/*
 Copyright (c) 2008-2009 TrueCrypt Developers Association. All rights reserved.

 Governed by the TrueCrypt License 3.0 the full text of which is contained in
 the file License.txt included in TrueCrypt binary and source code distribution
 packages.
*/

#include "TCdefs.h"
#include "Apidrvr.h"
#include "Ntdriver.h"
#include "DriveFilter.h"
#include "EncryptedIoQueue.h"
#include "EncryptionThreadPool.h"
#include "Volumes.h"


static void AcquireBufferPoolMutex (EncryptedIoQueue *queue)
{
	NTSTATUS status;

	status = KeWaitForMutexObject (&queue->BufferPoolMutex, Executive, KernelMode, FALSE, NULL);
	if (!NT_SUCCESS (status))
		TC_BUG_CHECK (status);
}


static void ReleaseBufferPoolMutex (EncryptedIoQueue *queue)
{
	KeReleaseMutex (&queue->BufferPoolMutex, FALSE);
}


static void *GetPoolBuffer (EncryptedIoQueue *queue, ULONG requestedSize)
{
	EncryptedIoQueueBuffer *buffer;
	void *bufferAddress = NULL;
	BOOL requestedSizePresentInPool = FALSE;

	while (TRUE)
	{
		AcquireBufferPoolMutex (queue);

		for (buffer = queue->FirstPoolBuffer; ; buffer = buffer->NextBuffer)
		{
			if (buffer && buffer->Size == requestedSize)
			{
				requestedSizePresentInPool = TRUE;

				if (!buffer->InUse)
				{
					// Reuse a free buffer
					buffer->InUse = TRUE;
					bufferAddress = buffer->Address;
					break;
				}
			}

			if (!buffer || !buffer->NextBuffer)
			{
				EncryptedIoQueueBuffer *newBuffer;

				if (requestedSizePresentInPool && !queue->StartPending)
					break;

				// Allocate a new buffer
				newBuffer = TCalloc (sizeof (EncryptedIoQueueBuffer));
				if (!newBuffer)
				{
					bufferAddress = NULL;
					break;
				}

				bufferAddress = TCalloc (requestedSize);
				if (bufferAddress)
				{
					newBuffer->NextBuffer = NULL;
					newBuffer->Address = bufferAddress;
					newBuffer->Size = requestedSize;
					newBuffer->InUse = TRUE;

					if (!buffer)
						queue->FirstPoolBuffer = newBuffer;
					else
						buffer->NextBuffer = newBuffer;
				}
				else
					TCfree (newBuffer);

				break;
			}
		}

		ReleaseBufferPoolMutex (queue);

		if (bufferAddress || !requestedSizePresentInPool || queue->StartPending)
			break;

		KeWaitForSingleObject (&queue->PoolBufferFreeEvent, Executive, KernelMode, FALSE, NULL);
	}

	return bufferAddress;
}


static void ReleasePoolBuffer (EncryptedIoQueue *queue, void *address)
{
	EncryptedIoQueueBuffer *buffer;
	AcquireBufferPoolMutex (queue);
	
	for (buffer = queue->FirstPoolBuffer; buffer != NULL; buffer = buffer->NextBuffer)
	{
		if (buffer->Address == address)
		{
			ASSERT (buffer->InUse);

			buffer->InUse = FALSE;
			break;
		}
	}

	ReleaseBufferPoolMutex (queue);
	KeSetEvent (&queue->PoolBufferFreeEvent, IO_DISK_INCREMENT, FALSE);
}


static void FreePoolBuffers (EncryptedIoQueue *queue)
{
	EncryptedIoQueueBuffer *buffer;
	AcquireBufferPoolMutex (queue);

	for (buffer = queue->FirstPoolBuffer; buffer != NULL; )
	{
		EncryptedIoQueueBuffer *nextBuffer = buffer->NextBuffer;

		ASSERT (!buffer->InUse || queue->StartPending);

		TCfree (buffer->Address);
		TCfree (buffer);

		buffer = nextBuffer;
	}

	queue->FirstPoolBuffer = NULL;
	ReleaseBufferPoolMutex (queue);
}


static void DecrementOutstandingIoCount (EncryptedIoQueue *queue)
{
	if (InterlockedDecrement (&queue->OutstandingIoCount) == 0 && (queue->SuspendPending || queue->StopPending))
		KeSetEvent (&queue->NoOutstandingIoEvent, IO_DISK_INCREMENT, FALSE);
}


static void OnItemCompleted (EncryptedIoQueueItem *item, BOOL freeItem)
{
	DecrementOutstandingIoCount (item->Queue);
	IoReleaseRemoveLock (&item->Queue->RemoveLock, item->OriginalIrp);

	if (NT_SUCCESS (item->Status))
	{
		if (item->Write)
			item->Queue->TotalBytesWritten += item->OriginalLength;
		else
			item->Queue->TotalBytesRead += item->OriginalLength;
	}

	if (freeItem)
		ReleasePoolBuffer (item->Queue, item);
}


static NTSTATUS CompleteOriginalIrp (EncryptedIoQueueItem *item, NTSTATUS status, ULONG_PTR information)
{
#ifdef TC_TRACE_IO_QUEUE
	Dump ("< %I64d [%I64d] %c status=%x info=%I64d\n", item->OriginalIrpOffset, GetElapsedTime (&item->Queue->LastPerformanceCounter), item->Write ? 'W' : 'R', status, (int64) information);
#endif

