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Date: Wed, 25 Jul 2007 16:16:10 -0500
From: Nathan Lynch <ntl@pobox.com>
To: Sam Ravnborg <sam@ravnborg.org>
Subject: Re: "do section mismatch check on full vmlinux" breaks powerpc build
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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).