Windows NT Driver >> Assembly >> File

DO_DIRECT_IO(PIO)


參考資訊:
1. Four-F
2. Source Code

DO_DIRECT_IO的概念就是直接Mapping User Buffer,然後Driver使用該Mapped的MDL(Memory Description List)操作,相較於DO_BUFFERED_IO,因為不須I/O Manager更新回User Buffer,因此,效率會比較好,而如果Driver會操作到DMA(Direct Memory Access)記憶體的話,不適用此方式,雖然司徒目前還沒有寫過DMA相關的Windows Driver,不過依據Microsoft的說明文件來看,使用DMA的話,必須使用另一個API(MmGetMdlVirtualAddress)去取得DMA實體記憶體位址,反之,如果不是DMA的操作,就是PIO(Programmed I/O)方式。

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 (MDL)
MmGetSystemAddressForMdlSafe
(MDL)
MmGetMdlByteCount
IRP_MJ_WRITE (MDL)
MmGetSystemAddressForMdlSafe
(MDL)
MmGetMdlByteCount

main.asm

.386p
.model flat, stdcall
option casemap:none
 
include c:\masm32\include\w2k\ntstatus.inc
include c:\masm32\include\w2k\ntddk.inc
include c:\masm32\include\w2k\ntoskrnl.inc
include c:\masm32\include\w2k\ntddkbd.inc
include c:\masm32\include\wxp\wdm.inc
include c:\masm32\Macros\Strings.mac
includelib c:\masm32\lib\wxp\i386\ntoskrnl.lib
 
public DriverEntry
 
OurDeviceExtension struct
  pNextDevice PDEVICE_OBJECT ?
  szBuffer byte 255 dup(?)
OurDeviceExtension ends

.const
DEV_NAME word "\","D","e","v","i","c","e","\","M","y","D","r","i","v","e","r",0
SYM_NAME word "\","D","o","s","D","e","v","i","c","e","s","\","M","y","D","r","i","v","e","r",0
  
.code
IrpOpenClose proc pOurDevice:PDEVICE_OBJECT, pIrp:PIRP
  IoGetCurrentIrpStackLocation pIrp
  movzx eax, (IO_STACK_LOCATION PTR [eax]).MajorFunction
  .if eax == IRP_MJ_CREATE
    invoke DbgPrint, $CTA0("IRP_MJ_CREATE")
  .elseif eax == IRP_MJ_CLOSE
    invoke DbgPrint, $CTA0("IRP_MJ_CLOSE")
  .endif

  mov eax, pIrp
  and (_IRP PTR [eax]).IoStatus.Information, 0
  mov (_IRP PTR [eax]).IoStatus.Status, STATUS_SUCCESS
  fastcall IofCompleteRequest, pIrp, IO_NO_INCREMENT
  mov eax, STATUS_SUCCESS
  ret
IrpOpenClose endp

IrpReadWrite proc uses ebx pOurDevice:PDEVICE_OBJECT, pIrp:PIRP
  local dwLen:dword
  local pBuf:dword
  local pdx:PTR OurDeviceExtension
  
  and dwLen, 0
  mov eax, pOurDevice
  push (DEVICE_OBJECT PTR [eax]).DeviceExtension
  pop pdx
  
  IoGetCurrentIrpStackLocation pIrp
  movzx eax, (IO_STACK_LOCATION PTR [eax]).MajorFunction
  .if eax == IRP_MJ_WRITE
    invoke DbgPrint, $CTA0("IRP_MJ_WRITE")
    
    mov eax, pIrp
    MmGetMdlByteCount (_IRP ptr [eax]).MdlAddress
    push eax
    pop dwLen

    mov eax, pIrp
    MmGetSystemAddressForMdlSafe (_IRP ptr [eax]).MdlAddress, LowPagePriority
    push eax
    pop pBuf
    invoke DbgPrint, $CTA0("Buffer: %s, Length: %d"), pBuf, dwLen
    
    mov eax, pdx
    mov ebx, pBuf
    invoke memcpy, addr (OurDeviceExtension PTR [eax]).szBuffer, ebx, dwLen
  .elseif eax == IRP_MJ_READ
    invoke DbgPrint, $CTA0("IRP_MJ_READ")
    
    mov eax, pIrp
    MmGetMdlByteCount (_IRP ptr [eax]).MdlAddress
    push eax
    pop dwLen

    mov eax, pIrp
    MmGetSystemAddressForMdlSafe (_IRP ptr [eax]).MdlAddress, LowPagePriority
    push eax
    pop pBuf
    
    mov eax, pOurDevice
    push (DEVICE_OBJECT PTR [eax]).DeviceExtension
    pop pdx
  
    mov eax, pdx
    mov ebx, pBuf
    invoke strcpy, ebx, addr (OurDeviceExtension PTR [eax]).szBuffer
    
    mov eax, pdx
    invoke strlen, addr (OurDeviceExtension PTR [eax]).szBuffer
    inc eax
    push eax
    pop dwLen
  .endif
  
  mov eax, pIrp
  push dwLen
  pop (_IRP PTR [eax]).IoStatus.Information

  mov (_IRP PTR [eax]).IoStatus.Status, STATUS_SUCCESS
  fastcall IofCompleteRequest, pIrp, IO_NO_INCREMENT
  mov eax, STATUS_SUCCESS
  ret
IrpReadWrite endp

