Observing the Linux Kernel with eBPF

Before eBPF, getting deep visibility into the Linux kernel was a high risk operation. You either wrote a custom kernel module that could easily panic the server, or you patched the kernel source and recompiled the operating system.

In my work building container platforms, eBPF has changed how we trace system calls and route packets. It runs sandboxed code inside the kernel in response to system events, providing low latency observation and networking without the risk of system crashes.

How it works

At its core, eBPF allows developers to write C or Go code, compile it to eBPF bytecode, and load it directly into the kernel.

The magic happens in two places:

1. The Kernel Verifier: Before any code executes, the verifier reads the bytecode to guarantee safety. It checks that the program has no infinite loops, cannot access out of bounds memory, and terminates safely. If the verifier is not happy, the program does not run.
2. Dynamic Hooking: Once verified, the program attaches to specific kernel hooks. These can be system calls, tracepoints, network socket events, or kernel probes (kprobes).

This architecture allows us to run custom logic in kernel space without risking the stability of the entire system.

Why eBPF matters in production

Safety by design

If a traditional kernel module has a null pointer dereference, the machine crashes. With eBPF, the verifier catches these issues before the code ever runs. We get kernel level access with user space safety.

Zero context switches

Traditional observability tools poll system state from user space, requiring constant context switching between user space and kernel space. eBPF runs directly in the kernel, processing events as they happen and only sending aggregated metrics back up to user space. This keeps CPU overhead extremely low, even under heavy network load.

Dynamic system tracing

We can attach and detach programs on the fly. If you are debugging a socket leak or tracking down slow filesystem operations, you can load a bpftrace script, collect the data, and detach it without rebooting the server or disrupting running processes.

Real world orchestration

In modern Kubernetes environments, eBPF is moving from a debugging tool to a core infrastructure layer.

• Networking with Cilium: Traditional Kubernetes network policies rely on iptables, which processes rules sequentially. As clusters grow, iptables performance degrades. Cilium bypasses iptables entirely, using eBPF to route packets directly between container sockets.
• Runtime security with Falco: By hooking into system calls, Falco detects unexpected container behavior—like a shell running inside a pod or a process modifying a system binary—directly at the kernel layer, before the event can cause damage.
• Observability with Hubble: Instead of injecting sidecar proxies to capture network traces, Hubble uses eBPF to observe traffic at the kernel level, giving us complete visibility into HTTP, gRPC, and TCP flows with near zero impact on performance.