1/* 2 * Copyright (c) 1983 Regents of the University of California. 3 * All rights reserved. The Berkeley software License Agreement 4 * specifies the terms and conditions for redistribution. 5 */ 6 7#ifndef lint 8_sccsid:.asciz "@(#)Ovfork.s 5.2 (Berkeley) 06/05/85" 9#endif not lint 10 11/* 12 * @(#)vfork.s 4.1 (Berkeley) 12/21/80 13 * C library -- vfork 14 */ 15 16/* 17 * pid = vfork(); 18 * 19 * r1 == 0 in parent process, r1 == 1 in child process. 20 * r0 == pid of child in parent, r0 == pid of parent in child. 21 * 22 * trickery here, due to keith sklower, uses ret to clear the stack, 23 * and then returns with a jump indirect, since only one person can return 24 * with a ret off this stack... we do the ret before we vfork! 25 */ 26 27 .set vfork,66 28.globl _vfork 29 30_vfork: 31 .word 0x0000 32 movl 16(fp),r2 33 movab here,16(fp) 34 ret 35here: 36 chmk $vfork 37 bcc vforkok 38 jmp verror 39vforkok: 40 tstl r1 # child process ? 41 bneq child # yes 42 bcc parent # if c-bit not set, fork ok 43.globl _errno 44verror: 45 movl r0,_errno 46 mnegl $1,r0 47 jmp (r2) 48child: 49 clrl r0 50parent: 51 jmp (r2) 52