[unix-history] / usr / src / libc / sys / vfork.s

# C library -- vfork

# pid = vfork();
#
# r1 == 0 in parent process, r1 == 1 in child process.
# r0 == pid of child in parent, r0 == pid of parent in child.
#
# trickery here, due to keith sklower, uses ret to clear the stack,
# and then returns with a jump indirect, since only one person can return
# with a ret off this stack... we do the ret before we vfork!
# 

	.set	vfork,66
.globl	_vfork

_vfork:
	.word	0x0000
	movl	16(fp),r2
	movab	here,16(fp)
	ret
here:
	chmk	$vfork
	bcc	vforkok
	jmp	verror
vforkok:
	tstl	r1		# child process ?
	bneq	child	# yes
	bcc 	parent		# if c-bit not set, fork ok
.globl	_errno
verror:
	movl	r0,_errno
	mnegl	$1,r0
	jmp	(r2)
child:
	clrl	r0
parent:
	jmp	(r2)
Commit	Line	Data
b06f49cc BJ	1	# C library -- vfork
	2
	3	# pid = vfork();
	4	#
	5	# r1 == 0 in parent process, r1 == 1 in child process.
	6	# r0 == pid of child in parent, r0 == pid of parent in child.
	7	#
	8	# trickery here, due to keith sklower, uses ret to clear the stack,
	9	# and then returns with a jump indirect, since only one person can return
	10	# with a ret off this stack... we do the ret before we vfork!
	11	#
	12
	13	.set vfork,66
	14	.globl _vfork
	15
	16	_vfork:
	17	.word 0x0000
	18	movl 16(fp),r2
	19	movab here,16(fp)
	20	ret
	21	here:
	22	chmk $vfork
	23	bcc vforkok
	24	jmp verror
	25	vforkok:
	26	tstl r1 # child process ?
	27	bneq child # yes
	28	bcc parent # if c-bit not set, fork ok
	29	.globl _errno
	30	verror:
	31	movl r0,_errno
	32	mnegl $1,r0
	33	jmp (r2)
	34	child:
	35	clrl r0
	36	parent:
	37	jmp (r2)