xz: switch from public domain to BSD Zero Clause License (0BSD)

Remove the public domain notices and add SPDX license identifiers.

Change MODULE_LICENSE from "GPL" to "Dual BSD/GPL" because 0BSD should
count as a BSD license variant here.

The switch to 0BSD was done in the upstream XZ Embedded project because
public domain has (real or perceived) legal issues in some jurisdictions.

Link: https://lkml.kernel.org/r/20240721133633.47721-4-lasse.collin@tukaani.org
Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Reviewed-by: Sam James <sam@gentoo.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jubin Zhong <zhongjubin@huawei.com>
Cc: Jules Maselbas <jmaselbas@zdiv.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Rui Li <me@lirui.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/decompress/unxz.h

@@ -1,10 +1,9 @@
+/* SPDX-License-Identifier: 0BSD */
+
 /*
  * Wrapper for decompressing XZ-compressed kernel, initramfs, and initrd
  *
  * Author: Lasse Collin <lasse.collin@tukaani.org>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 #ifndef DECOMPRESS_UNXZ_H

include/linux/xz.h

@@ -1,11 +1,10 @@
+/* SPDX-License-Identifier: 0BSD */
+
 /*
  * XZ decompressor
  *
  * Authors: Lasse Collin <lasse.collin@tukaani.org>
  *          Igor Pavlov <https://7-zip.org/>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 #ifndef XZ_H

lib/decompress_unxz.c

@@ -1,10 +1,9 @@
+// SPDX-License-Identifier: 0BSD
+
 /*
  * Wrapper for decompressing XZ-compressed kernel, initramfs, and initrd
  *
  * Author: Lasse Collin <lasse.collin@tukaani.org>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 /*

lib/xz/xz_crc32.c

@@ -1,11 +1,10 @@
+// SPDX-License-Identifier: 0BSD
+
 /*
  * CRC32 using the polynomial from IEEE-802.3
  *
  * Authors: Lasse Collin <lasse.collin@tukaani.org>
  *          Igor Pavlov <https://7-zip.org/>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 /*

lib/xz/xz_dec_bcj.c

@@ -1,11 +1,10 @@
+// SPDX-License-Identifier: 0BSD
+
 /*
  * Branch/Call/Jump (BCJ) filter decoders
  *
  * Authors: Lasse Collin <lasse.collin@tukaani.org>
  *          Igor Pavlov <https://7-zip.org/>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 #include "xz_private.h"

lib/xz/xz_dec_lzma2.c

@@ -1,11 +1,10 @@
+// SPDX-License-Identifier: 0BSD
+
 /*
  * LZMA2 decoder
  *
  * Authors: Lasse Collin <lasse.collin@tukaani.org>
  *          Igor Pavlov <https://7-zip.org/>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 #include "xz_private.h"

lib/xz/xz_dec_stream.c

@@ -1,10 +1,9 @@
+// SPDX-License-Identifier: 0BSD
+
 /*
  * .xz Stream decoder
  *
  * Author: Lasse Collin <lasse.collin@tukaani.org>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 #include "xz_private.h"

lib/xz/xz_dec_syms.c

@@ -1,10 +1,9 @@
+// SPDX-License-Identifier: 0BSD
+
 /*
  * XZ decoder module information
  *
  * Author: Lasse Collin <lasse.collin@tukaani.org>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 #include <linux/module.h>
@@ -25,9 +24,4 @@ EXPORT_SYMBOL(xz_dec_microlzma_end);
 MODULE_DESCRIPTION("XZ decompressor");
 MODULE_VERSION("1.1");
 MODULE_AUTHOR("Lasse Collin <lasse.collin@tukaani.org> and Igor Pavlov");
-
+MODULE_LICENSE("Dual BSD/GPL");
-/*
- * This code is in the public domain, but in Linux it's simplest to just
- * say it's GPL and consider the authors as the copyright holders.
- */
-MODULE_LICENSE("GPL");

lib/xz/xz_dec_test.c

@@ -1,10 +1,9 @@
+// SPDX-License-Identifier: 0BSD
+
 /*
  * XZ decoder tester
  *
  * Author: Lasse Collin <lasse.collin@tukaani.org>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 #include <linux/kernel.h>
@@ -212,9 +211,4 @@ module_exit(xz_dec_test_exit);
 MODULE_DESCRIPTION("XZ decompressor tester");
 MODULE_VERSION("1.0");
 MODULE_AUTHOR("Lasse Collin <lasse.collin@tukaani.org>");
-
+MODULE_LICENSE("Dual BSD/GPL");
-/*
- * This code is in the public domain, but in Linux it's simplest to just
- * say it's GPL and consider the authors as the copyright holders.
- */
-MODULE_LICENSE("GPL");

lib/xz/xz_lzma2.h

@@ -1,11 +1,10 @@
+/* SPDX-License-Identifier: 0BSD */
+
 /*
  * LZMA2 definitions
  *
  * Authors: Lasse Collin <lasse.collin@tukaani.org>
  *          Igor Pavlov <https://7-zip.org/>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 #ifndef XZ_LZMA2_H

lib/xz/xz_private.h

@@ -1,10 +1,9 @@
+/* SPDX-License-Identifier: 0BSD */
+
 /*
  * Private includes and definitions
  *
  * Author: Lasse Collin <lasse.collin@tukaani.org>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 #ifndef XZ_PRIVATE_H

lib/xz/xz_stream.h

@@ -1,10 +1,9 @@
+/* SPDX-License-Identifier: 0BSD */
+
 /*
  * Definitions for handling the .xz file format
  *
  * Author: Lasse Collin <lasse.collin@tukaani.org>
- *
- * This file has been put into the public domain.
- * You can do whatever you want with this file.
  */
 
 #ifndef XZ_STREAM_H

scripts/xz_wrap.sh

@@ -1,13 +1,10 @@
 #!/bin/sh
+# SPDX-License-Identifier: 0BSD
 #
 # This is a wrapper for xz to compress the kernel image using appropriate
 # compression options depending on the architecture.
 #
 # Author: Lasse Collin <lasse.collin@tukaani.org>
-#
-# This file has been put into the public domain.
-# You can do whatever you want with this file.
-#
 
 BCJ=
 LZMA2OPTS=