IoSetTopLevelIrp

VOID __stdcall IoSetTopLevelIrp(_IRP *Irp){
  KeGetCurrentThread()[1].TrapFrame = (_KTRAP_FRAME *)Irp;
}

Referenced by:

FsRtlCopyRead
FsRtlCopyWrite
FsRtlMdlReadDev
FsRtlPrepareMdlWriteDev
MiCreateImageOrDataSection
MiShareExistingControlArea