IRP - NtDoc
Native API online documentation, based on the System Informer
(formerly Process Hacker) phnt
headers
// wdm.h
typedef struct _IRP {
CSHORT Type;
USHORT Size;
PMDL MdlAddress;
ULONG Flags;
union {
struct _IRP *MasterIrp;
__volatile LONG IrpCount;
PVOID SystemBuffer;
} AssociatedIrp;
LIST_ENTRY ThreadListEntry;
IO_STATUS_BLOCK IoStatus;
KPROCESSOR_MODE RequestorMode;
BOOLEAN PendingReturned;
CHAR StackCount;
CHAR CurrentLocation;
BOOLEAN Cancel;
KIRQL CancelIrql;
CCHAR ApcEnvironment;
UCHAR AllocationFlags;
union {
PIO_STATUS_BLOCK UserIosb;
PVOID IoRingContext;
};
PKEVENT UserEvent;
union {
struct {
union {
PIO_APC_ROUTINE UserApcRoutine;
PVOID IssuingProcess;
};
union {
PVOID UserApcContext;
#if ...
_IORING_OBJECT *IoRing;
#else
struct _IORING_OBJECT *IoRing;
#endif
};
} AsynchronousParameters;
LARGE_INTEGER AllocationSize;
} Overlay;
__volatile PDRIVER_CANCEL CancelRoutine;
PVOID UserBuffer;
union {
struct {
union {
KDEVICE_QUEUE_ENTRY DeviceQueueEntry;
struct {
PVOID DriverContext[4];
};
};
PETHREAD Thread;
PCHAR AuxiliaryBuffer;
struct {
LIST_ENTRY ListEntry;
union {
struct _IO_STACK_LOCATION *CurrentStackLocation;
ULONG PacketType;
};
};
PFILE_OBJECT OriginalFileObject;
} Overlay;
KAPC Apc;
PVOID CompletionKey;
} Tail;
} IRP;
View the official Windows Driver Kit DDI referenceNo description available.
The IRP structure is a partially opaque structure that represents an I/O request packet. Undocumented members of the IRP structure are reserved, used only by the I/O manager or in some cases, by file system drivers (FSDs).
TypeReserved for internal system use.
SizeReserved for internal system use.
MdlAddressPointer to an MDL describing a user buffer, if the driver is using direct I/O, and the IRP major function code is one of the following:
The MDL describes an empty buffer that the device or driver fills in.
The MDL describes a buffer that contains data for the device or driver.
IRP_MJ_DEVICE_CONTROL or IRP_MJ_INTERNAL_DEVICE_CONTROL
If the IOCTL code specifies the METHOD_IN_DIRECT transfer type, the MDL describes a buffer that contains data for the device or driver.
If the IOCTL code specifies the METHOD_OUT_DIRECT transfer type, the MDL describes an empty buffer that the device or driver fills in.
For more information about the buffers that are associated with METHOD_IN_DIRECT and METHOD_OUT_DIRECT transfer types in IOCTL codes, see Buffer Descriptions for I/O Control Codes.
If the driver is not using direct I/O, this pointer is NULL.
FlagsFile system drivers use this field, which is read-only for all drivers. Network and, possibly, highest-level device drivers also might read this field. This field is set either to zero or to the bitwise-OR of one or more of the following system-defined flag bits:
AssociatedIrpReserved for internal system use.
AssociatedIrp.MasterIrpPointer to the master IRP in an IRP that was created by a highest-level driver's call to IoMakeAssociatedIrp.
AssociatedIrp.IrpCountReserved for internal system use.
AssociatedIrp.SystemBufferPointer to a system-space buffer.
If the driver is using buffered I/O, the buffer's purpose is determined by the IRP major function code, as follows:
SystemBuffer.IRP_MJ_READ
The buffer receives data from the device or driver. The buffer's length is specified by Parameters.Read.Length in the driver's IO_STACK_LOCATION structure.
SystemBuffer.IRP_MJ_WRITE
The buffer supplies data for the device or driver. The buffer's length is specified by Parameters.Write.Length in the driver's IO_STACK_LOCATION structure.
SystemBuffer.IRP_MJ_DEVICE_CONTROL or IRP_MJ_INTERNAL_DEVICE_CONTROL
The buffer represents both the input and output buffers that are supplied to DeviceIoControl and IoBuildDeviceIoControlRequest. Output data overwrites input data.
For input, the buffer's length is specified by Parameters.DeviceIoControl.InputBufferLength in the driver's IO_STACK_LOCATION structure.
For output, the buffer's length is specified by Parameters.DeviceIoControl.OutputBufferLength in the driver's IO_STACK_LOCATION structure.
For more information, see Buffer Descriptions for I/O Control Codes.
The buffer represents the input buffer that is supplied to DeviceIoControl and IoBuildDeviceIoControlRequest.
