llext: Simple hello world test case

Adds a very simple hello world test case for llext. The loadable
extension is built and then included as a binary array into the test
making it very easy to load, debug, and inspect. The extension is
built using the same toolchain as the base image by default.

Signed-off-by: Tom Burdick <thomas.burdick@intel.com>

tests/subsys/llext/CMakeLists.txt

@@ -0,0 +1,26 @@
+# Copyright (c) 2023 Intel Corporation.
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(llext_test)
+
+add_subdirectory(hello_world)
+
+target_sources(app PRIVATE src/test_llext_simple.c)
+
+target_include_directories(app PRIVATE
+  ${ZEPHYR_BASE}/include
+  ${ZEPHYR_BASE}/kernel/include
+  ${ZEPHYR_BASE}/arch/${ARCH}/include
+  )
+
+set(gen_dir ${ZEPHYR_BINARY_DIR}/include/generated/)
+
+generate_inc_file_for_target(
+  app
+  ${HELLO_WORLD_LLEXT}
+  ${gen_dir}/hello_world.inc
+  )
+
+add_dependencies(app hello_world)

tests/subsys/llext/hello_world/CMakeLists.txt

@@ -0,0 +1,17 @@
+# Copyright (c) 2023 Intel Corporation.
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(hello_world)
+
+# TODO check which architecture is being used
+set(CMAKE_C_FLAGS "-mlong-calls" "-mthumb")
+
+add_custom_command(OUTPUT ${PROJECT_BINARY_DIR}/hello_world.llext
+    COMMAND ${CMAKE_C_COMPILER} ${CMAKE_C_FLAGS} -c -o ${PROJECT_BINARY_DIR}/hello_world.llext ${PROJECT_SOURCE_DIR}/hello_world.c
+)
+
+set(HELLO_WORLD_LLEXT ${PROJECT_BINARY_DIR}/hello_world.llext PARENT_SCOPE)
+
+add_custom_target(hello_world DEPENDS ${PROJECT_BINARY_DIR}/hello_world.llext)

tests/subsys/llext/hello_world/hello_world.c

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2023 Intel Corporation.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/*
+ * This very simple hello world C code can be used as a test case for building
+ * probably the simplest loadable extension. It requires a single symbol be
+ * linked, section relocation support, and the ability to export and call out to
+ * a function.
+ */
+
+/* Various build options should be documented here to generate the test elf for
+ * each architecture.
+ *
+ * armv7-thumb: -mlong-call -mthumb -c -o hello_world_armv7_thumb.elf hello_world.c
+ */
+
+extern void printk(char *fmt, ...);
+
+extern void hello_world(void)
+{
+	printk("hello world\n");
+}

tests/subsys/llext/prj.conf

@@ -0,0 +1,8 @@
+CONFIG_ZTEST=y
+CONFIG_ZTEST_NEW_API=y
+CONFIG_ZTEST_STACK_SIZE=8192
+CONFIG_LOG=y
+CONFIG_LOG_MODE_IMMEDIATE=y
+CONFIG_LLEXT=y
+CONFIG_LLEXT_HEAP_SIZE=32
+CONFIG_LLEXT_LOG_LEVEL_DBG=y

tests/subsys/llext/src/test_llext_simple.c

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2023 Intel Corporation.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/ztest.h>
+#include <zephyr/kernel.h>
+#include <zephyr/llext/llext.h>
+#include <zephyr/llext/buf_loader.h>
+
+#ifdef CONFIG_ARM /* ARMV7 */
+const static uint8_t hello_world_elf[] __aligned(4) = {
+#include "hello_world.inc"
+};
+#endif
+
+/**
+ * Attempt to load, list, list symbols, call a fn, and unload a
+ * hello world extension for each supported architecture
+ *
+ * This requires a single linked symbol (printk) and a single
+ * exported symbol from the extension ( void hello_world(void))
+ */
+ZTEST(llext, test_llext_simple)
+{
+	const char name[16] = {'h', 'e', 'l', 'l', 'o', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+	struct llext_buf_loader buf_loader =
+		LLEXT_BUF_LOADER(hello_world_elf, ARRAY_SIZE(hello_world_elf));
+	struct llext_loader *loader = &buf_loader.loader;
+	struct llext *ext;
+	const void * const printk_fn = llext_find_sym(NULL, "printk");
+
+	zassert_equal(printk_fn, printk, "printk should be an exported symbol");
+
+	int res = llext_load(loader, name, &ext);
+
+	zassert_ok(res, "load should succeed");
+
+	const void * const hello_world_fn = llext_find_sym(&ext->sym_tab, "hello_world");
+
+	zassert_not_null(hello_world_fn, "hello_world should be an exported symbol");
+
+	res = llext_call_fn(ext, "hello_world");
+
+	zassert_ok(res, "calling hello world should succeed");
+
+	llext_unload(ext);
+}
+
+ZTEST_SUITE(llext, NULL, NULL, NULL, NULL, NULL);

tests/subsys/llext/testcase.yaml

@@ -0,0 +1,11 @@
+common:
+  tags: llext
+tests:
+  llext.simple.arm:
+    filter: not CONFIG_CPU_HAS_MMU
+    arch_allow: arm
+    extra_configs:
+      - CONFIG_ARM_MPU=n
+    # Broken platforms
+    platform_exclude:
+      - nuvoton_pfm_m487 # See #63167