	TCCompleteDiskIrp (item->OriginalIrp, status, information);

	item->Status = status;
	OnItemCompleted (item, TRUE);

	return status;
}


static void AcquireFragmentBuffer (EncryptedIoQueue *queue, byte *buffer)
{
	NTSTATUS status = STATUS_INVALID_PARAMETER;

	if (buffer == queue->FragmentBufferA)
	{
		status = KeWaitForSingleObject (&queue->FragmentBufferAFreeEvent, Executive, KernelMode, FALSE, NULL);
	}
	else if (buffer == queue->FragmentBufferB)
	{
		status = KeWaitForSingleObject (&queue->FragmentBufferBFreeEvent, Executive, KernelMode, FALSE, NULL);
	}

	if (!NT_SUCCESS (status))
		TC_BUG_CHECK (status);
}


static void ReleaseFragmentBuffer (EncryptedIoQueue *queue, byte *buffer)
{
	if (buffer == queue->FragmentBufferA)
	{
		KeSetEvent (&queue->FragmentBufferAFreeEvent, IO_DISK_INCREMENT, FALSE);
	}
	else if (buffer == queue->FragmentBufferB)
	{
		KeSetEvent (&queue->FragmentBufferBFreeEvent, IO_DISK_INCREMENT, FALSE);
	}
	else
	{
		TC_BUG_CHECK (STATUS_INVALID_PARAMETER);
	}
}


static VOID CompletionThreadProc (PVOID threadArg)
{
	EncryptedIoQueue *queue = (EncryptedIoQueue *) threadArg;
	PLIST_ENTRY listEntry;
	EncryptedIoRequest *request;
	UINT64_STRUCT dataUnit;

	if (IsEncryptionThreadPoolRunning())
		KeSetPriorityThread (KeGetCurrentThread(), LOW_REALTIME_PRIORITY);

	while (!queue->ThreadExitRequested)
	{
		if (!NT_SUCCESS (KeWaitForSingleObject (&queue->CompletionThreadQueueNotEmptyEvent, Executive, KernelMode, FALSE, NULL)))
			continue;

		if (queue->ThreadExitRequested)
			break;

		while ((listEntry = ExInterlockedRemoveHeadList (&queue->CompletionThreadQueue, &queue->CompletionThreadQueueLock)))
		{
			request = CONTAINING_RECORD (listEntry, EncryptedIoRequest, CompletionListEntry);

			if (request->EncryptedLength > 0 && NT_SUCCESS (request->Item->Status))
			{
				ASSERT (request->EncryptedOffset + request->EncryptedLength <= request->Offset.QuadPart + request->Length);
				dataUnit.Value = (request->Offset.QuadPart + request->EncryptedOffset) / ENCRYPTION_DATA_UNIT_SIZE;

				if (queue->CryptoInfo->bPartitionInInactiveSysEncScope)
					dataUnit.Value += queue->CryptoInfo->FirstDataUnitNo.Value;
				else if (queue->RemapEncryptedArea)
					dataUnit.Value += queue->RemappedAreaDataUnitOffset;

				DecryptDataUnits (request->Data + request->EncryptedOffset, &dataUnit, request->EncryptedLength / ENCRYPTION_DATA_UNIT_SIZE, queue->CryptoInfo);
			}

			if (request->CompleteOriginalIrp)
			{
				CompleteOriginalIrp (request->Item, request->Item->Status,
					NT_SUCCESS (request->Item->Status) ? request->Item->OriginalLength : 0);
			}

			ReleasePoolBuffer (queue, request);
		}
	}

	PsTerminateSystemThread (STATUS_SUCCESS);
}


static NTSTATUS TCCachedRead (EncryptedIoQueue *queue, IO_STATUS_BLOCK *ioStatus, PVOID buffer, LARGE_INTEGER offset, ULONG length)
{
	queue->LastReadOffset = offset;
	queue->LastReadLength = length;

	if (queue->ReadAheadBufferValid && queue->ReadAheadOffset.QuadPart == offset.QuadPart && queue->ReadAheadLength >= length)
	{
		memcpy (buffer, queue->ReadAheadBuffer, length);

		if (!queue->IsFilterDevice)
		{
			ioStatus->Information = length;
			ioStatus->Status = STATUS_SUCCESS;
		}

		return STATUS_SUCCESS;
	}

	if (queue->IsFilterDevice)
		return TCReadDevice (queue->LowerDeviceObject, buffer, offset, length);

	return ZwReadFile (queue->HostFileHandle, NULL, NULL, NULL, ioStatus, buffer, length, &offset, NULL);
}


static VOID IoThreadProc (PVOID threadArg)
{
	EncryptedIoQueue *queue = (EncryptedIoQueue *) threadArg;
	PLIST_ENTRY listEntry;
	EncryptedIoRequest *request;

