linux-kernel - Re: [PATCH] udivdi3: 64 bit divide

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <Pine.LNX.4.63.0703010220210.21277@gockel.physik3.uni-rostock.de>
Date:	Thu, 1 Mar 2007 02:29:19 +0100 (CET)
From:	Tim Schmielau <tim@...sik3.uni-rostock.de>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] udivdi3: 64 bit divide

On Tue, 27 Feb 2007, Andrew Morton wrote:
> > On Mon, 26 Feb 2007 17:35:17 -0800 Stephen Hemminger <shemminger@...ux-foundation.org> wrote:
> > The kernel already has several implmentations and usages of 64 by 64 
> > bit divide.
> > 
> > Although it is significantly slower, there are places that need it so
> > provide one generic version using scaling, and allow existing platform
> > versions to continue.
> 
> The reason we implement 64/32 via do_div() is, for better or for worse, to
> make people think before they use it.  And to make it stand out, and so
> that we discover places that are using it by accident, where they could use
> something cheaper.

IMHO it is even more important that the user of your 64/64 div is aware 
that it only returns an approximate result.

I certainly don't want to have any code in the kernel that by accident 
makes an allocation a few bytes short of the actual size of the object 
(just to make up a drastic example).

Tim
-
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/