C++ MmBuildMdlForNonPagedPool函数代码示例

//
// file local helper functions.
//
NTSTATUS
InitScratchpad(
    IN PUSB_FDO_CONTEXT fdoContext)
{
    NTSTATUS status;
    KeInitializeEvent(&fdoContext->ScratchPad.CompletionEvent, NotificationEvent, FALSE);
    
    fdoContext->ScratchPad.Buffer = ExAllocatePoolWithTag(NonPagedPool, PAGE_SIZE, XVU1);
    if (!fdoContext->ScratchPad.Buffer)
    {
            status =  STATUS_NO_MEMORY;
            TraceEvents(TRACE_LEVEL_ERROR, TRACE_DEVICE,
                __FUNCTION__": Device %p ExAllocatePoolWithTag failed\n",
                fdoContext->WdfDevice);
            return status;
    }
    RtlZeroMemory(fdoContext->ScratchPad.Buffer, PAGE_SIZE);

    fdoContext->ScratchPad.Mdl = IoAllocateMdl(fdoContext->ScratchPad.Buffer,
        PAGE_SIZE,
        FALSE,
        FALSE,
        NULL);
    if (!fdoContext->ScratchPad.Mdl)
    {
        status =  STATUS_NO_MEMORY;
        TraceEvents(TRACE_LEVEL_ERROR, TRACE_DEVICE,
            __FUNCTION__": device %p IoAllocateMdl failed\n",
            fdoContext->WdfDevice);
        return status;
    }
    MmBuildMdlForNonPagedPool(fdoContext->ScratchPad.Mdl);

    return STATUS_SUCCESS;
}

PMDL
Ext2CreateMdl (
    IN PVOID Buffer,
    IN BOOLEAN bPaged,
    IN ULONG Length,
    IN LOCK_OPERATION Operation
)
{
    NTSTATUS Status;
    PMDL Mdl = NULL;

    ASSERT (Buffer != NULL);
    Mdl = IoAllocateMdl (Buffer, Length, FALSE, FALSE, NULL);
    if (Mdl == NULL) {
        Status = STATUS_INSUFFICIENT_RESOURCES;
    } else {
        __try {
            if (bPaged) {
                MmProbeAndLockPages(Mdl, KernelMode, Operation);
            } else {
                MmBuildMdlForNonPagedPool (Mdl);
            }
            Status = STATUS_SUCCESS;
        } __except (EXCEPTION_EXECUTE_HANDLER) {
            IoFreeMdl (Mdl);
            Mdl = NULL;
            DbgBreak();
            Status = STATUS_INVALID_USER_BUFFER;
        }
    }
    return Mdl;
}

NTSTATUS ChangeServiceTableMemoryFlags()
{
	// Map the memory into our domain and change the permissions on the memory page by using a MDL
	g_MappedSystemCallTableMDL = IoAllocateMdl(	KeServiceDescriptorTable.ServiceTableBase,		// starting virtual address
												KeServiceDescriptorTable.NumberOfServices*4,	// size of buffer
												FALSE,											// not associated with an IRP
												FALSE,											// charge quota, should be FALSE
												NULL											// IRP * should be NULL
												);
	if(!g_MappedSystemCallTableMDL)
	{
		DbgPrint("MDL could not be allocated...");
		return STATUS_UNSUCCESSFUL;
	}
	else
	{
		DbgPrint("The MDL is at 0x%x\n", g_MappedSystemCallTableMDL);
	}

	// MmBuildMdlForNonPagedPool fills in the corresponding physical page array 
	// of a given MDL for a buffer in nonpaged system space (pool).
	MmBuildMdlForNonPagedPool(g_MappedSystemCallTableMDL);
	// MDL's are supposed to be opaque, but this is the only way we know of getting to these flags...
	g_MappedSystemCallTableMDL->MdlFlags = g_MappedSystemCallTableMDL->MdlFlags | MDL_MAPPED_TO_SYSTEM_VA;
	// finish off the mapping...
	g_MappedSystemCallTable = MmMapLockedPages(g_MappedSystemCallTableMDL, KernelMode);

	return STATUS_SUCCESS;
}

NTSTATUS
NTAPI
USBPORT_ValidateTransferParametersURB(IN PURB Urb)
{
    struct _URB_CONTROL_TRANSFER *UrbRequest;
    PMDL Mdl;

