V10/sys/ml/access.s

	.text

#
# badaddr(addr, len)
#	see if access addr with a len type instruction causes a machine check
#	len is length of access (1=byte, 2=short, 4=long)
#
	.globl	_badaddr
_badaddr:
	.word	0
	movl	$1,r0
	mfpr	$IPL,r1
	mtpr	$0x16,$IPL	# low enough for very urgent interrupts
	movl	4(ap),r3
	movl	8(ap),r4
	movl	_nofault,r2
	movab	2f,_nofault
	bbc	$0,r4,1f; tstb	(r3)
1:	bbc	$1,r4,1f; tstw	(r3)
1:	bbc	$2,r4,1f; tstl	(r3)
1:
	movl	$10,r3
0:	sobgtr	r3,0b		# pause to allow error interrupt
	clrl	r0		# made it w/o machine checks
2:	movl	r2,_nofault
	mtpr	r1,$IPL
	ret

#
# Check address.
# Given virtual address, byte count, and rw flag
# returns 0 on no access.
#
_useracc:	.globl	_useracc
	.word	0x0
	movl	4(ap),r0		# get va
	movl	8(ap),r1		# count
	tstl	12(ap)			# test for read access ?
	bneq	userar			# yes
	cmpl	$NBPG,r1			# can we do it in one probe ?
	bgeq	uaw2			# yes
uaw1:
	probew	$3,$NBPG,(r0)
	beql	uaerr			# no access
	addl2	$NBPG,r0
	acbl	$NBPG+1,$-NBPG,r1,uaw1
uaw2:
	probew	$3,r1,(r0)
	beql	uaerr
	movl	$1,r0
	ret

userar:
	cmpl	$NBPG,r1
	bgeq	uar2
uar1:
	prober	$3,$NBPG,(r0)
	beql	uaerr
	addl2	$NBPG,r0
	acbl	$NBPG+1,$-NBPG,r1,uar1
uar2:
	prober	$3,r1,(r0)
	beql	uaerr
	movl	$1,r0
	ret
uaerr:
	clrl	r0
	ret

#
# kernacc - check for kernel access privileges
#
# We can't use the probe instruction directly because
# it ors together current and previous mode.
#
	.globl	_kernacc
_kernacc:
	.word	0x0
	movl	4(ap),r0	# virtual address
	bbcc	$31,r0,kacc1
	bbs	$30,r0,kacerr
	mfpr	$SBR,r2		# address and length of page table (system)
	bbss	$31,r2,0f; 0:
	mfpr	$SLR,r3
	brb	kacc2
kacc1:
	bbsc	$30,r0,kacc3
	mfpr	$P0BR,r2	# user P0
	mfpr	$P0LR,r3
	brb	kacc2
kacc3:
	mfpr	$P1BR,r2	# user P1 (stack)
	mfpr	$P1LR,r3
kacc2:
	addl3	8(ap),r0,r1	# ending virtual address
	addl2	$NBPG-1,r1
	ashl	$-PGSHIFT,r0,r0
	ashl	$-PGSHIFT,r1,r1
	bbs	$31,4(ap),kacc6
	bbc	$30,4(ap),kacc6
	cmpl	r0,r3		# user stack
	blss	kacerr		# address too low
	brb	kacc4
kacc6:
	cmpl	r1,r3		# compare last page to P0LR or SLR
	bgtr	kacerr		# address too high
kacc4:	
	movl	(r2)[r0],r3
	bbc	$31,4(ap),kacc4a
	bbc	$31,r3,kacerr	# valid bit is off
kacc4a:
	cmpzv	$27,$4,r3,$1	# check protection code
	bleq	kacerr		# no access allowed
	tstb	12(ap)
	bneq	kacc5		# only check read access
	cmpzv	$27,$2,r3,$3	# check low 2 bits of prot code
	beql	kacerr		# no write access
kacc5:
	aoblss	r1,r0,kacc4	# next page
	movl	$1,r0		# no errors
	ret
kacerr:
	clrl	r0		# error
	ret