ZwOpenKeyEx function (wdm.h)

The ZwOpenKeyEx routine opens an existing registry key.


  [out] PHANDLE            KeyHandle,
  [in]  ACCESS_MASK        DesiredAccess,
  [in]  POBJECT_ATTRIBUTES ObjectAttributes,
  [in]  ULONG              OpenOptions


[out] KeyHandle

A pointer to a HANDLE variable into which the routine writes the handle to the key.

[in] DesiredAccess

Specifies the type of access to the key that the caller requests. This parameter is an ACCESS_MASK value. For more information, see the description of the DesiredAccess parameter of the ZwCreateKey routine.

[in] ObjectAttributes

A pointer to the object attributes of the key being opened. This parameter points to an OBJECT_ATTRIBUTES structure that must have been previously initialized by the InitializeObjectAttributes routine. The caller must specify the name of the registry key as the ObjectName parameter in the call to InitializeObjectAttributes. If the caller is not running in a system thread context, it must set the OBJ_KERNEL_HANDLE attribute when it calls InitializeObjectAttributes.

[in] OpenOptions

Specifies the options to apply when opening the key. Set this parameter to zero or to the bitwise OR of one or more of the following REG_OPTION_XXX flag bits:

OpenOptions flag Description
REG_OPTION_OPEN_LINK The key is a symbolic link. This flag is not used by device and intermediate drivers.
REG_OPTION_BACKUP_RESTORE The key should be opened with special privileges that allow backup and restore operations. This flag is not used by device and intermediate drivers.

Return value

ZwOpenKeyEx returns STATUS_SUCCESS if the call succeeds in opening the key. Possible error return values include the following:

Return code Description
The OpenOptions parameter specifies invalid options.
The registry path in the object attributes is invalid.
The registry key name in the object attributes was not found.
The named registry key is a symbolic link, but the REG_OPTION_OPEN_LINK flag bit is not set in OpenOptions.
The caller did not have the required access rights to open a handle for the named registry key.
A memory allocation operation failed.


This routine supplies a handle with which the caller can access a registry key. If the specified key does not exist, the routine returns an error status value and does not supply a key handle.

The ZwOpenKey routine is similar to ZwOpenKeyEx but does not accept an OpenOptions parameter. The OpenOptions parameter of ZwOpenKeyEx enables the caller to open a key that is a symbolic link, or to open a key for backup and restore operations. A call to ZwOpenKeyEx with OpenOptions = 0 is equivalent to a call to ZwOpenKey.

After the handle pointed to by KeyHandle is no longer in use, the driver must call ZwClose to close it.

ZwOpenKeyEx ignores the security information in the structure that the ObjectAttributes parameter points to.

If the kernel-mode caller is not running in a system thread context, it must ensure that any handles it creates are kernel handles. Otherwise, the handle can be accessed by the process in whose context the driver is running. For more information, see Object Handles.

For more information about working with registry keys in kernel mode, see Using the Registry in a Driver.


Requirement Value
Minimum supported client Available in Windows 7 and later versions of Windows.
Target Platform Universal
Header wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe
DDI compliance rules HwStorPortProhibitedDDIs(storport), PowerIrpDDis(wdm)

See also