linux-kernel - Re: modules: Fix build error in the !CONFIG

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Message-ID: <20090828121406.GA24185@elte.hu>
Date:	Fri, 28 Aug 2009 14:14:06 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Helge Deller <deller@....de>
Subject: Re: modules: Fix build error in the !CONFIG_KALLSYMS case


* James Bottomley <James.Bottomley@...senPartnership.com> wrote:

> On Fri, 2009-08-28 at 10:44 +0200, Ingo Molnar wrote:
> > * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> > 
> > > James Bottomley (1):
> > >       module: workaround duplicate section names
> > 
> > -tip testing found that this patch breaks the build on x86 if 
> > CONFIG_KALLSYMS is disabled:
> > 
> >  kernel/module.c: In function ???load_module???:
> >  kernel/module.c:2367: error: ???struct module??? has no member named ???sect_attrs???
> >  distcc[8269] ERROR: compile kernel/module.c on ph/32 failed
> >  make[1]: *** [kernel/module.o] Error 1
> >  make: *** [kernel] Error 2
> >  make: *** Waiting for unfinished jobs....
> > 
> > Commit 1b364bf misses the fact that section attributes are only 
> > built and dealt with if kallsyms is enabled. The patch below fixes 
> > this.
> 
> Thanks for finding the bug.
> 
> > ( note, technically speaking this should depend on CONFIG_SYSFS as
> >   well but this patch is correct too and keeps the #ifdef less
> >   intrusive - in the KALLSYMS && !SYSFS case the code is a NOP. )
> 
> Agree with this, but there is a way of fixing it, see below.
> 
> > Signed-off-by: Ingo Molnar <mingo@...e.hu>
> > ---
> >  kernel/module.c |    2 ++
> >  1 files changed, 2 insertions(+), 0 deletions(-)
> > 
> > diff --git a/kernel/module.c b/kernel/module.c
> > index eccb561..b4016d1 100644
> > --- a/kernel/module.c
> > +++ b/kernel/module.c
> > @@ -2355,8 +2355,10 @@ static noinline struct module *load_module(void __user *umod,
> >  	if (err < 0)
> >  		goto unlink;
> >  	add_sect_attrs(mod, hdr->e_shnum, secstrings, sechdrs);
> > +#ifdef CONFIG_KALLSYMS
> >  	if (mod->sect_attrs)
> >  		add_notes_attrs(mod, hdr->e_shnum, secstrings, sechdrs);
> > +#endif
> 
> Rather than adding to the #ifdef litter in the file, isn't it better to
> move the test to a section of it that's already ifdef'd?
> 
> This also fixes the problem of depending on CONFIG_SYSFS you mention.
> 
> James
> 
> ---
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index eccb561..2d53718 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -1274,6 +1274,10 @@ static void add_notes_attrs(struct module *mod, unsigned int nsect,
>  	struct module_notes_attrs *notes_attrs;
>  	struct bin_attribute *nattr;
>  
> +	/* failed to create section attributes, so can't create notes */
> +	if (!mod->sect_attrs)
> +		return;

yep, this is cleaner.

	Ingo
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