GPL-only symbol Error

[greg@kroah.com (Greg KH)]

On Wed, Nov 23, 2011 at 10:31:19AM -0800, Jeff Haran wrote:
> > That's the actual bug: You assume that you can legally make a
> > proprietary Linux kernel module by simply declaring to do so (and going
> > deeper is not quite possible as we do not know the module ....).
> 
> I can clearly legally write a user space program that results in calls
> to kernel symbols without publishing it. To do that I load parameters
> into registers and onto the stack and issue a trap to generate a
> system call. A kernel module does almost the same thing, except
> instead of generating a trap, it makes a more traditional function
> call. The difference is technical and I don't see anything in the
> COPYING file that makes any reference to this difference. If I have
> missed that verbiage in the license, please point it out to me.

Please read the first paragraph in the COPYING file in the kernel, it
explains the differences and allows for userspace programs to not be
bound under the license of the rest of the kernel.

> > But your kernel module is very probably a derived work of the Linux
> > kernel anyway and thus automatically and implicitly GPL (even if your
> > whole company may want it, has been told or think otherwise).
> 
> "very probably a derived work". That is a big assumption. What in the
> license defines all code that makes calls into kernel symbols via the
> dynamic module loader mechanism different than code that calls into
> that code via a trap?

Again the very license of the kernel itself does that.

greg k-h