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Date: Fri, 01 May 2009 10:18:20 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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Subject: Re: [PATCH v2 1/6] Add new macros for page-aligned data and bss sections.
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To: Sam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@MIT.EDU>, Linux kernel mailing list <linux-kernel@vger.kernel.org>, Anders Kaseorg <andersk@MIT.EDU>, Waseem Daher <wdaher@MIT.EDU>, Denys Vlasenko <vda.linux@googlemail.com>, Jeff Arnold <jbarnold@MIT.EDU>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Bryan Wu <cooloney@kernel.org>, Chris Zankel <chris@zankel.net>, Cyrill Gorcunov <gorcunov@openvz.org>, David Howells <dhowells@redhat.com>, "David S. Miller" <davem@davemloft.net>, dev-etrax@axis.com, Geert Uytterhoeven <geert@linux-m68k.org>, Greg Ungerer <gerg@uclinux.org>, Haavard Skinnemoen <hskinnemoen@atmel.com>, Heiko Carstens <heiko.carstens@de.ibm.com>, Helge Deller <deller@gmx.de>, Hirokazu Takata <takata@linux-m32r.org>, Ingo Molnar <mingo@redhat.com>, Jeff Dike <jdike@addtoit.com>, Jesper Nilsson <jesper.nilsson@axis.com>, Kyle McMartin <kyle@mcmartin.ca>, Linus Torvalds <torvalds@linux-foundation.org>, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@vger.kernel.org, linux-mips@linux-mips.org, linux-parisc@vger.kernel.org, linuxppc-dev@ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, Martin Schwidefsky <schwidefsky@de.ibm.com>, Michal Simek <monstr@monstr.eu>, microblaze-uclinux@itee.uq.edu.au, Mikael Starvik <starvik@axis.com>, Paul Mackerras <paulus@samba.org>, Paul Mundt <lethal@linux-sh.org>, Ralf Baechle <ralf@linux-mips.org>, Richard Henderson <rth@twiddle.net>, Roman Zippel <zippel@linux-m68k.org>, Russell King <rmk+kernel@arm.linux.org.uk>, sparclinux@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>, Tony Luck <tony.luck@intel.com>, uclinux-dist-devel@blackfin.uclinux.org, user-mode-linux-devel@lists.sourceforge.net, Yoshinori Sato <ysato@users.sourceforge.jp>
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Sam Ravnborg wrote:
> On Fri, May 01, 2009 at 09:33:13AM -0700, H. Peter Anvin wrote:
>> Tim Abbott wrote:
>>> On Fri, 1 May 2009, Sam Ravnborg wrote:
>>>
>>>> On Thu, Apr 30, 2009 at 03:54:08PM -0400, Tim Abbott wrote:
>>>>> +#define __PAGE_ALIGNED_DATA	.section ".data.page_aligned", "aw", @progbits
>>>>> +#define __PAGE_ALIGNED_BSS	.section ".bss.page_aligned", "aw", @nobits
>>>> It is my understanding that the linker will automatically
>>>> assume nobits for section names starting with .bss and likewise
>>>> progbits for section names starting with .data - so we can leave them out?
>>> I believe that is correct.
>>>
>> ... but that doesn't mean it's the right thing to do.
>>
>> It's better to be fully explicit when macroizing this kind of stuff.
>> This is part of why macroizing it is good: it means we end up with *one*
>> place that determines this stuff, not some magic heuristics in the linker.
> 
> Do you know if we can use % in place of @?
> I could see that gas supports both - at least in trunk in cvs.
> 

I think it might depend on the architecture(!)... but it would
definitely have to be an issue with testing a bunch of different versions.

What's wrong with @?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.