ESP IDF fixes (#927)

Various fixes and beautifications coordinated with @1c3t3a,
fixes 2 of the 3 all remaining issues from #892:
- enable to os_mmap executable memory
- fix os_malloc/os_realloc/os_free issues
- implement os_thread_get_stack_boundary
- add build scripts to include with esp-idf to use wamr as
  an ESP-IDF component
- update sample and document

core/shared/platform/esp-idf/espidf_malloc.c

@@ -14,6 +14,9 @@ os_malloc(unsigned size)
     uintptr_t *addr_field;
 
     buf_origin = malloc(size + 8 + sizeof(uintptr_t));
+    if (!buf_origin) {
+        return NULL;
+    }
     buf_fixed = buf_origin + sizeof(void *);
     if ((uintptr_t)buf_fixed & (uintptr_t)0x7) {
         buf_fixed = (void *)((uintptr_t)(buf_fixed + 8) & (~(uintptr_t)7));
@@ -34,12 +37,15 @@ os_realloc(void *ptr, unsigned size)
     uintptr_t *addr_field;
 
     if (!ptr) {
-        return NULL;
+        return os_malloc(size);
     }
 
     addr_field = ptr - sizeof(uintptr_t);
     mem_origin = (void *)(*addr_field);
     mem_new = realloc(mem_origin, size + 8 + sizeof(uintptr_t));
+    if (!mem_new) {
+        return NULL;
+    }
 
     if (mem_origin != mem_new) {
         mem_new_fixed = mem_new + sizeof(uintptr_t);
@@ -61,7 +67,7 @@ void
 os_free(void *ptr)
 {
     void *mem_origin;
-    uintptr *addr_field;
+    uintptr_t *addr_field;
 
     if (ptr) {
         addr_field = ptr - sizeof(uintptr_t);

core/shared/platform/esp-idf/espidf_memmap.c

@@ -9,12 +9,34 @@
 void *
 os_mmap(void *hint, size_t size, int prot, int flags)
 {
-    return os_malloc((int)size);
+    if (prot & MMAP_PROT_EXEC) {
+        // Memory allocation with MALLOC_CAP_EXEC will return 4-byte aligned
+        // Reserve extra 4 byte to fixup alignment and size for the pointer to
+        // the originally allocated address
+        void *buf_origin =
+            heap_caps_malloc(size + 4 + sizeof(uintptr_t), MALLOC_CAP_EXEC);
+        if (!buf_origin) {
+            return NULL;
+        }
+        void *buf_fixed = buf_origin + sizeof(void *);
+        if ((uintptr_t)buf_fixed & (uintptr_t)0x7) {
+            buf_fixed = (void *)((uintptr_t)(buf_fixed + 4) & (~(uintptr_t)7));
+        }
+
+        uintptr_t *addr_field = buf_fixed - sizeof(uintptr_t);
+        *addr_field = (uintptr_t)buf_origin;
+        return buf_fixed;
+    }
+    else {
+        return os_malloc(size);
+    }
 }
 
 void
 os_munmap(void *addr, size_t size)
 {
+    // We don't need special handling of the executable allocations
+    // here, free() of esp-idf handles it properly
     return os_free(addr);
 }
 

core/shared/platform/esp-idf/espidf_platform.c

@@ -44,7 +44,13 @@ os_time_get_boot_microsecond(void)
 uint8 *
 os_thread_get_stack_boundary(void)
 {
+#if defined(CONFIG_FREERTOS_USE_TRACE_FACILITY)
+    TaskStatus_t pxTaskStatus;
+    vTaskGetInfo(xTaskGetCurrentTaskHandle(), &pxTaskStatus, pdTRUE, eInvalid);
+    return pxTaskStatus.pxStackBase;
+#else // !defined(CONFIG_FREERTOS_USE_TRACE_FACILITY)
     return NULL;
+#endif
 }
 
 int