linux-kernel - Re: Please include const-sections into linux-next

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Date:	Wed, 19 Oct 2011 15:04:53 -0500
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: Please include const-sections into linux-next

On Wed, 2011-10-19 at 21:05 +0200, Andi Kleen wrote:
> On Wed, Oct 19, 2011 at 01:55:57PM -0500, James Bottomley wrote:
> > On Wed, 2011-10-19 at 18:33 +0200, Andi Kleen wrote:
> > > > OK, look at it another way: why do we need the type annotations?  I
> > > > think it's only for section conflict checking, right?  If the compiler
> > > > gets it wrong anyway, why not just dump all the type annotations, then
> > > > it should have no type conflicts (spurious or otherwise) to complain
> > > > about.  We already have link time section checking scripts (they're the
> > > > useless ones that complain about section mismatches in dev annoations)
> > > > so why not put them to work to make up for compiler deficiencies?
> > > 
> > > You mean removing all the init sections stuff?  I think it has been proposed
> > > in the past, but it's a couple of hundred KB of memory usually.
> > > Would you accept that for PA-RISC? 
> > > 
> > > If you have init sections you need to annotate them correctly because
> > > a section is defined by its rwx attributes plus name and both need
> > > to match. We didn't always check this, so there was some bitrot,
> > > but it ultimatively has to be correct.
> > 
> > We're talking at cross purposes. But it doesn't matter, the error
> > doesn't seem to be anything to do with type.  This simple patch is
> > what's causing it (I can apply it alone to the working tree) and get the
> > error.
> > 
> > What I can't see is why.
> 
> For some reason your compiler sets the const section read/write:
> 
> .section        .devinit.data,"aw",@progbits     <---- writable
>         .align 8
>         .type   skel_netdrv_tbl, @object
>         .size   skel_netdrv_tbl, 48
> skel_netdrv_tbl:
> ; chip_name:
>         .dword  .LC56
> 
> while my x86 toolchain sets it to read only
> 
>         .string "1000/100/10M Ethernet PCI Adapter"
>         .section        .devinit.data,"a",@progbits   <---- not writable
>         .align 16
>         .type   skel_netdrv_tbl, @object
>         .size   skel_netdrv_tbl, 48

So most of our const stuff is "a" not "aw".  However, this particular
list is a list of strings ... this is probably something to do with
writeable strings?

James


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