ZwSetValueKey function

The ZwSetValueKey routine creates or replaces a registry key's value entry.


  HANDLE          KeyHandle,
  ULONG           TitleIndex,
  ULONG           Type,
  PVOID           Data,
  ULONG           DataSize



Handle to the registry key to write a value entry for. This handle is created by a successful call to ZwCreateKey or ZwOpenKey.


Pointer to the name of the value entry for which the data is to be written. This parameter can be a NULL pointer if the value entry has no name. If a name string is specified and the given name is not unique relative to its containing key, the data for an existing value entry is replaced.


This parameter is reserved. Device and intermediate drivers should set this parameter to zero.


One of the following system-defined types of data to write.

Type Value Meaning
REG_BINARY Binary data in any form.
REG_DWORD A 4-byte numerical value.
REG_DWORD_LITTLE_ENDIAN A 4-byte numerical value with the least significant byte at the lowest address. Identical to REG_DWORD.
REG_DWORD_BIG_ENDIAN A 4-byte numerical value with the least significant byte at the highest address.
REG_EXPAND_SZ A null-terminated Unicode string that contains unexpanded references to environment variables, such as "%PATH%".
REG_LINK A Unicode string that names a symbolic link. This type is irrelevant to device and intermediate drivers.
REG_MULTI_SZ An array of null-terminated strings, terminated by another zero.
REG_NONE Data with no particular type.
REG_SZ A null-terminated Unicode string.
REG_RESOURCE_LIST A device driver's list of hardware resources, used by the driver or one of the physical devices it controls, in the \ResourceMap tree
REG_RESOURCE_REQUIREMENTS_LIST A device driver's list of possible hardware resources it or one of the physical devices it controls can use, from which the system writes a subset into the \ResourceMap tree
REG_FULL_RESOURCE_DESCRIPTOR A list of hardware resources that a physical device is using, detected and written into the \HardwareDescription tree by the system
Note Device drivers should not attempt to call ZwSetValueKey to explicitly write value entries in a subkey of the \Registry...\ResourceMap key. Only the system can write value entries to the \Registry...\HardwareDescription tree.


Pointer to a caller-allocated buffer that contains the data for the value entry.


Specifies the size, in bytes, of the Data buffer. If Type is REG_XXX_SZ, this value must include space for any terminating zeros.

Return Value

ZwSetValueKey returns an NTSTATUS value. Possible return values include:


The KeyHandle passed to ZwSetValueKey must have been opened with the KEY_SET_VALUE DesiredAccess flag set for this call to succeed. For a description of possible values for DesiredAccess, see ZwCreateKey.

If the given key has no existing value entry with a name matching the given ValueName, ZwSetValueKey creates a new value entry with the given name. If a matching value entry name exists, this routine overwrites the original value entry for the given ValueName. Thus, ZwSetValueKey preserves a unique name for each value entry of any particular key. While each value entry name must be unique to its containing key, many different keys in the registry can have value entries with the same names.

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

Note If the call to this function occurs in user mode, you should use the name "NtSetValueKey" instead of "ZwSetValueKey".
For calls from kernel-mode drivers, the NtXxx and ZwXxx versions of a Windows Native System Services routine can behave differently in the way that they handle and interpret input parameters. For more information about the relationship between the NtXxx and ZwXxx versions of a routine, see Using Nt and Zw Versions of the Native System Services Routines.


Windows version Available starting with Windows 2000.
Target Platform Universal
Header wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe
DDI compliance rules IrqlZwPassive, PowerIrpDDis, ZwRegistryCreate, ZwRegistryOpen, HwStorPortProhibitedDDIs, ZwRegistryCreate(storport), ZwRegistryOpen(storport)

See Also





Using Nt and Zw Versions of the Native System Services Routines