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From: Peter on 28 Apr 2008 04:28
Hi,

I had used following technique in communication user-mode app <--> driver:

User app passes event handle to driver and driver retrieves pointer to
object body with help of ObReferenceObjectByHandle() .
Driver then signals some events to user mode application with KeSetEvent().

Problem is:
Currently I have 32-bit user mode app which communicates with 64-bit driver.
When 64-bit driver reads 32-bit HANDLE (32-bit number) passes from
user-mode, can it simple make conversion like:
HANDLE h64Bit = NULL;
h64Bit = (HANDLE)h32BitFromUserMode;
?
Will be retrieved handle in 64-bit driver valid and can be on such called
KeSetEvent()
in 64-bit driver ?

Peter

From: Gianluca Varenni on 28 Apr 2008 12:09

"Peter" <Peter(a)discussions.microsoft.com> wrote in message
news:2C2B95B6-23D8-4D62-BCC3-52C53EA8754A(a)microsoft.com...
> Hi,
>
> I had used following technique in communication user-mode app <--> driver:
>
> User app passes event handle to driver and driver retrieves pointer to
> object body with help of ObReferenceObjectByHandle() .
> Driver then signals some events to user mode application with
> KeSetEvent().
>
> Problem is:
> Currently I have 32-bit user mode app which communicates with 64-bit
> driver.
> When 64-bit driver reads 32-bit HANDLE (32-bit number) passes from
> user-mode, can it simple make conversion like:
> HANDLE h64Bit = NULL;
> h64Bit = (HANDLE)h32BitFromUserMode;
> ?
> Will be retrieved handle in 64-bit driver valid and can be on such called
> KeSetEvent()
> in 64-bit driver ?

Yes, it works. One bit of advice, however. In your IOCTL code in the driver,
you definitely need to distinguish between a 32-bit app and a 64-bit one, in
order to properly parse the HANDLE passed from user mode (which can be a 32
or a 64bit integer).

In case of WDM, the code is more or less this one

....
HANDLE hUserEvent;
PKEVENT pKernelEvent;
#ifdef _AMD64_
VOID*POINTER_32 hUserEvent32Bit;
#endif //_AMD64_
....

#ifdef _AMD64_
if (IoIs32bitProcess(Irp))
{
//
// validate the input
//
if (IrpSp->Parameters.DeviceIoControl.InputBufferLength != sizeof
(hUserEvent32Bit))
{
SET_FAILURE_INVALID_REQUEST();
break;
}

hUserEvent32Bit = *(VOID*POINTER_32*)Irp->AssociatedIrp.SystemBuffer;
hUserEvent = hUserEvent32Bit;
}
else
#endif //_AMD64_
{
//
// validate the input
//
if (IrpSp->Parameters.DeviceIoControl.InputBufferLength != sizeof
(hUserEvent))
{
SET_FAILURE_INVALID_REQUEST();
break;
}

hUserEvent = *(PHANDLE)Irp->AssociatedIrp.SystemBuffer;
}

Status = ObReferenceObjectByHandle(hUserEvent, EVENT_MODIFY_STATE,
*ExEventObjectType, Irp->RequestorMode, (PVOID*) &pKernelEvent, NULL);


Hope it helps
GV

--
Gianluca Varenni, Windows DDK MVP

CACE Technologies
http://www.cacetech.com




>
> Peter
>


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