linux-kernel - Re: [git pull] x86 updates

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Message-ID: <20080205211710.GA27589@uranus.ravnborg.org>
Date:	Tue, 5 Feb 2008 22:17:10 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [git pull] x86 updates

On Tue, Feb 05, 2008 at 10:05:08PM +0100, Ingo Molnar wrote:
> 
> * Sam Ravnborg <sam@...nborg.org> wrote:
> 
> > On Tue, Feb 05, 2008 at 10:47:07AM -0800, Linus Torvalds wrote:
> > > 
> > > 
> > > Ingo, Thomas,
> > >  should we not do this?
> > > 
> > > Otherwise, it seems we generate a section that isn't allocated?
> > > 
> > > I think toolchain should add the right flags automatically for 
> > > sections that start with ".[ro]data" and ".text", but not for the 
> > > kernel-specific ".init.*" sections.
> > 
> > With a bit of help from the bin-utils people (Alan Modra) I recently 
> > discovered that the linker generate sections with different names when 
> > the flags differs, so fogetting "aw" casues the linekr to generate a 
> > section named .init.data.1 (or some other number). But I nevet got to 
> > investigate if ld does something magically with these autogenerated 
> > section names. But I added a check in modpost and it should warn about 
> > the code below.
> > 
> > I would prefer the use of
> > __CPUINITDATA
> > __FINITDATA
> > 
> > as defined in linux/init.h but otherwise - yes it should be fixed.
> > With the use of __CPUINITDATA we can kill the ifdef too.
> 
> ok, i've queued up your patch.
> 
> btw., __CPUINITDATA/__FINITDATA is nice, except that the small patch 
> below is needed to make the fun complete ;-)
> 
> or, we could use __FINIT all the time.

I have no strong preference - I do not like the naming of
__FINIT but maybe thats just me and I have no better name right now.

> 
> btw., what's the practical consequence of getting these section flags 
> wrong - for example writable data can end up in executable section 
> accidentally and be marked readonly by RODATA? Or can anything more 
> serious happen? (they cannot get into any of the discarded sections, we 
> filter for them explicitly in the linker scripts)
I have not investigated this. My attention were due to section mismatch
warnings pointing to section names I could not find in the code.
When I did an objdump of vmlinux the funny section names were gone
so I expected ld had recognized them and merged them somehow - but I 
did not look closer as my focus was to get rid of them anyway.

I also did a quick skimming of info ld - but no luck.

	Sam
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