struct MMPTE_PROTOTYPE

typedef struct _MMPTE_PROTOTYPE
{
     ULONG Valid: 1;
     ULONG Unused0: 7;
     ULONG ReadOnly: 1;
     ULONG Unused1: 1;
     ULONG Prototype: 1;
     ULONG Protection: 5;
     ULONG Unused: 16;
     ULONG ProtoAddress: 32;
} MMPTE_PROTOTYPE, *PMMPTE_PROTOTYPE;

Windows Vista Kernel Structures