linux-kernel - Re: [PATCH 1/3] build system: section garbage collection for vmlinux

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Message-Id: <200709081602.28216.vda.linux@googlemail.com>
Date:	Sat, 8 Sep 2007 16:02:28 +0100
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] build system: section garbage collection for vmlinux

On Wednesday 05 September 2007 21:07, Sam Ravnborg wrote:
> On Wed, Sep 05, 2007 at 02:47:00PM +0100, Denys Vlasenko wrote:
> > On Wednesday 05 September 2007 14:43, Denys Vlasenko wrote:
> > > These patches fix section names and add
> > > CONFIG_DISCARD_UNUSED_SECTIONS. It is not enabled
> > > unconditionally because only newest binutils have
> > > ld --gc-sections which is stable enough for kernel use.
> > > IOW: this is an experimental feature for now.
> > 
> > Part 1: fix section names over entire source (all arches).
> > 
> > Patch is big and boring global s/.text.lock/.text_lock/
> > type thing.
> 
> The normal naming scheme seems to be:
> .<usage>.text so in your example it would be: .lock.text
> See the naming of init and exit sections (that was renamed
> during 2.5 to be compatible with -ffunction-sections).

Well, there seems to be a problem at least with .bss:

http://sourceware.org/bugzilla/show_bug.cgi?id=5006

With __attribute__((section(".bss.page_aligned")))
gcc will produce .bss.page_aligned section
with NOBITS attribute, purely on the basis
of section name starting by '.bss.'

With __attribute__((section(".bss_page_aligned"))),
section will get PROGBITS attribute instead.

Combining NOBITS and PROGBITS sections into one .bss
section is not funny.

IOW: at least for bss, we _must_ use ".bss.xxx" names.

I propose (and will implement in next round of patches)
.bss.k.page_aligned ('k' for 'kernel').

Lickily, we alctually have only one special bss section
on kernel today.

Sam, my question - should I also do the same for text/rodata/data,
just for paranoid reasons?
--
vda
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