linux-kernel - Re: [PATCH 14/23] make section names compatible with -ffunction-sections -fdata-sections: parisc

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Message-Id: <200807020200.49518.vda.linux@googlemail.com>
Date:	Wed, 2 Jul 2008 02:00:49 +0200
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	James Bottomley <James.Bottomley@...senpartnership.com>
Cc:	linux-arch@...r.kernel.org, Russell King <rmk@....linux.org.uk>,
	David Howells <dhowells@...hat.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Lennert Buytenhek <kernel@...tstofly.org>,
	Josh Boyer <jwboyer@...ux.vnet.ibm.com>,
	Paul Mackerras <paulus@...ba.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	linux-embedded@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tim Bird <tim.bird@...sony.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Dave Miller <davem@...emloft.net>
Subject: Re: [PATCH 14/23] make section names compatible with -ffunction-sections -fdata-sections: parisc

On Wednesday 02 July 2008 01:41, James Bottomley wrote:
> On Wed, 2008-07-02 at 02:39 +0200, Denys Vlasenko wrote:
> > The purpose of this patch is to make kernel buildable
> > with "gcc -ffunction-sections -fdata-sections".
> > This patch fixes parisc architecture.
> > 
> > Signed-off-by: Denys Vlasenko <vda.linux@...glemail.com>
> 
> Um ... if you look at the Makefile you'll see we already build parisc
> with -ffunction-sections; we have to: our relative jumps are too small
> to guarantee finding the stubs in large files.
> 
> Since our text is -ffunction-sections compatible already, I question the
> need for transformations like this:
> 
> > -               *(.text.do_softirq)
> > -               *(.text.sys_exit)
> > -               *(.text.do_sigaltstack)
> > -               *(.text.do_fork)
> > +               *(.do_softirq.text)
> > +               *(.sys_exit.text)
> > +               *(.do_sigaltstack.text)
> > +               *(.do_fork.text)

arch/parisc/kernel/vmlinux.lds.S contains these lines:

               TEXT_TEXT
               SCHED_TEXT
               LOCK_TEXT
               *(.text.do_softirq)
               *(.text.sys_exit)
               *(.text.do_sigaltstack)
               *(.text.do_fork)

which suggested to me that for parisc it is important to have
these sections in that place (after LOCK_TEXT) and order.

If you use -ffunction-sections, any function with the name
do_fork (say, a static function somewhere) will end up in
.text.do_fork function, and will be "mixed up" with
global do_fork(). For parisc it is maybe not a problem
(I am not an expert) but in other places/arches people
clearly would not want this kind of things to happen.

In order to handle these situations uniformly, in these patches
I decided to _never_ use .text.XXXX names for sections,
effectively leaving them "reserved for gcc's use".

Did I understand you right that in this chunk I need to
leave .text.FUNC_NAME as it was before?

> And thus by the same token the data transformations.

It would be easiest for me if you will reply to the parisc patch
and indicate all parts where I should NOT do name change.

Thanks!
--
vda
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