[unix-history] / usr / src / cmd / lisp / 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	_fork

_fork:
	.word	0x0000
	movl	16(fp),r2
	movab	here,16(fp)
	ret
here:
	chmk	$vfork
	tstl	r1		# child process ?
	bneq	child	# yes
	bcc 	parent		# if c-bit not set, fork ok
.globl	_errno
	movl	r0,_errno
	mnegl	$1,r0
	jmp	(r2)
child:
	clrl	r0
parent:
	jmp	(r2)
Commit	Line	Data
18d1c3cd JF	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 _fork
	15
	16	_fork:
	17	.word 0x0000
	18	movl 16(fp),r2
	19	movab here,16(fp)
	20	ret
	21	here:
	22	chmk $vfork
	23	tstl r1 # child process ?
	24	bneq child # yes
	25	bcc parent # if c-bit not set, fork ok
	26	.globl _errno
	27	movl r0,_errno
	28	mnegl $1,r0
	29	jmp (r2)
	30	child:
	31	clrl r0
	32	parent:
	33	jmp (r2)