Re: [Xen-devel] [VMI] How to add support for MOV-TO-DRx events ?

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 5/10/19 12:31 AM, Andrew Cooper wrote:
> What we'll have to do is end up in a position where we can have some
> real %dr settings given by the VMI agent, and some shadow %dr settings
> which the guest interacts with.  Also I should warn you at this point
> that, because of how the registers work, It will not be possible to have
> guest-shadowed %dr functioning at the same time as VMI-provided %dr
> settings.
> 
> I guess the main usecase here is simply hiding from the guest kernel
> that debugging activities are in use, and we are ok to break the real
> use of gdb/other inside the guest?  Razvan/Tamas: As your the
> maintainers, it is your call, ultimately.

What worries me here is that in that case it becomes easier for a rogue
application inside the guest to figure out that the guest's being
monitored, if I understand things correctly.

Of course, a dom0 introspection agent may choose to simply not subscribe
to DR events, and thus not alter the current flow at all, which makes
things better.


Thanks,
Razvan

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