• Greg Kroah-Hartman's avatar
    License cleanup: add SPDX GPL-2.0 license identifier to files with no license · b2441318
    Greg Kroah-Hartman authored
    Many source files in the tree are missing licensing information, which
    makes it harder for compliance tools to determine the correct license.
    
    By default all files without license information are under the default
    license of the kernel, which is GPL version 2.
    
    Update the files which contain no license information with the 'GPL-2.0'
    SPDX license identifier.  The SPDX identifier is a legally binding
    shorthand, which can be used instead of the full boiler plate text.
    
    This patch is based on work done by Thomas Gleixner and Kate Stewart and
    Philippe Ombredanne.
    
    How this work was done:
    
    Patches were generated and checked against linux-4.14-rc6 for a subset of
    the use cases:
     - file had no licensing information it it.
     - file was a */uapi/* one with no licensing information in it,
     - file was a */uapi/* one with existing licensing information,
    
    Further patches will be generated in subsequent months to fix up cases
    where non-standard license headers were used, and references to license
    had to be inferred by heuristics based on keywords.
    
    The analysis to determine which SPDX License Identifier to be applied to
    a file was done in a spreadsheet of side by side results from of the
    output of two independent scanners (ScanCode & Windriver) producing SPDX
    tag:value files created by Philippe Ombredanne.  Philippe prepared the
    base worksheet, and did an initial spot review of a few 1000 files.
    
    The 4.13 kernel was the starting point of the analysis with 60,537 files
    assessed.  Kate Stewart did a file by file comparison of the scanner
    results in the spreadsheet to determine which SPDX license identifier(s)
    to be applied to the file. She confirmed any determination that was not
    immediately clear with lawyers working with the Linux Foundation.
    
    Criteria used to select files for SPDX license identifier tagging was:
     - Files considered eligible had to be source code files.
     - Make and config files were included as candidates if they contained >5
       lines of source
     - File already had some variant of a license header in it (even if <5
       lines).
    
    All documentation files were explicitly excluded.
    
    The following heuristics were used to determine which SPDX license
    identifiers to apply.
    
     - when both scanners couldn't find any license traces, file was
       considered to have no license information in it, and the top level
       COPYING file license applied.
    
       For non */uapi/* files that summary was:
    
       SPDX license identifier                            # files
       ---------------------------------------------------|-------
       GPL-2.0                                              11139
    
       and resulted in the first patch in this series.
    
       If that file was a */uapi/* path one, it was "GPL-2.0 WITH
       Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:
    
       SPDX license identifier                            # files
       ---------------------------------------------------|-------
       GPL-2.0 WITH Linux-syscall-note                        930
    
       and resulted in the second patch in this series.
    
     - if a file had some form of licensing information in it, and was one
       of the */uapi/* ones, it was denoted with the Linux-syscall-note if
       any GPL family license was found in the file or had no licensing in
       it (per prior point).  Results summary:
    
       SPDX license identifier                            # files
       ---------------------------------------------------|------
       GPL-2.0 WITH Linux-syscall-note                       270
       GPL-2.0+ WITH Linux-syscall-note                      169
       ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
       ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
       LGPL-2.1+ WITH Linux-syscall-note                      15
       GPL-1.0+ WITH Linux-syscall-note                       14
       ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
       LGPL-2.0+ WITH Linux-syscall-note                       4
       LGPL-2.1 WITH Linux-syscall-note                        3
       ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
       ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1
    
       and that resulted in the third patch in this series.
    
     - when the two scanners agreed on the detected license(s), that became
       the concluded license(s).
    
     - when there was disagreement between the two scanners (one detected a
       license but the other didn't, or they both detected different
       licenses) a manual inspection of the file occurred.
    
     - In most cases a manual inspection of the information in the file
       resulted in a clear resolution of the license that should apply (and
       which scanner probably needed to revisit its heuristics).
    
     - When it was not immediately clear, the license identifier was
       confirmed with lawyers working with the Linux Foundation.
    
     - If there was any question as to the appropriate license identifier,
       the file was flagged for further research and to be revisited later
       in time.
    
    In total, over 70 hours of logged manual review was done on the
    spreadsheet to determine the SPDX license identifiers to apply to the
    source files by Kate, Philippe, Thomas and, in some cases, confirmation
    by lawyers working with the Linux Foundation.
    
    Kate also obtained a third independent scan of the 4.13 code base from
    FOSSology, and compared selected files where the other two scanners
    disagreed against that SPDX file, to see if there was new insights.  The
    Windriver scanner is based on an older version of FOSSology in part, so
    they are related.
    
    Thomas did random spot checks in about 500 files from the spreadsheets
    for the uapi headers and agreed with SPDX license identifier in the
    files he inspected. For the non-uapi files Thomas did random spot checks
    in about 15000 files.
    
    In initial set of patches against 4.14-rc6, 3 files were found to have
    copy/paste license identifier errors, and have been fixed to reflect the
    correct identifier.
    
    Additionally Philippe spent 10 hours this week doing a detailed manual
    inspection and review of the 12,461 patched files from the initial patch
    version early this week with:
     - a full scancode scan run, collecting the matched texts, detected
       license ids and scores
     - reviewing anything where there was a license detected (about 500+
       files) to ensure that the applied SPDX license was correct
     - reviewing anything where there was no detection but the patch license
       was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
       SPDX license was correct
    
    This produced a worksheet with 20 files needing minor correction.  This
    worksheet was then exported into 3 different .csv files for the
    different types of files to be modified.
    
    These .csv files were then reviewed by Greg.  Thomas wrote a script to
    parse the csv files and add the proper SPDX tag to the file, in the
    format that the file expected.  This script was further refined by Greg
    based on the output to detect more types of files automatically and to
    distinguish between header and source .c files (which need different
    comment types.)  Finally Greg ran the script using the .csv files to
    generate the patches.
    Reviewed-by: 's avatarKate Stewart <kstewart@linuxfoundation.org>
    Reviewed-by: 's avatarPhilippe Ombredanne <pombredanne@nexb.com>
    Reviewed-by: 's avatarThomas Gleixner <tglx@linutronix.de>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    b2441318