typedef struct _KTSS
{
     WORD Backlink;
     WORD Reserved0;
     ULONG Esp0;
     WORD Ss0;
     WORD Reserved1;
     ULONG NotUsed1[4];
     ULONG CR3;
     ULONG Eip;
     ULONG EFlags;
     ULONG Eax;
     ULONG Ecx;
     ULONG Edx;
     ULONG Ebx;
     ULONG Esp;
     ULONG Ebp;
     ULONG Esi;
     ULONG Edi;
     WORD Es;
     WORD Reserved2;
     WORD Cs;
     WORD Reserved3;
     WORD Ss;
     WORD Reserved4;
     WORD Ds;
     WORD Reserved5;
     WORD Fs;
     WORD Reserved6;
     WORD Gs;
     WORD Reserved7;
     WORD LDT;
     WORD Reserved8;
     WORD Flags;
     WORD IoMapBase;
     KiIoAccessMap IoMaps[1];
     UCHAR IntDirectionMap[32];
} KTSS, *PKTSS;

Windows Vista Kernel Structures