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

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Message-ID: <20111019190517.GK15908@one.firstfloor.org>
Date:	Wed, 19 Oct 2011 21:05:17 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	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, 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
skel_netdrv_tbl:
# chip_name:
        .quad   .LC32
# flags:
        .long   0
        .zero   4

If you check a few other const symbols with own
section are they all also writable?

-andi

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