Re: DeviceIoControl failed in WOW64 on 64bit XP Pro

From: Thomas F. Divine [DDK MVP] (tdivine_at_NOpcausaSPAM.com)
Date: 11/18/04 

Date: Thu, 18 Nov 2004 13:55:37 -0500

"hyfeng" <canttellyou@newsgroup.nospam> wrote in message
news:ehYKsqZzEHA.908@TK2MSFTNGP11.phx.gbl...
> "Maxim S. Shatskih" <maxim@storagecraft.com> wrote in
> news:ecwkyATzEHA.1196
> @TK2MSFTNGP15.phx.gbl:
>
>> Alignment can be an issue. Align all IOCTL buffers on 8 bytes.
>>
>
> Well, I understand alignment very likely is the issue and that is probably
> what I will do to get around the problem.
>
> However, WOW64 is supposed to provide thunking properly so that 32-bit
> applications do not need to change and that is why I think this is a
> problem from WOW64 and I need confirmation form Microsoft. Also, please
> keep in mind that there is no pointer-precision data in the buffer passed
> into DeviceIoControl(). All data in the buffer are fixed-precision type.
>
I understand that you are not passing any pointers... However, the data
passed two and from a driver intrinsically uses pointers in the IRP that,
depending on the I/O method, may be mapped for you.

HOWEVER, it has been my experience that some 64-bit components check for
64-bit alignment of IRP buffers before they check anything else. For
example, a call to read a 32-bit value may fail because the 32-bit value is
not aligned on a 64-bit boundary.

I think that this is a bug - or at least isn't documented sufficiently
anywhere that I looked.

Good luck,

Thomas F. Divine, Windows DDK MVP
http://www.rawether.net

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