V6/usr/source/mdec/fsboot.s

/ disk boot program to load and transfer
/ to a unix file system entry
/ must be assembled with tty.s and
/ appropriate disk driver

/ entry is made by jsr pc,*$0
/ so return can be rts pc

core = 24.	/ first core loc (in KW) not used
.. = [core*2048.]-512.
start:

/ copy self to 'core' - 512. bytes
/ strip of UNIX execute header if present

	mov	$..,sp
	mov	sp,r1
	clr	r0
	cmp	pc,r1
	bhis	2f
	cmp	(r0),$407
	bne	1f
	mov	$20,r0
1:
	mov	(r0)+,(r1)+
	cmp	r1,$core*2048.
	blo	1b
	jmp	(sp)

/ clear all of core

2:
	clr	(r0)+
	cmp	r0,sp
	blo	2b

/ prompt
/ read in path name
/ breaking on '/' into 14 ch names

	mov	$trvect,r5
	mov	$'@,r0
	jsr	pc,(r5)
	mov	$names,r2
1:
	mov	r2,r1
2:
	jsr	pc,getc
	cmp	r0,$'\n
	beq	1f
	cmp	r0,$'/
	beq	3f
	movb	r0,(r1)+
	br	2b
3:
	cmp	r2,r1
	beq	2b
	add	$14.,r2
	br	1b
1:

/ start of path name decoding
/ start with first name  and root ino

	mov	$names,r2
	mov	$1,r0

/ get next inode

1:
	clr	bno
	jsr	pc,iget
	tst	(r2)
	beq	1f

/ read next directory looking for next name

2:
	jsr	pc,rmblk
		br start
	mov	$buf,r1
3:
	mov	r2,r3
	mov	r1,r4
	add	$16.,r1
	tst	(r4)+
	beq	5f
4:
	cmpb	(r3)+,(r4)+
	bne	5f
	cmp	r4,r1
	blo	4b
	mov	-16.(r1),r0
	add	$14.,r2
	br	1b
5:
	cmp	r1,$buf+512.
	blo	3b
	br	2b

/ last entry was found
/ read into 0.

1:
	clr	r2
1:
	jsr	pc,rmblk
		br callout
	mov	$buf,r1
2:
	mov	(r1)+,(r2)+
	cmp	r1,$buf+512.
	blo	2b
	br	1b

/ subroutine will read in inode
/ number specified in r0
iget:
	add	$31.,r0
	mov	r0,r5
	ash	$-4.,r0
	jsr	pc,rblka
	bic	$!17,r5
	ash	$5.,r5
	add	$buf,r5
	mov	$inod,r4
1:
	mov	(r5)+,(r4)+
	cmp	r4,$addr+16.
	blo	1b
	rts	pc

/ routine to read in block
/ number specified by bno
/ after applying file system
/ mapping algorithm in inode.
/ bno is incremented, success
/ return is a skip, error (eof)
/ is direct return.
rmblk:
	add	$2,(sp)
	mov	bno,r0
	inc	bno
	bit	$LRG,mode
	bne	1f
	asl	r0
	mov	addr(r0),r0
	bne	rblka
2:
	sub	$2,(sp)
	rts	pc
/ large algorithm
/ huge algorithm is not implemented
1:
	clr	-(sp)
	movb	r0,(sp)
	clrb	r0
	swab	r0
	asl	r0
	mov	addr(r0),r0
	beq	2b
	jsr	pc,rblka
	mov	(sp)+,r0
	asl	r0
	mov	buf(r0),r0
	beq	2b
rblka:
	mov	r0,dska
	br	rblk

ba:	buf
wc:	-256.
.bss
end:
inod = ..-1024.
mode = inod
addr = inod+8.
buf = inod+32.
bno = buf+514.
dska = bno+2
names = dska+2
LRG = 10000
.text