scripts: Add SPDX checker script

scripts: Add SPDX checker script

The SPDX-License-Identifiers are growing in the kernel and so grow
expression failures and license IDs are used which have no corresponding
license text file in the LICENSES directory.

Add a script which gathers information from the LICENSES directory,
i.e. the various tags in the licenses and exception files and then scans
either input from stdin, which it treats as a single file or if started
without arguments it scans the full kernel tree.

It checks whether the license expression syntax is correct and also
validates whether the license identifiers used in the expressions are
available in the LICENSES files.

scripts/spdxcheck.py -h
usage: spdxcheck.py [-h] [-m MAXLINES] [-v] [path [path ...]]

SPDX expression checker

positional arguments:
  path                  Check path or file. If not given full git tree scan.
                        For stdin use "-"

optional arguments:
  -h, --help            show this help message and exit
  -m MAXLINES, --maxlines MAXLINES
                        Maximum number of lines to scan in a file. Default 15
  -v, --verbose         Verbose statistics output

include/dt-bindings/reset/amlogic,meson-axg-reset.h: 9:41 Invalid License ID: BSD

drivers/pinctrl/sh-pfc/pfc-r8a77965.c: 1:28 Invalid License ID: GPL-2.
include/dt-bindings/reset/amlogic,meson-axg-reset.h: 9:41 Invalid License ID: BSD

arch/x86/kernel/jailhouse.c: 1:28 Invalid License ID: GPL2.0
include/dt-bindings/reset/amlogic,meson-axg-reset.h: 9:41 Invalid License ID: BSD

arch/arm/mach-s3c24xx/h1940-bluetooth.c: 1:28 Invalid License ID: GPL-1.0
arch/x86/kernel/jailhouse.c: 1:28 Invalid License ID: GPL2.0
drivers/pinctrl/sh-pfc/pfc-r8a77965.c: 1:28 Invalid License ID: GPL-2.
include/dt-bindings/reset/amlogic,meson-axg-reset.h: 9:41 Invalid License ID: BSD
arch/x86/include/asm/jailhouse_para.h: 1:28 Invalid License ID: GPL2.0

arch/arm/mach-s3c24xx/h1940-bluetooth.c: 1:28 Invalid License ID: GPL-1.0
arch/x86/kernel/jailhouse.c: 1:28 Invalid License ID: GPL2.0
drivers/pinctrl/sh-pfc/pfc-r8a77965.c: 1:28 Invalid License ID: GPL-2.
include/dt-bindings/reset/amlogic,meson-axg-reset.h: 9:41 Invalid License ID: BSD
arch/x86/include/asm/jailhouse_para.h: 1:28 Invalid License ID: GPL2.0

License files:               14
Exception files:              1
License IDs                  19
Exception IDs                 1

Files checked:            61332
Lines checked:           669181
Files with SPDX:          16169
Files with errors:            5

real	0m2.642s
user	0m2.231s
sys	0m0.467s

That's a full tree sweep on my laptop. Note, this runs single threaded.

It scans by default the first 15 lines for a SPDX identifier where the
current max inside a top comment is at line 10. But that's going to be
faster once the identifiers are all in the first two lines as documented.

The python wizards will surely know how to do that smarter and faster, but
its at least better than no tool at all.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[jc: Fixed ironically erroneous SPDX tag and did chmod +x ]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>