bootutil_public: added hook for fetch image swap state

Added hook which allows to override boot_read_swap_state_by_id()
routine for the primary slot.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>

boot/bootutil/include/bootutil/boot_public_hooks.h

@@ -0,0 +1,52 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Copyright (c) 2021 Nordic Semiconductor ASA
+ *
+ * Original license:
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/**
+ * @file
+ * @brief Hooks definition implementation API
+ *
+ * This file contains API interface definition for hooks which can be
+ * implemented for overide some of MCUboot's native routines.
+ */
+
+#ifndef H_BOOTUTIL_PUBLIC_HOOKS
+#define H_BOOTUTIL_PUBLIC_HOOKS
+
+#include "bootutil/boot_hooks.h"
+
+/** Hook for provide primary image swap state.
+ *
+ * @param img_index the index of the image pair
+ * @param state image swap state structure to be populated
+ *
+ * @retval 0: header was read/populated
+ *         FIH_FAILURE: image is invalid,
+ *         BOOT_HOOK_REGULAR if hook not implemented for the image-slot,
+ *         othervise an error-code value.
+ */
+int boot_read_swap_state_primary_slot_hook(int image_index,
+                                           struct boot_swap_state *state);
+
+#endif /*H_BOOTUTIL_PUBLIC_HOOKS*/

boot/bootutil/src/bootutil_public.c

@@ -50,6 +50,8 @@
 #include "bootutil/enc_key_public.h"
 #endif
 
+#include "bootutil/boot_public_hooks.h"
+
 #ifdef CONFIG_MCUBOOT
 BOOT_LOG_MODULE_DECLARE(mcuboot);
 #else
@@ -418,8 +420,13 @@ boot_swap_type_multi(int image_index)
     int rc;
     size_t i;
 
-    rc = boot_read_swap_state_by_id(FLASH_AREA_IMAGE_PRIMARY(image_index),
+    rc = BOOT_HOOK_CALL(boot_read_swap_state_primary_slot_hook,
-                                    &primary_slot);
+                        BOOT_HOOK_REGULAR, image_index, &primary_slot);
+    if (rc == BOOT_HOOK_REGULAR)
+    {
+        rc = boot_read_swap_state_by_id(FLASH_AREA_IMAGE_PRIMARY(image_index),
+                                        &primary_slot);
+    }
     if (rc) {
         return BOOT_SWAP_TYPE_PANIC;
     }