linux-kernel - Re: [2.6 patch] re-add -ffreestanding

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: <20060906223748.GC12157@stusta.de>
Date:	Thu, 7 Sep 2006 00:37:48 +0200
From:	Adrian Bunk <bunk@...sta.de>
To:	Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...l.org>,
	linux-kernel@...r.kernel.org, Roman Zippel <zippel@...ux-m68k.org>
Subject: Re: [2.6 patch] re-add -ffreestanding

On Wed, Aug 30, 2006 at 07:39:05PM +0100, Russell King wrote:
> On Wed, Aug 30, 2006 at 08:13:58PM +0200, Andi Kleen wrote:
> > On Wednesday 30 August 2006 19:57, Adrian Bunk wrote:
> > > I got the following compile error with gcc 4.1.1 when trying to compile 
> > > kernel 2.6.18-rc4-mm2 for m68k:
> > 
> > If anything then -ffreestanding needs to be added to arch/m68k/Makefile
> > (assuming it doesn't compile at all right now)
> 
> Looking at the effect of -ffreestanding on ARM, it appears that on one
> hand, the overall image size is reduced by 0.016% but we end up with worse
> code - eg, strlen() of the same string in the same function evaluated
> multiple times vs once without -ffreestanding.
> 
> The difference probably comes down to the lack of __attribute__((pure))
> on our string functions in linux/string.h.
> 
> If we are going to go for -ffreestanding, we need to fix linux/string.h
> in that respect _first_.

We are talking about reverting the patch that removed -ffreestanding, 
and that broke at least two architectures although it wrongly claimed 
it would have been a safe patch.

I agree that there is room for improvement at our string functions, but 
small optimizations like the ones you are mentioning are not much 
when talking about reverting a patch that is both theoretically wrong 
and has proven practically to cause problems.

> Russell King

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

-
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/