	KeSetPriorityThread (KeGetCurrentThread(), LOW_REALTIME_PRIORITY);

	if (!queue->IsFilterDevice && queue->SecurityClientContext)
	{
#ifdef DEBUG
		NTSTATUS status =
#endif
		SeImpersonateClientEx (queue->SecurityClientContext, NULL);
		ASSERT (NT_SUCCESS (status));
	}

	while (!queue->ThreadExitRequested)
	{
		if (!NT_SUCCESS (KeWaitForSingleObject (&queue->IoThreadQueueNotEmptyEvent, Executive, KernelMode, FALSE, NULL)))
			continue;

		if (queue->ThreadExitRequested)
			break;

		while ((listEntry = ExInterlockedRemoveHeadList (&queue->IoThreadQueue, &queue->IoThreadQueueLock)))
		{
			InterlockedDecrement (&queue->IoThreadPendingRequestCount);
			request = CONTAINING_RECORD (listEntry, EncryptedIoRequest, ListEntry);
			
#ifdef TC_TRACE_IO_QUEUE
			Dump ("%c   %I64d [%I64d] roff=%I64d rlen=%d\n", request->Item->Write ? 'W' : 'R', request->Item->OriginalIrpOffset.QuadPart, GetElapsedTime (&queue->LastPerformanceCounter), request->Offset.QuadPart, request->Length);
#endif

			// Perform IO request if no preceding request of the item failed
			if (NT_SUCCESS (request->Item->Status))
			{
				if (queue->IsFilterDevice)
				{
					if (queue->RemapEncryptedArea && request->EncryptedLength > 0)
					{
						if (request->EncryptedLength != request->Length)
						{
							// Up to three subfragments may be required to handle a partially remapped fragment
							int subFragment;
							byte *subFragmentData = request->Data;

							for (subFragment = 0 ; subFragment < 3; ++subFragment)
							{
								LARGE_INTEGER subFragmentOffset;
								ULONG subFragmentLength;
								subFragmentOffset.QuadPart = request->Offset.QuadPart;

								switch (subFragment)
								{
								case 0:
									subFragmentLength = (ULONG) request->EncryptedOffset;
									break;

								case 1:
									subFragmentOffset.QuadPart += request->EncryptedOffset + queue->RemappedAreaOffset;
									subFragmentLength = request->EncryptedLength;
									break;

								case 2:
									subFragmentOffset.QuadPart += request->EncryptedOffset + request->EncryptedLength;
									subFragmentLength = (ULONG) (request->Length - (request->EncryptedOffset + request->EncryptedLength));
									break;
								}

								if (subFragmentLength > 0)
								{
									if (request->Item->Write)
										request->Item->Status = TCWriteDevice (queue->LowerDeviceObject, subFragmentData, subFragmentOffset, subFragmentLength);
									else
										request->Item->Status = TCCachedRead (queue, NULL, subFragmentData, subFragmentOffset, subFragmentLength);

									subFragmentData += subFragmentLength;
								}
							}
						}
						else
						{
							// Remap the fragment
							LARGE_INTEGER remappedOffset;
							remappedOffset.QuadPart = request->Offset.QuadPart + queue->RemappedAreaOffset;

							if (request->Item->Write)
								request->Item->Status = TCWriteDevice (queue->LowerDeviceObject, request->Data, remappedOffset, request->Length);
							else
								request->Item->Status = TCCachedRead (queue, NULL, request->Data, remappedOffset, request->Length);
						}
					}
					else
					{
						if (request->Item->Write)
							request->Item->Status = TCWriteDevice (queue->LowerDeviceObject, request->Data, request->Offset, request->Length);
						else
							request->Item->Status = TCCachedRead (queue, NULL, request->Data, request->Offset, request->Length);
					}
				}
				else
				{
					IO_STATUS_BLOCK ioStatus;

					if (request->Item->Write)
						request->Item->Status = ZwWriteFile (queue->HostFileHandle, NULL, NULL, NULL, &ioStatus, request->Data, request->Length, &request->Offset, NULL);
					else
						request->Item->Status = TCCachedRead (queue, &ioStatus, request->Data, request->Offset, request->Length);

					if (NT_SUCCESS (request->Item->Status) && ioStatus.Information != request->Length)
						request->Item->Status = STATUS_END_OF_FILE;
				}
			}

			if (request->Item->Write)
			{
				queue->ReadAheadBufferValid = FALSE;

				ReleaseFragmentBuffer (queue, request->Data);

				if (request->CompleteOriginalIrp)
				{
					CompleteOriginalIrp (request->Item, request->Item->Status,
						NT_SUCCESS (request->Item->Status) ? request->Item->OriginalLength : 0);
				}

				ReleasePoolBuffer (queue, request);
			}
			else
			{
				BOOL readAhead = FALSE;

				if (NT_SUCCESS (request->Item->Status))
					memcpy (request->OrigDataBufferFragment, request->Data, request->Length);

				ReleaseFragmentBuffer (queue, request->Data);
				request->Data = request->OrigDataBufferFragment;

				if (request->CompleteOriginalIrp
					&& queue->LastReadLength > 0
					&& NT_SUCCESS (request->Item->Status)
					&& InterlockedExchangeAdd (&queue->IoThreadPendingRequestCount, 0) == 0)
				{
					readAhead = TRUE;
					InterlockedIncrement (&queue->OutstandingIoCount);
				}

