[PATCH] Add note that lockdep is not allowed with non-GPL modules

[Petr Vandrovec]

Hi Ingo,
can you add this small notice to the lockdep option ?

Lock dependency infrastructure forces all legacy code which uses lock to now
depend on lockdep_init_map symbol, which is GPL-only. It means that almost
no modules can work on kernel with CONFIG_LOCKDEP set. Let's warn user about
that.

vmmon: module license 'unspecified' taints kernel.
vmmon: Unknown symbol lockdep_init_map

Thanks,
Petr Vandrovec

Signed-off-by: Petr Vandrovec <pe...@vandrovec.name>

--- linux-2.6.17-3130.dist/lib/Kconfig.debug 2006-07-04 19:31:36.000000000 +0200
+++ linux-2.6.17-3130/lib/Kconfig.debug 2006-07-04 21:55:35.000000000 +0200
@@ -214,6 +214,9 @@

For more details, see Documentation/lockdep-design.txt.

+ Do not enable this option if you are using non-GPL modules, or
+ they will fail to load due to missing symbol lockdep_init_map.
+
config LOCKDEP
bool
depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
-
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[Alexey Dobriyan]

On Tue, Jul 04, 2006 at 10:29:04PM +0200, Petr Vandrovec wrote:
> Hi Ingo,
> can you add this small notice to the lockdep option ?
>
> Lock dependency infrastructure forces all legacy code which uses lock to now
> depend on lockdep_init_map symbol, which is GPL-only. It means that almost
> no modules can work on kernel with CONFIG_LOCKDEP set. Let's warn user about
> that.

IANIngo, but the warning is already there:
* Proprietary module user probably already knows that major deviations from .config
and kernel its module is released is no-no.
* Unknown symbol name contains "lockdep" which attentive proprietary
module user will notice and correlate with enabling lockdep 5 minutes ago.
* Tomorrow Ingo will change it's name, add a couple of new lockdep only
exports so should he update help text every time _he_ changes _his_
code?
* Would you add similar notice to inotify help text? It also exports
GPL-only symbols doncha know. Would you add such notices to everything
exporting GPL-only symbols?

> vmmon: module license 'unspecified' taints kernel.
> vmmon: Unknown symbol lockdep_init_map

> + Do not enable this option if you are using non-GPL modules, or

> + they will fail to load due to missing symbol lockdep_init_map.

Lock validor found a bug in NVidia driver, film at 11.

[Petr Vandrovec]

Alexey Dobriyan wrote:
> On Tue, Jul 04, 2006 at 10:29:04PM +0200, Petr Vandrovec wrote:
>
>>Hi Ingo,
>> can you add this small notice to the lockdep option ?
>>
>>Lock dependency infrastructure forces all legacy code which uses lock to now
>>depend on lockdep_init_map symbol, which is GPL-only. It means that almost
>>no modules can work on kernel with CONFIG_LOCKDEP set. Let's warn user about
>>that.
>
>
> IANIngo, but the warning is already there:
> * Proprietary module user probably already knows that major deviations from .config
> and kernel its module is released is no-no.

Uh? How it comes? VMware modules work in any kernel configuration and
architecture. With exception of vmmon, which contains inline assembly
for i386 & x86-64 only. But all configs are supported.

> * Would you add similar notice to inotify help text? It also exports
> GPL-only symbols doncha know. Would you add such notices to everything
> exporting GPL-only symbols?

This is just nonsense. I am not talking about using new API, I'm saying
that API which was not GPL-only without lockdep has GPL-only portion
with lockdep, and this GPL-only portion is needed by implementation of
code which existed before lockdep. To me this looks like unexpected
change of kernel API, and as such should be documented and warned about.

>>vmmon: module license 'unspecified' taints kernel.
>>vmmon: Unknown symbol lockdep_init_map
>
>
>>+ Do not enable this option if you are using non-GPL modules, or
>>+ they will fail to load due to missing symbol lockdep_init_map.
>
>
> Lock validor found a bug in NVidia driver, film at 11.

I have no idea how NVidia managed to work around that problem, but
VMware modules suddenly depend on this GPL-only symbol, although nothing
in the module sources refers to lockdep (same sources which worked
yesterday are being used).
Thanks,
Petr Vandrovec

[Valdis.K...@vt.edu]

On Tue, 04 Jul 2006 23:20:53 +0200, Petr Vandrovec said:
> > Lock validor found a bug in NVidia driver, film at 11.

It almost certainly didn't, as you have to do some major ugly and evil
things to get the NVidia driver to build (it won't pass modpost if the
kernel is built with lockdep due to the GPL-only exports that get sucked in).

> I have no idea how NVidia managed to work around that problem, but
> VMware modules suddenly depend on this GPL-only symbol, although nothing
> in the module sources refers to lockdep (same sources which worked
> yesterday are being used).

It doesn't reference it directly - it gets sucked in via a #define.

[Petr Vandrovec]

VMware code is shoot down due to use of init_waitqueue_head(). It is
now virtually GPL-only because it is inlined and uses GPL-only function
lockdep_init_map :-(
Petr