Re: vfork

[Geoff Keating <geoffk@ozemail.com.au>]

> Reply-To: drepper@cygnus.com (Ulrich Drepper)
> From: Ulrich Drepper <drepper@cygnus.com>
> Date: 19 Jan 1999 15:43:55 -0800
> 
> I think I got the ix86 vfork implementation right now (after the
> kernel people again changed their code).  Now we should have correct
> code for ix86, alpha, and SPARC*.  Since I'd like to make 2.0.111 ASAP
> please try to get the implementations for m68, ARM, and PPC in place
> (or send them to me).  If somebody cares about MIPS I'd like to see it
> of course as well.

That's easy.  Please do not implement vfork() for powerpc for version
2.1.  I have some concerns about whether it would be safe,
particularly with varargs and suchlike---this feeds into interesting
optimisation issues of the form "can egcs ever do x".

I'll have some time to properly check its safety in about a month, by
which time I hope we'll be thinking of version 2.1.1.

I attach below a completely untested (not even compiled) version of
the new vfork assembler.

-- 
Geoffrey Keating <geoffk@ozemail.com.au>

===File ~/patches/vfork.S===================================
/* vfork system call for Linux/ppc.
   Copyright (C) 1995, 1996, 1997, 1999 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <sysdep.h>
#define _SCHED_H	1
#include <bits/sched.h>
#define _ERRNO_H	1
#include <bits/errno.h>

	.section ".text"
ENTRY(__vfork)
	li	%r3,CLONE_VFORK+CLONE_VM+SIGCHLD
	li	%r4,0
	DO_CALL(SYS_ify(clone))
	bnslr
	cmpwi	%cr1,%r3,ENOSYS
	bne	%cr1,0f
	DO_CALL(SYS_ify(fork))
	bnslr
0:	b	JUMPTARGET(__syscall_error)
END (__vfork)

weak_alias (__vfork, vfork)
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