linux-kernel - Re: [PATCH] i386 and x86

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.4.64.0709031130000.16753@jikos.suse.cz>
Date:	Mon, 3 Sep 2007 11:34:06 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Franck Bui-Huu <vagabon.xyz@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i386 and x86_64: randomize brk()

On Sun, 2 Sep 2007, Andrew Morton wrote:

> > What about using a weak function in that case ? It actually gives a 
> > default implementation in _one_ place and can be changed easily from a 
> > nop to something more complex later.
> Yeah, weak functions are by far the cleanest way of doing this - they're
> most elegant.  But they do add the overhead of an empty call/return, so
> some thought needs to go into the tradeoff.

Hi,

the problem I am seeing with __weak functions is that as far as I can see, 
gcc 4.1.0 optimizes the empty __weak function away with -O2, so it is not 
later properly overridden by the other non-weak function, as the callsite 
already doesn't have the corresponding call. (when I stick a printk() into 
the __weak function, everything works fine - it is not optimized away and 
non-weak version of the function gets called).

I persume this is a bug in gcc (4.1.1 doesn't seem to expose this 
behavior). I will look at it a little bit more.

Thanks,

-- 
Jiri Kosina
SUSE Labs
-
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/