On Thu, Dec 28, 2017 at 04:27:11PM +0100, Thomas Gleixner wrote: > Add a file to the Documentation directory to describe how file licenses > should be described in all kernel files, using the SPDX identifier, as well > as where all licenses should be in the kernel source tree for people to > refer to (LICENSES/). > > Thanks to Kate and Greg for review and editing and Jonas for the > suggestions concerning the meta tags in the licenses files. > > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Reviewed-by: Jonas Oberg <jonas@xxxxxxxx> > Reviewed-by: Jonathan Corbet <corbet@xxxxxxx> > Reviewed-by: Philippe Ombredanne <pombredanne@xxxxxxxx> > Reviewed-by: Kate Stewart <kstewart@xxxxxxxxxxxxxxxxxxx> > Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > /me hasn't done any deep dive legal analysis of this, but I can live with this as a tag-file-with-license convention, so... Acked-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --D > --- > Documentation/index.rst | 12 + > Documentation/process/license-rules.rst | 370 ++++++++++++++++++++++++++++++++ > 2 files changed, 382 insertions(+) > create mode 100644 Documentation/license-rules.rst > > --- a/Documentation/index.rst > +++ b/Documentation/index.rst > @@ -13,6 +13,18 @@ documents into a coherent whole. Please > documentation are welcome; join the linux-doc list at vger.kernel.org if > you want to help out. > > +Licensing documentation > +----------------------- > + > +The following describes the license of the Linux kernel source code > +(GPLv2), how to properly mark the license of individual files in the source > +tree, as well as links to the full license text. > + > +.. toctree:: > + :maxdepth: 2 > + > + process/license-rules.rst > + > User-oriented documentation > --------------------------- > > --- /dev/null > +++ b/Documentation/process/license-rules.rst > @@ -0,0 +1,370 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +Linux kernel licensing rules > +============================ > + > +The Linux Kernel is provided under the terms of the GNU General Public > +License version 2 only (GPL-2.0), as published by the Free Software > +Foundation, and provided in the COPYING file. This documentation file is > +not meant to replace the COPYING file, but provides a description of how > +each source file should be annotated to make the licensing it is governed > +under clear and unambiguous. > + > +The license in the COPYING file applies to the kernel source as a whole, > +though individual source files can have a different license which is > +required to be compatible with the GPL-2.0:: > + > + GPL-1.0+ : GNU General Public License v1.0 or later > + GPL-2.0+ : GNU General Public License v2.0 or later > + LGPL-2.0 : GNU Library General Public License v2 only > + LGPL-2.0+ : GNU Library General Public License v2 or later > + LGPL-2.1 : GNU Lesser General Public License v2.1 only > + LGPL-2.1+ : GNU Lesser General Public License v2.1 or later > + > +Aside from that, individual files can be provided under a dual license, > +e.g. one of the compatible GPL variants and alternatively under a > +permissive license like BSD, MIT etc. > + > +The User-space API (UAPI) header files, which describe the interface of > +user-space programs to the kernel are a special case. According to the > +note in the kernel COPYING file, the syscall interface is a clear boundary, > +which does not extend the GPL requirements to any software which uses it to > +communicate with the kernel. Because the UAPI headers must be includable > +into any source files which create an executable running on the Linux > +kernel, the exception must be documented by a special license expression. > + > +The common way of expressing the license of a source file is to add the > +matching boilerplate text into the top comment of the file. Due to > +formatting, typos etc. these "boilerplates" are hard to validate for > +tools which are used in the context of license compliance. > + > +An alternative to boilerplate text is the use of Software Package Data > +Exchange (SPDX) license identifiers in each source file. SPDX license > +identifiers are machine parsable and precise shorthands for the license > +under which the content of the file is contributed. SPDX license > +identifiers are managed by the SPDX Workgroup at the Linux Foundation and > +have been agreed on by partners throughout the industry, tool vendors, and > +legal teams. For further information see https://spdx.org/ > + > +The Linux kernel requires the precise SPDX identifier in all source files. > +The valid identifiers used in the kernel are explained in the section > +`License identifiers`_ and have been retrieved from the official SPDX > +license list at https://spdx.org/licenses/ along with the license texts. > + > +License identifier syntax > +------------------------- > + > +1. Placement: > + > + The SPDX license identifier in kernel files shall be added at the first > + possible line in a file which can contain a comment. For the majority > + or files this is the first line, except for scripts which require the > + '#!PATH_TO_INTERPRETER' in the first line. For those scripts the SPDX > + identifier goes into the second line. > + > +| > + > +2. Style: > + > + The SPDX license identifier is added in form of a comment. The comment > + style depends on the file type:: > + > + C source: // SPDX-License-Identifier: <SPDX License Expression> > + C header: /* SPDX-License-Identifier: <SPDX License Expression> */ > + ASM: /* SPDX-License-Identifier: <SPDX License Expression> */ > + scripts: # SPDX-License-Identifier: <SPDX License Expression> > + .rst: .. SPDX-License-Identifier: <SPDX License Expression> > + .dts{i}: // SPDX-License-Identifier: <SPDX License Expression> > + > + If a specific tool cannot handle the standard comment style, then the > + appropriate comment mechanism which the tool accepts shall be used. This > + is the reason for having the "/\* \*/" style comment in C header > + files. There was build breakage observed with generated .lds files where > + 'ld' failed to parse the C++ comment. This has been fixed by now, but > + there are still older assembler tools which cannot handle C++ style > + comments. > + > +| > + > +3. Syntax: > + > + A <SPDX License Expression> is either an SPDX short form license > + identifier found on the SPDX License List, or the combination of two > + SPDX short form license identifiers separated by "WITH" when a license > + exception applies. When multiple licenses apply, an expression consists > + of keywords "AND", "OR" separating sub-expressions and surrounded by > + "(", ")" . > + > + License identifiers for licenses like [L]GPL with the 'or later' option > + are constructed by using a "+" for indicating the 'or later' option.:: > + > + // SPDX-License-Identifier: GPL-2.0+ > + // SPDX-License-Identifier: LGPL-2.1+ > + > + WITH should be used when there is a modifier to a license needed. > + For example, the linux kernel UAPI files use the expression:: > + > + // SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note > + // SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note > + > + Other examples using WITH exceptions found in the kernel are:: > + > + // SPDX-License-Identifier: GPL-2.0 WITH mif-exception > + // SPDX-License-Identifier: GPL-2.0+ WITH GCC-exception-2.0 > + > + Exceptions can only be used with particular License identifiers. The > + valid License identifiers are listed in the tags of the exception text > + file. For details see the point `Exceptions`_ in the chapter `License > + identifiers`_. > + > + OR should be used if the file is dual licensed and only one license is > + to be selected. For example, some dtsi files are available under dual > + licenses:: > + > + // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause > + > + Examples from the kernel for license expressions in dual licensed files:: > + > + // SPDX-License-Identifier: GPL-2.0 OR MIT > + // SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause) > + // SPDX-License-Identifier: GPL-2.0 OR Apache-2.0) > + // SPDX-License-Identifier: GPL-2.0 OR MPL-1.1) > + // SPDX-License-Identifier: (GPL-2.0 WITH Linux-syscall-note) OR MIT > + // SPDX-License-Identifier: GPL-1.0+ OR BSD-3-Clause OR OpenSSL) > + > + AND should be used if the file has multiple licenses whose terms all > + apply to use the file. For example, if code is inherited from another > + project and permission has been given to put it in the kernel, but the > + original license terms need to remain in effect:: > + > + // SPDX-License-Identifier: (GPL-2.0 WITH Linux-syscall-note) AND MIT > + > + Another other example where both sets of license terms need to be > + adhered to is:: > + > + // SPDX-License-Identifier: GPL-1.0+ AND LGPL-2.1+ > + > +License identifiers > +------------------- > + > +The licenses currently used, as well as the licenses for code added to the > +kernel, can be broken down into: > + > +1. _`Preferred licenses`: > + > + Whenever possible these licenses should be used as they are known to be > + fully compatible and widely used. These licenses are available from the > + directory:: > + > + LICENSES/preferred/ > + > + in the kernel source tree. > + > + The files in this directory contain the full license text and > + `Metatags`_. The file names are identical to the SPDX license > + identifier which shall be used for the license in source files. > + > + Examples:: > + > + LICENSES/preferred/GPL-2.0 > + > + Contains the GPL version 2 license text and the required metatags:: > + > + LICENSES/preferred/MIT > + > + Contains the MIT license text and the required metatags > + > + _`Metatags`: > + > + The following meta tags must be available in a license file: > + > + - Valid-License-Identifier: > + > + One or more lines which declare which License Identifiers are valid > + inside the project to reference this particular license text. Usually > + this is a single valid identifier, but e.g. for licenses with the 'or > + later' options two identifiers are valid. > + > + - SPDX-URL: > + > + The URL of the SPDX page which contains additional information related > + to the license. > + > + - Usage-Guidance: > + > + Freeform text for usage advice. The text must include correct examples > + for the SPDX license identifiers as they should be put into source > + files according to the `License identifier syntax`_ guidelines. > + > + - License-Text: > + > + All text after this tag is treated as the original license text > + > + File format examples:: > + > + Valid-License-Identifier: GPL-2.0 > + Valid-License-Identifier: GPL-2.0+ > + SPDX-URL: https://spdx.org/licenses/GPL-2.0.html > + Usage-Guide: > + To use this license in source code, put one of the following SPDX > + tag/value pairs into a comment according to the placement > + guidelines in the licensing rules documentation. > + For 'GNU General Public License (GPL) version 