Re: ntdev] Transfer very large amounts of data from kernel to user mode

How would you change to a specific comtext?

Sent from my T-Mobile 4G LTE Device

-------- Original message --------
From: xxxxx@osr.com
Date: 4/29/17 11:40 AM (GMT-05:00)
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Transfer very large amounts of data from kernel to user mode

(Following-up my own post… bad form, I know)

Worse, it doesn’t even matter.

Let’s say I AM called in an arbitrary process context. Nothing stops me from changing to a specific context to do the mapping.

I’ll say it again: There IS no “context issue”…

Peter
OSR
@OSRDrivers


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The oddly name kestackattachprocess is one way.

Mark Roddy

On Sat, Apr 29, 2017 at 4:55 PM, Daryl Fowlkes <
xxxxx@hotmail.com> wrote:

How would you change to a specific comtext?

Sent from my T-Mobile 4G LTE Device

-------- Original message --------
From: xxxxx@osr.com
Date: 4/29/17 11:40 AM (GMT-05:00)
To: Windows System Software Devs Interest List
> Subject: RE:[ntdev] Transfer very large amounts of data from kernel to
> user mode
>
> (Following-up my own post… bad form, I know)
>
> Worse, it doesn’t even matter.
>
> Let’s say I AM called in an arbitrary process context. Nothing stops me
> from changing to a specific context to do the mapping.
>
> I’ll say it again: There IS no “context issue”…
>
> Peter
> OSR
> @OSRDrivers
>
>
> —
> NTDEV is sponsored by OSR
>
> Visit the list online at: http:> showlists.cfm?list=ntdev>
>
> MONTHLY seminars on crash dump analysis, WDF, Windows internals and
> software drivers!
> Details at http:
>
> To unsubscribe, visit the List Server section of OSR Online at <
> http://www.osronline.com/page.cfm?name=ListServer&gt;
>
> —
> NTDEV is sponsored by OSR
>
> Visit the list online at: http:> showlists.cfm?list=ntdev>
>
> MONTHLY seminars on crash dump analysis, WDF, Windows internals and
> software drivers!
> Details at http:
>
> To unsubscribe, visit the List Server section of OSR Online at <
> http://www.osronline.com/page.cfm?name=ListServer&gt;
></http:></http:></http:></http:>

You have options. One way is to create a system thread in the context of
the process you’re interested in, and use an event to trigger when you want
to be in that context.

On Sat, Apr 29, 2017, 4:56 PM Daryl Fowlkes
wrote:

> How would you change to a specific comtext?
>
>
>
> Sent from my T-Mobile 4G LTE Device
>
>
> -------- Original message --------
> From: xxxxx@osr.com
> Date: 4/29/17 11:40 AM (GMT-05:00)
> To: Windows System Software Devs Interest List
> Subject: RE:[ntdev] Transfer very large amounts of data from kernel to
> user mode
>
> (Following-up my own post… bad form, I know)
>
> Worse, it doesn’t even matter.
>
> Let’s say I AM called in an arbitrary process context. Nothing stops me
> from changing to a specific context to do the mapping.
>
> I’ll say it again: There IS no “context issue”…
>
> Peter
> OSR
> @OSRDrivers
>
>
> —
> NTDEV is sponsored by OSR
>
> Visit the list online at: <
> http://www.osronline.com/showlists.cfm?list=ntdev&gt;
>
> MONTHLY seminars on crash dump analysis, WDF, Windows internals and
> software drivers!
> Details at http:
>
> To unsubscribe, visit the List Server section of OSR Online at <
> http://www.osronline.com/page.cfm?name=ListServer&gt;
>
> —
> NTDEV is sponsored by OSR
>
> Visit the list online at: <
> http://www.osronline.com/showlists.cfm?list=ntdev&gt;
>
> MONTHLY seminars on crash dump analysis, WDF, Windows internals and
> software drivers!
> Details at http:
>
> To unsubscribe, visit the List Server section of OSR Online at <
> http://www.osronline.com/page.cfm?name=ListServer&gt;
></http:></http:>

This can be *very* performant and efficient. You basically wind up with a kernel-mode “helper thread” dedicated to moving data for the process.

Like many of Mr. Kirby’s designs, this is complicated to do well. More complicated, in fact, than it may first seem. Easy for someone of Mr. Kirby’s experience. Not so easy if your experience is limited to developing a couple WDF drivers.

Peter
OSR
@OSRDrivers