Everhart, Glenn (FUSA)
From:	Jamey Kirby [jkirby@storagecraft.com]
Sent:	Friday, April 16, 1999 8:23 PM
To:	'George Blat'; ntdev@atria.com
Subject:	RE: [ntdev] New book by Dekker and Newcomer
George,

From my recent experience, if you create the system thread in the context of
a user-mode process, the thread always runs in the context of that process
at PASSIVE_LEVEL. This means that the user-mode address space is valid and
mapped. Paged I/O between the driver and the user-mode application works.

I needed to access a network file resource from a KM driver with
ZwCreateFile(). We developed a service that would logon using a special
account with the appropriate network rights to access the file the driver
needed. When the service opened our drivers control device object using
CreateFile(), on first open, I created the system thread using -1 as the
process. Once I did this, I was able to access the network resource just
like the service was able to access the resource. On my last close, I
terminated the thread.  This driver has been running under extream network
loads owing the drivers file I/O (20 - 50 gigabytes per day) and it has been
very, very solid. No BSODs.

We have a virtual storage technology. We have drivers that emulate disk,
CD-ROM and tape using normal file I/O. Using this technique to map virtual
storage devices to network file resources works quite well in SAN
envoironments.

Regards,

Jamey Kirby
StorageCraft, Inc.
jkirby@storagecraft.com
www.storagecraft.com


-----Original Message-----
From: owner-ntdev@atria.com [mailto:owner-ntdev@atria.com]On Behalf Of
George Blat
Sent: Friday, April 16, 1999 9:47 AM
To: ntdev@atria.com
Subject: Re: [ntdev] New book by Dekker and Newcomer


Question: How is a system thread for a process defined: Is it a thread that
can read anything in system memory above 0x80000000 and is also attached
to the context of the non-system process that was passed when created
by the driver?

Is that true or false. If false, what is the true definition?

Thanks in advance,

George




At 04:46 PM 4/15/99 -0700, you wrote:
>Well, I just got the monster today and started looking it over. It seems to
>have been quite an industrious effort. I have not read the whole thing, but
>I do have a comment regarding pages 974 and 975.
>
>Quote:
>
>"The _ProcessHandle_ parameter must not be used for driver-created threads
>and must be NULL".
>
>This is incorrect. Using a specific process ID or using NtCurrentProcess()
>[which is -1], you can create a system thread for any process in the
system.
>
>Anyway, just a note on what I have seen so far.
>
>Regards,
>
>Jamey Kirby
>StorageCraft, Inc.
>jkirby@storagecraft.com
>www.storagecraft.com
>
>
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