Underneath that hauberk he would wear a gambeson: a quilted jacket worn beneath a knight's armor to cushion the blows of battle. I couldn't find a free clip art picture of a gambeson to show you, but you can see what one looks like by clicking here. (Scroll down to the picture beneath the "jack".)
That chain mail covering the knight's legs is called chausses: that portion of the chain mail that covered the feet, legs, and body below the waist.
Now toss on a helmet, strap on a sword, grab your shield, and you're all ready for battle!
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