The project aims to illustrate how to construct RISV-V toolchains for developers. In the following steps, We first prepare a ChroimumOS develop environment, replace overlays with our private overlays to build basic cross compilers in Gentoo chroot. Finally, build ChroimumOS packages in RISC-V by cross compilers.

Known issue: Chromium can't be built successfully.

System requirement:

OS Ubuntu Linux 18.04 LTS

200G free disk space

32G RAM

Stable network

Typography conventions

Shell Commands are shown with different labels to indicate whether they apply to

• your build computer (the computer on which you're doing development)
• the chroot (Chromium OS SDK) on your build computer
• your Chromium OS computer (the device on which you run the images you build)

Label	Commands
(outside)	on your build computer, outside the chroot
(inside)	inside the chroot on your build computer

Install necessary tools

Git and curl as the essential tools that need to be installed in the host OS, you will also need Python3 for most of the scripting work in the build process.

(outside)
sudo apt-get install git-core gitk git-gui curl lvm2 thin-provisioning-tools \
     python-pkg-resources python-virtualenv python-oauth2client xz-utils \
     python3.6

# If Python 3.5 is the default, switch it to Python 3.6.
python3 --version
# If above version says 3.5, you'll need to run:
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.5 1
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.6 2
sudo update-alternatives --config python3

This command also installs git's graphical front end (git gui) and revision history browser (gitk).

Install Google depot_tools

The depot_tools is a package of useful scripts, provided by Google, to manage source code checkouts and code reviews. We need it to fetch the Chromium OS source code.

(outside)
$ sudo mkdir -p /usr/local/repo
$ sudo chmod 777 /usr/local/repo
$ cd /usr/local/repo
$ git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git

Then add the depot_tools directory to PATH and set up proper umask for the user who is going to perform the build. Add below lines to the file ~/.bash_profile of that user. Or if you are using a different shell, handle that accordingly.

(outside)
export PATH=/usr/local/repo/depot_tools:$PATH
umask 022

Then re-login to your shell session to make the above changes take effect.

Configure git

You should configure git now or it may complain in some operations later.

(outside)
$ git config --global user.email "you@email.address"
$ git config --global user.name "Your Name"

Get source code

The directory structure described here is a recommendation based on the best practice in the Fyde Innovations team. You may host the files in a different way as you wish.

(outside)
# This is the directory to hold Chromium OS source code， aka cros-sdk
$ mkdir -p r96 

Fetch Chromium OS repo

First, you need to find out the reference name of the release you would like to build, by visiting this page https://chromium.googlesource.com/chromiumos/manifest.git:

You will see a list of git commit IDs and its name in the form of refs/heads/release-Rxx-xxxx.B. That release-Rxx-XXXX.B link is what you need for fetching the code of that specific Chromium OS release. For example, release-R96-14268.B for release r96.

Now run these commands to fetch the source code. Find and use a different release name if you would like to build a different release.

(outside)
$ cd r96

$ repo init -u https://chromium.googlesource.com/chromiumos/manifest.git --repo-url https://chromium.googlesource.com/external/repo.git -b release-R96-14268.B

$ repo sync -j4 -vvv

$ git clone https://github.com/FydeOS/chromium_os-riscv64

$ ln -snfr chromium_os-riscv64/private-overlays src/private-overlays

Fetch Chromium code

$ cd r96

$ mkdir chromium

$ cd chromium

$ git clone https://github.com/chromium/chromium.git src -b 96.0.4664.118

$ git clone https://github.com/openFyde/dotgclient.git -b chromium

$ ln -sf dotgclient/dotgclient .gclient

$ gclient sync --force

Applying patches

$ cd r96/src/third_party/breakpad/src/third_party/lss

$ patch < r96/chromium_os-riscv64/private-overlays/third_party-lss.patch

$ cd r96/chromite

$ patch -p1 < ../src/private-overlays/chromium_host_patches/chromite*

$ cd r96/src/scripts

$  patch -p1 < ../private-overlays/chromium_host_patches/src-script-root-layout.patch

$ cd r96/src/third_party/portage-stable

$ patch -p1 < ../../private-overlays/chromium_host_patches/portage-stable-arch.patch

$ cd r96/src/third_party/chromiumos-overlay

$ patch -p1 < ../../private-overlays/chromium_host_patches/chromiumos*patch

Create chroot

$ cd r96
$ cp chromium_os-riscv64/bin/setup_board.sh src/scripts/
$ cros_sdk --nouse-image   --chrome-root $(realpath chromium)

Then you will see the shell prompt looks like:

(cr) (release-R96-14268.B/(f993911...)) foo@bar ~/chromiumos/src/scripts $

Prepare cross-compilers and build packages(inside)

# download necessary binary tools from google sites
~/chromiumos/src/scripts $ setup_board --board=amd64-generic


~/chromiumos/src/scripts $ ./setup_board.sh --board=jh7100


~/chromiumos/src/scripts $ ./build_packages --board=jh7100 --nowithautotest --autosetgov

