Sounds feasible. Some questions:
- Which build configs? Just -release builders, or -chromium-pfq and -paladin as well?
- Which unit test binaries? A whitelist of certain ebuilds, or everything?

One approach might be to add a "archive unittests" eclass that implements this behavior, and have certain ebuilds inherit it. +vapier ?

A simpler approach would be to just write a script that hunts through the buildroot and vacuums up the binaries of interest.

we're already generating the binpkgs on every build that has a UnitTest phase.  from the logs:
11:58:31: INFO: RunCommand: sudo 'PARALLEL_EMERGE_STATUS_FILE=/tmp/tmptZdxL4' 'FEATURES=test' 'PKGDIR=/build/daisy/test-packages' -- /mnt/host/source/chromite/bin/parallel_emerge '--sysroot=/build/daisy' '--jobs=10' ...all the packages...

so we can update one of the Archive steps to upload /build/$BOARD/test-packages/.

Adding more bugs-- folks + Caroline.

Do you build the tests with ASan?

It didn't sound like a problem when we last chatted, but just want to emphasize that we intend to use running ASanified unit tests as a stepping stone on our way to running actual fuzzers. If this ends up creating a lot of extra work for you by being very specific to unit tests, we could consider skipping right to fuzzers.

If the process makes sense to you there's no need to change anything, just wanted to bring this up now since I'm not familiar with how much work this would be on the infra side. Hopefully once we have something to upload the unit tests in place and libfuzzer working properly, a similar implementation for actual fuzz targets shouldn't be too hard to develop.

only ASAN bots build packages with ASAN enabled.  uploading of test-packages would be the same regardless of the config.

Returning to jorgelo@. This all sounds feasible. #2 has spelled out how we can proceed.

Who owns the artifact upload code? I.e. who should either change the Archive step or would be a good person to review such a CL?

vapier or somebody on cbuildbot side of infra (nxia, dgarrett, myself) can review.

I can look into uploading the UnitTest packages in buildbot scripts. 

Thanks Manoj!

CL @ https://chromium-review.googlesource.com/c/chromiumos/chromite/+/740871 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/097cb280beefc3c3255fdc97046abe19a3c634a3

commit 097cb280beefc3c3255fdc97046abe19a3c634a3
Author: Manoj Gupta <manojgupta@google.com>
Date: Tue Nov 07 01:26:20 2017

Package UnitTest Binaries in a tarball.

To enable fuzzing, package the unit tests artifacts in a tar ball.

BUG= chromium:776875 
TEST=buildbot + pre-cq testing -  Artifacts are uploaded. Chromite Unittests pass.

Change-Id: Ic135feed7a0d7ab20956c8bdca7a0cabf7c26e33
Reviewed-on: https://chromium-review.googlesource.com/740871
Commit-Ready: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/097cb280beefc3c3255fdc97046abe19a3c634a3/cbuildbot/stages/test_stages_unittest.py
[modify] https://crrev.com/097cb280beefc3c3255fdc97046abe19a3c634a3/lib/constants.py
[modify] https://crrev.com/097cb280beefc3c3255fdc97046abe19a3c634a3/lib/chroot_util.py
[modify] https://crrev.com/097cb280beefc3c3255fdc97046abe19a3c634a3/cbuildbot/commands.py
[modify] https://crrev.com/097cb280beefc3c3255fdc97046abe19a3c634a3/cbuildbot/stages/test_stages.py

UnitTest binaries are now uploaded.
https://pantheon.corp.google.com/storage/browser/chromeos-image-archive/amd64-generic-asan/R64-10105.0.0-b21855 -> unit_tests.tar

$ gsutil ls -l  gs://chromeos-image-archive/amd64-generic-asan/R64-10105.0.0-b21855/unit_tests.tar
6991759360  2017-11-07T03:25:59Z  gs://chromeos-image-archive/amd64-generic-asan/R64-10105.0.0-b21855/unit_tests.tar

Cool! I've download unit_tests.tar, and it seems to have a bunch of archive in bunch of folders. What should I do to run any tests?

This is what I am thinking:

1. Create a working sysroot for the binaries to put in.

amd64-generic-full builder ( https://uberchromegw.corp.google.com/i/chromiumos/builders/amd64-generic-full/ ) uploads a sysroot_chromeos-base_chromeos-chrome.tar.xz for chrome builds. Maybe that will work?

$ gsutil ls gs://chromeos-image-archive/amd64-generic-full/R64-10107.0.0-b20197|grep -e sysroot
gs://chromeos-image-archive/amd64-generic-full/R64-10107.0.0-b20197/sysroot_chromeos-base_chromeos-chrome.tar.xz

$ gsutil cp gs://chromeos-image-archive/amd64-generic-full/R64-10107.0.0-b20197/sysroot_chromeos-base_chromeos-chrome.tar.xz .
$ mkdir -p sysroot_dir
$ tar -Jxf sysroot_chromeos-base_chromeos-chrome.tar.xz -C sysroot_dir

2. Extract the unit test packages to the sysroot directory (since some packages may depend on others):

find . -iname "*.tbz2" -exec tar -C sysroot_dir -jxvf {} \;

3. sudo chroot sysroot_dir /path/to/uni_test ? (Maybe setting LD_LIBRARY_PATH is enough instead of running through chroot?)

Thanks for the instructions. I filed another bug for the pending actions items:  issue 785518 .