    DPRINT_URB("USBPORT_ValidateTransferParametersURB: Urb - %p\n", Urb);

    UrbRequest = &Urb->UrbControlTransfer;

    if (UrbRequest->TransferBuffer == NULL &&
        UrbRequest->TransferBufferMDL == NULL &&
        UrbRequest->TransferBufferLength > 0)
    {
        DPRINT1("USBPORT_ValidateTransferParametersURB: Not valid parameter\n");
        USBPORT_DumpingURB(Urb);
        return STATUS_INVALID_PARAMETER;
    }

    if ((UrbRequest->TransferBuffer != NULL) &&
        (UrbRequest->TransferBufferMDL != NULL) &&
        UrbRequest->TransferBufferLength == 0)
    {
        DPRINT1("USBPORT_ValidateTransferParametersURB: Not valid parameter\n");
        USBPORT_DumpingURB(Urb);
        return STATUS_INVALID_PARAMETER;
    }

    if (UrbRequest->TransferBuffer != NULL &&
        UrbRequest->TransferBufferMDL == NULL &&
        UrbRequest->TransferBufferLength != 0)
    {
        DPRINT_URB("USBPORT_ValidateTransferParametersURB: TransferBuffer - %p, TransferBufferLength - %x\n",
                   UrbRequest->TransferBuffer,
                   UrbRequest->TransferBufferLength);

        Mdl = IoAllocateMdl(UrbRequest->TransferBuffer,
                            UrbRequest->TransferBufferLength,
                            FALSE,
                            FALSE,
                            NULL);

        if (!Mdl)
        {
            DPRINT1("USBPORT_ValidateTransferParametersURB: Not allocated Mdl\n");
            return STATUS_INSUFFICIENT_RESOURCES;
        }

        MmBuildMdlForNonPagedPool(Mdl);

        UrbRequest->TransferBufferMDL = Mdl;
        Urb->UrbHeader.UsbdFlags |= USBD_FLAG_ALLOCATED_MDL;

        DPRINT_URB("USBPORT_ValidateTransferParametersURB: Mdl - %p\n", Mdl);
    }

    return STATUS_SUCCESS;
}

//-----------------------------------------------------------------------------
// MAIN
//-----------------------------------------------------------------------------
NTSTATUS DriverEntry(PDRIVER_OBJECT driver_object, 
	                 PUNICODE_STRING registry_path)
{
	NTSTATUS ret;

	if (!driver_object)
	{
		DbgPrint("\n!!! ERROR: invalid driver_object in DriverEntry()\n");
		return STATUS_UNSUCCESSFUL;
	}
	driver_object->DriverUnload  = OnUnload;

	DbgPrint("---------------- Driver Loaded\n");

	// routine allocates a memory descriptor list (MDL) 
	mdl_sys_call = IoAllocateMdl(KeServiceDescriptorTable.ServiceTableBase, 
		                         KeServiceDescriptorTable.NumberOfServices * 4, 
								 FALSE, FALSE, NULL);
	if (!mdl_sys_call )
	{
		DbgPrint("\n!!! ERROR: invalid mdl in DriverEntry()\n");
		return STATUS_UNSUCCESSFUL;
	}

	MmBuildMdlForNonPagedPool(mdl_sys_call);

	mdl_sys_call->MdlFlags = mdl_sys_call->MdlFlags | MDL_MAPPED_TO_SYSTEM_VA;

	// map the physical pages 
    syscall_tbl = MmMapLockedPagesSpecifyCache(mdl_sys_call, KernelMode,
											   MmNonCached, NULL, FALSE,
											   HighPagePriority);

	if (!syscall_tbl)
	{
		DbgPrint("\n!!! ERROR: invalid mapped syscall table in DriverEntry()\n");
		return STATUS_UNSUCCESSFUL;
	}

	hook_syscalls();

	debug("register our callback for when our target proc is loaded:\n %ws\n\n",
		     target_file_loc);

