def _extract_symbols(self, symbols, default=None):
        """! @brief Fill 'symbols' field with required flash algo symbols"""
        to_ret = {}
        for symbol in symbols:
            symbolInfo = self.elf.symbol_decoder.get_symbol_for_name(symbol)
            if symbolInfo is None:
                if default is not None:
                    to_ret[symbol] = default
                    continue
                raise FlashAlgoException("Missing symbol %s" % symbol)
            to_ret[symbol] = symbolInfo.address
        return to_ret