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Licensing for Chromium OS Developers

User oriented documentation is here: Licensing for Chromium OS Package Owners

Goal

Chrome OS ships with an html file that should contain a list of all the licenses used by packages shipped with Chrome OS. We also chose to include some build packages in the license output and while most are not required to be listed, we included them to include some required build packages that provide static libraries (.a) linked in other projects and therefore part of Chrome OS, but not part of the package list.

During the build, as part of emerging the packages, licences.py will create a license.yaml file in $SYSROOT/var/db/pkg/$CATEGORY/$PACKAGE that will contain the information, needed for final post-processing.

This is done by parsing the ebuild and if the license is set to something like MIT or BSD, we’re forced to unpack the source and look for a license file for copyright attribution, which is required by the BSD and MIT style licenses.

Later, during creation of the ChromeOS image, licenses.py will be invoked with --output argument to use the generated license.yaml files to create the final HTML page, which will be compressed and put under /opt/google/chrome/resources/about_os_credits.html.gz on the generated image.

Read the comments at the top of licenses.py for more instructions.

Pointers

HOWTO

You don't usually need to re-generate licensing for individual packages, as it will be generated during emerge, but you can do so with this command:

(cr) pkg_name=dev-util/meson-0.61.1
(cr) ~/chromiumos/chromite/licensing $ ./licenses --debug --board $BOARD -p $pkg_name --generate -o out-single.html

You can generate the HTML license file with:

(cr) ~/chromiumos/chromite/licensing $ ./licenses --debug --board $BOARD --generate-licenses --output outall.html

How the license generation can fail and exit

The code has multiple asserts. They should be self documenting for us, but they are not meant to be understandable for the end user, so I’m not going to list them here. Also, I can’t say how they would happen since the whole point is that they catch cases that aren’t supposed to happen :)

I’ll list a few special ones.

raise AssertionError("license %s could not be found in %s"

This will happen if a license specified in LICENSE= doesn’t exist anywhere in STOCK_LICENSE_DIRS and CUSTOM_LICENSE_DIRS.

Arguably this should likely be a better error message instead of an assert and once the presubmit that stops a non existing license to be referred to exists, this code should never have to trigger.

See http://crbug.com/318364

Assert DO NOT USE OUTPUT!!!

This one runs at the end, but tells the user to scroll back up and find the relevant message in the logs for that package.

It’s not super user friendly, maybe it should capture all those logs so that it can print them again at the end?

Note that the script is recommended to be run as

%(prog)s [--debug] $board out.html 2>&1 | tee output.sav

so that you can look in output.sav and scroll back up for the errors relevant to each package.

raise PackageLicenseError()

This one comes with a suitable logging.error:

logging.error(""" %s: unable to find usable license. Typically this will happen because the ebuild says it's MIT or BSD, but there was no license file that this script could find to include along with a copyright attribution (required for BSD/MIT). If this is Google source, please change LICENSE="BSD" to LICENSE="BSD-Google" If not, go investigate the unpacked source in %s, and find which license to assign. Once you found it, you should copy that license to a file under %s (unless you can modify LICENSE_FILENAMES to pick up a license file that isn't being scraped currently).""",

TODO for the code