linux-kernel - Re: linux-next: build warnings after merge of the kbuild tree

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Message-ID: <20160819153228.43a582b2@roar.ozlabs.ibm.com>
Date:   Fri, 19 Aug 2016 15:32:28 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Michal Marek <mmarek@...e.cz>, linux-kernel@...r.kernel.org,
        linux-next@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        PowerPC <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: linux-next: build warnings after merge of the kbuild tree

On Fri, 19 Aug 2016 15:09:14 +1000
Stephen Rothwell <sfr@...b.auug.org.au> wrote:

> Hi Nick,
> 
> On Fri, 19 Aug 2016 13:38:54 +1000 Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> >
> > On Thu, 18 Aug 2016 11:09:48 +1000 Nicholas Piggin <npiggin@...il.com> wrote:  
> > >
> > > On Wed, 17 Aug 2016 14:59:59 +0200
> > > Michal Marek <mmarek@...e.cz> wrote:
> > >     
> > > > On 2016-08-17 03:44, Stephen Rothwell wrote:      
> > > > > 
> > > > > After merging the kbuild tree, today's linux-next build (powerpc
> > > > > ppc64_defconfig) produced these warnings:
> > > > > 
> > > > > WARNING: 25 bad relocations
> > > > > c000000000cf2570 R_PPC64_ADDR64    __crc___arch_hweight16        
> > > > [...]      
> > > > > Introduced by commit
> > > > > 
> > > > >   9445aa1a3062 ("ppc: move exports to definitions")
> > > > > 
> > > > > I have reverted that commit for today.
> > > > > 
> > > > > [cc-ing the ppc guys for clues - also involved is commit
> > > > > 
> > > > >   22823ab419d8 ("EXPORT_SYMBOL() for asm")
> > > > > ]        
> > > > 
> > > > FWIW, I see these warnings as well. Any help from ppc developers is
> > > > appreciated - should the R_PPC64_ADDR64 be whitelisted for exported asm
> > > > symbols (their CRCs actually)?      
> > > 
> > > The dangling relocation is a side effect of linker unable to resolve the
> > > reference to the undefined weak symbols. So the real question is, why has
> > > genksyms not overridden these symbols with their CRC values?
> > > 
> > > This may not even be powerpc specific, but  I'll poke at it a bit more
> > > when I get a chance.    
> > 
> > Not sure if this is relevant, but with the commit reverted, the
> > __crc___... symbols are absolute.
> > 
> > 00000000f55b3b3d A __crc___arch_hweight16  
> 
> Ignore that :-)
> 
> I just had a look at a x86_64 allmodconfig result and it looks like the
> weak symbols are not resolved their either ...
> 
> I may be missing something, but genksyms generates the crc's off the
> preprocessed C source code and we don't have any for the asm files ...

Looks like you're right, good find!

Thanks,
Nick