it8xxx2: ensure kernel in ram code section

This change was made to make sure kernel still can run from ram code
section under LTO enabled.

Signed-off-by: Tim Lin <tim2.lin@ite.corp-partner.google.com>

Author: GTLin08

soc/ite/ec/it8xxx2/CMakeLists.txt

@@ -1,3 +1,7 @@
+if(CONFIG_LTO AND CONFIG_SOC_IT8XXX2_KERNEL_IN_RAM)
+  include(${CMAKE_CURRENT_SOURCE_DIR}/kernel_no_lto.cmake)
+endif()
+
 zephyr_sources(soc.c check_regs.c vector.S)
 zephyr_include_directories(.)
 

soc/ite/ec/it8xxx2/cleanup_injected_code.py

@@ -0,0 +1,25 @@
+#!/usr/bin/env python3
+
+# Copyright (c) 2025 ITE Corporation. All Rights Reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+import re
+import sys
+from pathlib import Path
+
+MARKER = "# AUTO_INJECTED_NO_LTO"
+kernel_cmake = Path(sys.argv[1])
+
+if not kernel_cmake.exists():
+    sys.exit(0)
+
+content = kernel_cmake.read_text()
+
+# Remove injected block
+cleaned = re.sub(rf"{re.escape(MARKER)}[^\n]*\n.*$", "", content, flags=re.S)
+cleaned = cleaned.rstrip() + "\n"
+
+if content != cleaned:
+    kernel_cmake.write_text(cleaned)
+    print(f"[no-LTO] Cleaned up injection from {kernel_cmake}")

soc/ite/ec/it8xxx2/kernel_no_lto.cmake

@@ -0,0 +1,38 @@
+set(KERNEL_CMAKE "${ZEPHYR_BASE}/kernel/CMakeLists.txt")
+set(MARKER "# AUTO_INJECTED_NO_LTO")
+
+execute_process(
+  COMMAND ${CMAKE_COMMAND} -E env python3
+          ${CMAKE_CURRENT_LIST_DIR}/cleanup_injected_code.py
+          ${KERNEL_CMAKE}
+  RESULT_VARIABLE CLEAN_RESULT
+  OUTPUT_QUIET
+  ERROR_QUIET
+)
+
+if(NOT CLEAN_RESULT EQUAL 0)
+  message(WARNING "[no-LTO] Warning: cleanup script encountered an issue, continuing anyway.")
+endif()
+
+# Prepare the code snippet to inject
+message(STATUS "[no-LTO] Injecting no-LTO configuration into kernel/CMakeLists.txt...")
+set(INJECT_CODE "${MARKER}
+set_source_files_properties(busy_wait.c device.c kheap.c idle.c mutex.c sem.c work.c
+                            thread.c sched.c timeout.c time.c poll.c events.c banner.c
+                            system_work_q.c
+                            PROPERTIES COMPILE_FLAGS \"-fno-lto -g\")")
+
+# Append the injected code to the end of the file
+file(APPEND ${KERNEL_CMAKE} "${INJECT_CODE}")
+message(STATUS "[no-LTO] Injection complete.")
+
+# Define a cleanup target to remove the injected code after the build
+add_custom_target(cleanup_kernel_injection ALL
+  COMMAND ${CMAKE_COMMAND} -E env python3
+          ${CMAKE_CURRENT_LIST_DIR}/cleanup_injected_code.py
+          ${KERNEL_CMAKE}
+  COMMENT "Cleaning up kernel injection"
+)
+
+# Ensure the cleanup target runs after the final build stage
+add_dependencies(cleanup_kernel_injection zephyr_final)