				ExInterlockedInsertTailList (&queue->CompletionThreadQueue, &request->CompletionListEntry, &queue->CompletionThreadQueueLock);
				KeSetEvent (&queue->CompletionThreadQueueNotEmptyEvent, IO_DISK_INCREMENT, FALSE);

				if (readAhead)
				{
					queue->ReadAheadBufferValid = FALSE;
					queue->ReadAheadOffset.QuadPart = queue->LastReadOffset.QuadPart + queue->LastReadLength;
					queue->ReadAheadLength = queue->LastReadLength;

					if (queue->ReadAheadOffset.QuadPart + queue->ReadAheadLength <= queue->MaxReadAheadOffset.QuadPart)
					{
#ifdef TC_TRACE_IO_QUEUE
						Dump ("A   %I64d [%I64d] roff=%I64d rlen=%d\n", request->Item->OriginalIrpOffset.QuadPart, GetElapsedTime (&queue->LastPerformanceCounter), queue->ReadAheadOffset, queue->ReadAheadLength);
#endif
						if (queue->IsFilterDevice)
						{
							queue->ReadAheadBufferValid = NT_SUCCESS (TCReadDevice (queue->LowerDeviceObject, queue->ReadAheadBuffer, queue->ReadAheadOffset, queue->ReadAheadLength));
						}
						else
						{
							IO_STATUS_BLOCK ioStatus;
							queue->ReadAheadBufferValid = NT_SUCCESS (ZwReadFile (queue->HostFileHandle, NULL, NULL, NULL, &ioStatus, queue->ReadAheadBuffer, queue->ReadAheadLength, &queue->ReadAheadOffset, NULL));
							queue->ReadAheadLength = (ULONG) ioStatus.Information;
						}
					}

					DecrementOutstandingIoCount (queue);
				}
			}
		}
	}

	PsTerminateSystemThread (STATUS_SUCCESS);
}


static VOID MainThreadProc (PVOID threadArg)
{
	EncryptedIoQueue *queue = (EncryptedIoQueue *) threadArg;
	PLIST_ENTRY listEntry;
	EncryptedIoQueueItem *item;

	LARGE_INTEGER fragmentOffset;
	ULONG dataRemaining;
	PUCHAR activeFragmentBuffer = queue->FragmentBufferA;
	PUCHAR dataBuffer;
	EncryptedIoRequest *request;
	uint64 intersectStart;
	uint32 intersectLength;

	if (IsEncryptionThreadPoolRunning())
		KeSetPriorityThread (KeGetCurrentThread(), LOW_REALTIME_PRIORITY);

	while (!queue->ThreadExitRequested)
	{
		if (!NT_SUCCESS (KeWaitForSingleObject (&queue->MainThreadQueueNotEmptyEvent, Executive, KernelMode, FALSE, NULL)))
			continue;

		while ((listEntry = ExInterlockedRemoveHeadList (&queue->MainThreadQueue, &queue->MainThreadQueueLock)))
		{
			PIRP irp = CONTAINING_RECORD (listEntry, IRP, Tail.Overlay.ListEntry);
			PIO_STACK_LOCATION irpSp = IoGetCurrentIrpStackLocation (irp);
			
			if (queue->Suspended)
				KeWaitForSingleObject (&queue->QueueResumedEvent, Executive, KernelMode, FALSE, NULL);

			item = GetPoolBuffer (queue, sizeof (EncryptedIoQueueItem));
			item->Queue = queue;
			item->OriginalIrp = irp;
			item->Status = STATUS_SUCCESS;

			IoSetCancelRoutine (irp, NULL);
			if (irp->Cancel)
			{
				CompleteOriginalIrp (item, STATUS_CANCELLED, 0);
				continue;
			}

			switch (irpSp->MajorFunction)
			{
			case IRP_MJ_READ:
				item->Write = FALSE;
				item->OriginalOffset = irpSp->Parameters.Read.ByteOffset;
				item->OriginalLength = irpSp->Parameters.Read.Length;
				break;

			case IRP_MJ_WRITE:
				item->Write = TRUE;
				item->OriginalOffset = irpSp->Parameters.Write.ByteOffset;
				item->OriginalLength = irpSp->Parameters.Write.Length;
				break;

			default:
				CompleteOriginalIrp (item, STATUS_INVALID_PARAMETER, 0);
				continue;
			}

#ifdef TC_TRACE_IO_QUEUE
			item->OriginalIrpOffset = item->OriginalOffset;
#endif

