Date: Fri, 4 Mar 2005 14:11:13 -0500 (EST)
From: Kai Germaschewski <kai.germaschewski@unh.edu>
To: Rusty Russell <rusty@rustcorp.com.au>
cc: Adrian Bunk <bunk@stusta.de>, Andrew Morton <akpm@osdl.org>,
       <kai@germaschewski.name>, Sam Ravnborg <sam@ravnborg.org>,
       Vincent Vanackere <vincent.vanackere@gmail.com>,
       <keenanpepper@gmail.com>,
       lkml - Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Undefined symbols in 2.6.11-rc5-mm1
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On Fri, 4 Mar 2005, Rusty Russell wrote:

> On Wed, 2005-03-02 at 15:00 +0100, Adrian Bunk wrote:
> > Why doesn't an EXPORT_SYMBOL create a reference?
> 
> It does: EXPORT_SYMBOL(x) drops the address of "x", including
> __attribute_used__, in the __ksymtab section.

Well, the problem is that this is still an internal reference in the same 
object file. So ld looks into the lib .a archive, determines that none of 
the symbols in that object file are needed to resolve a reference and 
drops the entire .o file. Doing so, it drops the __ksymtab section as 
well, which otherwise would be used by the kernel to look up that symbol. 

So it drops the reference and the referencee ;), which is normally fine -- 
no unresolved symbols occur. Unfortunately, the kernel really needs to 
know the contents of the __ksymtab sections to correctly export those 
symbols, but it doesn't reference it in any explicit way.

I don't think there's an easy fix, except for not putting such objects 
into an archive/lib, but to link them directly.

--Kai


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