linux-kernel - Re: section breakage on ppc64 (aka _

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Date:	Fri, 08 Feb 2008 08:14:11 +0000
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	"Sam Ravnborg" <sam@...nborg.org>,
	"Chuck Ebbert" <cebbert@...hat.com>
Cc:	<linux-kernel@...r.kernel.org>, "Al Viro" <viro@...IV.linux.org.uk>
Subject: Re: section breakage on ppc64 (aka __devinitconst is broken by
	design)

>I cannot see any other way out of this than to loose all the newly added
>consts. We have to different behavior across platforms to find a suitable
>solution that is reliable.
>
>[Kept rest of mail as I added Jan - hope he have some ideas to throw in].

I'd first of all need a better understanding of what these comments are
really based upon:

/* On some platforms relocations to global data cannot go into read-only
   sections, so 'const' makes no sense and even causes compile failures
   with some compilers. */

While I can see such behavior as reasonable for, say, shared objects,
I severely doubt that this is generally appropriate for executables, not
to say for the kernel. This is particularly in the light of this comment in
gcc/output.h:

  /* To optimize loading of shared programs, define following subsections
     of data section:

which clearly says that the resulting (default) object placement (of read-
only data in writeable sections) is an optimization, not a requirement,
and even then only for shared programs (which the kernel clearly isn't).
Has there been any communication with the gcc folks on this subject?

Jan

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