From mboxrd@z Thu Jan  1 00:00:00 1970
From: Helge Deller <deller@gmx.de>
Subject: Re: [PATCH] parisc: fix module loading failure of large kernel modules
 (take 4)
Date: Wed, 31 Dec 2008 18:39:55 +0100
Message-ID: <495BAE6B.2030100@gmx.de>
References: <4959346E.7060600@gmx.de> <200812310915.41693.rusty@rustcorp.com.au> <495B5806.3080505@gmx.de> <alpine.LFD.2.00.0812310926450.5086@localhost.localdomain>
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Cc: linux-parisc <linux-parisc@vger.kernel.org>,
	Linux Kernel Development <linux-kernel@vger.kernel.org>,
	Kyle McMartin <kyle@mcmartin.ca>,
	Randolph Chung <randolph@tausq.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Sam Ravnborg <sam@ravnborg.org>,
	John David Anglin <dave@hiauly1.hia.nrc.ca>
To: Linus Torvalds <torvalds@linux-foundation.org>,
	Rusty Russell <rusty@rustcorp.com.au>
Return-path: <linux-parisc-owner@vger.kernel.org>
In-Reply-To: <alpine.LFD.2.00.0812310926450.5086@localhost.localdomain>
List-ID: <linux-parisc.vger.kernel.org>
List-Id: linux-parisc.vger.kernel.org

Linus Torvalds wrote:
> 
> On Wed, 31 Dec 2008, Helge Deller wrote:
>> [PATCH 1/2] module.c: fix module loading failure of large kernel modules
>>
>> When creating the final layout of a kernel module in memory, allow the
>> module loader to reserve some additional memory in front of a given section.
>> This is currently only needed for the parisc port which needs to put the
>> stub entries there to fulfill the 17/22bit PCREL relocations with large
>> kernel modules like xfs.
>>
>> Differences of this patch to previous versions:
>> - added weak funtion arch_module_section_size()
> 
> This doesn't work.
> 
> We've had this bug several times now, and one of them just very recently.
> 
> Some gcc versions will inline weak functions if they are in scope - even 
> if there is a non-weak function somewhere else. So you MUST NOT have the 
> weak definition in the same file (or indirectly called through some inline 
> functions in a header file) as the call. Because if you do, then any user 
> with the wrong version of gcc will get the weak function semantics, even 
> if it was meant to be overridden by something else.

Ok, that might explain why I saw some strange things in the unwind tables
after that I switched to using the weak function (hppa-crosscompiler, gcc-3.3.4).

>> +/* Additional bytes needed by arch in front of individual sections */
>> +unsigned int __attribute__ ((weak)) arch_module_section_size(
>> +		struct module *mod, unsigned int section)
> 
> We don't write out that whole "__attribute__" crud. We use
> 
> 	unsigned in __weak arch_module_section_size(struct module *mod, unsigned int section)
> 
> instead.

Ok.

> But as mentioned, it needs to be in another compilation unit.

Understood.

Rusty, back to you for an advise on how to continue ;-)
(I assume Rusty is just right now celebrating new-year)

Helge