			// Handle misaligned read operations to work around a bug in Windows System Assessment Tool which does not follow FILE_FLAG_NO_BUFFERING requirements when benchmarking disk devices
			if (queue->IsFilterDevice
				&& !item->Write
				&& item->OriginalLength > 0
				&& (item->OriginalLength & (ENCRYPTION_DATA_UNIT_SIZE - 1)) == 0
				&& (item->OriginalOffset.QuadPart & (ENCRYPTION_DATA_UNIT_SIZE - 1)) != 0)
			{
				byte *buffer;
				ULONG alignedLength = item->OriginalLength + ENCRYPTION_DATA_UNIT_SIZE;
				LARGE_INTEGER alignedOffset;
				alignedOffset.QuadPart = item->OriginalOffset.QuadPart & ~((LONGLONG) ENCRYPTION_DATA_UNIT_SIZE - 1);

				buffer = TCalloc (alignedLength);
				if (!buffer)
				{
					CompleteOriginalIrp (item, STATUS_INSUFFICIENT_RESOURCES, 0);
					continue;
				}

				item->Status = TCReadDevice (queue->LowerDeviceObject, buffer, alignedOffset, alignedLength);

				if (NT_SUCCESS (item->Status))
				{
					UINT64_STRUCT dataUnit;

					dataBuffer = (PUCHAR) MmGetSystemAddressForMdlSafe (irp->MdlAddress, HighPagePriority);
					if (!dataBuffer)
					{
						TCfree (buffer);
						CompleteOriginalIrp (item, STATUS_INSUFFICIENT_RESOURCES, 0);
						continue;
					}

					if (queue->EncryptedAreaStart != -1 && queue->EncryptedAreaEnd != -1)
					{
						GetIntersection (alignedOffset.QuadPart, alignedLength, queue->EncryptedAreaStart, queue->EncryptedAreaEnd, &intersectStart, &intersectLength);
						if (intersectLength > 0)
						{
							dataUnit.Value = intersectStart / ENCRYPTION_DATA_UNIT_SIZE;
							DecryptDataUnits (buffer + (intersectStart - alignedOffset.QuadPart), &dataUnit, intersectLength / ENCRYPTION_DATA_UNIT_SIZE, queue->CryptoInfo);
						}
					}

					memcpy (dataBuffer, buffer + (item->OriginalOffset.LowPart & (ENCRYPTION_DATA_UNIT_SIZE - 1)), item->OriginalLength);
				}

				TCfree (buffer);
				CompleteOriginalIrp (item, item->Status, NT_SUCCESS (item->Status) ? item->OriginalLength : 0);
				continue;
			}

			// Validate offset and length
			if (item->OriginalLength == 0
				|| (item->OriginalLength & (ENCRYPTION_DATA_UNIT_SIZE - 1)) != 0
				|| (item->OriginalOffset.QuadPart & (ENCRYPTION_DATA_UNIT_SIZE - 1)) != 0
				|| (!queue->IsFilterDevice && item->OriginalOffset.QuadPart + item->OriginalLength > queue->VirtualDeviceLength))
			{
				CompleteOriginalIrp (item, STATUS_INVALID_PARAMETER, 0);
				continue;
			}

#ifdef TC_TRACE_IO_QUEUE
			Dump ("Q  %I64d [%I64d] %c len=%d\n", item->OriginalOffset.QuadPart, GetElapsedTime (&queue->LastPerformanceCounter), item->Write ? 'W' : 'R', item->OriginalLength);
#endif

			if (!queue->IsFilterDevice)
			{
				// Adjust the offset for host file or device
				if (queue->CryptoInfo->hiddenVolume)
					item->OriginalOffset.QuadPart += queue->CryptoInfo->hiddenVolumeOffset;
				else
					item->OriginalOffset.QuadPart += queue->CryptoInfo->volDataAreaOffset; 

				// Hidden volume protection
				if (item->Write && queue->CryptoInfo->bProtectHiddenVolume)
				{
					// If there has already been a write operation denied in order to protect the
					// hidden volume (since the volume mount time)
					if (queue->CryptoInfo->bHiddenVolProtectionAction)	
					{
						// Do not allow writing to this volume anymore. This is to fake a complete volume
						// or system failure (otherwise certain kinds of inconsistency within the file
						// system could indicate that this volume has used hidden volume protection).
						CompleteOriginalIrp (item, STATUS_INVALID_PARAMETER, 0);
						continue;
					}

					// Verify that no byte is going to be written to the hidden volume area
					if (RegionsOverlap ((unsigned __int64) item->OriginalOffset.QuadPart,
						(unsigned __int64) item->OriginalOffset.QuadPart + item->OriginalLength - 1,
						queue->CryptoInfo->hiddenVolumeOffset,
						(unsigned __int64) queue->CryptoInfo->hiddenVolumeOffset + queue->CryptoInfo->hiddenVolumeProtectedSize - 1))
					{
						Dump ("Hidden volume protection triggered: write %I64d-%I64d (protected %I64d-%I64d)\n", item->OriginalOffset.QuadPart, item->OriginalOffset.QuadPart + item->OriginalLength - 1, queue->CryptoInfo->hiddenVolumeOffset, queue->CryptoInfo->hiddenVolumeOffset + queue->CryptoInfo->hiddenVolumeProtectedSize - 1);
						queue->CryptoInfo->bHiddenVolProtectionAction = TRUE;

						// Deny this write operation to prevent the hidden volume from being overwritten
						CompleteOriginalIrp (item, STATUS_INVALID_PARAMETER, 0);
						continue;
					}
				}
			}
			else if (item->Write
				&& RegionsOverlap (item->OriginalOffset.QuadPart, item->OriginalOffset.QuadPart + item->OriginalLength - 1, TC_BOOT_VOLUME_HEADER_SECTOR_OFFSET, TC_BOOT_VOLUME_HEADER_SECTOR_OFFSET + TC_BOOT_ENCRYPTION_VOLUME_HEADER_SIZE - 1))
			{
				// Prevent inappropriately designed software from damaging important data that may be out of sync with the backup on the Rescue Disk (such as the end of the encrypted area).
				Dump ("Preventing write to the system encryption key data area\n");
				CompleteOriginalIrp (item, STATUS_MEDIA_WRITE_PROTECTED, 0);
				continue;
			}
			else if (item->Write && IsHiddenSystemRunning()
				&& (RegionsOverlap (item->OriginalOffset.QuadPart, item->OriginalOffset.QuadPart + item->OriginalLength - 1, TC_SECTOR_SIZE_BIOS, TC_BOOT_LOADER_AREA_SECTOR_COUNT * TC_SECTOR_SIZE_BIOS - 1)
				 || RegionsOverlap (item->OriginalOffset.QuadPart, item->OriginalOffset.QuadPart + item->OriginalLength - 1, GetBootDriveLength(), _I64_MAX)))
			{
				Dump ("Preventing write to boot loader or host protected area\n");
				CompleteOriginalIrp (item, STATUS_MEDIA_WRITE_PROTECTED, 0);
				continue;
			}

			dataBuffer = (PUCHAR) MmGetSystemAddressForMdlSafe (irp->MdlAddress, HighPagePriority);

			if (dataBuffer == NULL)
			{
				CompleteOriginalIrp (item, STATUS_INSUFFICIENT_RESOURCES, 0);
				continue;
			}

			// Divide data block to fragments to enable efficient overlapping of encryption and IO operations

			dataRemaining = item->OriginalLength;
			fragmentOffset = item->OriginalOffset;

			while (dataRemaining > 0)
			{
				BOOL isLastFragment = dataRemaining <= TC_ENC_IO_QUEUE_MAX_FRAGMENT_SIZE;
				
				ULONG dataFragmentLength = isLastFragment ? dataRemaining : TC_ENC_IO_QUEUE_MAX_FRAGMENT_SIZE;
				activeFragmentBuffer = (activeFragmentBuffer == queue->FragmentBufferA ? queue->FragmentBufferB : queue->FragmentBufferA);

				InterlockedIncrement (&queue->IoThreadPendingRequestCount);

				// Create IO request
				request = GetPoolBuffer (queue, sizeof (EncryptedIoRequest));
				request->Item = item;
				request->CompleteOriginalIrp = isLastFragment;
				request->Offset = fragmentOffset;
				request->Data = activeFragmentBuffer;
				request->OrigDataBufferFragment = dataBuffer;
				request->Length = dataFragmentLength;

				if (queue->IsFilterDevice)
				{
					if (queue->EncryptedAreaStart == -1 || queue->EncryptedAreaEnd == -1)
					{
						request->EncryptedLength = 0;
					}
					else
					{
						// Get intersection of data fragment with encrypted area
						GetIntersection (fragmentOffset.QuadPart, dataFragmentLength, queue->EncryptedAreaStart, queue->EncryptedAreaEnd, &intersectStart, &intersectLength);

						request->EncryptedOffset = intersectStart - fragmentOffset.QuadPart;
						request->EncryptedLength = intersectLength;
					}
				}
				else
				{
					request->EncryptedOffset = 0;
					request->EncryptedLength = dataFragmentLength;
				}

				AcquireFragmentBuffer (queue, activeFragmentBuffer);

				if (item->Write)
				{
					// Encrypt data
					memcpy (activeFragmentBuffer, dataBuffer, dataFragmentLength);

					if (request->EncryptedLength > 0)
					{
						UINT64_STRUCT dataUnit;
						ASSERT (request->EncryptedOffset + request->EncryptedLength <= request->Offset.QuadPart + request->Length);

						dataUnit.Value = (request->Offset.QuadPart + request->EncryptedOffset) / ENCRYPTION_DATA_UNIT_SIZE;

						if (queue->CryptoInfo->bPartitionInInactiveSysEncScope)
							dataUnit.Value += queue->CryptoInfo->FirstDataUnitNo.Value;
						else if (queue->RemapEncryptedArea)
							dataUnit.Value += queue->RemappedAreaDataUnitOffset;
								
						EncryptDataUnits (activeFragmentBuffer + request->EncryptedOffset, &dataUnit, request->EncryptedLength / ENCRYPTION_DATA_UNIT_SIZE, queue->CryptoInfo);
					}
				}

				// Queue IO request
				ExInterlockedInsertTailList (&queue->IoThreadQueue, &request->ListEntry, &queue->IoThreadQueueLock);
				KeSetEvent (&queue->IoThreadQueueNotEmptyEvent, IO_DISK_INCREMENT, FALSE);

				if (isLastFragment)
					break;

				dataRemaining -= TC_ENC_IO_QUEUE_MAX_FRAGMENT_SIZE;
				dataBuffer += TC_ENC_IO_QUEUE_MAX_FRAGMENT_SIZE;
				fragmentOffset.QuadPart += TC_ENC_IO_QUEUE_MAX_FRAGMENT_SIZE;
			}
		}
	}

