The process space of any ELF binary includes a special section, called the `Global Offset Table' (GOT). Every library function used by the program has an entry there that contains an address where the real function is located. This is done to allow easy relocation of libraries within the process memory instead of using hardcoded addresses. Before the program has used the function the first time the entry contains an address of the run-time-linker (rtl). If the function is called by the program the control is passed to the rtl and the functions real address is resolved and inserted into the GOT. Every call to that function passes the control directly to it and the rtl is not called anymore for this function 

địa chỉ của entry chứa address của hàm printf trong GOT của challenge là : 0x080497cc