Messages in this thread |  | | | Date | Wed, 24 Sep 2008 21:54:28 -0700 | | From | "H. Peter Anvin" <> | | Subject | Re: [PATCH 1/2] VMware detection support for x86 and x86-64 |
Alok Kataria wrote:
> On Wed, 2008-09-24 at 21:38 -0700, H. Peter Anvin wrote:
>> Alok kataria wrote:
>>> Even if there is anything on that port on native hardware it would
>>> work perfectly well and is _safe_.
>>> First let me post the code to access this backdoor port (the way it
>>> should really be done )
>>>
>>> So whenever we query port 0x5658 , with the GETVERSION command (which
>>> is the first thing we do with this port), we expect that eax !=
>>> 0xFFFFFFFF and ebx has a VMWARE specific MAGIC value. Please note
>>> that ebx has been initialized to zero in the code above.
>>>
>> You have no idea what you just did to a real piece of hardware.
> Why ? what do you mean ?
> ebx is a local variable in the code above that i posted.
> Only when on hypervisor will we write the magic value over there.
> How can this affect native hardware, i fail to understand.
> Please explain.
>
You accessed a bloody I/O port!
If you think it's harmless because it was an IN, you're sorely mistaken.
-hpa
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