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Date: Sun, 4 May 2008 21:24:34 +0200
From: Sam Ravnborg <sam@ravnborg.org>
To: Kumar Gala <galak@kernel.crashing.org>
Subject: Re: How to link a .o with all modules
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On Sun, May 04, 2008 at 01:22:38PM -0500, Kumar Gala wrote:
> Sam,
> 
> We have a case in powerpc in which we want to link some library  
> routines with all module objects.  The routines are intended for  
> handling out-of-line function call register save/restore so having  
> them as EXPORT_SYMBOL() is counter productive (we do also need to link  
> the same "library" code into the kernel).
> 
> Any suggestions on how to handle this?

I assume you have the .o file build somewhere as part of the
normal kernel build.

Then you in
arch/powerpc/Makefile adds the following assignment:

LDFLAGS_MODULE += arch/powerpc/lib/my_magic_file.o

kbuild will then during the modpost stage link this
file on all modules.
To add the same file to the kernel just include it
in a obj-y += my_magic_file.o

One trap is that my_magic_file.o needs to be built
for a modules build too.
I think you need to assign it to always:

   always := my_magic_file.o

to accomplish this.

So in the end we will have:

arch/powerpc/Makefile:
LDFLAGS_MODULE += arch/powerpc/lib/my_magic_file.o

arch/powerpc/lib/Makefile:
always := my_magic_file.o
obj-y += my_magic_file.o


Let me know if this does address your question.

	Sam