The buffer's length is specified by Parameters.DeviceIoControl.InputBufferLength in the driver's IO_STACK_LOCATION structure.
For more information, see Buffer Descriptions for I/O Control Codes.
If the driver is using direct I/O, the buffer's purpose is determined by the IRP major function code, as follows:
ThreadListEntryReserved for internal system use.
IoStatusContains the IO_STATUS_BLOCK structure in which a driver stores status and information before calling IoCompleteRequest.
RequestorModeIndicates the execution mode of the original requester of the operation, one of UserMode or KernelMode.
PendingReturnedIf set to TRUE, a driver has marked the IRP pending. Each IoCompletion routine should check the value of this flag. If the flag is TRUE, and if the IoCompletion routine will not return STATUS_MORE_PROCESSING_REQUIRED, the routine should call IoMarkIrpPending to propagate the pending status to drivers above it in the device stack.
StackCountReserved for internal system use.
CurrentLocationReserved for internal system use.
CancelIf set to TRUE, the IRP either is or should be canceled.
CancelIrqlContains the IRQL at which a driver is running when IoAcquireCancelSpinLock is called.
ApcEnvironmentReserved for internal system use.
AllocationFlagsReserved for internal system use.
UserIosbReserved for internal system use.
IoRingContextReserved for internal system use.
UserEventReserved for internal system use.
OverlayReserved for internal system use.
Overlay.AsynchronousParametersReserved for internal system use.
Overlay.AsynchronousParameters.UserApcRoutineReserved for internal system use.
Overlay.AsynchronousParameters.IssuingProcessReserved for internal system use.
Overlay.AsynchronousParameters.UserApcContextReserved for internal system use.
Overlay.AsynchronousParameters.IoRingReserved for internal system use.
Overlay.AllocationSizeReserved for internal system use.
CancelRoutineContains the entry point for a driver-supplied Cancel routine to be called if the IRP is canceled. NULL indicates that the IRP is not currently cancelable.
UserBufferContains the address of an output buffer if both of the following conditions apply:
The major function code in the I/O stack location is IRP_MJ_DEVICE_CONTROL or IRP_MJ_INTERNAL_DEVICE_CONTROL.
The I/O control code was defined with METHOD_NEITHER or METHOD_BUFFERED.
For METHOD_BUFFERED, the driver should use the buffer pointed to by Irp->AssociatedIrp.SystemBuffer as the output buffer. When the driver completes the request, the I/O manager copies the contents of this buffer to the output buffer that is pointed to by Irp->UserBuffer. The driver should not write directly to the buffer pointed to by Irp->UserBuffer. For more information, see Buffer Descriptions for I/O Control Codes.
TailReserved for internal system use.
Tail.OverlayReserved for internal system use.
Tail.Overlay.DeviceQueueEntryIf IRPs are queued in the device queue associated with the driver's device object, this field links IRPs in the device queue. These links can be used only while the driver is processing the IRP.
Tail.Overlay.DriverContextIf IRPs are not queued in the device queue associated with the driver's device object, this field can be used by the driver to store up to four pointers. This field can be used only while the driver owns the IRP.
Tail.Overlay.ThreadA pointer to the caller's thread control block (TCB). For requests that originate in user-mode, the I/O manager always sets this field to point to the TCB of the thread that issued the request.
Tail.Overlay.AuxiliaryBufferReserved for internal system use.
Tail.Overlay.ListEntryIf a driver manages its own internal queues of IRPs, it uses this field to link one IRP to the next. These links can be used only while the driver is holding the IRP in its queue or is processing the IRP.
Tail.Overlay.CurrentStackLocationReserved for internal system use.
Tail.Overlay.PacketTypeReserved for internal system use.
Tail.Overlay.OriginalFileObjectReserved for internal system use.
Tail.ApcReserved for internal system use.
Tail.CompletionKeyReserved for internal system use.
Undocumented members of the IRP structure are reserved, used only by the I/O manager or in some cases, by file system drivers (FSDs).
An IRP is the basic I/O manager structure used to communicate with drivers and to allow drivers to communicate with each other. A packet consists of two different parts:
Header, or fixed part of the packet— This is used by the I/O manager to store information about the original request, such as the caller's device-independent parameters, the address of the device object upon which a file is open, and so on. It is also used by drivers to store information such as the final status of the request.
I/O stack locations — Following the header is a set of I/O stack locations, one per driver in the chain of layered drivers for which the request is bound. Each stack location contains the parameters, function codes, and context used by the corresponding driver to determine what it is supposed to be doing. For more information, see the IO_STACK_LOCATION structure.
While a higher-level driver might check the value of the Cancel Boolean in an IRP, that driver cannot assume the IRP will be completed with STATUS_CANCELLED by a lower-level driver even if the value is TRUE.