linux-kernel - Re: Build failure in -next due to 'kbuild: allow archs to select link dead code/data elimination'

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Date:   Tue, 13 Sep 2016 13:51:15 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Michal Marek <mmarek@...e.com>, Chen Liqin <liqin.linux@...il.com>,
        Lennox Wu <lennox.wu@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: Build failure in -next due to 'kbuild: allow archs to select
 link dead code/data elimination'

On Mon, 12 Sep 2016 20:17:30 -0700
Guenter Roeck <linux@...ck-us.net> wrote:

> Hi Nicholas,
> 
> On 09/12/2016 07:00 PM, Nicholas Piggin wrote:
> > On Mon, 12 Sep 2016 15:24:43 -0700
> > Guenter Roeck <linux@...ck-us.net> wrote:
> >  
> >> Hi,
> >>
> >> your commit 'kbuild: allow archs to select link dead code/data elimination'
> >> is causing the following build failure in -next when building score:defconfig.
> >>
> >> arch/score/kernel/built-in.o: In function `work_resched':
> >> arch/score/kernel/entry.o:(.text+0xe84):
> >> 	relocation truncated to fit: R_SCORE_PC19 against `schedule'
> >>
> >> Reverting the commit fixes the problem.
> >>
> >> Please let me know if I can help tracking down the problem.
> >> In case you need a score toochain, you can find the one I use at
> >> http://server.roeck-us.net/toolchains/score.tgz.
> >>
> >> Thanks,
> >> Guenter  
> >
> > It's not supposed to have any real effect unless the
> > option is selected, but there are a few changes to linker
> > script which must be causing it.
> >
> > There are two changes to vmlinux.lds.h. One is to KEEP a
> > few input sections, that *should* be kept anyway. The other
> > is to bring in additional sections into their correct output
> > section.
> >
> > Could you try reverting those lines of vmlinux.lds.h that
> > change the latter, i.e.:
> >
> > -		*(.text.hot .text .text.fixup .text.unlikely)		\
> > +		*(.text.hot .text .text.fixup .text.unlikely .text.*)	\  
> 
> This is the culprit. After removing " .text.*" it builds fine.

Thanks for testing it. Some architectures have .text.x sections
not included here, I should have seen that. We should possibly
just revert that line and require implementing archs to do the
right thing.

[ Convention is to use '.' to avoid C identifiers, so we should
use .text..x for these things. But that's not done completely
throughout the kernel, and a little invasive to do with this
series. I'll revisit this and clean things up subsequently after
this round gets merged. ]

Thanks,
Nick