linux-kernel - Re: [PPC64/Power7 - 2.6.35-rc5] Bad relocation warnings while Building a CONFIG_RELOCATABLE kernel with CONFIG

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Message-Id: <8C4BCF61-7F5D-4C80-A311-93CF8521FBF5@suse.de>
Date:	Mon, 19 Jul 2010 09:36:39 +0200
From:	Alexander Graf <agraf@...e.de>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	subrata@...ux.vnet.ibm.com, Paul Mackerras <paulus@...ba.org>,
	sachinp <sachinp@...ux.vnet.ibm.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Linuxppc-dev <Linuxppc-dev@...abs.org>,
	Paul Mackerras <paulus@....ibm.com>, divya.vikas@...ibm.com
Subject: Re: [PPC64/Power7 - 2.6.35-rc5] Bad relocation warnings while Building a CONFIG_RELOCATABLE kernel with CONFIG_ISERIES enabled


On 19.07.2010, at 03:11, Benjamin Herrenschmidt wrote:

> On Thu, 2010-07-15 at 17:05 +0530, Subrata Modak wrote:
>> commit e62cee42e66dcca83aae02748535f62e0f564a0c solved the problem for
>> 2.6.34-rc6. However some other bad relocation warnings generated against
>> 2.6.35-rc5 on Power7/ppc64 below:
>> 
>> MODPOST 2004 modules^M
>> WARNING: 2 bad relocations^M
>> c000000000008590 R_PPC64_ADDR32    .text+0x4000000000008460^M
>> c000000000008594 R_PPC64_ADDR32    .text+0x4000000000008598^M
> 
> I think this is KVM + CONFIG_RELOCATABLE. Caused by:
> 
> .global kvmppc_trampoline_lowmem
> kvmppc_trampoline_lowmem:
> 	.long kvmppc_handler_lowmem_trampoline - CONFIG_KERNEL_START
> 
> .global kvmppc_trampoline_enter
> kvmppc_trampoline_enter:
> 	.long kvmppc_handler_trampoline_enter - CONFIG_KERNEL_START
> 
> Alex, can you turn these into 64-bit on ppc64 so the relocator
> can grok them ?

If I turn them into 64-bit, will the values be > RMA? In that case things would break anyways. How does relocation work on PPC? Are the first few megs copied over to low memory? Would I have to mask anything in the above code to make sure I use the real values?

Alex

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