	PsTerminateSystemThread (STATUS_SUCCESS);
}


NTSTATUS EncryptedIoQueueAddIrp (EncryptedIoQueue *queue, PIRP irp)
{
	NTSTATUS status;

	InterlockedIncrement (&queue->OutstandingIoCount);
	if (queue->StopPending)
	{
		Dump ("STATUS_DEVICE_NOT_READY  out=%d\n", queue->OutstandingIoCount);
		status = STATUS_DEVICE_NOT_READY;
		goto err;
	}

	status = IoAcquireRemoveLock (&queue->RemoveLock, irp);
	if (!NT_SUCCESS (status))
		goto err;

#ifdef TC_TRACE_IO_QUEUE
	{
		PIO_STACK_LOCATION irpSp = IoGetCurrentIrpStackLocation (irp);
		Dump ("* %I64d [%I64d] %c len=%d out=%d\n", irpSp->MajorFunction == IRP_MJ_WRITE ? irpSp->Parameters.Write.ByteOffset : irpSp->Parameters.Read.ByteOffset, GetElapsedTime (&queue->LastPerformanceCounter), irpSp->MajorFunction == IRP_MJ_WRITE ? 'W' : 'R', irpSp->MajorFunction == IRP_MJ_WRITE ? irpSp->Parameters.Write.Length : irpSp->Parameters.Read.Length, queue->OutstandingIoCount);
	}
#endif

	IoMarkIrpPending (irp);

	ExInterlockedInsertTailList (&queue->MainThreadQueue, &irp->Tail.Overlay.ListEntry, &queue->MainThreadQueueLock);
	KeSetEvent (&queue->MainThreadQueueNotEmptyEvent, IO_DISK_INCREMENT, FALSE);
	
	return STATUS_PENDING;

err:
	DecrementOutstandingIoCount (queue);
	return status;
}


NTSTATUS EncryptedIoQueueHoldWhenIdle (EncryptedIoQueue *queue, int64 timeout)
{
	NTSTATUS status;
	ASSERT (!queue->Suspended);

	queue->SuspendPending = TRUE;
	
	while (TRUE)
	{
		while (InterlockedExchangeAdd (&queue->OutstandingIoCount, 0) > 0)
		{
			LARGE_INTEGER waitTimeout;

			waitTimeout.QuadPart = timeout * -10000;
			status = KeWaitForSingleObject (&queue->NoOutstandingIoEvent, Executive, KernelMode, FALSE, timeout != 0 ? &waitTimeout : NULL);

			if (status == STATUS_TIMEOUT)
				status = STATUS_UNSUCCESSFUL;

			if (!NT_SUCCESS (status))
			{
				queue->SuspendPending = FALSE;
				return status;
			}

			TCSleep (1);
			if (InterlockedExchangeAdd (&queue->OutstandingIoCount, 0) > 0)
			{
				queue->SuspendPending = FALSE;
				return STATUS_UNSUCCESSFUL;
			}
		}

		KeClearEvent (&queue->QueueResumedEvent);
		queue->Suspended = TRUE;

		if (InterlockedExchangeAdd (&queue->OutstandingIoCount, 0) == 0)
			break;

		queue->Suspended = FALSE;
		KeSetEvent (&queue->QueueResumedEvent, IO_DISK_INCREMENT, FALSE);
	}

	queue->ReadAheadBufferValid = FALSE;

	queue->SuspendPending = FALSE;
	return STATUS_SUCCESS;
}


BOOL EncryptedIoQueueIsSuspended (EncryptedIoQueue *queue)
{
	return queue->Suspended;
}


BOOL EncryptedIoQueueIsRunning (EncryptedIoQueue *queue)
{
	return !queue->StopPending;
}


NTSTATUS EncryptedIoQueueResumeFromHold (EncryptedIoQueue *queue)
{
	ASSERT (queue->Suspended);
	
	queue->Suspended = FALSE;
	KeSetEvent (&queue->QueueResumedEvent, IO_DISK_INCREMENT, FALSE);

	return STATUS_SUCCESS;
}


NTSTATUS EncryptedIoQueueStart (EncryptedIoQueue *queue)
{
	NTSTATUS status;
	EncryptedIoQueueBuffer *buffer;
	int i;

	queue->StartPending = TRUE;
	queue->ThreadExitRequested = FALSE;

	queue->OutstandingIoCount = 0;
	queue->IoThreadPendingRequestCount = 0;

	queue->FirstPoolBuffer = NULL;
	KeInitializeMutex (&queue->BufferPoolMutex, 0);

