linux-kernel - Re: [Devel] Re: [PATCH 08/10] Introduce functions to restart a process

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1224679455.4210.24.camel@localhost.localdomain>
Date:	Wed, 22 Oct 2008 14:44:15 +0200
From:	Greg Kurz <gkurz@...ibm.com>
To:	Louis.Rilling@...labs.com
Cc:	Andrey Mirkin <major@...nvz.org>,
	containers@...ts.linux-foundation.org,
	Cedric Le Goater <clg@...ibm.com>,
	linux-kernel@...r.kernel.org, Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [Devel] Re: [PATCH 08/10] Introduce functions to restart a
	process

On Wed, 2008-10-22 at 12:44 +0200, Louis Rilling wrote:
> On Wed, Oct 22, 2008 at 12:06:19PM +0200, Greg Kurz wrote:
> > On Wed, 2008-10-22 at 11:25 +0200, Louis Rilling wrote:
> > > Do you checkpoint uninterruptible syscalls as well? If only interruptible
> > > syscalls are checkpointed, I'd say that either this syscall uses ERESTARTSYS or
> > > ERESTART_RESTARTBLOCK, and then signal handling code already does the trick, or
> > > this syscall does not restart itself when interrupted, and well, this is life,
> > > userspace just sees -EINTR, which is allowed by the syscall spec.
> > > Actually this is how we checkpoint/migrate tasks in interruptible syscalls in
> > > Kerrighed and this works.
> > > 
> > > Louis
> > > 
> > 
> > I don't know Kerrighed internals but I understand you perform checkpoint
> > with a signal handler. Right ?
> 
> Right. This is an kernel-internal-only signal, so all signals remain available
> for userspace.
> 
> > This approach has a huge benefit: the
> > signal handling code do all the arch dependant stuff to save registers
> > in user memory.
> 
> Hm, I'm not sure to understand what you mean here. We just rely on arch code
> that jumps to signal handling to correctly setup struct pt_regs, which is then
> passed to the checkpoint code. So yes, userspace registers are mostly saved by
> existing arch code. But in x86-64 for instance, segment registers still need to
> be saved by the checkpoint code (a bit like copy_thread() does), and I don't
> know arch-independent functions doing this.
> 

You're right, some segment registers need to be saved on x86 also... I
should have written 'most of' in my previous mail.

-- 
Gregory Kurz                                     gkurz@...ibm.com
Software Engineer @ IBM/Meiosys                  http://www.ibm.com
Tel +33 (0)534 638 479                           Fax +33 (0)561 400 420

"Anarchy is about taking complete responsibility for yourself."
        Alan Moore.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/