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!ioctldecode

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The !ioctldecode extension displays the Device Type, Required Access, Function Code and Transfer Type as specified by the given IOCTL code. For more information about IOCTL control codes, see Defining I/O Control Codes.

!ioctldecode IoctlCode

Parameters

IoctlCode

Specifies the hexadecimal IOCTL Code. The !irp command displays the IOCTL code in its output.

DLL

Kdexts.dll

Additional Information

To see information on the IOCTL, we first locate an IRP of interest. You can use the !irpfind command to locate an irp of interest.

Use the !irp command to display information about the irp.

0: kd> !irp ffffd581a6c6cd30
Irp is active with 6 stacks 6 is current (= 0xffffd581a6c6cf68)
No Mdl: No System Buffer: Thread 00000000:  Irp stack trace.  
     cmd  flg cl Device   File     Completion-Context
[N/A(0), N/A(0)]
            0  0 00000000 00000000 00000000-00000000    

                                                Args: 00000000 00000000 00000000 00000000
[N/A(0), N/A(0)]
            0  0 00000000 00000000 00000000-00000000    

                                                Args: 00000000 00000000 00000000 00000000
[N/A(0), N/A(0)]
            0  0 00000000 00000000 00000000-00000000    

                                                Args: 00000000 00000000 00000000 00000000
[N/A(0), N/A(0)]
            0  0 00000000 00000000 00000000-00000000    

                                                Args: 00000000 00000000 00000000 00000000
[N/A(0), N/A(0)]
            0  0 00000000 00000000 00000000-00000000    

                                                Args: 00000000 00000000 00000000 00000000
>[IRP_MJ_INTERNAL_DEVICE_CONTROL(f), N/A(0)]
            0 e1 ffffd581a5fbd050 00000000 fffff806d2412cf0-ffffd581a5cce050 Success Error Cancel pending
                       \Driver\usbehci        (IopUnloadSafeCompletion)
                                                Args: ffffd581a6c61a50 00000000 0x220003 00000000

The third argument displayed, in this case 0x220003, is the IOCTL code. Use the IOCTL code to display information about the IOCTL, in this case IOCTL_INTERNAL_USB_SUBMIT_URB.

0: kd> !ioctldecode 0x220003

IOCTL_INTERNAL_USB_SUBMIT_URB

Device Type    : 0x22 (FILE_DEVICE_WINLOAD) (FILE_DEVICE_USER_MODE_BUS) (FILE_DEVICE_USB) (FILE_DEVICE_UNKNOWN)
Method         : 0x3 METHOD_NEITHER 
Access         : FILE_ANY_ACCESS
Function       : 0x0

If you provide an IOCTL code that is not available, you will see this type of output.

0: kd> !ioctldecode 0x1280ce

Unknown IOCTL  : 0x1280ce 

Device Type    : 0x12 (FILE_DEVICE_NETWORK)
Method         : 0x2 METHOD_OUT_DIRECT 
Access         : FILE_WRITE_ACCESS 
Function       : 0x33

Although the IOCTL is not identified, information about the IOCTL fields are displayed.

Note that only a subset of publicly defined IOCTLs are able to be identified by the !ioctldecode command.

For more information about IOCTLs see Introduction to I/O Control Codes.

For more general information about IRPs and IOCTLs, refer to Windows Internals by Mark E. Russinovich, David A. Solomon and Alex Ionescu.