Add an example of how to embed WAMR in Zephyr user mode (#3998)

product-mini/platforms/zephyr/user-mode/src/main.c

@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include <stdio.h>
+
+#include <zephyr/version.h>
+#include <zephyr/app_memory/app_memdomain.h>
+
+#define MAIN_THREAD_STACK_SIZE 2048
+#define MAIN_THREAD_PRIORITY 5
+
+static struct k_thread iwasm_user_mode_thread;
+K_THREAD_STACK_DEFINE(iwasm_user_mode_thread_stack, MAIN_THREAD_STACK_SIZE);
+
+extern struct k_mem_partition z_libc_partition;
+K_APPMEM_PARTITION_DEFINE(wamr_partition);
+
+/* WAMR memory domain */
+struct k_mem_domain wamr_domain;
+
+extern void
+iwasm_main(void *arg1, void *arg2, void *arg3);
+
+bool
+iwasm_user_mode(void)
+{
+    struct k_mem_partition *wamr_domain_parts[] = { &wamr_partition,
+                                                    &z_libc_partition };
+
+    printk("wamr_partition start addr: %ld, size: %zu\n", wamr_partition.start,
+           wamr_partition.size);
+
+    /* Initialize the memory domain with single WAMR partition */
+    if (k_mem_domain_init(&wamr_domain, 2, wamr_domain_parts) != 0) {
+        printk("Failed to initialize memory domain.\n");
+        return false;
+    }
+
+    k_tid_t tid =
+        k_thread_create(&iwasm_user_mode_thread, iwasm_user_mode_thread_stack,
+                        MAIN_THREAD_STACK_SIZE, iwasm_main, NULL, NULL, NULL,
+                        MAIN_THREAD_PRIORITY, K_USER, K_FOREVER);
+
+    /* Grant WAMR memory domain access to user mode thread */
+    if (k_mem_domain_add_thread(&wamr_domain, tid) != 0) {
+        printk("Failed to add memory domain to thread.\n");
+        return false;
+    }
+
+#if KERNEL_VERSION_NUMBER < 0x040000 /* version 4.0.0 */
+    /* k_thread_start is a legacy API for compatibility. Modern Zephyr threads
+     * are initialized in the "sleeping" state and do not need special handling
+     * for "start".*/
+    k_thread_start(tid);
+#else
+    /* wakes up thread from sleeping */
+    k_wakeup(tid);
+#endif
+
+    return tid ? true : false;
+}
+
+#if KERNEL_VERSION_NUMBER < 0x030400 /* version 3.4.0 */
+void
+main(void)
+{
+    iwasm_user_mode();
+}
+#else
+int
+main(void)
+{
+    iwasm_user_mode();
+    return 0;
+}
+#endif