typedef struct _DBGKD_LOAD_SYMBOLS64
{
     ULONG PathNameLength;
     UINT64 BaseOfDll;
     UINT64 ProcessId;
     ULONG CheckSum;
     ULONG SizeOfImage;
     UCHAR UnloadSymbols;
} DBGKD_LOAD_SYMBOLS64, *PDBGKD_LOAD_SYMBOLS64;

Windows Vista Kernel Structures