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Annotation of 43BSDTahoe/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 the above copyright notice and this paragraph are
                      7:  * duplicated in all such forms and that any documentation,
                      8:  * advertising materials, and other materials related to such
                      9:  * distribution and use acknowledge that the software was developed
                     10:  * by the University of California, Berkeley.  The name of the
                     11:  * University may not be used to endorse or promote products derived
                     12:  * from this software without specific prior written permission.
                     13:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     14:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     15:  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     16:  */
                     17: 
                     18: #if defined(SYSLIBC_SCCS) && !defined(lint)
                     19:        .asciz "@(#)Ovfork.s    5.5 (Berkeley) 6/27/88"
                     20: #endif /* SYSLIBC_SCCS and not lint */
                     21: 
                     22: /*
                     23:  * @(#)vfork.s 4.1 (Berkeley) 12/21/80
                     24:  * C library -- vfork
                     25:  */
                     26: 
                     27: /*
                     28:  * pid = vfork();
                     29:  *
                     30:  * r1 == 0 in parent process, r1 == 1 in child process.
                     31:  * r0 == pid of child in parent, r0 == pid of parent in child.
                     32:  *
                     33:  * trickery here, due to keith sklower, uses ret to clear the stack,
                     34:  * and then returns with a jump indirect, since only one person can return
                     35:  * with a ret off this stack... we do the ret before we vfork!
                     36:  */
                     37: 
                     38:        .set    vfork,66
                     39: .globl _vfork
                     40: 
                     41: _vfork:
                     42:        .word   0x0000
                     43:        movl    16(fp),r2
                     44:        movab   here,16(fp)
                     45:        ret
                     46: here:
                     47:        chmk    $vfork
                     48:        bcc     vforkok
                     49:        jmp     verror
                     50: vforkok:
                     51:        tstl    r1              # child process ?
                     52:        bneq    child   # yes
                     53:        bcc     parent          # if c-bit not set, fork ok
                     54: .globl _errno
                     55: verror:
                     56:        movl    r0,_errno
                     57:        mnegl   $1,r0
                     58:        jmp     (r2)
                     59: child:
                     60:        clrl    r0
                     61: parent:
                     62:        jmp     (r2)

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