#if BREAK_POINT
	// register a callback func that is invoked when our target proc is loaded
	ret = PsSetLoadImageNotifyRoutine(add_one_time_bp);
#endif

#if DATA_MINING
	ret = PsSetLoadImageNotifyRoutine(add_hooks_for_data_mining);
#endif

	if (ret != STATUS_SUCCESS)
		DbgPrint("\n!!! ERROR: PsSetLoadImageNotifyRoutine()\n\n");

	return STATUS_SUCCESS;
}

//------------------------------------------------------------------------------
tOplkError drv_mapPdoMem(UINT8** ppKernelMem_p, UINT8** ppUserMem_p,
                         size_t* pMemSize_p)
{
    tOplkError      ret;

    // Get PDO memory
    ret = pdokcal_getPdoMemRegion((UINT8**)&pdoMemInfo_l.pKernelVa,
                                  &pdoMemInfo_l.memSize);

    if (ret != kErrorOk || pdoMemInfo_l.pKernelVa == NULL)
        return kErrorNoResource;

    if (*pMemSize_p > pdoMemInfo_l.memSize)
    {
        DEBUG_LVL_ERROR_TRACE("%s() Higher Memory requested (Kernel-%d User-%d) !\n",
                              __func__, pdoMemInfo_l.memSize, *pMemSize_p);
        *pMemSize_p = 0;
        return kErrorNoResource;
    }

    // Allocate new MDL pointing to PDO memory
    pdoMemInfo_l.pMdl = IoAllocateMdl(pdoMemInfo_l.pKernelVa, pdoMemInfo_l.memSize, FALSE, FALSE,
                                      NULL);

    if (pdoMemInfo_l.pMdl == NULL)
    {
        DEBUG_LVL_ERROR_TRACE("%s() Error allocating MDL !\n", __func__);
        return kErrorNoResource;
    }

    // Update the MDL with physical addresses
    MmBuildMdlForNonPagedPool(pdoMemInfo_l.pMdl);

    // Map the memory in user space and get the address
    pdoMemInfo_l.pUserVa = MmMapLockedPagesSpecifyCache(pdoMemInfo_l.pMdl,    // MDL
                                                        UserMode,             // Mode
                                                        MmCached,             // Caching
                                                        NULL,                 // Address
                                                        FALSE,                // Bug-check?
                                                        NormalPagePriority);  // Priority

    if (pdoMemInfo_l.pUserVa == NULL)
    {
        MmUnmapLockedPages(pdoMemInfo_l.pUserVa, pdoMemInfo_l.pMdl);
        IoFreeMdl(pdoMemInfo_l.pMdl);
        DEBUG_LVL_ERROR_TRACE("%s() Error mapping MDL !\n", __func__);
        return kErrorNoResource;
    }

    *ppKernelMem_p = pdoMemInfo_l.pKernelVa;
    *ppUserMem_p = pdoMemInfo_l.pUserVa;
    *pMemSize_p = pdoMemInfo_l.memSize;

    TRACE("Mapped memory info U:%p K:%p size %x", pdoMemInfo_l.pUserVa,
                                                 (UINT8*)pdoMemInfo_l.pKernelVa,
                                                 pdoMemInfo_l.memSize);
    return kErrorOk;
}

NTSTATUS
AsyncReadWriteSec(
    IN PDEVICE_OBJECT DeviceObject,
	IN PIRP	 ParentIrp,
	IN ULONG ulStartSec,
	IN ULONG ulSectors,
	IN PVOID pBuffer,
    IN UCHAR MajorFunction
)
{
	PMDL				MDL;
    KEVENT				event;
    PIRP				Irp;
	ULONG				ulBytes;
    LARGE_INTEGER		Start;
    IO_STATUS_BLOCK		ioStatus;
	NTSTATUS			status = STATUS_SUCCESS;
    PIO_STACK_LOCATION	NextIrpStack;
	PDEVICE_EXTENSION	deviceExtension = DeviceObject->DeviceExtension;

	ulBytes = ulSectors * SECTOR_SIZE;
	Start.QuadPart = ((LONGLONG)ulStartSec)*SECTOR_SIZE;

