This is xnu-8019. See this file in:
pexpert/arm/pe_bootargs.c            standard
pexpert/arm/pe_fiq.c                 standard
pexpert/arm/pe_identify_machine.c    standard
pexpert/arm/pe_init.c                standard
pexpert/arm/pe_kprintf.c             standard
pexpert/arm/pe_serial.c              standard
pexpert/arm/pe_consistent_debug.c    standard