From: Andreas Schwab <schwab@suse.de>
To: Jakub Jelinek <jakub@redhat.com>
Cc: Ulrich Drepper <drepper@redhat.com>,
Glibc hackers <libc-hacker@sources.redhat.com>
Subject: Re: [PATCH] getpid/vfork/raise fix
Date: Wed, 10 Mar 2004 14:33:00 -0000 [thread overview]
Message-ID: <jeznaoixge.fsf@sykes.suse.de> (raw)
In-Reply-To: <20040310101515.GS3822@sunsite.ms.mff.cuni.cz> (Jakub Jelinek's message of "Wed, 10 Mar 2004 11:15:15 +0100")
Jakub Jelinek <jakub@redhat.com> writes:
> Can you use a local register for saving oldval accross the syscall though?
> Registers in the register window can be saved to the backing store, if that
> happens, vfork child restores it from the backing store, calls some routine
> and something else is stored into that location in backing store, vfork
> parent will afterwards restore a different value.
I think you are right.
> IMHO only a call clobbered register preserved accross system call can be
> used, and is it is not available, vfork has to choose a slower way:
>
> int oldval = self->pid;
> int newval = oldval ? -oldval : 0x80000000;
> self->pid = newval;
> vfork syscall
> newval = self->pid;
> oldval = (newval & 0x7fffffff) ? -newval : 0;
> self->pid = oldval;
That doesn't seem to work, though. I'm getting p3 != p4 in the posix
vfork tests. Or do you see any error in my implementation?
ENTRY(__vfork)
alloc r2=ar.pfs,0,0,2,0
adds r14=PID,r13
;;
ld4 r16=[r14]
;;
sub r15=0,r16
cmp.eq p0,p6=0,r16
;;
(p6) movl r15=0x80000000
mov out0=CLONE_VM+CLONE_VFORK+SIGCHLD
mov out1=0 /* Standard sp value. */
;;
st4 [r14]=r15
DO_CALL_VIA_BREAK (SYS_ify (clone))
cmp.eq p6,p0=0,r8
adds r14=PID,r13
(p6) br.cond.dptk 1f
;;
ld4 r15=[r14]
;;
extr.u r16=r15,0,31
;;
cmp.eq p0,p6=0,r16
;;
(p6) sub r16=0,r15
;;
st4 [r14]=r16
1:
cmp.eq p6,p0=-1,r10
(p6) br.cond.spnt.few __syscall_error
ret
PSEUDO_END(__vfork)
Andreas.
--
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux AG, MaxfeldstraÃe 5, 90409 Nürnberg, Germany
Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
next prev parent reply other threads:[~2004-03-10 14:33 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-07 23:18 getpid/vfork broken Andreas Schwab
2004-03-07 23:30 ` Ulrich Drepper
2004-03-08 2:22 ` Roland McGrath
2004-03-08 2:28 ` Ulrich Drepper
2004-03-08 2:37 ` Roland McGrath
2004-03-08 13:10 ` Jakub Jelinek
2004-03-09 1:28 ` Roland McGrath
2004-03-09 2:04 ` Ulrich Drepper
2004-03-09 3:50 ` Richard Henderson
2004-03-09 7:48 ` Ulrich Drepper
2004-03-09 13:01 ` Andreas Schwab
2004-03-09 13:59 ` [PATCH] getpid/vfork/raise fix Jakub Jelinek
2004-03-09 16:44 ` Andreas Schwab
2004-03-09 19:38 ` Jakub Jelinek
2004-03-10 5:53 ` Ulrich Drepper
2004-03-10 10:37 ` Andreas Schwab
2004-03-10 12:24 ` Jakub Jelinek
2004-03-10 14:33 ` Andreas Schwab [this message]
2004-03-10 15:01 ` Jakub Jelinek
2004-03-10 15:06 ` Andreas Schwab
2004-03-10 16:56 ` David Mosberger
2004-03-10 17:02 ` Jakub Jelinek
2004-03-10 17:45 ` David Mosberger
2004-03-10 18:19 ` Jakub Jelinek
2004-03-10 19:24 ` David Mosberger
2004-03-10 18:44 ` Ulrich Drepper
2004-03-10 19:18 ` [PATCH] IA-64 pt-vfork fix Jakub Jelinek
2004-03-10 23:10 ` Ulrich Drepper
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