《Windows NT FileSystem Internals》学习笔记之IO_STACK

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NTDDK定义的Stack Location结构体由以下几个字段组成：

MajorFunction:

该字段定义了一个函数功能集，内核模式驱动可以实现其中的每一个函数。每一个函数由一个函数代码对应。

当内核模式驱动接收到一个IRP时，驱动首先检查当前StackLocation中的MajorFunction字段，得出驱动将要执行的功能，可能的MajorFunction功能代码如下：

#define IRP_MJ_CREATE 0x00

#define IRP_MJ_CREATE_NAMED_PIPE 0x01

#define IRP_MJ_CLOSE 0x02

#define IRP_MJ_READ 0x03

#define IRP_MJ_WRITE 0x04

#define IRP_MJ_QUERY_INFORMATION 0x05

#define IRP_MJ_SET_INFORMATION 0x06

#define IRP_MJ_QUERY_EA 0x07

#define IRP_MJ_SET_EA 0x08

#define IRP_MJ_FLUSH_BUFFERS 0x09

#define IRP_MJ_QUERY_VOLUME_INFORMATION 0x 0a

#define IRP_MJ_SET_VOLUME_INFORMATION 0x0b

#define IRP_MJ_DIRECTORY_CONTROL 0x 0c

#define IRP_MJ_FILE_SYSTEM_CONTROL 0x0d

#define IRP_MJ_DEVICE_CONTROL 0x0e

#define IRP_MJ_INTERNAL_DEVICE_CONTROL 0x 0f

#define IRP_MJ_SHUTDOWN 0x10

#define IRP_MJ_LOCK_CONTROL 0x11

#define IRP_MJ_CLEANUP 0x12

#define IRP_MJ_CREATE_MAILSLOT 0x13

#define IRP_MJ_QUERY_SECURITY 0x14

#define IRP_MJ_SET_SECURITY 0x15

#define IRP_MJ_POWER 0x16

#define IRP_MJ_SYSTEM_CONTROL 0x17

#define IRP_MJ_DEVICE_CHANGE 0x18

#define IRP_MJ_QUERY_QUOTA 0x19

#define IRP_MJ_SET_QUOTA 0x 1a

#define IRP_MJ_PNP 0x1b

#define IRP_MJ_PNP_POWER IRP_MJ_PNP // Obsolete....

#define IRP_MJ_MAXIMUM_FUNCTION 0x1b

MinorFunction

MinorFunction提供了MajorFunction更详细的信息

Flags

Flags提供了函数期望驱动执行的附加信息

Control

当内核驱动异步处理IRP时，驱动可以通过调用IoMarkIrpPending()将IRP标记为Pending状态，以排队IRP处理。IoMarkIrpPending实际上只是将当前Stack Location的Control字段设定为SL_PENDING_RETURNED。内核驱动可以检查该字段查询是否有该标记。

DeviceObject

当调用IoCallDriver()时，NT I/O管理器设定该字段，该字段的内容被设定为目标设备对象的指针。

Win2K源代码中可以看出上面的过程：

NTSTATUS

FASTCALL

IopfCallDriver(

IN PDEVICE_OBJECT DeviceObject,

IN OUT PIRP Irp

)

/*++

Routine Description:

This routine is invoked to pass an I/O Request Packet (IRP) to another

driver at its dispatch routine.

Arguments:

DeviceObject - Pointer to device object to which the IRP should be passed.

Irp - Pointer to IRP for request.

Return Value:

Return status from driver's dispatch routine.

--*/

{

PIO_STACK_LOCATION irpSp;

PDRIVER_OBJECT driverObject;

NTSTATUS status;

// Ensure that this is really an I/O Request Packet.

ASSERT( Irp->Type == IO_TYPE_IRP );

// Update the IRP stack to point to the next location.

Irp->CurrentLocation--;

if (Irp->CurrentLocation <= 0)

{

KeBugCheckEx( NO_MORE_IRP_STACK_LOCATIONS, (ULONG_PTR) Irp, 0, 0, 0 );

}

irpSp = IoGetNextIrpStackLocation( Irp );

Irp->Tail.Overlay.CurrentStackLocation = irpSp;

// Save a pointer to the device object for this request so that it can

// be used later in completion.

irpSp->DeviceObject = DeviceObject;

// Invoke the driver at its dispatch routine entry point.

driverObject = DeviceObject->DriverObject;

PERFINFO_DRIVER_MAJORFUNCTION_CALL(Irp, irpSp, driverObject);

status = driverObject->MajorFunction[irpSp->MajorFunction]( DeviceObject,

Irp );

PERFINFO_DRIVER_MAJORFUNCTION_RETURN(Irp, irpSp, driverObject);

return status;

}

FileObject

I/O管理器将该字段设定为指向I/O操作的目标文件对象

CompletionRoutine

当调用IoSetCompletionRoutine()函数时，设定该字段。I/O管理器在IRP处理完成时，要进行一系列的事后处理，其中就包括检查CompletionRoutine。如果指定了CompletionRoutine，该函数就将在执行事后处理的线程中调用；一般情况下就是调用IoCompleteRequest()函数的线程上下文中。

CompletionRoutine采用堆栈顺序调用，即最后指定的CompletionRoutine最先调用，因此最高层驱动的完成函数最后被调用。如果某个驱动CompletionRoutine返回了STATUS_MORE_PROCESSING_REQUIRED，I/O管理器将立即停止IRP事后处理。返回STATUS_MORE_PROCESSING_REQUIRED的驱动有责任释放IRP占用的内存。