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Annotation of 43BSD/lib/libc/vax/sys/Ovfork.c, revision 1.1.1.1

1.1       root        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: #ifdef SYSLIBC_SCCS
                      8: _sccsid:.asciz "@(#)Ovfork.c   5.3 (Berkeley) 3/9/86"
                      9: #endif SYSLIBC_SCCS
                     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
                     35: here:
                     36:        chmk    $vfork
                     37:        bcc     vforkok
                     38:        jmp     verror
                     39: vforkok:
                     40:        tstl    r1              # child process ?
                     41:        bneq    child   # yes
                     42:        bcc     parent          # if c-bit not set, fork ok
                     43: .globl _errno
                     44: verror:
                     45:        movl    r0,_errno
                     46:        mnegl   $1,r0
                     47:        jmp     (r2)
                     48: child:
                     49:        clrl    r0
                     50: parent:
                     51:        jmp     (r2)

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