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Annotation of 43BSDReno/lib/libc/tahoe/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    5.4 (Berkeley) 6/1/90"
                     22: #endif /* SYSLIBC_SCCS and not lint */
                     23: 
                     24: /*
                     25:  * C library -- vfork
                     26:  * pid = vfork();
                     27:  *
                     28:  * r1 == 0 in parent process, r1 == 1 in child process.
                     29:  * r0 == pid of child in parent, r0 == pid of parent in child.
                     30:  *
                     31:  * trickery here, due to keith sklower, uses ret to clear the stack,
                     32:  * and then returns with a jump indirect, since only one person can return
                     33:  * with a ret off this stack... we do the ret before we vfork!
                     34:  * 
                     35:  */
                     36: 
                     37:        .set    vfork,66
                     38: .globl _vfork
                     39: 
                     40: _vfork:
                     41:        .word   0x0000
                     42:        movl    -8(fp),r2
                     43:        movab   here,-8(fp)
                     44:        ret
                     45: here:
                     46:        kcall   $vfork
                     47:        bcc     vforkok
                     48:        jmp     verror
                     49: vforkok:
                     50:        tstl    r1              # child process ?
                     51:        bneq    child   # yes
                     52:        jbr     parent
                     53: .globl _errno
                     54: verror:
                     55:        movl    r0,_errno
                     56:        mnegl   $1,r0
                     57:        jmp     (r2)
                     58: child:
                     59:        clrl    r0
                     60: parent:
                     61:        jmp     (r2)

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