linux-kernel - Re: [PATCH 5/23] make section names compatible with -ffunction-sections -fdata-sections: blackfin

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Message-ID: <8bd0f97a0807011909i53a347f5me4410a24dd27d5ab@mail.gmail.com>
Date:	Tue, 1 Jul 2008 22:09:20 -0400
From:	"Mike Frysinger" <vapier.adi@...il.com>
To:	"Denys Vlasenko" <vda.linux@...glemail.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 5/23] make section names compatible with -ffunction-sections -fdata-sections: blackfin

On Tue, Jul 1, 2008 at 8:08 PM, Denys Vlasenko wrote:
> On Wednesday 02 July 2008 00:58, Mike Frysinger wrote:
>> On Tue, Jul 1, 2008 at 8:35 PM, Denys Vlasenko wrote:
>> > The purpose of this patch is to make kernel buildable
>> > with "gcc -ffunction-sections -fdata-sections".
>> > This patch fixes blackfin architecture.
>>
>> the comment right above what you changed says it already works for
>> Blackfin.  so you arent fixing it at all.
>> >                /* This gets done first, so the glob doesn't suck it in */
>> >                . = ALIGN(32);
>> > -               *(.data.cacheline_aligned)
>> > +               *(.cacheline_aligned.data)
>
> This may pull in an unrelated data object named "cacheline_aligned"
> (say, a static variable in a driver). If that variable is not
> itself aligned to the cacheline size, it will mess up alignment of all
> objects in .data.cacheline_aligned which follow. Not good.
>
> To be safe from such weird and hard to debug problems
> it's better to not use names like .data.XXXX at all.
> I just uniformly renamed al such "special sections"
> in the kernel to .XXXXX.data

you're right of course ... i obviously hadnt thought of this.  please
however still abstract this stuff into the common header.

i just tested the current Blackfin kernel and it does build/link/run
fine with -ffunction-sections/-fdata-sections.  however, --gc-sections
still causes crashes (but this is because all of the .init.setup
sections are flagged as unused).
-mike
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