Re: [Xen-devel] Reading guest page flags

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Thu, Sep 13, 2018 at 11:48 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.

LibVMI does that for guest PTEs:
https://github.com/libvmi/libvmi/blob/master/libvmi/libvmi.h#L936

Tamas

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