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vfork.s
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1993-05-23
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83 lines
INCLUDE inc.i
;
; vfork for MiNT. Note that the return address must be popped off the stack,
; or else it could be clobbered by the child and the parent would be left
; returning to la-la land. Also note that MiNT guarantees that register a1
; will be preserved across a vfork() system call.
;
XFUNC
IF _REGARG
xdef @vfork
xref @tfork
ELSE
xdef _vfork
xref _tfork
ENDC
XDATA
xref ___mint ; MiNT version kept here
xref _errno
XFAR
comm L_vfsav,128 ; Absolute long
TEXT
IF _REGARG
@vfork:
ELSE
_vfork:
ENDC
move.l (sp)+,a1 ; save return address; this is important!
IF _SHORT
tst.w ___mint
ELSE
tst.l ___mint
ENDC
beq.s L_TOS ; go do the TOS thing
move.w #$113,-(sp) ; push MiNT Pvfork() parameter
trap #1 ; Vfork
addq.l #2,sp
tst.l d0 ; error??
bmi L_err
jmp (a1) ; return
L_TOS:
movem.l d2-d7/a1-a6,L_vfsav ; save registers
IF _REGARG
move.l L_vfsav,d0
lea L_newprog,a0
bsr @tfork
ELSE
pea L_vfsav
pea L_newprog
bsr _tfork ; tfork(L_newprog,L_vfsav)
add.l #8,sp
ENDC
movem.l L_vfsav,d2-d7/a1-a6 ; restore reggies
tst.l d0 ; fork went OK??
bmi.s L_err ; no -- error
jmp (a1) ; return to caller
L_err:
IF _SHORT
neg.w d0
move.w d0,_errno
ELSE
neg.l d0
move.l d0,_errno ; save error code in errno
ENDC
moveq.l #-1,d0 ; return -1
jmp (a1) ; return
;
; L_newprog: here is where the child starts executing,with argument
; L_vfsav. We restore registers,zero d0, and jump back to parent
;
L_newprog:
addq.l #4,sp ; pop useless return address
move.l (sp)+,a0 ; get address of save area
movem.l (a0),d2-d7/a1-a6 ; restore reggies
clr.l d0 ; child always returns 0 from vfork
jmp (a1) ; back to caller, as child process
end