linux-kernel - Re: 2.6.22-rc3-mm1: __attribute_

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20070605035903.GD9045@flint.arm.linux.org.uk>
Date:	Tue, 5 Jun 2007 04:59:03 +0100
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Martin Peschke <mp3@...ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Adrian Bunk <bunk@...sta.de>, linux-kernel@...r.kernel.org
Subject: Re: 2.6.22-rc3-mm1: __attribute__((weak)) considered harmful

On Tue, Jun 05, 2007 at 01:52:38AM +0200, Martin Peschke wrote:
> Andrew Morton wrote:
> >On Sat, 2 Jun 2007 19:14:25 +0200
> >Adrian Bunk <bunk@...sta.de> wrote:
> >
> >>statistics-infrastructure-make-printk_clock-a-generic-kernel-wide-nsec-resolution.patch 
> >>shows why __attribute__((weak)) is harmful because you don't see if a 
> >>required non-weak implemtation is missing:
> >>
> >>In this case, the weak printk_clock() was renamed to timestamp_clock(), 
> >>but the ARM and i386 implementations weren't renamed...
> >>
> >
> >printk_clock() is sched_clock() in disguise, and I'm not sure that making
> >sched_clock() more widely available in this fashion is something that we
> >want to do anyway.

Note that sched_clock() can not be used early on ARM; it might want to
access MMIO which is not accessible until later in setup_arch().  This
is why ARM's printk_clock() divorces itself from sched_clock().

> As to timestamp_clock(): its useful for statistics, but still a minor 
> feature. It would be unfortuante if that was the stumbling block for my 
> patches. Am I right that the fix for the issue pointed at by Adrian is to 
> rename those two occurrences of printk_clock()? Do you want me to submit a 
> patch?

If it's ends up being based upon sched_clock() instead of printk_clock()
on ARM then it'll break stuff horribly (== non-bootable kernels.)

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
-
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/