Unload proc pOurDriver:PDRIVER_OBJECT
  local szSymName:UNICODE_STRING
    
  invoke RtlInitUnicodeString, addr szSymName, offset SYM_NAME
  invoke IoDeleteSymbolicLink, addr szSymName
    
  mov eax, pOurDriver
  invoke IoDeleteDevice, (DRIVER_OBJECT PTR [eax]).DeviceObject
  ret
Unload endp
 
DriverEntry proc pOurDriver:PDRIVER_OBJECT, pOurRegistry:PUNICODE_STRING
  local pOurDevice:PDEVICE_OBJECT
  local suDevName:UNICODE_STRING
  local szSymName:UNICODE_STRING
    
  mov eax, pOurDriver
  mov (DRIVER_OBJECT PTR [eax]).MajorFunction[IRP_MJ_CREATE * (sizeof PVOID)], offset IrpOpenClose
  mov (DRIVER_OBJECT PTR [eax]).MajorFunction[IRP_MJ_CLOSE  * (sizeof PVOID)], offset IrpOpenClose
  mov (DRIVER_OBJECT PTR [eax]).MajorFunction[IRP_MJ_WRITE  * (sizeof PVOID)], offset IrpReadWrite
  mov (DRIVER_OBJECT PTR [eax]).MajorFunction[IRP_MJ_READ   * (sizeof PVOID)], offset IrpReadWrite
  mov (DRIVER_OBJECT PTR [eax]).DriverUnload, offset Unload
    
  invoke RtlInitUnicodeString, addr suDevName, offset DEV_NAME
  invoke RtlInitUnicodeString, addr szSymName, offset SYM_NAME
  invoke IoCreateDevice, pOurDriver, sizeof OurDeviceExtension, addr suDevName, FILE_DEVICE_UNKNOWN, 0, FALSE, addr pOurDevice
  .if eax == STATUS_SUCCESS
    mov eax, pOurDevice
    or (DEVICE_OBJECT PTR [eax]).Flags, DO_DIRECT_IO
    and (DEVICE_OBJECT PTR [eax]).Flags, not DO_DEVICE_INITIALIZING
    invoke IoCreateSymbolicLink, addr szSymName, addr suDevName
  .endif
  ret
DriverEntry endp
end DriverEntry
.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.asm

.386p
.model flat, stdcall
option casemap:none

include c:\masm32\include\windows.inc
include c:\masm32\include\masm32.inc
include c:\masm32\include\user32.inc
include c:\masm32\include\msvcrt.inc
include c:\masm32\include\kernel32.inc

includelib c:\masm32\lib\user32.lib
includelib c:\masm32\lib\masm32.lib
includelib c:\masm32\lib\msvcrt.lib
includelib c:\masm32\lib\kernel32.lib

.const
DEV_NAME db "\\.\MyDriver",0
MSG_ERR  db "failed to open mydriver",0
MSG_SEND db "I am error",0
MSG_WR   db "WR: %s, %d",10,13,0
MSG_RD   db "RD: %s, %d",10,13,0

.data?
hFile    dd ?
dwRet    dd ?
szBuffer db 255 dup(?)

.code
start:
  invoke CreateFile, offset DEV_NAME, GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0
  .if eax == INVALID_HANDLE_VALUE
    invoke crt_printf, offset MSG_ERR
    invoke ExitProcess, -1
  .endif
  
  mov hFile, eax
  invoke StrLen, offset MSG_SEND
  inc eax
  mov dwRet, eax
  invoke crt_printf, offset MSG_WR, offset MSG_SEND, dwRet
  invoke WriteFile, hFile, offset MSG_SEND, dwRet, offset dwRet, 0
  invoke crt_memset, offset szBuffer, 0, 255
  invoke ReadFile, hFile, offset szBuffer, 255, offset dwRet, 0
  invoke crt_printf, offset MSG_RD, offset szBuffer, dwRet
  invoke CloseHandle, hFile
  invoke ExitProcess, 0

end start

結果


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