To make room for Hall on the 40-man roster, Arizona designated right-handed pitcher Matt Stites for assignment.
Hall, 28, had a 3.46 ERA in 43 games last season with Triple-A Sacramento. He made his big league debut with the Giants on Sept. 3 against the Rockies. Hall allowed six earned runs in 8 1/3 innings over seven games.
Hall's best outing came against the Rockies on Oct. 2, when he struck out three over two scoreless innings.
Hall was the Giants' 19th-round pick in 2011 out of Southern University. He was added to the Giants' 40-man roster last fall and still has Minor League options.
Stites, 25, had a 12.46 ERA out of the bullpen a year ago for the D-backs in 8 2/3 innings. Stites has a 7.13 ERA in 41 2/3 innings in the big leagues, all with the D-backs.
With the Hall acquisition on Wednesday, the D-backs' 40-man roster is full.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.