Hi,
My basic need is that I have to pass a structure from my filter driver to the user mode, which will do some
processing based on the structure, and then let the driver know once it is finished.
Presently I have thought of 2 solutions,
-
Call the user mode directly using “IOCTL” and pass the structure along with it. What I would like to know is how I can make
the “IOCTL” calls from kernel to the user mode.
-
Have a thread in the user mode which would wait for an event. I can set this event in the kernel and then
the user mode can make the IOCTL, but I am not sure of how I can share an event between the user mode and kernel mode and secondly,
this solution would be a bit more expensive (with two calls involved) than the first one. So I would prefer the first solution, since
the volume of calls being made will be high.
Any help will be appreciated,
thanks,
Almas
A first solution could be calling from user mode to kernel (by IOCTL) and
keep this thread waiting in kernel mode, i.e, not returning to user mode
until
being signaled.
Then signal from kernel to the waiting thread when you have some data to
transfer. The IOCTL thread
then will pick the data and return to user mode. This simulates the effect
you want, i.e, you dont call from driver to
user mode but it looks the same.
The second technique is to share a memory space between kernel and user mode
and then use
events to synchronize kernel and user threads. This technique is better than
above when you have a high traffic.
No calls at all are necessary because this way the user mode thread will not
do the trip to kernel (by calling IOCTL), but instead will pick the data
from the shared buffer. The easiest way to share a buffer between kernel and
user mode is mapping a section.
Hope this helps.
Inaki.
-----Original Message-----
From: Almas Khan
Sent: martes 4 de abril de 2000 13:19
To: File Systems Developers
Subject: [ntfsd] Sending IOCTL’s from kernel to user mode
Hi,
My basic need is that I have to pass a structure from my filter driver to
the user mode, which will do some
processing based on the structure, and then let the driver know once it is
finished.
Presently I have thought of 2 solutions,
-
Call the user mode directly using “IOCTL” and pass the structure along
with it. What I would like to know is how I can make
the “IOCTL” calls from kernel to the user mode.
-
Have a thread in the user mode which would wait for an event. I can set
this event in the kernel and then
the user mode can make the IOCTL, but I am not sure of how I can share an
event between the user mode and kernel mode and secondly,
this solution would be a bit more expensive (with two calls involved) than
the first one. So I would prefer the first solution, since
the volume of calls being made will be high.
Any help will be appreciated,
thanks,
Almas
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Hello,
AFAIK it is not possible to make IOCTL calls from
kernel mode to user mode.
For event sharing, one can create the event in user
mode using CreateEvent call and open the event in
kernel mode using ZwOpenEvent call. e.g If you create
a event say “MyEvent” in user mode then you can open
the event in kernel mode using the name
“\BaseNamedObjects\MyEvent”.
Alternatively you can create a event named
\BaseNamedObjects\MyEvent in kernel mode using the
ZwCreateEvent call and open it in user mode using
OpenEvent call.
The better approach would be to create a named section
object and pair of event objects.
e.g Create two events say “DataArrived” and
“DataCaptured” and one section (memory mapping) object
say “DataBuffer” in user mode. The user mode thread
will wait on the “DataArrived” event. Whenever the
filter driver needs to send some data, it will open
the section object \BaseNamedObjects\DataBuffer using
ZwOpenSection call, map view using ZwMapViewOfSection
and write data structure in to it. Next it will open
the events named \BaseNamedObjects\DataArrived and
\BaseNamedObjects\DataCaptured. It will signal the
“DataArrived” event and wait on the “DataCaptured”
event. When the “DataArrived” event is signalled, the
user mode code will pick up the data in shared section
and signal the “DataCaptured” event. This will allow
your filter driver to come out of wait.
Hope this helps.
-Prasad
— Almas Khan wrote:
> Hi,
>
> My basic need is that I have to pass a structure
> from my filter driver to the user mode, which will
> do some
> processing based on the structure, and then let the
> driver know once it is finished.
>
> Presently I have thought of 2 solutions,
>
> - Call the user mode directly using “IOCTL” and pass
> the structure along with it. What I would like to
> know is how I can make
> the “IOCTL” calls from kernel to the user mode.
>
> - Have a thread in the user mode which would wait
> for an event. I can set this event in the kernel and
> then
> the user mode can make the IOCTL, but I am not sure
> of how I can share an event between the user mode
> and kernel mode and secondly,
> this solution would be a bit more expensive (with
> two calls involved) than the first one. So I would
> prefer the first solution, since
> the volume of calls being made will be high.
>
> Any help will be appreciated,
>
> thanks,
> Almas
>
> —
> You are currently subscribed to ntfsd as:
> xxxxx@yahoo.com
> To unsubscribe send a blank email to
> $subst(‘Email.Unsub’)
>
>
=====
Prasad S. Dabak
Director of Engineering, Windows NT/2000 Division
Cybermedia Software Private Limited
http://www.cybermedia.co.in
Co-author of the book “Undocumented Windows NT”
ISBN 0764545698
__________________________________________________
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Many thanks for the help. I am going for the first solution, though, and just putting in more user threads so that they can handle
the volume of traffic.
Almas
A first solution could be calling from user mode to kernel (by IOCTL) and
keep this thread waiting in kernel mode, i.e, not returning to user mode
until
being signaled.
Then signal from kernel to the waiting thread when you have some data to
transfer. The IOCTL thread
then will pick the data and return to user mode. This simulates the effect
you want, i.e, you dont call from driver to
user mode but it looks the same.
The second technique is to share a memory space between kernel and user mode
and then use
events to synchronize kernel and user threads. This technique is better than
above when you have a high traffic.
No calls at all are necessary because this way the user mode thread will not
do the trip to kernel (by calling IOCTL), but instead will pick the data
from the shared buffer. The easiest way to share a buffer between kernel and
user mode is mapping a section.
Hope this helps.
Inaki.
> -----Original Message-----
> From: Almas Khan
> Sent: martes 4 de abril de 2000 13:19
> To: File Systems Developers
> Subject: [ntfsd] Sending IOCTL’s from kernel to user mode
>
> Hi,
>
> My basic need is that I have to pass a structure from my filter driver to
> the user mode, which will do some
> processing based on the structure, and then let the driver know once it is
> finished.
>
> Presently I have thought of 2 solutions,
>
> - Call the user mode directly using “IOCTL” and pass the structure along
> with it. What I would like to know is how I can make
> the “IOCTL” calls from kernel to the user mode.
>
> - Have a thread in the user mode which would wait for an event. I can set
> this event in the kernel and then
> the user mode can make the IOCTL, but I am not sure of how I can share an
> event between the user mode and kernel mode and secondly,
> this solution would be a bit more expensive (with two calls involved) than
> the first one. So I would prefer the first solution, since
> the volume of calls being made will be high.
>
> Any help will be appreciated,
>
> thanks,
> Almas
>
> —
> You are currently subscribed to ntfsd as: xxxxx@pandasoftware.es
> To unsubscribe send a blank email to $subst(‘Email.Unsub’)
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