"do section mismatch check on full vmlinux" breaks powerpc build

"do section mismatch check on full vmlinux" breaks powerpc build

[Nathan Lynch]

Hello-

2.6.23-rc1 breaks the build for 64-bit powerpc for me (using
maple_defconfig):

  LD      vmlinux.o
powerpc64-unknown-linux-gnu-ld: dynreloc miscount for
kernel/built-in.o, section .opd
powerpc64-unknown-linux-gnu-ld: can not edit opd Bad value
make: *** [vmlinux.o] Error 1

This is on a i386 host with:
powerpc64-unknown-linux-gnu-gcc (GCC) 4.1.2
GNU ld version 2.16.1

Reverting the following commit fixes it:

commit 741f98fe298a73c9d47ed53703c1279a29718581
Author: Sam Ravnborg <sam@ravnborg.org>
Date:   Tue Jul 17 10:54:06 2007 +0200

    kbuild: do section mismatch check on full vmlinux


However, I see a possibly related binutils patch:
http://article.gmane.org/gmane.comp.gnu.binutils/33650

Will there be a kbuild fix for this or should I update my binutils?

Re: "do section mismatch check on full vmlinux" breaks powerpc build

[Sam Ravnborg]

On Tue, Jul 24, 2007 at 05:41:05PM -0500, Nathan Lynch wrote:
> Hello-
> 
> 2.6.23-rc1 breaks the build for 64-bit powerpc for me (using
> maple_defconfig):
> 
>   LD      vmlinux.o
> powerpc64-unknown-linux-gnu-ld: dynreloc miscount for
> kernel/built-in.o, section .opd
> powerpc64-unknown-linux-gnu-ld: can not edit opd Bad value
> make: *** [vmlinux.o] Error 1
> 
> This is on a i386 host with:
> powerpc64-unknown-linux-gnu-gcc (GCC) 4.1.2
> GNU ld version 2.16.1
> 
> Reverting the following commit fixes it:
> 
> commit 741f98fe298a73c9d47ed53703c1279a29718581
> Author: Sam Ravnborg <sam@ravnborg.org>
> Date:   Tue Jul 17 10:54:06 2007 +0200
> 
>     kbuild: do section mismatch check on full vmlinux
> 
> 
> However, I see a possibly related binutils patch:
> http://article.gmane.org/gmane.comp.gnu.binutils/33650
> 
> Will there be a kbuild fix for this or should I update my binutils?
> 
What kbuild does is a very basic link of a number of .o files.
Why this suddenly breaks I do not fully understand and I see no obvious
way to fix it in kbuild.

And browsing arch/ppc/kernel/vmlinux.lds.S I see no special handling of .opd.

Puzzeled?
I'm not sure how to deal with this one. Would prefer to say that this is
a binutils bug so fix it there but then I like to provide a workaround
for those with faulty toolchains.
I could put the link and the additional modpost check inside a
CONFIG_SOMETHING....

	Sam

Re: "do section mismatch check on full vmlinux" breaks powerpc build

[Sam Ravnborg]

On Tue, Jul 24, 2007 at 05:41:05PM -0500, Nathan Lynch wrote:
> Hello-
> 
> 2.6.23-rc1 breaks the build for 64-bit powerpc for me (using
> maple_defconfig):
> 
>   LD      vmlinux.o
> powerpc64-unknown-linux-gnu-ld: dynreloc miscount for
> kernel/built-in.o, section .opd
> powerpc64-unknown-linux-gnu-ld: can not edit opd Bad value
> make: *** [vmlinux.o] Error 1
> 
> This is on a i386 host with:
> powerpc64-unknown-linux-gnu-gcc (GCC) 4.1.2
> GNU ld version 2.16.1
> 
> Reverting the following commit fixes it:
> 
> commit 741f98fe298a73c9d47ed53703c1279a29718581
> Author: Sam Ravnborg <sam@ravnborg.org>
> Date:   Tue Jul 17 10:54:06 2007 +0200
> 
>     kbuild: do section mismatch check on full vmlinux
> 
> 
> However, I see a possibly related binutils patch:
> http://article.gmane.org/gmane.comp.gnu.binutils/33650
> 
> Will there be a kbuild fix for this or should I update my binutils?

Did a bit more testing.
Im am down to the following to reproduce the fault:
 /opt/crosstool/gcc-4.1.0-glibc-2.3.6/powerpc64-unknown-linux-gnu/bin/powerpc64-unknown-linux-gnu-ld -m elf64ppc  -r -o vmlinux.o kernel/signal.o arch/powerpc/kernel/vdso.o

Seems that vdso.o and signal.o does not like each other??

	Sam

Re: "do section mismatch check on full vmlinux" breaks powerpc build

[Sam Ravnborg]

On Tue, Jul 24, 2007 at 05:41:05PM -0500, Nathan Lynch wrote:
> Hello-
> 
> 2.6.23-rc1 breaks the build for 64-bit powerpc for me (using
> maple_defconfig):
> 
>   LD      vmlinux.o
> powerpc64-unknown-linux-gnu-ld: dynreloc miscount for
> kernel/built-in.o, section .opd
> powerpc64-unknown-linux-gnu-ld: can not edit opd Bad value
> make: *** [vmlinux.o] Error 1
> 
> This is on a i386 host with:
> powerpc64-unknown-linux-gnu-gcc (GCC) 4.1.2
> GNU ld version 2.16.1
> 
> Reverting the following commit fixes it:
> 
> commit 741f98fe298a73c9d47ed53703c1279a29718581
> Author: Sam Ravnborg <sam@ravnborg.org>
> Date:   Tue Jul 17 10:54:06 2007 +0200
> 
>     kbuild: do section mismatch check on full vmlinux
> 
> 
> However, I see a possibly related binutils patch:
> http://article.gmane.org/gmane.comp.gnu.binutils/33650
> 
> Will there be a kbuild fix for this or should I update my binutils?


