linux-kernel - Re: SyS symbol munging.

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Message-ID: <20130510211716.GN25399@ZenIV.linux.org.uk>
Date:	Fri, 10 May 2013 22:17:16 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: SyS symbol munging.

On Fri, May 10, 2013 at 04:56:22PM -0400, Steven Rostedt wrote:
> On Fri, May 10, 2013 at 09:05:03PM +0100, Al Viro wrote:
> > On Fri, May 10, 2013 at 09:55:00PM +0200, Borislav Petkov wrote:
> > > On Fri, May 10, 2013 at 12:35:10PM -0700, Andrew Morton wrote:
> > > > I forget who did this initially and peeling back those layers with git
> > > > is tiresome.
> > > 
> > > 1a94bc34768e4 from 2009, although those SyS* things started appearing in
> > > stack traces only recently AFAIR.
> > 
> > Note that both sys_something and SyS_something end up in vmlinux symbol
> > table, refering to the same address.  AFAICS, what matters is which one
> > goes first.  May be even linker-dependent...
> 
> Actually, it's the first one that kallsyms finds in its binary search.
> 
> If the table is layed out a little differently, it may find the first
> one or the second one.

Then maybe it's worth trying to kill these aliases in kallsyms.  We also
have compat_SyS_something stuff.  Actually, most of the aliases seem to be
of those forms - after removing (a_sys_b,a_SyS_b) pairs the list of duplicates
in System.map shrinks by factor of 15 or so...
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