The ZwQueryValueKey routine returns a value entry for a registry key.

NTSTATUS 
  ZwQueryValueKey(
    IN HANDLE  KeyHandle,
    IN PUNICODE_STRING  ValueName,
    IN KEY_VALUE_INFORMATION_CLASS  KeyValueInformationClass,
    OUT PVOID  KeyValueInformation,
    IN ULONG  Length,
    OUT PULONG  ResultLength
    );

Parameters

KeyHandle

Handle to the key to read value entries from. This handle is created by a successful call to ZwCreateKey or ZwOpenKey.

ValueName

Pointer to the name of the value entry to obtain data for.

KeyValueInformationClass

A KEY_VALUE_INFORMATION_CLASS value that determines the type of information returned in the KeyValueInformation buffer.

KeyValueInformation

Pointer to a caller-allocated buffer that receives the requested information.

Length

Specifies the size, in bytes, of the KeyValueInformation buffer.

ResultLength

Pointer to a variable that receives the size, in bytes, of the key information. If the ZwQueryValueKey routine returns STATUS_SUCCESS, callers can use the value of this variable to determine the amount of data returned. If the routine returns STATUS_BUFFER_OVERFLOW or STATUS_BUFFER_TOO_SMALL, callers can use the value of this variable to determine the size of buffer required to hold the key information.

Return Value

ZwQueryValueKey returns STATUS_SUCCESS on success, or the appropriate error code on failure. Possible error code values include:

STATUS_BUFFER_OVERFLOW

The buffer supplied is too small, and only partial data has been written to the buffer. *ResultLength is set to the minimum size required to hold the requested information.

STATUS_BUFFER_TOO_SMALL

The buffer supplied is too small, and no data has been written to the buffer. *ResultLength is set to the minimum size required to hold the requested information.

STATUS_INVALID_PARAMETER

The KeyInformationClass parameter is not a valid KEY_VALUE_INFORMATION_CLASS value.

Warning If you specify KeyValueBasicInformation for KeyValueInformationClass, Microsoft Windows 98 and Microsoft Windows Me return STATUS_SUCCESS even if the registry key or value name does not exist.

Comments

The KeyHandle passed to ZwQueryValueKey must have been opened with KEY_QUERY_VALUE access. This is accomplished by passing KEY_QUERY_VALUE, KEY_READ, or KEY_ALL_ACCESS as the DesiredAccess parameter to ZwCreateKey or ZwOpenKey.

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 "NtQueryValueKey" instead of "ZwQueryValueKey".

Requirements

IRQL: PASSIVE_LEVEL

Headers: Declared in wdm.h. Include wdm.h, ntddk.h, or ntifs.h.

See Also

KEY_VALUE_BASIC_INFORMATION, KEY_VALUE_FULL_INFORMATION, KEY_VALUE_INFORMATION_CLASS, KEY_VALUE_PARTIAL_INFORMATION, ZwCreateKey, ZwEnumerateValueKey, ZwOpenKey