linux-kernel - Re: kernel segv with 2.6.31-rc6 ?

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Message-Id: <20090819013124.7539E4730F@magilla.sf.frob.com>
Date:	Tue, 18 Aug 2009 18:31:24 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Helge Deller <deller@....de>,
	linux-parisc <linux-parisc@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: kernel segv with 2.6.31-rc6 ?

> Actually, I think we do; the module loader is a runtime linker, after
> all.  [...]

Indeed you do.  I've just read some of the parts of ld that normally
address this issue for HPPA.  They don't run for ld -r.  So this is just
another fine example of the lunacy of the ET_REL .ko madness that would be
naturally avoided by a sensible tweaked ET_DYN scheme.  But that battle was
lost way, way back in the long, long ago, so long ago they were probably
even still making HPPA machines then.

> Now, of course, if the final linker could be persuaded to sprinkle
> needed stubs through the text section and all we have to do is GOT
> relocations, we don't need all the jiggery-pokery ... but I'm told this
> can't be done.

Not with ld -r as it is today.  That's what ld does for you in proper final
links.  It looks to me like you might be able to enable some special mode
("finalish link" for -r) with a hack to HPPA ld to apply this stub-creation
logic based on the assumption that the symbols in the relocs will be
resolved to themselves, and barf on you if they're used for SHN_UNDEF symbols.
But nobody cares enough to fiddle with ld.

Thanks,
Roland
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