MDL Scope
in [Device Drivers]
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From: Sushma on 17 Feb 2010 08:08 Hi All, I want to retrieve the MDL pointer from WDF request and then complete the request. I want to use the MDL at later point of time. Is the MDL still valid after completing the request? Thank You. Regards, Sushma
From: Don Burn on 17 Feb 2010 08:25 No the MDL goes with the request. You should not assume the memory described by a request in a MDL (or just a buffer) is valid once the request is completed. The memory may be deallocated, or be used for something else. If you want to use the memory you should be pending the request. Don Burn (MVP, Windows DKD) Windows Filesystem and Driver Consulting Website: http://www.windrvr.com Blog: http://msmvps.com/blogs/WinDrvr "Sushma" <sushma.yella(a)gmail.com> wrote in message news:0ad1fbce-d26a-43df-b17e-ffe6119971bf(a)b36g2000pri.googlegroups.com: > Hi All, > > I want to retrieve the MDL pointer from WDF request and then complete > the request. I want to use the MDL at later point of time. > > Is the MDL still valid after completing the request? > > Thank You. > > Regards, > Sushma __________ Information from ESET Smart Security, version of virus signature database 4873 (20100217) __________ The message was checked by ESET Smart Security. http://www.eset.com
From: Sushma on 17 Feb 2010 09:07 > No the MDL goes with the request. You should not assume the memory > described by a request in a MDL (or just a buffer) is valid once the > request is completed. The memory may be deallocated, or be used for > something else. If you want to use the memory you should be pending the > request. > Is there a way I can find if memory is deallocated. I cannot pend the request because requests arrive sequentially. Unless I complete it the driver does not get next request. I did like: virtualAddress = (ULONG_PTR) MmGetSystemAddressForMdlSafe(Irp- >MdlAddress, NormalPagePriority); totalLength = pUrb->UrbBulkOrInterruptTransfer.TransferBufferLength; DeviceExtension->newMdl = IoAllocateMdl((PVOID) virtualAddress,totalLength,FALSE,FALSE,NULL); IoCompleteRequest(Irp, IO_NO_INCREMENT); Now, I want to use DeviceExtension->newMdl. If I see the addres of newMdl, it looks like a valid one. I'm not sure of it. Any suggestions. Thank You. Regards, Sushma
From: Don Burn on 17 Feb 2010 09:35 No there is no way to do this. Your basic design is flawed, all you have done is create code that will inevitably crash the system. -- Don Burn (MVP, Windows DKD) Windows Filesystem and Driver Consulting Website: http://www.windrvr.com Blog: http://msmvps.com/blogs/WinDrvr Remove StopSpam to reply "Sushma" <sushma.yella(a)gmail.com> wrote in message news:fbc73e55-b16b-4d55-8af8-71ae3d5a4c7e(a)s33g2000prm.googlegroups.com... > No the MDL goes with the request. You should not assume the memory > described by a request in a MDL (or just a buffer) is valid once the > request is completed. The memory may be deallocated, or be used for > something else. If you want to use the memory you should be pending the > request. > Is there a way I can find if memory is deallocated. I cannot pend the request because requests arrive sequentially. Unless I complete it the driver does not get next request. I did like: virtualAddress = (ULONG_PTR) MmGetSystemAddressForMdlSafe(Irp- >MdlAddress, NormalPagePriority); totalLength = pUrb->UrbBulkOrInterruptTransfer.TransferBufferLength; DeviceExtension->newMdl = IoAllocateMdl((PVOID) virtualAddress,totalLength,FALSE,FALSE,NULL); IoCompleteRequest(Irp, IO_NO_INCREMENT); Now, I want to use DeviceExtension->newMdl. If I see the addres of newMdl, it looks like a valid one. I'm not sure of it. Any suggestions. Thank You. Regards, Sushma __________ Information from ESET NOD32 Antivirus, version of virus signature database 4874 (20100217) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com __________ Information from ESET NOD32 Antivirus, version of virus signature database 4874 (20100217) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com
From: Maxim S. Shatskih on 17 Feb 2010 09:44
> Is the MDL still valid after completing the request? No. Neither is in WDM. Pend this IRP for all this long time. -- Maxim S. Shatskih Windows DDK MVP maxim(a)storagecraft.com http://www.storagecraft.com |