linux-kernel - Re: [PATCH] x86_32: Fix module version table mismatch.

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Message-ID: <51772EBC.1050600@zytor.com>
Date:	Tue, 23 Apr 2013 18:00:44 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
CC:	arjan@...radead.org, james.hogan@...tec.com, rusty@...tcorp.com.au,
	linux-kernel@...r.kernel.org, andy.shevchenko@...il.com
Subject: Re: [PATCH] x86_32: Fix module version table mismatch.

On 04/23/2013 05:52 PM, H. Peter Anvin wrote:
> On 04/23/2013 05:40 AM, Tetsuo Handa wrote:
>> Commit a4b6a77b "module: fix symbol versioning with symbol prefixes" broke
>> loading of net/ipv6/ipv6.ko built with CONFIG_MODVERSIONS=y for x86_32.
> 
> This really does seem to be the offending commit, although I'm still
> confused how the heck that is possible.
> 

OK, now I grok.

The bug is the use of VMLINUX_SYMBOL_STR(%s) which expands at the time
the output of modpost is compiled.  However, VMLINUX_SYMBOL_STR() unlike
__VMLINUX_SYMBOL_STR() does macro expansion on its argument, which is
actively wrong here.

I think the choice is either to change this to __VMLINUX_SYMBOL_STR() or
re-introduce CONFIG_SYMBOL_PREFIX (or its equivalent) so that modprobe
can emit it at compile time (assuming there even should *be* a prefix on
the symbol here, i.e. that the compiler won't add it.)

Either way -- James, Rusty, this is in your court.

	-hpa

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