Re: [Xen-devel] EPT question - XENMEM_get_access_op

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.02.15 at 05:47, <bsingharora@xxxxxxxxx> wrote:
> I'm trying to use the memevent channel to extract the permission for a
> particular text section. I expect to see rx as the permission, instead
> I am seeing rwx. I have not spent a whole lot of time looking at
> memaccess[] and p2m-ept.c, but I am puzzled. The OS definitely has
> this text segment marked as COPY-ON-WRITE, I am a little confused with
> the permissions returned. Is there a way to get the right thing?

What the guest OS specifies doesn't matter here - EPT is not OS
(L1) but hypervisor (L2) paging, and hence the permissions there
are controlled by the hypervisor. Of course guest memory
accesses have to pass both paging levels' access checks in order
to be carried out (and not fault).

Jan


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