Add some debug assertions in BL1 FWU copy code

These debug assertions sanity check the state of the internal
FWU state machine data when resuming an incomplete image copy
operation.

Change-Id: I38a125b0073658c3e2b4b1bdc623ec221741f43e
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>

bl1/bl1_fwu.c

@@ -158,7 +158,19 @@ static int bl1_fwu_image_copy(unsigned int image_id,
 	}
 
 	if (image_desc->state == IMAGE_STATE_COPYING) {
+		/*
+		 * There must have been at least 1 copy operation for this image
+		 * previously.
+		 */
+		assert(image_desc->copied_size != 0);
+		/*
+		 * The image size must have been recorded in the 1st copy
+		 * operation.
+		 */
 		image_size = image_desc->image_info.image_size;
+		assert(image_size != 0);
+		assert(image_desc->copied_size < image_size);
+
 		INFO("BL1-FWU: Continuing image copy in blocks\n");
 	} else { /* image_desc->state == IMAGE_STATE_RESET */
 		INFO("BL1-FWU: Initial call to copy an image\n");