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Date:   Tue, 13 Jun 2023 12:01:40 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Heiko =?iso-8859-1?Q?St=FCbner?= <heiko@sntech.de>
Cc:     palmer@dabbelt.com, paul.walmsley@sifive.com,
        aou@eecs.berkeley.edu, herbert@gondor.apana.org.au,
        davem@davemloft.net, conor.dooley@microchip.com,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-crypto@vger.kernel.org, christoph.muellner@vrull.eu
Subject: Re: [PATCH v5 4/4] RISC-V: crypto: add accelerated GCM GHASH
 implementation
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 <20230613031006.GD883@sol.localdomain>
 <2236193.NgBsaNRSFp@diego>
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On Tue, Jun 13, 2023 at 10:00:44AM +0200, Heiko St?bner wrote:
> Am Dienstag, 13. Juni 2023, 05:10:06 CEST schrieb Eric Biggers:
> > Hi Heiko,
> > 
> > On Mon, Jun 12, 2023 at 11:04:42PM +0200, Heiko Stuebner wrote:
> > > diff --git a/arch/riscv/crypto/ghash-riscv64-zbc.pl b/arch/riscv/crypto/ghash-riscv64-zbc.pl
> > > new file mode 100644
> > > index 000000000000..677c438a44bf
> > > --- /dev/null
> > > +++ b/arch/riscv/crypto/ghash-riscv64-zbc.pl
> > > @@ -0,0 +1,427 @@
> > > +#! /usr/bin/env perl
> > > +# Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
> > > +#
> > > +# Licensed under the Apache License 2.0 (the "License").  You may not use
> > > +# this file except in compliance with the License.  You can obtain a copy
> > > +# in the file LICENSE in the source distribution or at
> > > +# https://www.openssl.org/source/license.html
> > > +
> > > +# This file is dual-licensed and is also available under the following
> > > +# terms:
> > > +#
> > > +# Copyright (c) 2023, Christoph M?llner <christoph.muellner@vrull.eu>
> > > +# All rights reserved.
> > > +#
> > > +# Redistribution and use in source and binary forms, with or without
> > > +# modification, are permitted provided that the following conditions
> > > +# are met:
> > > +# 1. Redistributions of source code must retain the above copyright
> > > +#    notice, this list of conditions and the following disclaimer.
> > > +# 2. Redistributions in binary form must reproduce the above copyright
> > > +#    notice, this list of conditions and the following disclaimer in the
> > > +#    documentation and/or other materials provided with the distribution.
> > 
> > Is this worded properly for a dual license?  The paragraph about the Apache
> > License makes it sound like the Apache License must always be complied with:
> > "You may not use this file except in compliance with the License."
> > 
> > So I worry that this could be interpreted as:
> > 
> >     Apache-2.0 AND BSD-2-Clause
> > 
> > instead of
> > 
> >     Apache-2.0 OR BSD-2-Clause
> > 
> > It needs to be the latter.
> > 
> > So I think the file header needs to be clarified w.r.t. the dual license.
> 
> Hmm, I think the 
> 	"This file is dual-licensed and is also available under the following terms"
> should be pretty clear?

As I said, IMO the problem is that it contradicts the Apache license blurb just
above it, specifically the part "You may not use this file except in compliance
with the License".  So it's not clear what is meant.  That sentence does not
appear in other common license blurbs; it seems to be unique to Apache's.

I know that people often treat these blurbs as magic incantations, but I'm just
looking at the plain English meaning here.

To fix this ambiguity I think either that sentence should be removed, or the
intent to dual license should be clearly described in the *first paragraph*
before listing the two licenses.  (Or do both of those.)

- Eric