He said: "The signing of Djibril shows how far this club have moved on since the end of last season.
"His experience will bring a lot to the squad and he will hopefully add some goals to the side.
He then moved on to Marseille, initially on loan before making the move permanent in 2007 but he claimed he was tempted to return to England by the Black Cats' ambition.
"I'm really pleased to join a good club with good players.
"Sunderland are a club I think is going to achieve things, they have big ambitions, that is why I chose to come here.
"I liked what the club had to say to me."