SDK Subtools Builder

The SDK Subtools Builder creates CIPD packages from Portage packages which can be used outside of the SDK. This is useful for a variety of applications, such as pre-upload hooks, distributing developer tools, and specialized workflows like signing.

Currently available subtools packages are visible in the CIPD Web UI.

Adding a package to the subtools builder

You'll need to write a config for the package. The config is in textproto format and subtools.proto is the schema for it. Here is a simple example config:

name: "futility"
type: EXPORT_CIPD
max_files: 200
paths: [
  {
    input: "/usr/bin/futility"
  }
]

The config can be placed anywhere that you like, as long as it's accessible during the ebuild src_install phase (which means, you can even generate the config with a script, should you need). Common locations are in ${FILESDIR} of the ebuild, or in your project's source tree.

To install the config, make sure your ebuild inherits cros-subtool, and add to your src_install:

src_install() {
	...
	cros-subtool_src_install path/to/subtool.textproto
}

Finally, you need to tell the subtools builder to build your package. List it in virtual/target-sdk-subtools.

After landing your changes, your package will be available in CIPD after the next build-chromeos-sdk-subtools run (kicked off every 24 hours).

Running the subtools builder locally

To test your subtools changes, you can run the subtools builder locally. To do so, execute:

(outside) ~/chromiumos $ chromite/bin/build_sdk_subtools

This tool will create its own specialized chroot for building in, so it should be run outside the SDK.

How it works

Internally, the subtools builder uses lddtree to bundle both your package and its shared library dependencies (e.g., libc), replacing binaries with wrapper scripts using the correct ld-linux.so to load your programs. This creates a portable archive that should work on most any x86_64 linux distribution without depending on system libraries.