Re: [Xen-devel] Reading guest page flags

[Spencer Michaels <sxmichaels@xxxxxxxxx>]

Thanks! Sorry, I should have been more specific - I do indeed mean the regular guest PTEs (and I'm using PV guests which as I understand don't use EPT anyway). So, it seems I'll have to write my own code for this. I'll take a look at libvmi's implementation; if anyone knows any other libraries / programs that read guest PTEs, that would be helpful to know as well.

On Thu, Sep 13, 2018, 10:47 AM Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> wrote:

On 9/13/18 8:29 PM, Spencer Michaels wrote:
> I'm writing an application that can read/write guest memory, and as part
> of that I need to check whether the page being manipulated is
> readable/writable by the guest itself. Does Xen have an API that would
> allow me to read the flags of an arbitrary page on a guest, given either
> its address or its PFN? I've only been able to find functions that
> update the existing memory mappings, but none to read them.

If you mean EPT, yes: look at xc_get_mem_access() in xenctrl.h / libxc.
If you mean "regular" PTEs, no - you'd have to write your own code to
retrieve that.

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