	Irp = IoAllocateIrp(LOBYTE(LOWORD(deviceExtension->TargetDeviceObject->StackSize+1)),FALSE);
	//Irp = IoBuildSynchronousFsdRequest( MajorFunction,
	//	                                deviceExtension->TargetDeviceObject,
	//	                                pBuffer,ulBytes,
	//	                                &Start,&event,
	//	                                &ioStatus );

	ASSERT(Irp);
	if (!Irp)
	{
	    return STATUS_INSUFFICIENT_RESOURCES;
	}

	MDL = IoAllocateMdl(pBuffer,ulBytes,FALSE,FALSE,Irp);
	if (!MDL)
		return STATUS_INSUFFICIENT_RESOURCES;

	MmBuildMdlForNonPagedPool(MDL);
	IoSetNextIrpStackLocation(Irp);
	NextIrpStack = IoGetNextIrpStackLocation(Irp);

	NextIrpStack->DeviceObject  = deviceExtension->TargetDeviceObject;
	NextIrpStack->MajorFunction = MajorFunction;
	NextIrpStack->MinorFunction = 0;

	NextIrpStack->Parameters.Read.Length = ulBytes;
	NextIrpStack->Parameters.Read.Key		 = 0;
	NextIrpStack->Parameters.Read.ByteOffset.QuadPart = Start.QuadPart;

	RtlCopyMemory(&(NextIrpStack->Parameters.Write),&(NextIrpStack->Parameters.Read),sizeof(NextIrpStack->Parameters.Read));
	IoSetCompletionRoutine(Irp,AsyncCompletion,ParentIrp,TRUE,TRUE,TRUE);
	status = IoCallDriver(deviceExtension->TargetDeviceObject,Irp);
	return status;
} // end SyncReadWriteSec()

int dump_hook_init(PDRIVER_OBJECT drv_obj)
{
	PLDR_DATA_TABLE_ENTRY table;
	PHYSICAL_ADDRESS      high_addr;
	PLIST_ENTRY           entry;
	NTSTATUS              status;
	int                   resl = 0;

	ExInitializeFastMutex(&dump_sync);

	ExAcquireFastMutex(&dump_sync);

	/* find PsLoadedModuleListHead */
	entry = ((PLIST_ENTRY)(drv_obj->DriverSection))->Flink;

	while (entry != drv_obj->DriverSection)
	{
		table = CONTAINING_RECORD(entry, LDR_DATA_TABLE_ENTRY, InLoadOrderLinks);
		entry = entry->Flink;

		if ( (table->BaseDllName.Length == 0x18) && 
			 (p32(table->BaseDllName.Buffer)[0] == 0x0074006E) )
		{
			ps_loaded_mod_list = pv(table->InLoadOrderLinks.Blink);
			break;
		}
	}

	ExReleaseFastMutex(&dump_sync);

	do
	{
		if (ps_loaded_mod_list == NULL) break;

		status = PsSetLoadImageNotifyRoutine(load_img_routine);
		if (NT_SUCCESS(status) == FALSE) break;

		high_addr.HighPart = 0;
		high_addr.LowPart  = 0xFFFFFFFF;

		dump_mem = MmAllocateContiguousMemory(DUMP_MEM_SIZE, high_addr);
		if (dump_mem == NULL) break;
		dump_mdl = IoAllocateMdl(dump_mem, DUMP_MEM_SIZE, FALSE, FALSE, NULL); 
		if (dump_mdl == NULL) break;

		MmBuildMdlForNonPagedPool(dump_mdl);
		memset(dump_mem, 0, DUMP_MEM_SIZE);
		resl = 1;
	} while (0);

	if (resl == 0) {
		if (dump_mdl != NULL) IoFreeMdl(dump_mdl);
		if (dump_mem != NULL) MmFreeContiguousMemory(dump_mem);
	}
	return resl;	
}

