Maximize L2 norm under linear constraints?

I want to maximize L2 norm of a vector under some linear constraints. i.e,

          max |x|^2
  subject to Ax ≤ b

Could you please help me to find out a way to solve this in Matlab?

Answer 1

[John D'Errico]

help quadprog

Use

H = -eye(n,n)

[Anver Hisham]

@John D'Errico: I see quadprog solves only convex problems. I see my problem is non-convex, and also NP-hard.