Let me suggest a solution to the apeture problem that I use.  I think
the kernel proper should be secure and should let you map the space
that SVGA accelerated drivers use.  I add the following case to
sys/arch/i386/i386/mem.c: mmmmap(dev, off, prot)
	case 13:
		if (off > ctob(physmem) ||
		    ((off >= 0xA0000 && off < 0x100000)) ||
		    (off == 0))
			return i386_btop(off);
		else
			return -1;
This says: allow memory to be mapped that is beyound the end of
physical memory or in the bios hole or page 0 (also used for bios).
You would then
		mknod /dev/xf86 c 2 13
And now you don't worry about apeture drivers any more!