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Annotation of 43BSDReno/lib/libc/vax/sys/Ovfork.s, revision 1.1.1.1

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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