ObReferenceObjectByPointerWithTag function (wdm.h)

The ObReferenceObjectByPointerWithTag routine increments the reference count of the specified object, and writes a four-byte tag value to the object to support object reference tracing.

Syntax

NTSTATUS ObReferenceObjectByPointerWithTag(
  [in]           PVOID           Object,
  [in]           ACCESS_MASK     DesiredAccess,
  [in, optional] POBJECT_TYPE    ObjectType,
  [in]           KPROCESSOR_MODE AccessMode,
  [in]           ULONG           Tag
);

Parameters

[in] Object

A pointer to the object. The caller obtains this pointer either when it creates the object, or from a previous call to the ObReferenceObjectByHandleWithTag routine after it opens the object.

[in] DesiredAccess

Specifies the types of access to the object that the caller requests. This parameter is a bitmask of type ACCESS_MASK. The interpretation of this field depends on the object type. Do not use any generic access rights.

[in, optional] ObjectType

A pointer to an opaque structure that specifies the object type. This parameter points to an OBJECT_TYPE structure. Set ObjectType to NULL or to one of the following pointer values, which are declared in the Wdm.h header file: *ExEventObjectType, *ExSemaphoreObjectType, *IoFileObjectType, *PsProcessType, *PsThreadType, *SeTokenObjectType, *TmEnlistmentObjectType, *TmResourceManagerObjectType, *TmTransactionManagerObjectType, or *TmTransactionObjectType. This parameter can be NULL if AccessMode is KernelMode. If ObjectType is not NULL, the routine verifies that the supplied object type matches the object type of the object that the Handle parameter specifies.

[in] AccessMode

Indicates the access mode to use for the access check. Set this parameter to one of the following MODE enumeration values:

• UserMode

• KernelMode

Lower-level drivers should specify KernelMode.

[in] Tag

Specifies a four-byte, custom tag value. For more information, see the following Remarks section.

Return value

ObReferenceObjectByPointerWithTag returns STATUS_SUCCESS if the call is successful. Possible error return values include the following:

Remarks

This routine does access validation of the specified object. If access can be granted, the routine increments the object reference count. This increment prevents the object from being deleted while the caller uses the object. When the object is no longer needed, the caller should decrement the reference count by calling the ObDereferenceObjectWithTag or ObDereferenceObjectDeferDeleteWithTag routine.

For more information about object references, see Life Cycle of an Object.

The ObReferenceObjectByPointer routine is similar to ObReferenceObjectByPointerWithTag, except that it does not enable the caller to write a custom tag to an object. In Windows 7 and later versions of Windows, ObReferenceObjectByPointer always writes a default tag value ('tlfD') to the object. A call to ObReferenceObjectByPointer has the same effect as a call to ObReferenceObjectByPointerWithTag that specifies Tag = 'tlfD'.

To view an object reference trace in the Windows debugging tools, use the !obtrace kernel-mode debugger extension. In Windows 7, the !obtrace extension is enhanced to display object reference tags, if object reference tracing is enabled. By default, object reference tracing is turned off. Use the Global Flags Editor (Gflags) to enable object reference tracing. For more information, see Object Reference Tracing with Tags.

Requirements

See also

ACCESS_MASK

OBJECT_TYPE

ObDereferenceObjectDeferDeleteWithTag

ObDereferenceObjectWithTag

ObReferenceObjectByPointer

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