Kernel Events

Falco uses different instrumentations to analyze the system workload and pass security events to userspace. We usually refer to these instrumentations as syscall sources since the generated events are strictly related to the syscall context.

There are different supported syscall sources:

• Kernel module (default)
• eBPF probe
• Userspace instrumentation
• modern eBPF probe (experimental)

Kernel module

By default, the kernel module will be installed when installing the Falco debian/rpm package, when running the falco-driver-loader script shipped within the binary package, or when running the falcosecurity/falco-driver-loader docker image (that just wraps the aforementioned script).

To install the kernel module, please refer to the installation page.

eBPF probe

The eBPF probe is an alternative source to the one described above.

To install the eBPF probe, please refer to the installation page.

To enable the eBPF support in Falco set the FALCO_BPF_PROBE environment variable to an empty value (ie. FALCO_BPF_PROBE="", in this way Falco will search under $HOME/.falco directory for a file called falco-bpf.o) or otherwise explicitly set it to the path where the eBPF probe resides.

Userspace instrumentation

Differently from the other drivers, as the name suggests, userspace instrumentation happens 100% in userspace.

The Falco community, in 0.24.0 promoted the userspace instrumentation feature to official support to be included in Falco.

However, there's a difference between userspace instrumentation and the other drivers. At the moment of writing, the Falco project does not have any officially supported userspace instrumentation implementation.

To summarize: the code that defines the contracts to do userspace instrumentation in Falco itself is stable and under official support. While there's no implementation that reached the status of official support yet

The community is working on an implementation based on PTRACE(2) that you can find falcosecurity/pdig.

How to enable userspace instrumentation in Falco:

• Start Falco with the --userspace flag. This will tell Falco to look at userspace instrumentation instead of looking at the Kernel module (the default).
• Select the userspace instrumentation implementation you want to use (let's take pdig as it is the only one available now)
• Now, since pdig is still incubating - a very early stage - it's not included in our release process. This, for you, means that to install it, you will need to compile it yourself. Follow the instructions here.
• Now that you have pdig installed, you will need to start it. Remember, in the case of pdig, it does not know the root process tree you want to instrument by itself. You have to specify that via the -p flag or start the process with pdig itself. It's very similar to running a debugger against a binary. You can run a process directly using it or instrument an existing process. Full instructions here.

There are attempts at making the installation process easier, but the community didn't pick one yet and it's likely that many iterations will go into making any one of the below GA. However, here's a list of projects you can look at if you want to get Falco with userspace instrumentation in Kubernetes.

• Falco Trace - a convenient container image to use as a base to add userspace instrumentation to your images.
• Falco Inject - a tool that uses Falco Trace artifacts to inject Falco and userspace instrumentation into your containers via the Kubernetes API.

As you probably already understood, the userspace instrumentation drivers are a bit different, handle them with care!

Modern eBPF probe (experimental)

Falco 0.34 ships a new experimental driver: the modern eBPF Probe. It is experimental for 2 main reasons:

• It implements only ~80 syscalls. (The -A flag will not add further syscalls.)
• It is not production-proven like the kernel module and the current eBPF probe.

What's new

The modern probe will be embedded into Falco, which means that you don't have to download or build anything, if your kernel is recent enough Falco will automatically inject it!

The new probe is highly customizable, you are not obliged to use one buffer for each CPU you can also use just one huge buffer for all your CPUs! And obviously, also the buffer size is customizable! All this is possible thanks to new outstanding features like the CO-RE paradigm, the BPF ring buffer and many others, if you are curious you can read more about them in this blog post.

Requirements

1. A Linux kernel version >=5.8. Some features could also be backported into older kernels, so it wouldn't be completely fair to define the 5.8 as the first supported version, this is just a strict assumption that we put in place for this first release. If your kernel is older than 5.8 you should face this error:

   Error: Actual kernel version is: 'x.y.z' while the minimum required is: '5.8.0'
   

2. A kernel that exposes BTF. This shouldn't be a big issue since we already require a kernel version >=5.8 and most recent Linux distributions come with kernel BTF capabilities.

   If you want to be sure you can easily check their presence by typing:

   ls /sys/kernel/btf/vmlinux
   

   If your kernel supports them you should see:

   /sys/kernel/btf/vmlinux
   

How to run it

The modern eBPF probe supports all the installation methods of other drivers:

• Falco packages
• Falco binary
• Docker
• Helm chart

Useful resources

• Modern BPF blog post
• Modern BPF proposal
• Supported syscalls
• eBPF day presentation