	KeInitializeEvent (&queue->NoOutstandingIoEvent, SynchronizationEvent, FALSE);
	KeInitializeEvent (&queue->PoolBufferFreeEvent, SynchronizationEvent, FALSE);
	KeInitializeEvent (&queue->QueueResumedEvent, SynchronizationEvent, FALSE);

	queue->FragmentBufferA = TCalloc (TC_ENC_IO_QUEUE_MAX_FRAGMENT_SIZE);
	if (!queue->FragmentBufferA)
		goto noMemory;

	queue->FragmentBufferB = TCalloc (TC_ENC_IO_QUEUE_MAX_FRAGMENT_SIZE);
	if (!queue->FragmentBufferB)
		goto noMemory;

	KeInitializeEvent (&queue->FragmentBufferAFreeEvent, SynchronizationEvent, TRUE);
	KeInitializeEvent (&queue->FragmentBufferBFreeEvent, SynchronizationEvent, TRUE);

	queue->ReadAheadBufferValid = FALSE;
	queue->ReadAheadBuffer = TCalloc (TC_ENC_IO_QUEUE_MAX_FRAGMENT_SIZE);
	if (!queue->ReadAheadBuffer)
		goto noMemory;

	// Preallocate buffers
	for (i = 0; i < TC_ENC_IO_QUEUE_PREALLOCATED_IO_REQUEST_COUNT; ++i)
	{
		if (i < TC_ENC_IO_QUEUE_PREALLOCATED_ITEM_COUNT && !GetPoolBuffer (queue, sizeof (EncryptedIoQueueItem)))
			goto noMemory;

		if (!GetPoolBuffer (queue, sizeof (EncryptedIoRequest)))
			goto noMemory;
	}

	for (buffer = queue->FirstPoolBuffer; buffer != NULL; buffer = buffer->NextBuffer)
	{
		buffer->InUse = FALSE;
	}

	// Main thread
	InitializeListHead (&queue->MainThreadQueue);
	KeInitializeSpinLock (&queue->MainThreadQueueLock);
	KeInitializeEvent (&queue->MainThreadQueueNotEmptyEvent, SynchronizationEvent, FALSE);

	status = TCStartThread (MainThreadProc, queue, &queue->MainThread);
	if (!NT_SUCCESS (status))
		goto err;

	// IO thread
	InitializeListHead (&queue->IoThreadQueue);
	KeInitializeSpinLock (&queue->IoThreadQueueLock);
	KeInitializeEvent (&queue->IoThreadQueueNotEmptyEvent, SynchronizationEvent, FALSE);

	status = TCStartThread (IoThreadProc, queue, &queue->IoThread);
	if (!NT_SUCCESS (status))
	{
		queue->ThreadExitRequested = TRUE;
		TCStopThread (queue->MainThread, &queue->MainThreadQueueNotEmptyEvent);
		goto err;
	}

	// Completion thread
	InitializeListHead (&queue->CompletionThreadQueue);
	KeInitializeSpinLock (&queue->CompletionThreadQueueLock);
	KeInitializeEvent (&queue->CompletionThreadQueueNotEmptyEvent, SynchronizationEvent, FALSE);

	status = TCStartThread (CompletionThreadProc, queue, &queue->CompletionThread);
	if (!NT_SUCCESS (status))
	{
		queue->ThreadExitRequested = TRUE;
		TCStopThread (queue->MainThread, &queue->MainThreadQueueNotEmptyEvent);
		TCStopThread (queue->IoThread, &queue->IoThreadQueueNotEmptyEvent);
		goto err;
	}

#ifdef TC_TRACE_IO_QUEUE
	GetElapsedTimeInit (&queue->LastPerformanceCounter);
#endif

	queue->StopPending = FALSE;
	queue->StartPending = FALSE;

	Dump ("Queue started\n");
	return STATUS_SUCCESS;

noMemory:
	status = STATUS_INSUFFICIENT_RESOURCES;

err:
	if (queue->FragmentBufferA)
		TCfree (queue->FragmentBufferA);
	if (queue->FragmentBufferB)
		TCfree (queue->FragmentBufferB);
	if (queue->ReadAheadBuffer)
		TCfree (queue->ReadAheadBuffer);

	FreePoolBuffers (queue);

	queue->StartPending = FALSE;
	return status;
}


NTSTATUS EncryptedIoQueueStop (EncryptedIoQueue *queue)
{
	ASSERT (!queue->StopPending);
	queue->StopPending = TRUE;
	
	while (InterlockedExchangeAdd (&queue->OutstandingIoCount, 0) > 0)
	{
		KeWaitForSingleObject (&queue->NoOutstandingIoEvent, Executive, KernelMode, FALSE, NULL);
	}

	Dump ("Queue stopping  out=%d\n", queue->OutstandingIoCount);

	queue->ThreadExitRequested = TRUE;

	TCStopThread (queue->MainThread, &queue->MainThreadQueueNotEmptyEvent);
	TCStopThread (queue->IoThread, &queue->IoThreadQueueNotEmptyEvent);
	TCStopThread (queue->CompletionThread, &queue->CompletionThreadQueueNotEmptyEvent);

	TCfree (queue->FragmentBufferA);
	TCfree (queue->FragmentBufferB);
	TCfree (queue->ReadAheadBuffer);

	FreePoolBuffers (queue);

	Dump ("Queue stopped  out=%d\n", queue->OutstandingIoCount);
	return STATUS_SUCCESS;
}