linux-kernel - Re: module version magic and arches with symbol prefixes

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Message-ID: <8bd0f97a0906190614x2ed27fcdrb59ea339eb45ba82@mail.gmail.com>
Date:	Fri, 19 Jun 2009 09:14:00 -0400
From:	Mike Frysinger <vapier.adi@...il.com>
To:	Robin Getz <rgetz@...ckfin.uclinux.org>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: module version magic and arches with symbol prefixes

On Fri, Jun 19, 2009 at 08:54, Robin Getz wrote:
> On Fri 19 Jun 2009 01:38, Rusty Russell pondered:
>> On Fri, 19 Jun 2009 12:54:44 am Mike Frysinger wrote:
>> > the current check_modstruct_version() does this:
>> > {
>> >     const unsigned long *crc;
>> >
>> >     if (!find_symbol("module_layout", NULL, &crc, true, false))
>> >         BUG();
>> >     return check_version(sechdrs, versindex, "module_layout", mod, crc);
>> > }
>> > the trouble here is that it looks for a literal "module_layout" symbol
>> > and for ports that have symbol prefixes (a quick check shows Blackfin
>> > & h8300), this aint going to work.
>>
>> MODULE_SYMBOL_PREFIX is the fix for this, ie:
>>
>>       if (!find_symbol(MODULE_SYMBOL_PREFIX "module_layout), ...
>>
>> > also, using BUG() here seems pretty damn harsh.  wouldnt it make more
>> > sense to do something like:
>> >     if (WARN_ON(!find_symbol("module_layout", NULL, &crc, true, false)))
>> >         return 0;
>> > this way the module is simply not loaded rather than killing the kernel
>>
>> No, it means the kernel didn't build properly.
>
> Or a module didn't build properly.

nah, when i talked to you earlier i was wrong -- this find_symbol() is
looking up the symbol in the kernel, not in the module.  the lookup of
the symbol in the requested module actually works.
-mike
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