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Date:      Mon, 23 Apr 2001 11:36:40 -0700
From:      Marcel Moolenaar <marcel@cup.hp.com>
To:        Robert Watson <rwatson@FreeBSD.org>
Cc:        emulation@FreeBSD.org
Subject:   Re: Linux-specific jail code in linuxulator
Message-ID:  <20010423113640.C42858@gauss.cup.hp.com>
In-Reply-To: <Pine.NEB.3.96L.1010422164814.63356E-100000@fledge.watson.org>; from rwatson@FreeBSD.org on Sun, Apr 22, 2001 at 04:54:25PM -0400
References:  <Pine.NEB.3.96L.1010422164814.63356E-100000@fledge.watson.org>

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On Sun, Apr 22, 2001 at 04:54:25PM -0400, Robert Watson wrote:
> 
> CVS annotate on linux_mib.c indicates that these features were present in
> 1.1 of the file when it was originally added, so I was wondering if (a) 
> you were the author of the code and

Yes, I was.

> (b) what you knew about its use.

I discussed this with phk at the time. The reason for this IIRC is that
you could run a Linux binary in a jail, have these parameters tuned
without affecting other Linux binaries. For example, some people objected
I changed the name of the OS as returned by uname(2) from FreeBSD to
Linux. Those were Netscape users, BTW. It is now possible to have
netscape run in a jail and have the OS set to FreeBSD for those caring
about web statistics and still have Linux returned in the normal cases.

> Since
> I'm rewriting largely from scratch (although keeping fairly close to the
> original implementation when it comes to most features), now appears to be
> the opportunity to determine if these features are used, if so whether
> they are useful.

From a security perspective they might have some value, but mostly to have
the kld tuned for different Linux binaries without affecting each other.

> Apparently they weren't part of Poul-Henning's orginal
> implementation, so I assume they were added later.

Correct.

> If they are used, I
> should make sure to include them in the revised version, and possibly
> clean up interactions between optional components (such as sysvipc,
> linuxlator, etc) and jail.  If they're not used, removing them makes sense
> because they do introduce complexity (especially in light of fine-grained
> threading/protection in the kernel).

I see. It's hard for me to say what the best action is here. I don't use
the feature myself and I don't have any indication of people who do
depend on this. So if people could speak up here.

Maybe this is something for -arch as well.

I think we should keep it if possible, if only to maintain current
behaviour. But if that's too complicated, as you say, then I wouldn't
have a problem with it being changed.

-- 
Marcel Moolenaar
  mail: marcel@cup.hp.com / marcel@FreeBSD.org
  tel:  (408) 447-4222

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