Port WAMR to ESP-IDF (#892)

This PR introduces an implementation of the WAMR platform APIs for ESP-IDF and enables support for Espressif microcontrollers, and adds the documentation around how to build WAMR for ESP-IDF.

This PR is related to the following issues at WAMR: closes #883, #628, #449 and #668 as well as [#4735](https://github.com/espressif/esp-idf/issues/4735) at the esp-idf repo. It implements most functions required by [platform_api_vmcore.h](https://github.com/bytecodealliance/wasm-micro-runtime/blob/main/core/shared/platform/include/platform_api_vmcore.h).

The PR works in interpreter mode on Esp32c3 and Esp32. For the AOT mode, currently errors occur on both platforms with `Guru Meditation Error`. It seems that the AOT code isn't run with shared memory as os_mmap() allocates memory with malloc() API, it is to be fixed in the future.

product-mini/platforms/esp-idf/main.c

@@ -2,38 +2,104 @@
  * Copyright (C) 2019 Intel Corporation.  All rights reserved.
  * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  */
-
+#include <stdio.h>
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "wasm_export.h"
 #include "bh_platform.h"
+#include "test_wasm.h"
 
-extern void
-iwasm_main(void);
-
-static void
-wamr_task(void *param)
+static void *
+app_instance_main(wasm_module_inst_t module_inst)
 {
-    os_printf("WAMR task started\n");
+    const char *exception;
 
-    iwasm_main();
+    wasm_application_execute_main(module_inst, 0, NULL);
+    if ((exception = wasm_runtime_get_exception(module_inst)))
+        printf("%s\n", exception);
+    return NULL;
+}
 
-    while (1) {
-        task_sleep(1000);
-        /*os_printf("Hello WAMR\n");*/
+void *
+iwasm_main(void *arg)
+{
+    (void)arg; /* unused */
+    /* setup variables for instantiating and running the wasm module */
+    uint8_t *wasm_file_buf = NULL;
+    unsigned wasm_file_buf_size = 0;
+    wasm_module_t wasm_module = NULL;
+    wasm_module_inst_t wasm_module_inst = NULL;
+    char error_buf[128];
+    void *ret;
+    RuntimeInitArgs init_args;
+
+    /* configure memory allocation */
+    memset(&init_args, 0, sizeof(RuntimeInitArgs));
+    init_args.mem_alloc_type = Alloc_With_Allocator;
+    init_args.mem_alloc_option.allocator.malloc_func = (void *)os_malloc;
+    init_args.mem_alloc_option.allocator.realloc_func = (void *)os_realloc;
+    init_args.mem_alloc_option.allocator.free_func = (void *)os_free;
+
+    printf("wasm_runtime_full_init\n");
+    /* initialize runtime environment */
+    if (!wasm_runtime_full_init(&init_args)) {
+        printf("Init runtime failed.\n");
+        return NULL;
     }
-    (void)param;
+
+    /* load WASM byte buffer from byte buffer of include file */
+    printf("use an internal test file, that's going to output Hello World\n");
+    wasm_file_buf = (uint8_t *)wasm_test_file;
+    wasm_file_buf_size = sizeof(wasm_test_file);
+
+    /* load WASM module */
+    if (!(wasm_module = wasm_runtime_load(wasm_file_buf, wasm_file_buf_size,
+                                          error_buf, sizeof(error_buf)))) {
+        printf("Error in wasm_runtime_load: %s\n", error_buf);
+        goto fail1;
+    }
+
+    printf("about to call wasm_runtime_instantiate\n");
+    if (!(wasm_module_inst =
+              wasm_runtime_instantiate(wasm_module, 32 * 1024, // stack size
+                                       32 * 1024,              // heap size
+                                       error_buf, sizeof(error_buf)))) {
+        printf("Error while instantiating: %s\n", error_buf);
+        goto fail2;
+    }
+
+    printf("run main() of the application\n");
+    ret = app_instance_main(wasm_module_inst);
+    assert(!ret);
+
+    /* destroy the module instance */
+    printf("wasm_runtime_deinstantiate\n");
+    wasm_runtime_deinstantiate(wasm_module_inst);
+
+fail2:
+    /* unload the module */
+    printf("wasm_runtime_unload\n");
+    wasm_runtime_unload(wasm_module);
+
+fail1:
+    /* destroy runtime environment */
+    printf("wasm_runtime_destroy\n");
+    wasm_runtime_destroy();
+
+    return NULL;
 }
 
-static bool
-app_init(uint32_t id)
+void
+app_main(void)
 {
-    os_printf("WAMR init, id: %d\n", id);
-    task_start("wamr_task", 8192, 4, wamr_task, NULL);
-    return true;
-}
+    pthread_t t;
+    int res;
 
-static void
-app_exit(uint32_t id)
-{
-    os_printf("WAMR exit, id: %d\n", id);
-}
+    res = pthread_create(&t, NULL, iwasm_main, (void *)NULL);
+    assert(res == 0);
 
-INTERNAL_APP_DEFINE("WAMR", APP_VERSION(0, 0, 0, 1), 0, app_init, app_exit);
+    res = pthread_join(t, NULL);
+    assert(res == 0);
+
+    printf("Exiting... \n");
+}