boot: bootutils: Add image in image support

This is source code update to provide images in images
feature support. As mentioned in prev commit:

MCUBoot multi image support mode requires each image
be procedded individually that requires multiple signature
check during boot. If there be 4 imageis it requires 4 times
signature validatation. This feature increase boot time.
Depend on the project requirement long boot time may not be accapted.

In this commit the loader.c file update to search subimages and copy them
in the related load_address.
By this solution:
- Image update will be handled as regularly
- Signature check will be executed for combined image
- Boot time will be decreased

This featue only support for (BOOT_IMAGE_NUMBER == 1 && MCUBOOT_RAM_LOAD) case.

Signed-off-by: Sadik Ozer <sadik.ozer@analog.com>

Author: ozersa

boot/bootutil/src/loader.c

@@ -5,6 +5,7 @@
  * Copyright (c) 2016-2019 JUUL Labs
  * Copyright (c) 2019-2023 Arm Limited
  * Copyright (c) 2024-2025 Nordic Semiconductor ASA
+ * Portions Copyright (c) 2025 Analog Devices Inc.
  *
  * Original license:
  *
@@ -2990,6 +2991,130 @@ boot_update_hw_rollback_protection(struct boot_loader_state *state)
 #endif
 }
 
+
+#if (BOOT_IMAGE_NUMBER == 1) && defined(MCUBOOT_RAM_LOAD)
+
+static int
+read_image_info(uint32_t addr, struct image_header *hdr,
+                uint32_t *total_size, uint32_t *footer_size)
+{
+    struct image_tlv_info info;
+    uint32_t off;
+    uint32_t protect_tlv_size;
+
+    memcpy(hdr, (unsigned char *)addr, sizeof(struct image_header));
+    if (hdr->ih_magic != IMAGE_MAGIC) {
+        BOOT_LOG_INF("IMAGE_MAGIC not correct.");
+        return BOOT_EBADIMAGE;
+    }
+
+    off = BOOT_TLV_OFF(hdr);
+
+    memcpy(&info, (unsigned char *)(addr + off), sizeof(info));
+
+    protect_tlv_size = hdr->ih_protect_tlv_size;
+    if (info.it_magic == IMAGE_TLV_PROT_INFO_MAGIC) {
+        if (protect_tlv_size != info.it_tlv_tot) {
+            return BOOT_EBADIMAGE;
+        }
+
+        memcpy(&info, (unsigned char *)(addr + off + info.it_tlv_tot), sizeof(info));
+    } else if (protect_tlv_size != 0) {
+        return BOOT_EBADIMAGE;
+    }
+
+    if (info.it_magic != IMAGE_TLV_INFO_MAGIC) {
+        return BOOT_EBADIMAGE;
+    }
+
+    *footer_size = protect_tlv_size + info.it_tlv_tot;
+    *total_size = off + *footer_size;
+
+    return 0;
+}
+
+/**
+ * Check the main image and find sub images, then copy them to the target addr.
+ * Set boot image address with the first image that found in the list.
+ *
+ *      -------------------------
+ *      |         Header        |
+ *      -------------------------
+ *      |  SubImage (optional)  |
+ *      |  (Header+Data+Footer) |
+ *      -------------------------
+ *      |  SubImage (optional)  |
+ *      |  (Header+Data+Footer) |
+ *      -------------------------
+ *      |        .....          |
+ *      -------------------------
+ *      |         Footer        |
+ *      -------------------------
+ *
+ * @param addr    Image start address
+ * @param rsp     On success, indicates how booting should occur.
+ *
+ * @return        0 on success; nonzero on failure.
+ */
+static int
+process_sub_images(uint32_t addr, struct boot_rsp *rsp)
+{
+    int rc = 0;
+    bool first_subimage = true;
+    uint32_t main_image_size;
+    struct image_header hdr;
+    uint32_t img_total_size;
+    uint32_t img_footer_size;
+
+    /* read main image info */
+    rc = read_image_info(addr, &hdr, &img_total_size, &img_footer_size);
+    if (rc != 0) {
+        /* No valid image header, main image format not correct. */
+        return rc;
+    }
+
+    /* Set main image size */
+    main_image_size  = img_total_size;
+    /* Decrease image header size and footer size */
+    main_image_size -= (hdr.ih_hdr_size + img_footer_size);
+
+    /* Pass image header */
+    addr += hdr.ih_hdr_size;
+
+    while (main_image_size) {
+        /* read sub image info */
+        rc = read_image_info(addr, &hdr, &img_total_size, &img_footer_size);
+        if (rc != 0) {
+            /* No valid sub-image header, so it migth be single image return 0 */
+            rc = 0;
+            break;
+        }
+
+        /* copy image to target addr */
+        if (hdr.ih_flags & IMAGE_F_RAM_LOAD) {
+            /* 
+             *  For heterogenous system that have multi core on same IC.
+             *  Assuming main core that execute MCUBoot able to access other cores ITCM/DTCM
+             */
+            memcpy((unsigned char *)(hdr.ih_load_addr), (unsigned char *)addr, img_total_size);
+            BOOT_LOG_INF("Copying image from 0x%x to 0x%x is succeeded.", addr, hdr.ih_load_addr);
+        }
+
+        /* Execute first sub image */
+        if ((first_subimage) && !(hdr.ih_flags & IMAGE_F_NON_BOOTABLE)) {
+            first_subimage = false;
+            rsp->br_hdr = (struct image_header *)hdr.ih_load_addr;
+        }
+
+        /* go next image */
+        main_image_size -= img_total_size;
+        addr += img_total_size;
+    }
+
+    return rc;
+}
+#endif // #if (BOOT_IMAGE_NUMBER == 1) && defined(MCUBOOT_RAM_LOAD)
+
 fih_ret
 context_boot_go(struct boot_loader_state *state, struct boot_rsp *rsp)
 {
@@ -3055,6 +3180,10 @@ context_boot_go(struct boot_loader_state *state, struct boot_rsp *rsp)
 
     fill_rsp(state, rsp);
 
+#if (BOOT_IMAGE_NUMBER == 1) && defined(MCUBOOT_RAM_LOAD)
+    (void) process_sub_images(rsp->br_hdr->ih_load_addr, rsp);
+#endif
+
 close:
     boot_close_all_flash_areas(state);