linux-kernel - Re: [PATCH] x86,nmi: Fix section mismatch warnings on 32-bit

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Message-Id: <4FCE4D800200007800088546@nat28.tlf.novell.com>
Date:	Tue, 05 Jun 2012 17:18:40 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Sam Ravnborg" <sam@...nborg.org>
Cc:	<x86@...nel.org>, "Don Zickus" <dzickus@...hat.com>,
	"LKML" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86,nmi: Fix section mismatch warnings on 32-bit

>>> On 05.06.12 at 18:13, Sam Ravnborg <sam@...nborg.org> wrote:
> On Tue, Jun 05, 2012 at 10:47:34AM -0400, Don Zickus wrote:
>> On Tue, Jun 05, 2012 at 09:12:13AM +0100, Jan Beulich wrote:
>> > >>> On 04.06.12 at 21:56, Don Zickus <dzickus@...hat.com> wrote:
>> > > It was reported that compiling for 32-bit caused a bunch of section
>> > > mismatch warnings:
>> > > 
>> > >  VDSOSYM arch/x86/vdso/vdso32-syms.lds
>> > >   LD      arch/x86/vdso/built-in.o
>> > >   LD      arch/x86/built-in.o
>> > > WARNING: arch/x86/built-in.o(.data+0x5af0): Section mismatch in reference 
>> > > from the variable
>> > > test_nmi_ipi_callback_na.10451 to the function 
>> > 
>> > Did you check what this (compiler introduced) variable actually
>> > represents? The problem clearly is that the compiler has no way
>> > of knowing that data it generates referencing an __init function
>> > would actually need to go into .init.data or alike.
>> 
>> I do not know enough about behind the scene compiler magic to track this
>> down correctly.  So any insight/help is greatly appreciated. :-)
> 
> We register a function annotated __init. And the normal use of this 
> register()
> is for functions that survive the init phase.
> So drop the __init annotation on the function we register and the mismatch 
> is fixed.

But in the case here the function really is being used at init time
only. Plus it still escapes me why there would be differences in
behavior depending on bit-ness or compiler version.

Jan

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