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Annotation of 42BSD/lib/libc/vax/sys/Ovfork.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * @(#)vfork.s 4.1 (Berkeley) 12/21/80
        !             3:  * C library -- vfork
        !             4:  */
        !             5: 
        !             6: /*
        !             7:  * pid = vfork();
        !             8:  *
        !             9:  * r1 == 0 in parent process, r1 == 1 in child process.
        !            10:  * r0 == pid of child in parent, r0 == pid of parent in child.
        !            11:  *
        !            12:  * trickery here, due to keith sklower, uses ret to clear the stack,
        !            13:  * and then returns with a jump indirect, since only one person can return
        !            14:  * with a ret off this stack... we do the ret before we vfork!
        !            15:  */
        !            16: 
        !            17:        .set    vfork,66
        !            18: .globl _vfork
        !            19: 
        !            20: _vfork:
        !            21:        .word   0x0000
        !            22:        movl    16(fp),r2
        !            23:        movab   here,16(fp)
        !            24:        ret
        !            25: here:
        !            26:        chmk    $vfork
        !            27:        bcc     vforkok
        !            28:        jmp     verror
        !            29: vforkok:
        !            30:        tstl    r1              # child process ?
        !            31:        bneq    child   # yes
        !            32:        bcc     parent          # if c-bit not set, fork ok
        !            33: .globl _errno
        !            34: verror:
        !            35:        movl    r0,_errno
        !            36:        mnegl   $1,r0
        !            37:        jmp     (r2)
        !            38: child:
        !            39:        clrl    r0
        !            40: parent:
        !            41:        jmp     (r2)

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