NTSTATUS DumpKernelMemory(PVOID DstAddr, PVOID SrcAddr, ULONG Size)
{
    PMDL  pSrcMdl, pDstMdl;
    PUCHAR pAddress, pDstAddress;
    NTSTATUS st = STATUS_UNSUCCESSFUL;
    ULONG r;

	// Создаем MDL для буфера-источника
    pSrcMdl = IoAllocateMdl(SrcAddr, Size, FALSE, FALSE, NULL);

	if (pSrcMdl)
	{
		// Построение MDL
		MmBuildMdlForNonPagedPool(pSrcMdl);
		// Получение адреса из MDL
		pAddress = (PUCHAR)MmGetSystemAddressForMdlSafe(pSrcMdl, NormalPagePriority);
		zDbgPrint("pAddress = %x", pAddress);
		if (pAddress != NULL)
		{
			pDstMdl = IoAllocateMdl(DstAddr, Size, FALSE, FALSE, NULL);
			zDbgPrint("pDstMdl = %x", pDstMdl);
			if (pDstMdl != NULL)
			{
				__try
				{
					MmProbeAndLockPages(pDstMdl, KernelMode, IoWriteAccess);
					pDstAddress = (PUCHAR)MmGetSystemAddressForMdlSafe(pDstMdl, NormalPagePriority);
					zDbgPrint("pDstAddress = %x", pDstAddress);
					if (pDstAddress != NULL)
					{
						memset(pDstAddress, 0, Size);
						zDbgPrint("Copy block");
						for (r = 1; r < Size; r++)
						{
							if (MmIsAddressValid(pAddress)) 
								*pDstAddress = *pAddress;
							else
								*pDstAddress = 0;
							pAddress++;
							pDstAddress++;
						}

						st = STATUS_SUCCESS;
					}

					MmUnlockPages(pDstMdl);
				}
				__except(EXCEPTION_EXECUTE_HANDLER)
				{    
					zDbgPrint("Copy block exception");
				}
				IoFreeMdl(pDstMdl);
			}
		}            

BOOLEAN AllocateSharedMemory(PSHARED_MEMORY lpSharedMemory, POOL_TYPE PoolType, ULONG dwSizeRegion)
{
  if (!_MmIsAddressValid(lpSharedMemory))
    return FALSE;
  if (!dwSizeRegion)
    return FALSE;

  memset(lpSharedMemory, 0, sizeof(SHARED_MEMORY));

  #ifndef __MISC_USE_KHEAP
  lpSharedMemory->m_lpKernelMemory = ExAllocatePool(PoolType, dwSizeRegion);
  #else
  lpSharedMemory->m_lpKernelMemory = (CHAR*) _AllocatePoolFromKHeap(hKHeapMiscDefault, dwSizeRegion);
  #endif //!__MISC_USE_KHEAP
  if (!lpSharedMemory->m_lpKernelMemory)
    return FALSE;

  lpSharedMemory->m_Mdl = IoAllocateMdl(lpSharedMemory->m_lpKernelMemory, dwSizeRegion, FALSE, FALSE, NULL);
  if (!lpSharedMemory->m_Mdl)
  {
    #ifndef __MISC_USE_KHEAP
    ExFreePool(lpSharedMemory->m_lpKernelMemory);
    #else
    FreePoolToKHeap(hKHeapMiscDefault, lpSharedMemory->m_lpKernelMemory);
    #endif //!__MISC_USE_KHEAP
    memset(lpSharedMemory, 0, sizeof(SHARED_MEMORY));
    return FALSE;
  }

  MmBuildMdlForNonPagedPool(lpSharedMemory->m_Mdl);

  lpSharedMemory->m_lpUserPage = MmMapLockedPages(lpSharedMemory->m_Mdl, UserMode);
  lpSharedMemory->m_lpUserMemory = (PVOID) (((ULONG)PAGE_ALIGN(lpSharedMemory->m_lpUserPage))+MmGetMdlByteOffset(lpSharedMemory->m_Mdl));
  if (!_MmIsAddressValid(lpSharedMemory->m_lpUserMemory))
  {
    MmUnmapLockedPages(lpSharedMemory->m_lpUserPage, lpSharedMemory->m_Mdl);
    IoFreeMdl(lpSharedMemory->m_Mdl);
    #ifndef __MISC_USE_KHEAP
    ExFreePool(lpSharedMemory->m_lpKernelMemory);
    #else
    FreePoolToKHeap(hKHeapMiscDefault, lpSharedMemory->m_lpKernelMemory);
    #endif //!__MISC_USE_KHEAP
    memset(lpSharedMemory, 0, sizeof(SHARED_MEMORY));
    return FALSE;
  }
  lpSharedMemory->m_dwSizeRegion = dwSizeRegion;

