@Override
    boolean execute() {
		message="";
		try {
			length = block.getStart().subtract(startAddr);
			if (length == 0) {
				return true;
			}
			if (length != block.getSize() ||
				startAddr.compareTo(block.getStart()) != 0) {
				return expandBlock();
			}
		} catch(Exception e) {
			message = e.getMessage();
			if (message  == null) {
				message = e.toString();
			}
		}
		return false;
	}
Expand the block.
@return true if the block was expanded successfully
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/memory/ExpandBlockUpModel.java