This is xnu-8019. See this file in:
#!/bin/bash

#
# kasan_install: set up a system to run the KASan kernel. Run with "--uninstall"
# to reverse the setup.
#
# Adds kcsuffix=kasan to boot-args.
#


if [[ `whoami` != root ]] ; then
	echo "Re-running with sudo"
	sudo "$0" "$@"
	exit $?
fi

sip_enabled() {
	csrutil status |grep -q enabled
}

prompt() {
	echo -n "$@ [y/N] "
	read ans
	case "$ans" in
		[yY]*) return 0 ;;
		*) return 1 ;;
	esac
}

kasan_install() {

	dobootargs=0

	echo -n "Checking KASan boot args... "

	bootargs=$(nvram boot-args | cut -f2)
	cursuffix=$(echo $bootargs | sed -n 's/.*kcsuffix=\([^ ]\)/\1/p')

	if [[ "$cursuffix" == kasan ]] ; then
		echo "already set."
	elif [[ -n "$cursuffix" ]] ; then
		prompt "custom kcsuffix ($cursuffix) is set. Overwrite?" && {
			bootargs=$(echo "$bootargs" | sed 's/[ ]*kcsuffix=[^ ]*//')
			dobootargs=1
		}
	else
		prompt "not set. Modify?" && {
			dobootargs=1
		}
	fi

	[[ $dobootargs -eq 1 ]] && {
		echo -n "Adding boot arg kcsuffix=kasan... "
		newlen=$(echo -n "$bootargs kcsuffix=kasan" |wc -c)
		if [[ $newlen -ge 512 ]] ; then
			echo "boot-args too long. Bailing."
			exit 3
		fi

		nvram boot-args="$bootargs kcsuffix=kasan" || exit $?
		echo "done."
	}

}


kasan_uninstall() {

	echo -n "Removing boot args... "

	bootargs=$(nvram boot-args | cut -f2)
	cursuffix=$(echo $bootargs | sed -n 's/.*kcsuffix=\([^ ]\)/\1/p')

	if [[ $cursuffix == "kasan" ]] ; then
		prompt "remove kcsuffix=kasan?" && {
			echo -n "Removing kcsuffix... "
			bootargs=$(echo "$bootargs" | sed 's/[ ]*kcsuffix=[^ ]*//')
			nvram boot-args="$bootargs"
			echo "done."
		}
	else
		echo "not set."
	fi

}

case "$1" in
	*uninstall|*del*|*remove|*rm)
		kasan_uninstall ;;
	*)
		kasan_install ;;
esac