llext: move all flags to compiler specific cmake files

Minimize the amount of flags that are hardcoded in the llext.cmake
module by moving them to the compiler specific cmake files.

The llext.cmake module will now use the new LLEXT_REMOVE_FLAGS and
LLEXT_APPEND_FLAGS global variables to adjust the set of flags used
to compile the llext code. This will make it easier to add support
for new architectures and compilers.

Signed-off-by: Luca Burelli <[email protected]>

cmake/bintools/gnu/target_bintools.cmake

@@ -93,6 +93,7 @@ set_property(TARGET bintools PROPERTY strip_flag_final "")
 set_property(TARGET bintools PROPERTY strip_flag_all --strip-all)
 set_property(TARGET bintools PROPERTY strip_flag_debug --strip-debug)
 set_property(TARGET bintools PROPERTY strip_flag_dwo --strip-dwo)
+set_property(TARGET bintools PROPERTY strip_flag_remove_section -R )
 
 set_property(TARGET bintools PROPERTY strip_flag_infile "")
 set_property(TARGET bintools PROPERTY strip_flag_outfile -o )

cmake/compiler/gcc/target.cmake

@@ -76,6 +76,8 @@ elseif("${ARCH}" STREQUAL "sparc")
   include(${CMAKE_CURRENT_LIST_DIR}/target_sparc.cmake)
 elseif("${ARCH}" STREQUAL "mips")
   include(${CMAKE_CURRENT_LIST_DIR}/target_mips.cmake)
+elseif("${ARCH}" STREQUAL "xtensa")
+  include(${CMAKE_CURRENT_LIST_DIR}/target_xtensa.cmake)
 endif()
 
 if(SYSROOT_DIR)

cmake/compiler/gcc/target_arm.cmake

@@ -41,3 +41,22 @@ endif()
 
 list(APPEND TOOLCHAIN_C_FLAGS ${ARM_C_FLAGS})
 list(APPEND TOOLCHAIN_LD_FLAGS NO_SPLIT ${ARM_C_FLAGS})
+
+# Flags not supported by llext linker
+# (regexps are supported and match whole word)
+set(LLEXT_REMOVE_FLAGS
+  -fno-pic
+  -fno-pie
+  -ffunction-sections
+  -fdata-sections
+  -g.*
+  -Os
+  -mcpu=.*
+)
+
+# Flags to be added to llext code compilation
+set(LLEXT_APPEND_FLAGS
+  -mlong-calls
+  -mthumb
+  -mcpu=cortex-m33+nodsp
+)

cmake/compiler/gcc/target_xtensa.cmake

@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: Apache-2.0
+
+# Flags not supported by llext linker
+# (regexps are supported and match whole word)
+set(LLEXT_REMOVE_FLAGS
+  -fno-pic
+  -fno-pie
+  -ffunction-sections
+  -fdata-sections
+  -g.*
+  -Os
+  -mcpu=.*
+)
+
+# Flags to be added to llext code compilation
+set(LLEXT_APPEND_FLAGS
+  -fPIC
+  -nostdlib
+  -nodefaultlibs
+  -shared
+)

cmake/modules/extensions.cmake

@@ -4807,9 +4807,13 @@ endmacro()
 # Output and source files must be specified using the OUTPUT and SOURCES
 # arguments. Only one source file is currently supported.
 #
-# Arch-specific flags will be added automatically. The C_FLAGS argument
-# can be used to pass additional compiler flags to the compilation of
-# the source file.
+# The llext code will be compiled with mostly the same C compiler flags used
+# in the Zephyr build, but with some important modifications. The list of
+# flags to remove and flags to append is controlled respectively by the
+# LLEXT_REMOVE_FLAGS and LLEXT_APPEND_FLAGS global variables.
+
+# The C_FLAGS argument can be used to pass additional compiler flags to the
+# compilation of this particular llext.
 #
 # Example usage:
 #   add_llext_target(hello_world
@@ -4851,14 +4855,19 @@ function(add_llext_target target_name)
     DEPENDS ${output_file}
   )
 
-  # Define arch-specific flags for the supported architectures
-  if(CONFIG_ARM)
-    list(PREPEND LLEXT_C_FLAGS "-mlong-calls" "-mthumb")
-  elseif(CONFIG_XTENSA)
-    list(PREPEND LLEXT_C_FLAGS "-shared" "-fPIC" "-nostdlib" "-nodefaultlibs")
-  else()
-    message(FATAL_ERROR "add_llext_target: unsupported architecture")
-  endif()
+  # Convert the LLEXT_REMOVE_FLAGS list to a regular expression, and use it to
+  # filter out these flags from the Zephyr target settings
+  list(TRANSFORM LLEXT_REMOVE_FLAGS
+       REPLACE "(.+)" "^\\1$"
+       OUTPUT_VARIABLE llext_remove_flags_regexp
+  )
+  string(REPLACE ";" "|" llext_remove_flags_regexp "${llext_remove_flags_regexp}")
+  set(zephyr_flags
+      "$<TARGET_PROPERTY:zephyr_interface,INTERFACE_COMPILE_OPTIONS>"
+  )
+  set(zephyr_filtered_flags
+      "$<FILTER:${zephyr_flags},EXCLUDE,${llext_remove_flags_regexp}>"
+  )
 
   # Compile the source file to an object file using current Zephyr settings
   # but a different set of flags
@@ -4867,12 +4876,12 @@ function(add_llext_target target_name)
     $<TARGET_PROPERTY:zephyr_interface,INTERFACE_COMPILE_DEFINITIONS>
   )
   target_compile_options(${target_name}_lib PRIVATE
+    ${zephyr_filtered_flags}
+    ${LLEXT_APPEND_FLAGS}
     ${LLEXT_C_FLAGS}
-    -imacros "${AUTOCONF_H}"
   )
   target_include_directories(${target_name}_lib PRIVATE
     $<TARGET_PROPERTY:zephyr_interface,INTERFACE_INCLUDE_DIRECTORIES>
-    -I${PROJECT_BINARY_DIR}/include/generated
   )
   target_include_directories(${target_name}_lib SYSTEM PUBLIC
     $<TARGET_PROPERTY:zephyr_interface,INTERFACE_SYSTEM_INCLUDE_DIRECTORIES>
@@ -4903,14 +4912,19 @@ function(add_llext_target target_name)
     add_custom_command(
       OUTPUT ${output_file}
       BYPRODUCTS ${pre_output_file}
-      COMMAND ${CMAKE_C_COMPILER} ${LLEXT_C_FLAGS}
+      COMMAND ${CMAKE_C_COMPILER} ${LLEXT_APPEND_FLAGS}
               -o ${pre_output_file}
               $<TARGET_OBJECTS:${target_name}_lib>
-      COMMAND ${CROSS_COMPILE}strip -R .xt.*
-              -o ${output_file}
-              ${pre_output_file}
+      COMMAND $<TARGET_PROPERTY:bintools,strip_command>
+              $<TARGET_PROPERTY:bintools,strip_flag>
+              $<TARGET_PROPERTY:bintools,strip_flag_remove_section>.xt.*
+              $<TARGET_PROPERTY:bintools,strip_flag_infile>${pre_output_file}
+              $<TARGET_PROPERTY:bintools,strip_flag_outfile>${output_file}
+              $<TARGET_PROPERTY:bintools,strip_flag_final>
       DEPENDS ${target_name}_lib $<TARGET_OBJECTS:${target_name}_lib>
     )
 
+  else()
+    message(FATAL_ERROR "add_llext_target: unsupported architecture")
   endif()
 endfunction()