  return TRUE;
}

void __ConsPacket(OUT PPACKET_BASE pPacket)
{
    PVOID               Va;
    PMDL                pMdl;

    Va = ExAllocatePoolWithTag(
            NonPagedPool,
            MDL_BUFFER_SIZE, 
            (ULONG)'TTWH');
    
    RtlZeroMemory(Va, MDL_BUFFER_SIZE);
    pMdl = IoAllocateMdl(Va, MDL_BUFFER_SIZE, FALSE, FALSE, NULL);
    MmBuildMdlForNonPagedPool(pMdl);
    pPacket->pMdl = pMdl;

}

NTSTATUS SafeCopyMemory(PVOID SrcAddr, PVOID DstAddr, ULONG Size)
{
	PMDL  pSrcMdl, pDstMdl;
	PUCHAR pSrcAddress, pDstAddress;
	NTSTATUS st = STATUS_UNSUCCESSFUL;
	ULONG r;
	BOOL bInit = FALSE;

	pSrcMdl = IoAllocateMdl(SrcAddr, Size, FALSE, FALSE, NULL);
	if (MmIsAddressValidEx(pSrcMdl))
	{
		MmBuildMdlForNonPagedPool(pSrcMdl);
		pSrcAddress = (PUCHAR)MmGetSystemAddressForMdlSafe(pSrcMdl, NormalPagePriority);
		if (MmIsAddressValidEx(pSrcAddress))
		{
			pDstMdl = IoAllocateMdl(DstAddr, Size, FALSE, FALSE, NULL);
			if (MmIsAddressValidEx(pDstMdl))
			{
				__try
				{
					MmProbeAndLockPages(pDstMdl, KernelMode, IoWriteAccess);
					pDstAddress = (PUCHAR)MmGetSystemAddressForMdlSafe(pDstMdl, NormalPagePriority);
					if (MmIsAddressValidEx(pDstAddress))
					{
						RtlZeroMemory(pDstAddress,Size);
						RtlCopyMemory(pDstAddress, pSrcAddress, Size);
						st = STATUS_SUCCESS;
					}
					MmUnlockPages(pDstMdl);
				}
				__except(EXCEPTION_EXECUTE_HANDLER)
				{                 
					if (pDstMdl) MmUnlockPages(pDstMdl);

					if (pDstMdl) IoFreeMdl(pDstMdl);

					if (pSrcMdl) IoFreeMdl(pSrcMdl);

					return GetExceptionCode();
				}
				IoFreeMdl(pDstMdl);
			}
		}            
		IoFreeMdl(pSrcMdl);
	}
	return st;
}

//----------------------------------------------------------------------
//
// RegmonMapServiceTable
//
// If we are running on Whistler then we have
// to double map the system service table to get around the 
// fact that the system service table is write-protected on systems
// with > 128MB memory. Since there's no harm in always double mapping,
// we always do it, regardless of whether or not we are on Whistler.
//
//----------------------------------------------------------------------
PVOID *
RegmonMapServiceTable(
    SERVICE_HOOK_DESCRIPTOR **HookDescriptors
    )
{
    //
    // Allocate an array to store original function addresses in. This
    // makes us play well with other hookers.
    //
    *HookDescriptors = (SERVICE_HOOK_DESCRIPTOR *) ExAllocatePool( NonPagedPool,
                          KeServiceDescriptorTable->Limit * sizeof(SERVICE_HOOK_DESCRIPTOR));
    if( !*HookDescriptors ) {

        return NULL;
    }
    memset( *HookDescriptors, 0, 
            KeServiceDescriptorTable->Limit * sizeof(SERVICE_HOOK_DESCRIPTOR));

