Add original unix v6

source/s5/mcrt0.s

@@ -0,0 +1,60 @@
+/ C runtime startoff including monitoring
+
+cbufs	= 150.
+
+.globl	_monitor
+.globl	_sbrk
+.globl	_main
+.globl	_exit
+.globl	_etext
+.comm	countbase,2
+
+.comm	savr5,2
+
+start:
+	setd
+	mov	sp,r0
+	mov	(r0),-(sp)
+	tst	(r0)+
+	mov	r0,2(sp)
+
+	mov	$_etext,r1
+	sub	$eprol,r1
+	add	$7,r1
+	ash	$-3,r1
+	bic	$!17777,r1
+	mov	$cbufs,-(sp)
+	add	$3*[cbufs+1],r1
+	mov	r1,-(sp)
+	asl	r1
+	mov	r1,-(sp)
+	jsr	pc,_sbrk
+	tst	(sp)+
+	cmp	r0,$-1
+	beq	9f
+	mov	r0,-(sp)
+	add	$6,r0
+	mov	r0,countbase
+	mov	$_etext,-(sp)
+	mov	$eprol,-(sp)
+	jsr	pc,_monitor
+	add	$10.,sp
+	jsr	pc,_main
+	cmp	(sp)+,(sp)+
+	jsr	pc,_exit
+
+9:
+	mov	$2,r0
+	sys	write; 8f; 9f-8f
+
+.data; 8: <No space for monitor buffer\n>; 9:.even; .text
+
+_exit:
+	mov	r5,-(sp)
+	mov	sp,r5
+	clr	-(sp)
+	jsr	pc,_monitor
+	tst	(sp)+
+	mov	4(r5),r0
+	sys	exit
+eprol: