Re: Compiler Produces Incorrect Code

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: cristalink (cristalink_at_nospam.nospam)
Date: 12/30/04 

Date: Fri, 31 Dec 2004 07:19:41 +1300

> > because MyControlInternal is static. Where's the code for
> MyControlInternal?
> [...]
>
> A bit lengthy, but here it is:

I meant the assembly code, at least up to the first use of eax... 

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"Matt Taylor" <com.sisecure@mtaylor> wrote in message
news:e7SAd.203679$6w6.183910@tornado.tampabay.rr.com...
> "cristalink" <cristalink@nospam.nospam> wrote in message
> news:OJqmpLg7EHA.3836@tk2msftngp13.phx.gbl...
> > eax may well be used as a parameter due to compiler optimizations, esp.
> > because MyControlInternal is static. Where's the code for
> MyControlInternal?
> [...]
>
> A bit lengthy, but here it is:
>
> static NTSTATUS MyIoControlInternal(PDEVICE_OBJECT DeviceObject,
>                                     PFILE_OBJECT FileObject,
>                                     ULONG IoControlCode,
>                                     PVOID InputBuffer,
>                                     ULONG InputBufferLength,
>                                     PVOID OutputBuffer,
>                                     ULONG OutputBufferLength,
>                                     IO_STATUS_BLOCK *pISB)
> {
>  KEVENT ke;
>  PIRP Irp;
>  PIO_STACK_LOCATION IrpSp;
>  PVOID Buffer, TempInputBuffer, TempOutputBuffer;
>  NTSTATUS stat;
>
>  // NOTE: This can never overflow
>  if ((InputBufferLength + OutputBufferLength) > 0)
>  {
>   if ((Buffer = ExAllocatePool(NonPagedPool, InputBufferLength +
> OutputBufferLength)) == NULL)
>   {
>    MyDebugLog("ExAllocatePoolWithTag failed\n");
>    return STATUS_INSUFFICIENT_RESOURCES;
>   }
>
>   TempInputBuffer = Buffer;
>   TempOutputBuffer = (PVOID)((size_t) TempInputBuffer +
InputBufferLength);
>
>   if (InputBufferLength > 0)
>    RtlCopyMemory(TempInputBuffer, InputBuffer, InputBufferLength);
>  }
>  else
>  {
>   Buffer = NULL;
>  }
>
>  KeInitializeEvent(&ke, NotificationEvent, FALSE);
>
>  Irp = IoBuildDeviceIoControlRequest(IoControlCode,
>                                      DeviceObject,
>                                      TempInputBuffer,
>                                      InputBufferLength,
>                                      TempOutputBuffer,
>                                      OutputBufferLength,
>                                      FALSE,
>                                      &ke,
>                                      pISB);
>
>  if (Irp == NULL)
>  {
>   if (Buffer != NULL)
>    ExFreePool(Buffer);
>
>   MyDebugLog("IoBuildDeviceIoControlRequest failed\n");
>   return STATUS_INSUFFICIENT_RESOURCES;
>  }
>
>  IrpSp = IoGetCurrentIrpStackLocation(Irp) - 1;
>  IrpSp->FileObject = FileObject;
>
>  // NOTE: seems the event is not getting set for certain IOCTLs.
> IoCompletion seems to fix it.
>  IoSetCompletionRoutine(Irp, MySetEventIoCompletion, &ke, TRUE, TRUE,
TRUE);
>  stat = IoCallDriver(DeviceObject, Irp);
>  KeWaitForSingleObject(&ke, Executive, KernelMode, FALSE, NULL);
>  IoFreeIrp(Irp);
>
>  stat = pISB->Status;
>
>  if (Buffer != NULL)
>  {
>   if (OutputBufferLength > 0)
>    RtlCopyMemory(OutputBuffer, TempOutputBuffer, OutputBufferLength);
>
>   if (Buffer != NULL)
>    ExFreePool(Buffer);
>  }
>
>  return stat;
> }
>
> -Matt
>
>

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