Re: [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks - v2

["Daniel P. Berrange" <berrange@redhat.com>]

On Mon, Jul 14, 2008 at 12:34:48PM +0200, Jan Kiszka wrote:
> This is the second version of my segment type and register check. It
> reduces the impact on the translator code significantly, and it also
> fixes a bug of the "size" helper variant in the previous version.
> 
> The idea of this patch is to generate calls to a check helper only in
> case the user requested this support via "-seg-checks". This feature
> remains off by default as most x86 OSes do not care about protection via
> segmentation anymore (and it was even removed from 64-bit modes by the
> CPU vendors). 

Two current users of protection via segmentation I know of

 - 32-bit linux with the ExecShield capability will still use segmentation 
   to split the address space into executable vs non-executable regions, if
   the CPU doesn't have NX bit support.
 - 32-bit Xen uses segmentation for protecting the hypervisor.

Regards,
Daniel
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