linux-kernel - Re: [PATCH] x86: fix improper .init-type section references

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Date:	Wed, 13 Jun 2007 08:48:29 +0530
From:	"Satyam Sharma" <satyam.sharma@...il.com>
To:	"Sam Ravnborg" <sam@...nborg.org>
Cc:	"Jan Beulich" <jbeulich@...ell.com>,
	"Venkatesh Pallipadi" <venkatesh.pallipadi@...el.com>,
	"Andi Kleen" <ak@...e.de>, linux-kernel@...r.kernel.org,
	patches@...-64.org
Subject: Re: [PATCH] x86: fix improper .init-type section references

Hi Sam,

On 6/12/07, Sam Ravnborg <sam@...nborg.org> wrote:
> On Tue, Jun 12, 2007 at 07:39:30PM +0530, Satyam Sharma wrote:
> > On 6/12/07, Jan Beulich <jbeulich@...ell.com> wrote:
> > >>> And from a purely theoretical
> > >>> perspective I don't think such references should be considered bad -
> > >>> .exit.* should be discarded together with .init.* if unloading is
> > >>> impossible (built-in or configured off), not before module/kernel
> > >>> initialization.
> > >>
> > >>Hmm, but that's not how things are, presently. __exit marked
> > >>functions are simply not linked into the kernel (when that module
> > >>is being built-in) at all -- this "discard" happens at _build time_
> > >>(to save on kernel image size).
> > >
> > >Not really, at least not for i386 and x86-64 - see their vmlinux.lds.S
> > >files.
> >
> > For those archs, yes, you're right that modpost should be
> > special-casing (based on arch) before complaining for
> > .init -> .exit references.
> No.
> References from __init to __exit is wrong independent on architecture.
[...]
> So for the latter we will have an oops where we for the first have a build
> time failure.

Is that (oops possibility on i386) really true? (.exit.{text, data}) is also
between __init_begin and __init_end and hence will be discarded
_along_ with (not before) .init.{text, data} during run-time I think,
which means .init -> .exit reference modpost warnings (on said
archs) are truly bogus ...

> powerpc discards them at buildtime, i386 at runtime.

Yup, we were only discussing possibility that modpost not complain
about .init -> .exit references that will never go oops (because the arch
guarantees that).

Satyam
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