Arm backend: Add support for ubsan in executor_runner (#15894)

A lightweight Undefinedsanitizer runtime tailored for the ExecuTorch
bare metal examples. The goal is to provide basic memory safety
diagnostics while keeping the runtime self-contained.

Signed-off-by: per.held@arm.com

Author: perheld

backends/arm/scripts/build_executorch.sh

@@ -5,7 +5,7 @@
 # LICENSE file in the root directory of this source tree.
 
 # Optional parameter:
-# --build_type= "Release" | "Debug" | "RelWithDebInfo"
+# --build_type= "Release" | "Debug" | "RelWithDebInfo" | "UndefinedSanitizer"
 # --etdump      build with devtools-etdump support
 
 set -eu
@@ -28,7 +28,7 @@ help() {
     echo "Usage: $(basename $0) [options]"
     echo "Options:"
     echo "  --et_build_root=<FOLDER>  Build output root folder to use, defaults to ${et_build_root}"
-    echo "  --build_type=<TYPE>       Build with Release, Debug or RelWithDebInfo, default is ${build_type}"
+    echo "  --build_type=<TYPE>       Build with Release, Debug, RelWithDebInfo or UndefinedSanitizer, default is ${build_type}"
     echo "  --devtools                Build Devtools libs"
     echo "  --etdump                  Adds Devtools etdump support to track timing, etdump area will be base64 encoded in the log"
     echo "  --toolchain=<TOOLCHAIN>   Toolchain can be specified (e.g. bare metal as arm-none-eabi-gcc or zephyr as arm-zephyr-eabi-gcc Default: ${toolchain}"
@@ -78,7 +78,7 @@ cd "${et_root_dir}"
 
 # Build
 cmake -DCMAKE_TOOLCHAIN_FILE=${toolchain_cmake} \
--DCMAKE_BUILD_TYPE=Release \
+-DCMAKE_BUILD_TYPE=${build_type} \
 -DEXECUTORCH_BUILD_DEVTOOLS=$build_devtools \
 -DEXECUTORCH_BUILD_ARM_ETDUMP=$build_with_etdump \
 --preset arm-baremetal -B${et_build_dir}

backends/arm/test/test_arm_baremetal.sh

@@ -394,4 +394,14 @@ test_memory_allocation() {
     echo "${TEST_SUITE_NAME}: PASS"
 }
 
+test_undefinedbehavior_sanitizer() {
+    echo "${TEST_SUITE_NAME}: Test ethos-u executor_runner with UBSAN"
+
+    mkdir -p arm_test/test_run
+    # Ethos-U85
+    echo "${TEST_SUITE_NAME}: Test target Ethos-U85"
+    examples/arm/run.sh --et_build_root=arm_test/test_run --target=ethos-u85-128 --model_name=examples/arm/example_modules/add.py --build_type=UndefinedSanitizer
+    echo "${TEST_SUITE_NAME}: PASS"
+}
+
 ${TEST_SUITE}

examples/arm/executor_runner/CMakeLists.txt

@@ -326,12 +326,29 @@ endif()
 
 # Need whole-archive to ensure C++ ctor's are called - this may be wasteful for
 # bin size as we link in a number of other symbols
-target_link_libraries(arm_executor_runner ${arm_executor_runner_link})
+target_link_libraries(arm_executor_runner PUBLIC ${arm_executor_runner_link})
 
 target_link_options(
   arm_executor_runner PUBLIC LINKER:-Map=arm_executor_runner.map
 )
 
+# Sanitizers
+if(CMAKE_BUILD_TYPE MATCHES "UndefinedSanitizer")
+  set(_et_runner_ubsan_flag -fsanitize=undefined)
+  target_compile_options(arm_executor_runner PRIVATE ${_et_runner_ubsan_flag})
+  target_link_options(arm_executor_runner PRIVATE ${_et_runner_ubsan_flag})
+  if(NOT TARGET executorch_ubsan)
+    add_subdirectory(
+      ${ET_DIR_PATH}/examples/arm/ubsan
+      ${CMAKE_CURRENT_BINARY_DIR}/ubsan_runtime
+    )
+  endif()
+  target_link_directories(
+    arm_executor_runner PRIVATE $<TARGET_FILE_DIR:executorch_ubsan>
+  )
+  target_link_libraries(arm_executor_runner PRIVATE executorch_ubsan)
+endif()
+
 # ET headers and generated headers includes
 target_include_directories(
   arm_executor_runner

examples/arm/run.sh

@@ -61,7 +61,7 @@ function help() {
     echo "  --output=<FOLDER>                      Target build output folder Default: ${output_folder}"
     echo "  --bundleio                             Create Bundled pte using Devtools BundelIO with Input/RefOutput included"
     echo "  --etdump                               Adds Devtools etdump support to track timing, etdump area will be base64 encoded in the log"
-    echo "  --build_type=<TYPE>                    Build with Release, Debug or RelWithDebInfo, default is ${build_type}"
+    echo "  --build_type=<TYPE>                    Build with Release, Debug, RelWithDebInfo or UndefinedSanitizer, default is ${build_type}"
     echo "  --extra_build_flags=<FLAGS>            Extra flags to pass to cmake like -DET_ARM_BAREMETAL_METHOD_ALLOCATOR_POOL_SIZE=60000 Default: none "
     echo "  --build_only                           Only build, don't run"
     echo "  --toolchain=<TOOLCHAIN>                Ethos-U: Toolchain can be specified (e.g. bare metal as arm-none-eabi-gcc or zephyr as arm-zephyr-eabi-gcc Default: ${toolchain}"

examples/arm/ubsan/CMakeLists.txt

@@ -0,0 +1,18 @@
+# Copyright 2025 Arm Limited and/or its affiliates.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+add_library(executorch_ubsan STATIC ubsan_runtime.c)
+
+target_compile_features(executorch_ubsan PRIVATE c_std_11)
+
+target_compile_options(executorch_ubsan PRIVATE -fno-sanitize=undefined)
+
+set_target_properties(executorch_ubsan PROPERTIES OUTPUT_NAME "ubsan")
+
+install(
+  TARGETS executorch_ubsan
+  EXPORT ExecuTorchTargets
+  ARCHIVE DESTINATION lib
+)