linux-kernel - Re: Testing of function/data-sections on linux-2.6.35-rc4

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Message-ID: <20100726072825.GC10061@merkur.ravnborg.org>
Date:	Mon, 26 Jul 2010 09:28:25 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	Tim Abbott <tabbott@...lice.com>, Tim Bird <tim.bird@...sony.com>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	linux-kernel@...r.kernel.org,
	Matt Fleming <matt@...sole-pimps.org>,
	linux-arch@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	Michal Marek <mmarek@...e.cz>,
	Parisc List <linux-parisc@...r.kernel.org>
Subject: Re: Testing of function/data-sections on linux-2.6.35-rc4

On Mon, Jul 26, 2010 at 03:31:34AM +0200, Denys Vlasenko wrote:
> Hi Sam,
> 
> On Friday 23 July 2010 22:35, Sam Ravnborg wrote:
> > > 
> > > Then, in order to also garbage-collect the sections, I added
> > > 
> > > LDFLAGS_vmlinux += --gc-sections
> > > 
> > > in top-level Makefile.
> > > 
> > > This requires the additional patch (linux-2.6.35-rc4-fsgs.patch)
> > > which adds KEEP(section) directives to kernel linker stripts.
> > > Otherwise, linker will discard some crucial sections.
> > > 
> > 
> > Changelog does not address why you need:
> > 
> >      -Map $@...map
> > 
> > and what effect they have.
> 
> I didn't plan to push the last step (--gc-sections) to mainline yet.
> Thus the patch has debugging stuff in it.
> 
> 
> > And it is obvious that some archs should consolidate a little more from
> > asm-generic/vmlinux.lds.h.
> > But that said this patch looks much better than the initial versions posted.
> > 
> > How do you determine which sections needs the KEEP()?
> > Worth documenting for future when we add new sections.
> 
> No problem, I will be adding comments at every KEEP() why it's needed.

A general comment in vmlinux.lds.h and a careful explanation
in the changelog should be enough.

You should not comment each of the KEEP().

	Sam
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