Windows Driver Model >> Pascal >> File
DO_BUFFERED_IO
參考資訊:
1. Source Code
2. delphidriverdevelopmentkit
DO_BUFFERED_IO的處理手法就是I/O Manager會在Kernel配置一塊跟User Buffer一樣大小的記憶體,Driver只能對該配置的記憶體做讀寫的操作,而讀寫的操作都會同步回User Buffer,也因為結果都需要整塊複製回User Buffer,因此,DO_BUFFERED_IO的方式會消耗比較大的資源,速度也比較慢。
參考如下微軟的圖表說明(IRP_MJ_READ):
記憶體指標:
IRP | Buffer | Length |
---|---|---|
IRP_MJ_READ | (Irp) AssociatedIrp.SystemBuffer |
(IrpStack) Parameters.Read.Length |
IRP_MJ_WRITE | (Irp) AssociatedIrp.SystemBuffer |
(IrpStack) Parameters.Write.Length |
在做Driver的檔案操作時,其讀寫是順序性的,除非Driver使用Pending IRP的處理手法,不然,不需擔心指標複寫錯誤的問題。
main.pas
unit main; interface uses DDDK; const DEV_NAME = '\Device\MyDriver'; SYM_NAME = '\DosDevices\MyDriver'; function _DriverEntry(pOurDriver:PDRIVER_OBJECT; pOurRegistry:PUNICODE_STRING):NTSTATUS; stdcall; implementation var pNextDevice: PDEVICE_OBJECT; szBuf: array[0..255] of char; procedure Unload(pOurDriver:PDRIVER_OBJECT); stdcall; begin end; function IrpFile(pOurDevice:PDEVICE_OBJECT; pIrp:PIRP):NTSTATUS; stdcall; var len: ULONG; psk: PIO_STACK_LOCATION; begin len:= 0; psk:= IoGetCurrentIrpStackLocation(pIrp); case psk^.MajorFunction of IRP_MJ_CREATE: DbgPrint('IRP_MJ_CREATE', []); IRP_MJ_READ: begin DbgPrint('IRP_MJ_READ', []); len:= strlen(@szBuf[0])+1; memcpy(pIrp^.AssociatedIrp.SystemBuffer, @szBuf[0], len); end; IRP_MJ_WRITE: begin DbgPrint('IRP_MJ_WRITE', []); len:= psk.Parameters.Write.Length; memcpy(@szBuf[0], pIrp^.AssociatedIrp.SystemBuffer, len); DbgPrint('Buffer: %s, Length: %d', [szBuf, len]); end; IRP_MJ_CLOSE: DbgPrint('IRP_MJ_CLOSE', []); end; Result:= STATUS_SUCCESS; pIrp^.IoStatus.Status:= Result; pIrp^.IoStatus.Information:= len; IoCompleteRequest(pIrp, IO_NO_INCREMENT); end; function IrpPnp(pOurDevice:PDEVICE_OBJECT; pIrp:PIRP):NTSTATUS; stdcall; var psk: PIO_STACK_LOCATION; suSymName: UNICODE_STRING; begin psk:= IoGetCurrentIrpStackLocation(pIrp); if psk^.MinorFunction = IRP_MN_REMOVE_DEVICE then begin RtlInitUnicodeString(@suSymName, SYM_NAME); IoDetachDevice(pNextDevice); IoDeleteDevice(pOurDevice); IoDeleteSymbolicLink(@suSymName); end; IoSkipCurrentIrpStackLocation(pIrp); Result:= IoCallDriver(pNextDevice, pIrp); end; function AddDevice(pOurDriver:PDRIVER_OBJECT; pPhyDevice:PDEVICE_OBJECT):NTSTATUS; stdcall; var suDevName: UNICODE_STRING; suSymName: UNICODE_STRING; pOurDevice: PDEVICE_OBJECT; begin RtlInitUnicodeString(@suDevName, DEV_NAME); RtlInitUnicodeString(@suSymName, SYM_NAME); IoCreateDevice(pOurDriver, 0, @suDevName, FILE_DEVICE_UNKNOWN, 0, FALSE, pOurDevice); pNextDevice:= IoAttachDeviceToDeviceStack(pOurDevice, pPhyDevice); pOurDevice^.Flags:= pOurDevice^.Flags or DO_BUFFERED_IO; pOurDevice^.Flags:= pOurDevice^.Flags and not DO_DEVICE_INITIALIZING; Result:= IoCreateSymbolicLink(@suSymName, @suDevName); end; function _DriverEntry(pOurDriver:PDRIVER_OBJECT; pOurRegistry:PUNICODE_STRING):NTSTATUS; stdcall; begin pOurDriver^.MajorFunction[IRP_MJ_PNP]:= @IrpPnp; pOurDriver^.MajorFunction[IRP_MJ_CREATE]:= @IrpFile; pOurDriver^.MajorFunction[IRP_MJ_READ]:= @IrpFile; pOurDriver^.MajorFunction[IRP_MJ_WRITE]:= @IrpFile; pOurDriver^.MajorFunction[IRP_MJ_CLOSE]:= @IrpFile; pOurDriver^.DriverExtension^.AddDevice:=@AddDevice; pOurDriver^.DriverUnload:=@Unload; Result:=STATUS_SUCCESS; end; end.
IrpFile()收到IRP_MJ_WRITE時,Driver複製User Buffer的內容到szBuffer,而收到IRP_MJ_READ時,將szBuffer內容又複製回User Buffer,完成暫存的功能,IoStatus.Information的數值就是ReadFile()或WriteFile()完成的長度。
app.pas
program main; {$APPTYPE CONSOLE} uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, DIALOGS; var fd: DWORD; ret: DWORD; len: DWORD; szBuf: array[0..255] of char; begin fd:= CreateFile('\\.\MyDriver', GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ, Nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0); if (fd <> INVALID_HANDLE_VALUE) then begin StrCopy(szBuf, 'I am error'); len:= strlen(szBuf)+1; WriteLn(Output, Format('WR: %s, %d', [szBuf, len])); WriteFile(fd, szBuf, len, ret, Nil); ReadFile(fd, szBuf, len, ret, Nil); WriteLn(Output, Format('RD: %s, %d', [szBuf, ret])); CloseHandle(fd); end else begin WriteLn(Output, 'failed to open mydriver'); end; end.
結果