[PULL] use LRMI for real-mode calls

[Mark Kettenis]

> From: Adam Jackson <ajax at nwnk.net>
> Date: Fri, 30 Apr 2010 17:37:32 -0400
>
> - backend-x86emu.c looks like it loses the feature of mapping the 1M
> arena wherever the kernel pleases, and instead reverts to mapping it at
> the 0 page.  This is a security bug on arches where kernel virtual
> addresses equal user virtual addresses (which includes x86 and amd64).

And for this reason, The OpenBSD kernel will actually refuse to map a
page at virtual address zero.  And I believe the same is true on Linux
if you;re using a security conscious distro.