tests: llext: add relative jump test ext.c

Validate the new relocations for BL and BLX instructions by
creating a new test extension which contains a chain of global
functions in a pseudo random order to (hopefully) generate
relative jumps in both positive and negative directions.

Signed-off-by: Bjarki Arge Andreasen <bjarki@arge-andreasen.me>

tests/subsys/llext/simple/CMakeLists.txt

@@ -16,7 +16,7 @@ target_include_directories(app PRIVATE
 )
 
 # generate extension targets foreach extension given by name
-foreach(ext_name hello_world logging)
+foreach(ext_name hello_world logging relative_jump)
   set(ext_src ${PROJECT_SOURCE_DIR}/src/${ext_name}_ext.c)
   set(ext_bin ${ZEPHYR_BINARY_DIR}/${ext_name}.llext)
   set(ext_inc ${ZEPHYR_BINARY_DIR}/include/generated/${ext_name}.inc)

tests/subsys/llext/simple/src/relative_jump_ext.c

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2024 Trackunit Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/*
+ * This test is designed to test linking global symbols, which for some architectures
+ * like ARM generate relative jumps rather than jumping to absolute addresses. Multiple
+ * global functions are created to hopefully generate both positive and negative relative
+ * jumps.
+ */
+
+#include <stdint.h>
+#include <zephyr/llext/symbol.h>
+#include <zephyr/sys/printk.h>
+
+void test_relative_jump_1(void);
+void test_relative_jump_2(void);
+void test_relative_jump_3(void);
+void test_relative_jump_4(void);
+void test_relative_jump_5(void);
+
+void test_relative_jump_5(void)
+{
+	printk("relative jump 5\n");
+}
+
+void test_relative_jump_4(void)
+{
+	printk("relative jump 4\n");
+	test_relative_jump_5();
+}
+
+void test_relative_jump_2(void)
+{
+	printk("relative jump 2\n");
+	test_relative_jump_3();
+}
+
+void test_relative_jump_1(void)
+{
+	printk("relative jump 1\n");
+	test_relative_jump_2();
+}
+
+void test_relative_jump_3(void)
+{
+	printk("relative jump 3\n");
+	test_relative_jump_4();
+}
+
+void test_entry(void)
+{
+	printk("enter\n");
+	test_relative_jump_1();
+	printk("exit\n");
+}
+LL_EXTENSION_SYMBOL(test_entry);

tests/subsys/llext/simple/src/test_llext_simple.c

@@ -147,6 +147,11 @@ static LLEXT_CONST uint8_t logging_ext[] __aligned(4) = {
 };
 LLEXT_LOAD_UNLOAD(logging, true)
 
+static LLEXT_CONST uint8_t relative_jump_ext[] __aligned(4) = {
+	#include "relative_jump.inc"
+};
+LLEXT_LOAD_UNLOAD(relative_jump, true)
+
 /*
  * Ensure that EXPORT_SYMBOL does indeed provide a symbol and a valid address
  * to it.