This is xnu-8019. See this file in:
bsd/dev/i386/conf.c		standard
bsd/dev/i386/cons.c		standard
bsd/dev/i386/km.c		standard
bsd/dev/i386/kern_machdep.c	standard
bsd/dev/i386/stubs.c		standard
bsd/dev/i386/systemcalls.c	standard
bsd/dev/i386/sysctl.c           standard
bsd/dev/i386/unix_signal.c	standard
bsd/dev/i386/cpu_copy_in_cksum.s optional skywalk
bsd/dev/i386/cpu_memcmp_mask.s  optional skywalk


# Lightly ifdef'd to support K64 DTrace
bsd/dev/i386/dtrace_isa.c	optional config_dtrace
bsd/dev/i386/dtrace_subr_x86.c	optional config_dtrace
bsd/dev/i386/fbt_x86.c		optional config_dtrace
bsd/dev/i386/sdt_x86.c		optional config_dtrace
bsd/dev/i386/fasttrap_isa.c	optional config_dtrace
bsd/dev/i386/instr_size.c	optional config_dtrace
bsd/dev/i386/dis_tables.c	optional config_dtrace

# Support for identifying MACF calouts with locks held
bsd/kern/policy_check.c			optional config_macf

bsd/kern/bsd_stubs.c		standard