From owner-cvs-all  Mon Oct 29  0:50:22 2001
Delivered-To: cvs-all@freebsd.org
Received: from ipcard.iptcom.net (ipcard.iptcom.net [212.9.224.5])
	by hub.freebsd.org (Postfix) with ESMTP
	id EEF0C37B403; Mon, 29 Oct 2001 00:50:05 -0800 (PST)
Received: from vega.vega.com (h39.229.dialup.iptcom.net [212.9.229.39])
	by ipcard.iptcom.net (8.9.3/8.9.3) with ESMTP id KAA04955;
	Mon, 29 Oct 2001 10:49:58 +0200 (EET)
	(envelope-from max@vega.com)
Received: (from max@localhost)
	by vega.vega.com (8.11.6/8.11.3) id f9T8nBG39778;
	Mon, 29 Oct 2001 10:49:11 +0200 (EET)
	(envelope-from sobomax@FreeBSD.org)
From: Maxim Sobolev <sobomax@FreeBSD.ORG>
Message-Id: <200110290849.f9T8nBG39778@vega.vega.com>
Subject: Re: cvs commit: ports/devel/ORBit Makefile ports/devel/ORBit/files         patch-src::IIOP::giop-msg-buffer.c
To: rwatson@FreeBSD.ORG (Robert Watson)
Date: Mon, 29 Oct 2001 10:48:30 +0200 (EET)
Cc: sobomax@FreeBSD.ORG, cvs-committers@FreeBSD.ORG,
	cvs-all@FreeBSD.ORG
In-Reply-To: <Pine.NEB.3.96L.1011028122718.15623C-100000@fledge.watson.org> from "Robert Watson" at Oct 28, 2001 01:18:37 PM
X-Mailer: ELM [version 2.5 PL5]
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: owner-cvs-all@FreeBSD.ORG
Precedence: bulk
List-ID: <cvs-all.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20cvs-all>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20cvs-all>
X-Loop: FreeBSD.ORG

> 
> 
> On Sun, 28 Oct 2001, Maxim Sobolev wrote:
> 
> > > My local Linux box has:
> > > 
> > >   ...
> > >   linux/uio.h: *  UIO_MAXIOV shall be at least 16 1003.1g (5.4.1.1)
> > >   ...
> > >   #define UIO_MAXIOV      1024
> > >   #if 0
> > >   #define UIO_MAXIOV      16      /* Maximum iovec's in one operation 
> > >                                      16 matches BSD */
> > >                                   /* Beg pardon: BSD has 1024 --ANK */
> > >   #endif
> > 
> > I doubt that Linux is really enforces this limit, because if it does,
> > then the ORBit would be broken there as well. BTW, could you please do
> > me a favor and run the following program on your Linux box and send me
> > its output? It tests and reports real value of the limit. 
> 
> <snip>
> 
> Here's the output:
> 
> phoenix:/tmp/tmp> gcc -Wall -g -o o  o.c
> o.c: In function `main':
> o.c:10: warning: implicit declaration of function `exit'
> o.c:13: warning: implicit declaration of function `close'
> phoenix:/tmp/tmp> ./o 
> 16385
> 
> Interestingly, from the Linux source on that box:
> 
> linux-2.4/fs/read_write.c:
>         ret = -EINVAL;
>         if (count > UIO_MAXIOV)
>                 goto out_nofree;
> 
> So it really looks like, for a file readv or writev, it should reject high
> count values.  Likewise the socket code:
> 
> linux-2.4/net/socket.c:
> 
>         /* do not move before msg_sys is valid */
>         err = -EINVAL;
>         if (msg_sys.msg_iovlen > UIO_MAXIOV)
>                 goto out_put;
> 
> Pointing it at a file instead of a device doesn't seem to make a
> difference.
> 
> Not sure what to think :-).

I bet they have a writev(2) wrapper in glibc, which lifts this
UIO_MAXIOV limit. Nedless to say that this promotes writing
incompatible software, but do they really care?

-Maxim

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe cvs-all" in the body of the message