linux-kernel - Re: [PATCH 2/2] parisc: fix module loading failure of large modules

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Date:	Mon, 29 Dec 2008 17:09:44 +0100
From:	Helge Deller <deller@....de>
To:	Sam Ravnborg <sam@...nborg.org>
CC:	linux-parisc@...r.kernel.org,
	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	Kyle McMartin <kyle@...artin.ca>,
	Randolph Chung <randolph@...sq.org>,
	Moritz Muehlenhoff <jmm@...til.org>,
	Linus <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Helge Deller <deller@....de>
Subject: Re: [PATCH 2/2] parisc: fix module loading failure of large modules

Sam Ravnborg wrote:
> On Mon, Dec 29, 2008 at 03:10:28PM +0100, Helge Deller wrote:
>> [PATCH 2/2] parisc: fix module loading failure of large modules
>>
>> On 32bit (and sometimes 64bit) and with big kernel modules like xfs or
>> ipv6 the relocation types R_PARISC_PCREL17F and R_PARISC_PCREL22F may
>> fail to reach their PLT stub if we only create one big stub array for
>> all sections at the beginning of the core or init section.
>>
>> With this patch we now instead append individual PLT stub entries
>> directly at the end of the code sections where the stubs are actually
>> called. This reduces the distance between the PCREL location and the
>> stub entry so that the relocations can be fulfilled.
>>
>> The kernel module loader will call module_additional_section_size() and
>> request us to return the amount of additional memory we need for the
>> stubs of each section. The final section size of the code segment will
>> then be increased by that value when the kernel layouts the final
>> addresses of all sections.
>>
>> Tested with 32- and 64bit kernels.
>>
>> Signed-off-by: Helge Deller <deller@....de>
>>
> 
>> diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
>> index 644a70b..cbb622f 100644
>> --- a/arch/parisc/Kconfig
>> +++ b/arch/parisc/Kconfig
>> @@ -34,6 +34,9 @@ config RWSEM_GENERIC_SPINLOCK
>>  config RWSEM_XCHGADD_ALGORITHM
>>  	bool
>>  
>> +config ARCH_WANTS_STUBS_BEHIND_SECTIONS
>> +	def_bool y
>> +
> 
> The recommended practive today is:
> 
> In some relevant Kconfig file add:
> 
> config HAVE_MODULE_SECTION_STUBS
> 	bool
> 
> And then in arch/$ARCH/Kconfig do:
> 
> config PARISC
> 	...
> 	select HAVE_MODULE_SECTION_STUBS
> 	...
> 
> The select are supposed to be sorted alphabetically
> but people seems to use a different alphabet for
> each arch.

Thanks Sam,
I'll change that and respin.

Helge
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