Re: [Xen-devel] [PATCH V2] kdd.c: Add support for initial handshake in KD protocol for Win 7, 8 and 10 (64 bit)

[George Dunlap <dunlapg@xxxxxxxxx>]

On Fri, Nov 15, 2019 at 1:31 PM Paul Durrant <pdurrant@xxxxxxxxx> wrote:

On Thu, 14 Nov 2019 at 04:57, Julian Tuminaro <julian.tuminaro@xxxxxxxxx> wrote:
>
> From: Julian Tuminaro and Jenish Rakholiya <julian.tuminaro@xxxxxxxxx and rakholiyajenish.07@xxxxxxxxx>
>
> Current implementation of find_os is based on the hard-coded values for
> different Windows version. It uses the value for get the address to
> start looking for DOS header in the given specified range. However, this
> is not scalable to all version of Windows as it will require us to keep
> adding new entries and also due to KASLR, chances of not hitting the PE
> header is significant. We implement a way for 64-bit systems to use IDT
> entry to get a valid exception/interrupt handler and then move back into
> the memory to find the valid DOS header. Since IDT entries are protected
> by PatchGuard, we think our assumption that IDT entries will not be
> corrupted is valid for our purpose. Once we have the image base, we
> search for the DBGKD_GET_VERSION64 structure type in .data section to
> get information required for handshake.
>
> Currently, this is a work in progress feature and current patch only
> supports the handshake and memory read/write on 64-bit systems.
>
> NOTE: This is the Updated version of the previous patch submitted
> NOTE: This has currently been only tested when debugging was not enabled
> on the guest Windows.
>
> Signed-off-by: Jenish Rakholiya <rjenish@xxxxxxx>
> Signed-off-by: Julian Tuminaro <jtuminar@xxxxxxxxxxxxxx>

LGTM.

Reviewed-by: Paul Durrant <paul@xxxxxxx>

Paul, is this something worth adding a line to CHANGELOG about?

 -George