This is xnu-8019. See this file in:
Directory listing for xnu-8019//osfmk/kdp
Makefile
kdp.c
kdp.h
kdp_callout.h
kdp_core.c
kdp_core.h
kdp_dyld.h
kdp_en_debugger.h
kdp_internal.h
kdp_out_stage.h
kdp_private.h
kdp_protocol.h
kdp_serial.c
kdp_serial.h
kdp_udp.c
kdp_udp.h
ml/
output_stages/
processor_core.c
processor_core.h