Three Steps Down the Stairs: From Win32 User-Land through Native API to Kernel

#include <stdio.h>
#include <ntddk.h> 
typedef unsigned long DWORD;	// i like  DWORD so i define it to use in driver

// main function
NTSTATUS DriverEntry( IN PDRIVER_OBJECT  DriverObject,IN PUNICODE_STRING RegistryPath){	
	HANDLE fHandle;	// handle to file
	OBJECT_ATTRIBUTES ObjectAttributes;	// object attributes
	LARGE_INTEGER Interval;	// integer, we will use it for sleep function
	UNICODE_STRING FileName;	// file name
	IO_STATUS_BLOCK    ioStatusBlock;	// IO status block
	DWORD dwSeconds = 10;	// time to sleep
	char myString[] = {"OWNED!!!"};	// string to print to file
	Interval.QuadPart = -(unsigned __int64)dwSeconds * 10000 * 1000; // initialize our time interval
	if(KeGetCurrentIrql() != PASSIVE_LEVEL) return STATUS_INVALID_DEVICE_STATE; 

	RtlInitUnicodeString(&FileName, L"\\DosDevices\\C:\\0WN3ED.TXT");	// our file -> unicode string
	InitializeObjectAttributes( &ObjectAttributes, &FileName, OBJ_CASE_INSENSITIVE | OBJ_KERNEL_HANDLE, NULL, NULL );
	ZwCreateFile(	// create our file
					&fHandle,
					GENERIC_WRITE,
					&ObjectAttributes,
					&ioStatusBlock,
					NULL,
					FILE_ATTRIBUTE_NORMAL,
					0,
					FILE_OVERWRITE_IF,
					FILE_SYNCHRONOUS_IO_NONALERT,
					NULL,
					0
    );

	ZwWriteFile(fHandle, // write text to file
				NULL, 
				NULL, 
				NULL, 
				&ioStatusBlock,
	            myString, 
				strlen(myString), 
				NULL, 
				NULL
	);
	ZwClose(fHandle);	// close handle to file

	KeDelayExecutionThread(KernelMode,FALSE,&Interval );	// sleep for some time to let user read our message from native application
	return STATUS_SUCCESS; 
}
//--------------------------------------------------------------------------------------