Finally, We will error out when building chromeos-chrome:

[2602/71915] ACTION //chromeos/services/nearby/public/mojom:nearby_share_target_types__generate_message_ids(//build/toolchain/cros:targe
[2639/71915] ACTION //chrome/browser/ui/webui/settings/chromeos/search:mojo_bindings__generate_message_ids(//build/toolchain/cros:target
[2675/71915] ACTION //chrome/browser/ui/webui/settings/chromeos/search:mojo_bindings__generate_message_ids(//build/toolchain/cros:target
[2688/71915] LINK ./chrome_sandbox
chromeos-chrome-96.0.4664.72_rc-r1: FAILED: chrome_sandbox
chromeos-chrome-96.0.4664.72_rc-r1: python3 "../../../../../../../home/yue/chrome_root/src/build/toolchain/gcc_link_wrapper.py" --output
="./chrome_sandbox" -- riscv64-cros-linux-gnu-clang++ -fuse-ld=lld -Wl,--fatal-warnings -Wl,--build-id=sha1 -fPIC -Wl,-z,noexecstack -Wl
,-z,relro -Wl,-z,now -Wl,--icf=all -Wl,--color-diagnostics -Wl,-mllvm,-instcombine-lower-dbg-declare=0 -flto=thin -Wl,--thinlto-jobs=all
 -Wl,--thinlto-cache-dir=thinlto-cache -Wl,--thinlto-cache-policy=cache_size=10\%:cache_size_bytes=40g:cache_size_files=100000 -Wl,-mllv
m,-import-instr-limit=30 -fwhole-program-vtables -Wl,--no-call-graph-profile-sort --target=rv64gc -Wl,-melf64lriscv -mabi=lp64d -no-cano
nical-prefixes -Werror -Wl,-O2 -Wl,--gc-sections -Wl,--gdb-index --sysroot=../../../../../../../build/jh7100 -Wl,--lto-O0 -Wl,-z,defs -W
l,--as-needed -fsanitize=cfi-vcall -fsanitize=cfi-derived-cast -fsanitize=cfi-unrelated-cast -pie -Wl,--disable-new-dtags -Wl,-O2 -Wl,--
as-needed -Wl,--gc-sections -Wl,-mllvm -Wl,-generate-type-units -stdlib=libc++  -o "./chrome_sandbox" -Wl,--start-group @"./chrome_sandb
ox.rsp"  -Wl,--end-group  -ldl -lpthread -lrt
chromeos-chrome-96.0.4664.72_rc-r1: ld.lld: error: thinlto-cache/Thin-09d9bc.tmp.o: cannot link object files with different floating-poi
nt ABI
chromeos-chrome-96.0.4664.72_rc-r1: ld.lld: error: thinlto-cache/Thin-e1e979.tmp.o: cannot link object files with different floating-poi
nt ABI

workarounds(inside)

minijail/gobject-introspection

If build_packages stops due to failure of minijail/gobject-introspection. Run sudo USE="qemu_user_targets_riscv64 qemu_softmmu_targets_riscv64" emerge qemu then call emerge-7100 minijail/gobject-introspection.

Miscellaneous things

You may see the following issue because that the package::chromiumos is newer than packgae::arch-riscv. Here assume the package is attestation.

- Messages for package sys-apps/util-linux-2.36.2-r2:
- Log file: /var/log/portage/sys-apps:util-linux-2.36.2-r2:20220419-075948.log
- The mesg/wall/write tools have been disabled due to USE=-tty-helpers.
- Messages for package chromeos-base/attestation-0.0.1-r3305 merged to /build/jh7100/:
- Log file: /build/jh7100/tmp/portage/logs/chromeos-base:attestation-0.0.1-r3305:20220419-080115.log
- ERROR: chromeos-base/attestation-0.0.1-r3305::chromiumos failed (install phase):
- !!! newins: server/attestationd-seccomp-riscv.policy does not exist *
- Build log: /build/jh7100/tmp/portage/logs/chromeos-base:attestation-0.0.1-r3305:20220419-080115.log * Stable log symlink: /build/jh7100/tmp/portage/chromeos-base/attestation-0.0.1-r3305/temp/build.log
- CWD: /build/jh7100/tmp/portage/chromeos-base/attestation-0.0.1-r3305/work/attestation-0.0.1/attestation
- S: /build/jh7100/tmp/portage/chromeos-base/attestation-0.0.1-r3305/work/attestation-0.0.1/attestation
16:02:21 ERROR : Tue Apr 19 04:02:21 PM CST 2022

Find the package in our private-overlays:

(cr) (release-R96-14268.B/(f993911...)) ~/chromiumos/src/scripts $ find ../private-overlays/project-arch-riscv/ -name attestation
../private-overlays/project-arch-riscv/chromeos-base/attestation

Just add the package name attestation to ../private-overlays/project-arch-riscv/profiles/base/package.mask then call emerge-jh7100 attestation.