Getting started

Dependencies

  • rust: install through your package manager or with rustup:

    $ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
$ source "$HOME/.cargo/env"

  • udev and llvm: Check the .gitlab-ci.yml for FEDORA_PACKAGES.

Building all files

Clone the repo, cd into it, and build the loader and the various example HID-BPF programs using a standard meson build process:

$ git clone https://gitlab.freedesktop.org/libevdev/udev-hid-bpf.git
$ cd udev-hid-bpf/
$ meson setup builddir
$ meson compile -C builddir

The above meson commands will build the tool and any BPF programs it finds in src/bpf/*.bpf.c. Please see the meson documentation for more details on invoking meson.

Install all files

Note

The default meson invocation only installs the “testing” .bpf.o files (see here).

We can install the binary with the following command:

$ meson install -C builddir
# this will ask for your sudo password to install udev rules and hwdb files

The above command will (re)build the tool and any BPF programs it finds in src/bpf/*.bpf.c. It will then install

  • the tool itself into in /usr/local/bin

  • the compiled BPF objects in /usr/local/lib/firmware/hid/bpf.

  • a hwdb entry to tag matching devices in /etc/udev/hwdb.d/81-hid-bpf.hwdb

  • a udev rule to trigger the tool in /etc/udev/rules.d/81-hid-bpf.rules

Passing the –prefix option to meson setup will of course change the above paths.

Install a specific bpf.o file only

In many cases a user only wants to install a single file for testing. The easiest approach is to use udev-hid-bpf to install it:

$ ./builddir/udev-hid-bpf install ./builddir/src/bpf/userhacks/my_awesome_hid_bpf_filter.bpf.o
# or to install udev-hid-bpf itself too
$ ./builddir/udev-hid-bpf install --install-exe ./builddir/src/bpf/userhacks/my_awesome_hid_bpf_filter.bpf.o

This will install the .bpf.o file into /etc/udev-hid-bpf/ and also install a custom udev rule udev for this file. If --install-exe is given, udev-hid-bpf will also install itself in the given prefix’s bindir (/usr/local/bin by default) if required.

Running the BPF program

Once installed, unplug/replug any supported device, and the BPF program will automatically be attached to the HID kernel device.