RE: Re: Re: Clarification on bpftool dual licensing

On Wed, Nov 17, 2021 at 4:32 PM Martin Kelly
[off-list ref] wrote:

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On Tue, Nov 16, 2021 at 2:16 AM Daniel Borkmann

[off-list ref]

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wrote:

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On 11/15/21 7:20 PM, Martin Kelly wrote:

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Hi,

I have a question regarding the dual licensing provision of bpftool. I
understand that bpftool can be distributed as either GPL 2.0 or BSD 2-

clause.

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That said, bpftool can also auto-generate BPF code that gets specified

inline

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in the skeleton header file, and it's possible that the BPF code generated

is

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GPL. What I'm wondering is what happens if bpftool generates GPL-

licensed

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BPF

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code inside the skeleton header, so that you get a header like this:

something.skel.h:
/* this file is BSD 2-clause, by nature of dual licensing */

Fwiw, the generated header contains an SPDX identifier:

  /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
  /* THIS FILE IS AUTOGENERATED! */

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/* THIS FILE IS AUTOGENERATED! */

/* standard skeleton definitions */

...

s->data_sz = XXX;
s->data = (void *)"\
<eBPF bytecode, produced by GPL 2.0 sources, specified in binary>
";

My guess is that, based on the choice to dual-license bpftool, the header

is

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meant to still be BSD 2-clause, and the s->data inline code's GPL license

is

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not meant to change the licensing of the header itself, but I wanted to

Yes, definitely that is the intent (but not a lawyer either).

 Thanks everyone, that's what I assumed as well. Any objection to a patch

clarifying this more explicitly?

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One other, related question: vmlinux.h (generated by "bpftool btf dump file

/sys/kernel/btf/vmlinux format c"), does not currently contain a license
declaration. I assume this would have to be a GPL header, since vmlinux.h
references many GPL'd Linux kernel structs and similar, though again I'm not a
lawyer and therefore am not certain. Would you all agree with this? If so, any
objection to a patch adding an SPDX line to the generated vmlinux.h?

Is vmlinux DWARF data GPL'ed? I certainly hope not. So vmlinux.h
shouldn't be licensed under GPL.

I have no idea; I had assumed that a struct definition coming from a GPL-licensed header would have to be GPL, but again, not a lawyer, and I could totally be wrong. If not GPL though, what would the license be? Is it just "output of a program" and therefore license-less, even though the output happens to be code?

Martin Kelly [off-list ref] writes:

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One other, related question: vmlinux.h (generated by "bpftool btf dump file

/sys/kernel/btf/vmlinux format c"), does not currently contain a license
declaration. I assume this would have to be a GPL header, since vmlinux.h
references many GPL'd Linux kernel structs and similar, though again I'm not a
lawyer and therefore am not certain. Would you all agree with this? If so, any
objection to a patch adding an SPDX line to the generated vmlinux.h?

Is vmlinux DWARF data GPL'ed? I certainly hope not. So vmlinux.h
shouldn't be licensed under GPL.

I have no idea; I had assumed that a struct definition coming from a
GPL-licensed header would have to be GPL, but again, not a lawyer, and
I could totally be wrong. If not GPL though, what would the license
be? Is it just "output of a program" and therefore license-less, even
though the output happens to be code?

Totally not a lawyer either, but:

There's (generally, in many jurisdictions, etc), a minimum bar for when
something is considered a "creative work" and thus copyrightable. Debug
output *could* fall short of this (and thus not be copyrightable at
all). It could also fall under the same "API" umbrella as that famous
Google v Oracle case. Or it could fall under the "syscall exception" of
the kernel source.

I guess it would take a court decision to know either way. IMO it would
make sense if vmlinux.h is not copyrightable for whatever reason, but,
again, IANAL :)

Anyway, while we obviously can't resolve legal matters on the mailing,
we can express the *intention* of the community, which is what the
licensing document is trying to do. So it totally makes sense to mention
vmlinux.h here; the question is what should such a text say?

-Toke