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From: Mathieu Desnoyers <compudj@krystal.dyndns.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Paulo Marques <pmarques@grupopie.com>,
	linux-kernel@vger.kernel.org, rusty@rustcorp.com.au
Subject: Re: [-mm PATCH] kallsyms should prefer non weak symbols
Date: Tue, 4 Dec 2007 16:38:01 -0500	[thread overview]
Message-ID: <20071204213801.GA8543@Krystal> (raw)
In-Reply-To: <20071204131746.ede01c65.akpm@linux-foundation.org>

* Andrew Morton (akpm@linux-foundation.org) wrote:
> On Tue, 04 Dec 2007 20:35:32 +0000
> Paulo Marques <pmarques@grupopie.com> wrote:
> 
> > When resolving symbol names from addresses with aliased symbol names, 
> > kallsyms_lookup always returns the first symbol, even if it is a weak 
> > symbol.
> > 
> > This patch changes this by sorting the symbols with the weak symbols 
> > last before feeding them to the kernel. This way the kernel runtime 
> > isn't changed at all, only the kallsyms build system is changed.
> > 
> > Another side effect is that the symbols get sorted by address, too. So, 
> > even if future binutils version have some bug in "nm" that makes it fail 
> > to correctly sort symbols by address, the kernel won't be affected by this.
> > 
> > 
> 
> I don't understand the reason for making this change.
> 

I created a module in LTTng that uses kallsyms to get the symbol
corresponding to a specific system call address. Unfortunately, all the
unimplemented syscalls were all referring to the (same) weak symbol
identifying an unrelated system call rather that sys_ni (or whatever
non-weak symbol would be expected). Kallsyms was dumbly returning the
first symbol that matched.

This patch makes sure kallsyms returns the non-weak symbol when there is
one, which seems to be the expected result.

Mathieu

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

  reply	other threads:[~2007-12-04 21:38 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-04 20:35 [-mm PATCH] kallsyms should prefer non weak symbols Paulo Marques
2007-12-04 21:14 ` Mathieu Desnoyers
2007-12-05 12:07   ` Paulo Marques
2007-12-04 21:17 ` Andrew Morton
2007-12-04 21:38   ` Mathieu Desnoyers [this message]
2007-12-04 21:34 ` Arjan van de Ven
2007-12-04 22:31   ` Mathieu Desnoyers
2007-12-05  9:37     ` Rusty Russell
2007-12-05  2:05 ` Rusty Russell
2007-12-05  3:09 ` Andrew Morton
2007-12-05  3:14 ` Andrew Morton
2007-12-05  5:01   ` Mathieu Desnoyers

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