2 only' use: > + SPDX-License-Identifier: GPL-2.0 > + For 'GNU General Public License (GPL) version 2 or any later version' use: > + SPDX-License-Identifier: GPL-2.0+ > + License-Text: > + Full license text > + > + :: > + > + SPDX-License-Identifier: MIT > + SPDX-URL: https://spdx.org/licenses/MIT.html > + Usage-Guide: > + To use this license in source code, put the following SPDX > + tag/value pair into a comment according to the placement > + guidelines in the licensing rules documentation. > + SPDX-License-Identifier: MIT > + License-Text: > + Full license text > + > +| > + > +2. Not recommended licenses: > + > + These licenses should only be used for existing code or for importing > + code from a different project. These licenses are available from the > + directory:: > + > + LICENSES/other/ > + > + in the kernel source tree. > + > + The files in this directory contain the full license text and > + `Metatags`_. The file names are identical to the SPDX license > + identifier which shall be used for the license in source files. > + > + Examples:: > + > + LICENSES/other/ISC > + > + Contains the Internet Systems Consortium license text and the required > + metatags:: > + > + LICENSES/other/ZLib > + > + Contains the ZLIB license text and the required metatags. > + > + Metatags: > + > + The metatag requirements for 'other' licenses are identical to the > + requirements of the `Preferred licenses`_. > + > + File format example:: > + > + Valid-License-Identifier: ISC > + SPDX-URL: https://spdx.org/licenses/ISC.html > + Usage-Guide: > + Usage of this license in the kernel for new code is discouraged > + and it should solely be used for importing code from an already > + existing project. > + To use this license in source code, put the following SPDX > + tag/value pair into a comment according to the placement > + guidelines in the licensing rules documentation. > + SPDX-License-Identifier: ISC > + License-Text: > + Full license text > + > +| > + > +3. _`Exceptions`: > + > + Some licenses can be amended with exceptions which grant certain rights > + which the original license does not. These exceptions are available > + from the directory:: > + > + LICENSES/exceptions/ > + > + in the kernel source tree. The files in this directory contain the full > + exception text and the required `Exception Metatags`_. > + > + Examples:: > + > + LICENSES/exceptions/Linux-syscall-note > + > + Contains the Linux syscall exception as documented in the COPYING > + file of the Linux kernel, which is used for UAPI header files. > + e.g. /\* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note \*/:: > + > + LICENSES/exceptions/GCC-exception-2.0 > + > + Contains the GCC 'linking exception' which allows to link any binary > + independent of its license against the compiled version of a file marked > + with this exception. This is required for creating runnable executables > + from source code which is not compatible with the GPL. > + > + _`Exception Metatags`: > + > + The following meta tags must be available in an exception file: > + > + - SPDX-Exception-Identifier: > + > + One exception identifier which can be used with SPDX license > + identifiers. > + > + - SPDX-URL: > + > + The URL of the SPDX page which contains additional information related > + to the exception. > + > + - SPDX-Licenses: > + > + A comma separated list of SPDX license identifiers for which the > + exception can be used. > + > + - Usage-Guidance: > + > + Freeform text for usage advice. The text must be followed by correct > + examples for the SPDX license identifiers as they should be put into > + source files according to the `License identifier syntax`_ guidelines. > + > + - Exception-Text: > + > + All text after this tag is treated as the original exception text > + > + File format examples:: > + > + SPDX-Exception-Identifier: Linux-syscall-note > + SPDX-URL: https://spdx.org/licenses/Linux-syscall-note.html > + SPDX-Licenses: GPL-2.0, GPL-2.0+, GPL-1.0+, LGPL-2.0, LGPL-2.0+, LGPL-2.1, LGPL-2.1+ > + Usage-Guidance: > + This exception is used together with one of the above SPDX-Licenses > + to mark user-space API (uapi) header files so they can be included > + into non GPL compliant user-space application code. > + To use this exception add it with the keyword WITH to one of the > + identifiers in the SPDX-Licenses tag: > + SPDX-License-Identifier: <SPDX-License> WITH Linux-syscall-note > + Exception-Text: > + Full exception text > + > + :: > + > + SPDX-Exception-Identifier: GCC-exception-2.0 > + SPDX-URL: https://spdx.org/licenses/GCC-exception-2.0.html > + SPDX-Licenses: GPL-2.0, GPL-2.0+ > + Usage-Guidance: > + The "GCC Runtime Library exception 2.0" is used together with one > + of the above SPDX-Licenses for code imported from the GCC runtime > + library. > + To use this exception add it with the keyword WITH to one of the > + identifiers in the SPDX-Licenses tag: > + SPDX-License-Identifier: <SPDX-License> WITH GCC-exception-2.0 > + Exception-Text: > + Full exception text > + > + > +All SPDX license identifiers and exceptions must have a corresponding file > +in the LICENSE subdirectories. This is required to allow tool > +verification (e.g. checkpatch.pl) and to have the licenses ready to read > +and extract right from the source, which is recommended by various FOSS > +organizations, e.g. the `FSFE REUSE initiative <https://reuse.software/>`_. > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
