'Finds the beginning of the heap via __curbrk, which is an exported
symbol in the linker, which points to the current brk.'

def heap(self):

    curbrk = self.lookup('__curbrk', 'libc')
    brk = self.leak.p(curbrk)
    self.success(('*curbrk:    %#x' % brk))
    return brk
