERATOR)
+    if("${linker_pass_define}" STREQUAL "-DLINKER_ZEPHYR_PREBUILT")
+      set(PASS 1)
+    elseif("${linker_pass_define}" STREQUAL "-DLINKER_ZEPHYR_FINAL;-DLINKER_PASS2")
+      set(PASS 2)
+    endif()
+
+    add_custom_command(
+      OUTPUT ${linker_script_gen}
+      COMMAND ${CMAKE_COMMAND}
+        -DPASS=${PASS}
+        -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()
     # Different generators deal with depfiles differently.
     if(CMAKE_GENERATOR STREQUAL "Unix Makefiles")
       # Note that the IMPLICIT_DEPENDS option is currently supported only
@@ -76,6 +98,7 @@ macro(configure_linker_script linker_script_gen linker_pass_define)
       WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
       COMMAND_EXPAND_LISTS
     )
+  endif()
 endmacro()
 
 # Force symbols to be entered in the output file as undefined symbols