linux-kernel - Re: linux-next: Tree for Dec 7 (kallsyms failure)

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Date:   Thu, 8 Dec 2016 15:07:51 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Randy Dunlap <rdunlap@...radead.org>, linux-next@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sachin Sant <sachinp@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        PowerPC <linuxppc-dev@...ts.ozlabs.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Balbir Singh <bsingharora@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Linus <torvalds@...ux-foundation.org>
Subject: Re: linux-next: Tree for Dec 7 (kallsyms failure)

On Thu, 8 Dec 2016 15:29:35 +1100
Stephen Rothwell <sfr@...b.auug.org.au> wrote:

> Hi all,
> 
> On Wed, 7 Dec 2016 18:30:57 -0800 Randy Dunlap <rdunlap@...radead.org> wrote:
> >
> > On 12/07/16 15:56, Stephen Rothwell wrote:  
> > > 
> > > On Wed, 7 Dec 2016 15:42:32 -0800 Randy Dunlap <rdunlap@...radead.org> wrote:    
> > >>
> > >> I started seeing this yesterday (2016-1206).
> > >> This is on x86_64.
> > >>
> > >> Anybody know about it?
> > >>
> > >> kallsyms failure: relative symbol value 0xffffffff81000000 out of range in relative mode    
> > > 
> > > I got a similar failure starting a few days ago on my powerpc
> > > allyesconfig build.  I was assuming that it was PowerPC specific, but
> > > noone has found a cause yet.
> > >     
> > 
> > It may just be an invalid randconfig.  I modified scripts/kallsyms.c and
> > I see this message:
> > kallsyms failure: relative symbol value 0xffffffff81000000 [symbol: Tstartup_64] out of range in relative mode
> > 
> > and it makes sense that startup_64 would (or could) be at 0xffffffff81000000...
> > especially since CONFIG_PHYSICAL_START=0x1000000 and
> > (from Documentation/x86/x86_64/mm.txt)
> > ffffffff80000000 - ffffffff9fffffff (=512 MB)  kernel text mapping, from phys 0
> > 
> > 
> > Ard, what do you think about this?  
> 
> The similar failure I saw in the powerpc allyesconfig build
> 
> kallsyms failure: relative symbol value 0xc000000000000000 out of range in relative mode
> 
> was caused by commit
> 
>   8ab2ae655bfe ("default exported asm symbols to zero")
> 
> which has been reverted in Linus' tree today.
> 

Huh, so it seems like the explicit 0 symbols were being picked up as the
kallsyms relative base, putting the 0xc... symbols beyond reach.