The embedded controller (EC) is a UP5K FPGA responsible for secondary power management functions, and for intermediating between the trusted comms port on the SoC and the untrusted wifi stack.
From the strict security model, the EC is in the untrusted domain, and the core SoC must be robust against arbitrary remote exploits in the EC.
Compiled documentation: latest register set, latest rust API documentation
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Ensure you have a toolchain installed, including a compiler, Python 3.5+,
nextpnr-ice40, andyosys. These can all be obtained by downloading the Fomu toolchain and adding it to yourPATH. Note that the latest release of the toolchain does not work because the synthesis adds extra logic, causing the design to not fit. -
Install the xpack riscv toolchain
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Check out this repo with
git clone --recurse-submodules <repo>. It will consume ~800MiB of disk space (sorry!). -
Run
./betrusted_ec.py --revision=pvt(orpython3 ./betrusted_ec.py --revision=pvt) to build the "PVT" version of the EC -
Run
cargo xtask copy-precursorsto copy your newly built CPU to the staging area for firmware images -
(Optional) Run
cargo xtask docsto create an HTML document tree of all the CPU registers
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Ensure that you have a toolchain installed, including a gcc compiler and Rust. gcc is necessary to handle the FFI bindings.
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Run
cargo xtask hw-imageto build the burnable ROM image artifacts
When using the USB method, you either must trigger the update by bumping the semantic version
of the gateware and the firmware, or you need to rebuild xous.img with the custom argument
--feature=dbg-ecupdate to unlock the shellchat ecup command which allows you to force an
update, even if it is a downgrade. Once that is set up:
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Copy the resulting
ec_fw.binfile to a location where you can run the usb_update.py -
Plug in the device to the host that can run the script
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Execute
usb_update.py -e path-to/ec_fw.bin
Alternatively:
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Run
cargo xtask push <target> [idfile]to push the files to a Raspberry Pi with a debug hat for burning.idfileis the ssh ID file if you use one. -
On the Raspberry Pi, run
config_up5k.shfrom thebetrusted-scriptsrepo as explained below.
Serial output from the EC can be viewed over the debugging cable via the Precursor debug HAT. See instructions on installing the cable.
The EC UART port is selected by running the betrusted-scripts/uart_up5k.sh script.
You will need some terminal program to interact with the EC. One such program
is screen, for example, on a Raspberry Pi 3B+ you could run
sudo screen -fn /dev/ttyS0 115200 and access the EC UART after switching
to the UART port.
Note that varying generations and releases of Raspberry
Pi put the UART on either ttyS0 or AMA0, and you may need to run
raspi-config to enable serial ports first.
The EC image is intimately linked to the WF200 firmware image that is
presumed to be burned into the FLASH memory. Please consult hal_wf200.rs
for WFX_FIRMWARE_OFFSET and WFX_FIRMWARE_SIZE. In particular, when
updating the firmware, the WFX_FIRMWARE_SIZE parameter should also be
updated.
If you must update the bindings, you will need to be able to run bindgen.
Install it by doing something like this:
sudo apt install llvm-dev libclang-dev clang
sudo apt install gcc-multilib
cargo install bindgen-cliTo update the repo to the upstream version, including all dependencies, run:
git pull
git submodule update --recursivelxbuildenv is a Python module. It sets up the build environment and ensures you have the correct dependencies. To use it, start your program off with:
#!/usr/bin/env python3
import lxbuildenvlxbuildenv.py has some very surprising behaviors that you should be aware of:
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In order to set environment variables such as
PYTHONHASHSEED,lxbuildenvwill actually re-exec the Python interpreter. This will, among other things, cause the pid to change. This is why lxbuildenv should be imported first. -
The environment variable
PYTHONPATHis replaced to include every directory underdeps/. If you rely onPYTHONPATHto be something else, this may surprise you. -
lxbuildenvhas several command line parameters that it can accept. To display these, run your command with the--lx-helpparameter. -
The
deps/directory includes its ownsite.pyimplementation, adapted from a Debian implementation. This is because some distros force/usr/share/python/site-packages/to be first in the dependency list, which causes confusing dependency interactions. If you’re relying on site packages being in a certain order, this may cause problems. You can try deletingdeps/site/in order to disable this behavior.
In exchange for some deviation from other build environments, lxbuildenv gives you several benefits that come in handy for hardware projects:
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Python dicts enumerate in constant order, giving some consistency to build results.
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You will probably be modifying code in the dependencies. By keeping them inside the project directory, this becomes much simpler.
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Additionally, all dependencies remain under version control, which you would otherwise lose when installing dependencies as packages.
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Hardware, moreso than software, depends on exact version numbers. By using
gitto track dependency versions, this build becomes more reproducible. -
It is cross-platform, and works anywhere Xilinx does.
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The
lxbuildenvenvironment doesn’t rely on opaque environment variables, or otherwise have a special environment you enter. Everything is documented behind--helpflags.
Dependencies are managed through git, and managing their usage is largely an exercise
in working with git.
For example, if you would like to make a change to litex, go into deps/litex and checkout
a new branch and create a new upstream repo. If you’re working on Github, you would do
something like fork the repo to your own organization.
As an example, assume sutajiokousagi has forked upstream litex:
$ cd deps/litex
$ git checkout -b new-feature
$ git remote add kosagi git@github.com:sutajiokousagi/litex.git
$ cd -Then, make changes to deps/litex as needed.
When you want to merge changes upstream, go into deps/litex/ and push the branch to your remote:
$ cd deps/litex
$ git push kosagi new-feature
$ cd -Then you can go and open a Pull Request on Github.
Dependencies are designed to be independent, and you should update them as needed. To update a particular
dependency, go into that dependency’s subdirectory and run git pull. You may also find it easier to
pull updates from a particular dependency and merge them. For example, if you’re working on the new-feature
branch of litex and want to pull changes from upstream, run:
$ cd deps/litex
$ git fetch origin
$ git merge master
$ cd -This will merge all changes from upstream onto your own branch.
To use PyCharm, open this directory as a Project by going to the File menu and selecting Open…. Make sure you open the entire directory, and not just a single file in this directory.
When you first open this project, you’ll see lots of red squiggly lines indicating errors. PyCharm needs to know about the dependency structure in order to allow you to drill down into modules and auto-complete statements.
Open this directory in PyCharm and expand the deps/ directory. Then hold down Shift and select all subdirectories under deps/. This will include litedram, liteeth, and so on.
Then, right-click and select Mark directory as… and select Sources Root. The red squiggly lines should go away, and PyCharm should now be configured.
When running your module from within PyCharm, you may find it useful to set environment variables. You can use the --lx-print-env command. For example: ./betrusted-ec.py --lx-print-env > pycharm.env to create a .env-compatible file. There are several PyCharm plugins that can make use of this file.
Visual Studio Code needs to know where modules are. These are specified in environment variables, which are automatically read from a .env file in your project root. Create this file to enable pylint and debugging in Visual Studio Code:
$ python ./betrusted-ec.py --lx-print-env > .env[](CODE_OF_CONDUCT.md)
Please see [CONTRIBUTING](CONTRIBUTING.md) for details on how to make a contribution.
Please note that this project is released with a [Contributor Code of Conduct](CODE_OF_CONDUCT.md). By participating in this project you agree to abide its terms.
Copyright © 2019
Licensed under the [CERN OHL v1.2](https://ohwr.org/project/licenses/wikis/cern-ohl-v1.2) [LICENSE](LICENSE)