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Annotation of 43BSDReno/lib/libc/vax/sys/Ovfork.s, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1983 Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms are permitted
        !             6:  * provided that: (1) source distributions retain this entire copyright
        !             7:  * notice and comment, and (2) distributions including binaries display
        !             8:  * the following acknowledgement:  ``This product includes software
        !             9:  * developed by the University of California, Berkeley and its contributors''
        !            10:  * in the documentation or other materials provided with the distribution
        !            11:  * and in all advertising materials mentioning features or use of this
        !            12:  * software. Neither the name of the University nor the names of its
        !            13:  * contributors may be used to endorse or promote products derived
        !            14:  * from this software without specific prior written permission.
        !            15:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
        !            16:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
        !            17:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            18:  */
        !            19: 
        !            20: #if defined(SYSLIBC_SCCS) && !defined(lint)
        !            21:        .asciz "@(#)Ovfork.s    5.6 (Berkeley) 6/1/90"
        !            22: #endif /* SYSLIBC_SCCS and not lint */
        !            23: 
        !            24: /*
        !            25:  * @(#)vfork.s 4.1 (Berkeley) 12/21/80
        !            26:  * C library -- vfork
        !            27:  */
        !            28: 
        !            29: /*
        !            30:  * pid = vfork();
        !            31:  *
        !            32:  * r1 == 0 in parent process, r1 == 1 in child process.
        !            33:  * r0 == pid of child in parent, r0 == pid of parent in child.
        !            34:  *
        !            35:  * trickery here, due to keith sklower, uses ret to clear the stack,
        !            36:  * and then returns with a jump indirect, since only one person can return
        !            37:  * with a ret off this stack... we do the ret before we vfork!
        !            38:  */
        !            39: 
        !            40:        .set    vfork,66
        !            41: .globl _vfork
        !            42: 
        !            43: _vfork:
        !            44:        .word   0x0000
        !            45:        movl    16(fp),r2
        !            46:        movab   here,16(fp)
        !            47:        ret
        !            48: here:
        !            49:        chmk    $vfork
        !            50:        bcc     vforkok
        !            51:        jmp     verror
        !            52: vforkok:
        !            53:        tstl    r1              # child process ?
        !            54:        bneq    child   # yes
        !            55:        bcc     parent          # if c-bit not set, fork ok
        !            56: .globl _errno
        !            57: verror:
        !            58:        movl    r0,_errno
        !            59:        mnegl   $1,r0
        !            60:        jmp     (r2)
        !            61: child:
        !            62:        clrl    r0
        !            63: parent:
        !            64:        jmp     (r2)

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