Stoke centre-half Davies, 26, has been on trial with the Eagles this summer and 21-year-old Northern Ireland full-back McGivern arrives from Manchester City.
Both players have agreed an initial 28-day loan deal and are set to go straight into boss Dougie Freedman's squad for Saturday's season opener at Peterborough.
Freedman said: "Both bring experience to an area of the team where we need cover going into an important opening set of games.
"I see them as important additions to the players we already have available."
Source: Team Talk
Source: Team Talk