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    SubjectRe: [PATCH/RFC] alternative aproach to: Ban module license tag string termination trick
    On Sat, 3 Feb 2007, Jan Engelhardt wrote:
    > On Feb 3 2007 03:08, Bodo Eggert wrote:

    > >This patch changes the module license handling code to:
    > >- allow modules to have multiple licenses
    > >- access GPL symbols if at least one license is GPL-compatible
    > I strongly nak that. If you combine two object files (e.g. foo.o, bar.o)
    > that have different licenses, the resulting object file (comb.o) IMHO
    > constitutes a combined work, and hence the GPL should be applied to all of
    > it. That obviously "does not work" - what good is a GPL comb.o file if you
    > don't have the source to bar.o? I think a module (.ko) should be denied
    > access to GPL symbols if any of the MODULE_LICENSE()s are not GPL.

    IMO it's called MODULE_LICENSE, not CFILE_LICENSE, therefore license
    strings in the module apply to the complete module.

    > Otherwise, ndiswrapper, CiscoVPN, etc. would just add a dummy.c GPL file
    > with a MODULE_LICENSE("GPL") in there and get the symbols.

    Using an extra GPL .o is like MODULE_LICENSE("GPL")/* for nothing*/;,
    you can't really do something about it.

    > Though you
    > could still get at the GPL symbols by use of a dedicated wrapper (think
    > nvidia kernel module), I would not want to make it easier for them by
    > allowing your two points. At best, foo.o and bar.o should be compiled
    > independently to foo.ko and bar.ko and work with EXPORT_SYMBOLs.

    IMO, using separate modules is the only thing you can do if you don't want
    to license your complete code using GPL.

    > >The license handling code was kind of strange:
    > > - The kernel itself would only consider the first license, while modpost
    > > looks at all of them.
    > > - If you offer your module under a non-GPL license in addition to GPL,
    > > modpost would consider this module to be non-GPL. Therefore you can't
    > > say MODULE_LICENSE("GPL");\nMODULE_LICENSE("completely free");
    > The idea to allow MODULE_LICENSE("GPL");\nMODULE_LICENSE("Public Domain");
    > is good, but how would you interpret an .o file (with no source!) with
    > MODULE_LICENSE("GPL");\nMODULE_LICENSE("Proprietary") ? (Well, see above)

    reiserfs is available under a Proprietary license, too. Obviously this is OK.

    > >Prohibiting the \0-trick is done by storing the length of the license
    > >behind the license itself, uuencoded, as $=xyz.
    > >
    > >Currently, only 18 bits (256 KB) of the length are stored, but storing up
    > >to 30 bits is possible without changing anything besides the macro.
    > >
    > >You can still trick this code by including "...\0license=GPL\0$=$\0..." or
    > >by manually fabricating this string into .modinfo. Fix: Document this to
    > >mean that you actually GPL-license the module.
    > $=$ is interpreted as what? [Ah ok, uuencoded uint32_t] That does not look
    > good. What if the length thing does not immediately come after the license
    > string? (E.g. someone hand-crafted a .ko)

    In this case, the tag is not recognized and will be skipped as if it were
    misspelled. I could also just bail out and deny loading the module.

    > static const char *const gpl_compatible[];
    > >+ "GPL",
    > >+ "GPL v2",
    > >+ "GPL and additional rights",
    > >+ "Dual BSD/GPL",
    > >+ "Dual MIT/GPL",
    > >+ "Dual MPL/GPL",
    > If we allowed multiple MODULE_LICENSE()s, all the Dual XYZ/GPL
    > combinations and so can go, since it would be possible to have
    > MODULE_LICENSE("GPL")\nMODULE_LICENSE("BSD");, simplifying the
    > module loader code.

    ACK, and "BSD" etc. should be included. I kept the combinations for
    backward-compatibility. Possibly we could warn on using them.

    A bone to the dog is not charity. Charity is the bone shared with the dog, when
    you are just as hungry as the dog.
    -- Jack London
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      Last update: 2007-02-03 15:07    [W:0.027 / U:5.392 seconds]
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