I tried searching a bit more to find the culprint.
I narrowed it down to the following change to avoid the breakage:

diff --git a/include/linux/mm.h b/include/linux/mm.h
index c456c3a..2ea222f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1246,7 +1246,7 @@ void drop_slab(void);
 extern int randomize_va_space;
 #endif
 
-__attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma);
+//__attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma);
 
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */

So seems that something goes a bit fishy when using weak symbols and this trigges 
a binutils bug.

The above line was introdused in the following commit:

commit f269fdd1829acc5e53bf57b145003e5733133f2b
Author: David Howells <dhowells@redhat.com>
Date:   Wed Sep 27 01:50:23 2006 -0700

    [PATCH] NOMMU: move the fallback arch_vma_name() to a sensible place
    
    Move the fallback arch_vma_name() to a sensible place (kernel/signal.c).
    
    Currently it's in fs/proc/task_mmu.c, a file that is dependent on both
    CONFIG_PROC_FS and CONFIG_MMU being enabled, but it's used from
    kernel/signal.c from where it is called unconditionally.
    
    [akpm@osdl.org: build fix]
    Signed-off-by: David Howells <dhowells@redhat.com>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>


	Sam

Re: "do section mismatch check on full vmlinux" breaks powerpc build

[Nathan Lynch]

Hi Sam-

Sam Ravnborg wrote:
> On Tue, Jul 24, 2007 at 05:41:05PM -0500, Nathan Lynch wrote:
> > 
> > 2.6.23-rc1 breaks the build for 64-bit powerpc for me (using
> > maple_defconfig):
> > 
> >   LD      vmlinux.o
> > powerpc64-unknown-linux-gnu-ld: dynreloc miscount for
> > kernel/built-in.o, section .opd
> > powerpc64-unknown-linux-gnu-ld: can not edit opd Bad value
> > make: *** [vmlinux.o] Error 1
> > 
> 
> I narrowed it down to the following change to avoid the breakage:
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index c456c3a..2ea222f 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1246,7 +1246,7 @@ void drop_slab(void);
>  extern int randomize_va_space;
>  #endif
>  
> -__attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma);
> +//__attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma);
>  
>  #endif /* __KERNEL__ */
>  #endif /* _LINUX_MM_H */
> 
> So seems that something goes a bit fishy when using weak symbols and this trigges 
> a binutils bug.
> 
> The above line was introdused in the following commit:
> 
> commit f269fdd1829acc5e53bf57b145003e5733133f2b
> Author: David Howells <dhowells@redhat.com>
> Date:   Wed Sep 27 01:50:23 2006 -0700
> 
>     [PATCH] NOMMU: move the fallback arch_vma_name() to a sensible place


Thanks for looking into this.  Removing the "__attribute__((weak))"
from arch_vma_name's declaration in linux/mm.h unbreaks the build for
me.

Maybe it shouldn't matter, but it seems unusual to have the weak
attribute specified at the function's declaration.  I wasn't able to
find any examples of that for other weak functions in the kernel
(e.g. sched_clock).

Re: "do section mismatch check on full vmlinux" breaks powerpc build

[Sam Ravnborg]

On Wed, Jul 25, 2007 at 04:16:10PM -0500, Nathan Lynch wrote:
> Hi Sam-
> 
> Sam Ravnborg wrote:
> > On Tue, Jul 24, 2007 at 05:41:05PM -0500, Nathan Lynch wrote:
> > > 
> > > 2.6.23-rc1 breaks the build for 64-bit powerpc for me (using
> > > maple_defconfig):
> > > 
> > >   LD      vmlinux.o
> > > powerpc64-unknown-linux-gnu-ld: dynreloc miscount for
> > > kernel/built-in.o, section .opd
> > > powerpc64-unknown-linux-gnu-ld: can not edit opd Bad value
> > > make: *** [vmlinux.o] Error 1
> > > 
> > 
> > I narrowed it down to the following change to avoid the breakage:
> > 
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index c456c3a..2ea222f 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -1246,7 +1246,7 @@ void drop_slab(void);
> >  extern int randomize_va_space;
> >  #endif
> >  
> > -__attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma);
> > +//__attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma);
> >  
> >  #endif /* __KERNEL__ */
> >  #endif /* _LINUX_MM_H */
> > 
> > So seems that something goes a bit fishy when using weak symbols and this trigges 
> > a binutils bug.
> > 
> > The above line was introdused in the following commit:
> > 
> > commit f269fdd1829acc5e53bf57b145003e5733133f2b
> > Author: David Howells <dhowells@redhat.com>
> > Date:   Wed Sep 27 01:50:23 2006 -0700
> > 
> >     [PATCH] NOMMU: move the fallback arch_vma_name() to a sensible place
> 
> 
> Thanks for looking into this.  Removing the "__attribute__((weak))"
> from arch_vma_name's declaration in linux/mm.h unbreaks the build for
> me.
> 
> Maybe it shouldn't matter, but it seems unusual to have the weak
> attribute specified at the function's declaration.  I wasn't able to
> find any examples of that for other weak functions in the kernel
> (e.g. sched_clock).

Unfortunately removing the weak attribute uncovered that x86_64 has
two functions with the same name => link error.
Needs to have that sorted first out but ball is rolling.
(Se lkml for details)

	Sam