    //
    // Build an MDL that describes the system service table function 
    // pointers array.
    //
    KdPrint(("Reglib: KeServiceDescriptorTable: %I64x Pointers: %I64x Limit: %d\n",
              KeServiceDescriptorTable, KeServiceDescriptorTable->ServicePointers,
              KeServiceDescriptorTable->Limit ));
    KeServiceTableMdl = MmCreateMdl( NULL, KeServiceDescriptorTable->ServicePointers, 
                                     KeServiceDescriptorTable->Limit * sizeof(PVOID));
    if( !KeServiceTableMdl ) {

        return NULL;
    }

    //
    // Fill in the physical pages and then double-map the description. Note
    // that MmMapLockedPages is obsolete as of Win2K and has been replaced
    // with MmMapLockedPagesSpecifyCache. However, we use the same driver
    // on all NT platforms, so we use it anyway.
    //
    MmBuildMdlForNonPagedPool( KeServiceTableMdl );
    KeServiceTableMdl->MdlFlags |= MDL_MAPPED_TO_SYSTEM_VA;
#if defined(_M_IA64)
    return MmMapLockedPagesSpecifyCache( KeServiceTableMdl, KernelMode, 
                                         MmCached, NULL, FALSE, NormalPagePriority );
#else
    return MmMapLockedPages( KeServiceTableMdl, KernelMode );
#endif
}

NTSTATUS initMDL()
{  
   // map memory into our domain
   g_pmdlSystemCall = MmCreateMdl(NULL, KeServiceDescriptorTable.ServiceTableBase, 
                               KeServiceDescriptorTable.NumberOfServices*4);
   if(!g_pmdlSystemCall)
      return STATUS_UNSUCCESSFUL;

   MmBuildMdlForNonPagedPool(g_pmdlSystemCall);

   // change MDL permissions
   g_pmdlSystemCall->MdlFlags = g_pmdlSystemCall->MdlFlags | MDL_MAPPED_TO_SYSTEM_VA;
   MappedSystemCallTable = MmMapLockedPages(g_pmdlSystemCall, KernelMode);
   
   MDLinit = TRUE;

   return STATUS_SUCCESS;
}

// Does memcpy safely even if Destination is a read only region.
_Use_decl_annotations_ EXTERN_C NTSTATUS UtilForceMemCpy(void *Destination,
                                                         const void *Source,
                                                         SIZE_T Length) {
  auto mdl = std::experimental::make_unique_resource(
      IoAllocateMdl(Destination, static_cast<ULONG>(Length), FALSE, FALSE,
                    nullptr),
      &IoFreeMdl);
  if (!mdl) {
    return STATUS_INSUFFICIENT_RESOURCES;
  }
  MmBuildMdlForNonPagedPool(mdl.get());

#pragma warning(push)
#pragma warning(disable : 28145)
  //
  // Following MmMapLockedPagesSpecifyCache() call causes bug check in case
  // you are using Driver Verifier. The reason is explained as follows:
  //
  // A driver must not try to create more than one system-address-space
  // mapping for an MDL. Additionally, because an MDL that is built by the
  // MmBuildMdlForNonPagedPool routine is already mapped to the system
  // address space, a driver must not try to map this MDL into the system
  // address space again by using the MmMapLockedPagesSpecifyCache routine.
  // -- MSDN
  //
  // This flag modification hacks Driver Verifier's check and prevent leading
  // bug check.
  //
  mdl.get()->MdlFlags &= ~MDL_SOURCE_IS_NONPAGED_POOL;
  mdl.get()->MdlFlags |= MDL_PAGES_LOCKED;
#pragma warning(pop)

  auto writableDest = MmMapLockedPagesSpecifyCache(
      mdl.get(), KernelMode, MmCached, nullptr, FALSE, NormalPagePriority);
  if (!writableDest) {
    return STATUS_INSUFFICIENT_RESOURCES;
  }
  memcpy(writableDest, Source, Length);
  MmUnmapLockedPages(writableDest, mdl.get());
  return STATUS_SUCCESS;
}