---
title: "eBPF Programming for Observability"
description: "A comprehensive guide to using eBPF for system observability on Linux"
keywords: ["ebpf", "tracing", "observability", "bpftool", "libbpf"]
category: "linux"
---

The extended Berkeley Packet Filter (eBPF) is a powerful technology that allows running custom programs within the Linux kernel. eBPF provides several program types that can be leveraged for observability, including kprobes for tracing kernel functions, tracepoints for capturing kernel events, and XDP (eXpress Data Path) for high-performance packet processing. The bpftool utility (version 5.10) is a comprehensive command-line interface for managing eBPF programs and maps.

Compile-Once Run-Everywhere (CO-RE) is a feature in eBPF that enables writing portable eBPF programs using BTF (BPF Type Format) metadata, which describes the types and structures of the kernel. This allows eBPF programs to be compiled once and run on different kernel versions without recompilation. The libbpf library (version 0.7.0) provides a user-friendly API for loading and managing eBPF programs, including the ability to generate "skeleton" code to simplify program development.

eBPF programs can interact with in-kernel data structures called maps, which provide a variety of data storage types such as hash tables, arrays, and ring buffers. These maps allow eBPF programs to persist data and communicate between different eBPF programs or with user-space applications. The bpftrace tool (version 0.12.0) provides a high-level language for writing one-line eBPF observability scripts that leverage these maps.

Measuring the overhead of eBPF programs is crucial for ensuring they do not negatively impact system performance. The eBPF verifier enforces strict constraints on eBPF programs to ensure they are safe and efficient, including limitations on the number of instructions, memory access patterns, and use of kernel API calls. eBPF also provides a set of Linux Security Module (LSM) hooks that allow eBPF programs to integrate with the kernel's security subsystem for advanced monitoring and enforcement use cases.The eBPF kprobe program type allows tracing the entry and exit of kernel functions, providing visibility into the inner workings of the Linux kernel. Kprobes can be used to capture function arguments, return values, and other relevant data, enabling deep observability into kernel behavior. For example, the command `bpftool prog load kprobe/my_kprobe.bpf.o /sys/fs/bpf/my_kprobe` can be used to load a kprobe eBPF program named "my_kprobe" into the BPF file system.

Tracepoints are another eBPF program type that can be used for observability, allowing developers to instrument specific kernel events of interest. These tracepoints are pre-defined by the kernel and provide a stable interface for capturing data, making them a reliable choice for building observability tooling. The `bpftool prog list` command can be used to list all available tracepoints in the running kernel.

The XDP (eXpress Data Path) program type in eBPF enables high-performance packet processing within the Linux networking stack. XDP programs can be attached to network device drivers to perform tasks like packet filtering, load balancing, and telemetry at the earliest possible stage, minimizing the impact on overall system performance. The `tc` (Traffic Control) command can be used to attach an XDP program to a network interface, for example: `tc qdisc add dev eth0 clsact; tc filter add dev eth0 egress bpf da obj xdp_prog.o sec xdp`.

The BTF (BPF Type Format) metadata provided by the Linux kernel is essential for writing portable eBPF programs using the CO-RE (Compile-Once Run-Everywhere) approach. BTF describes the types, structures, and functions available in the kernel, allowing eBPF programs to access kernel data structures and APIs without relying on specific kernel version details. The `bpftool btf dump` command can be used to inspect the BTF information available in the running kernel.The libbpf library provides a user-friendly API for interacting with eBPF, simplifying the process of loading, managing, and communicating with eBPF programs. The libbpf "skeleton" feature generates boilerplate code for eBPF programs, handling the complex details of program loading, map creation, and event handling. This allows developers to focus on the core functionality of their eBPF observability tools, rather than the underlying mechanics. The libbpf library is actively maintained and provides comprehensive documentation, making it a popular choice for eBPF program development.

The bpftrace tool offers a high-level domain-specific language (DSL) for writing eBPF-based observability scripts. These one-liner scripts leverage the powerful capabilities of eBPF to capture and analyze system events, function calls, and other kernel-level data. bpftrace scripts can be used to quickly investigate performance issues, debug problems, and gain deep insights into the behavior of a running system. For example, the command `bpftrace -e 'tracepoint:syscalls:sys_enter_open { printf("%s(%s)\n", comm, str(args->filename)); }'` will trace all calls to the `open()` system call and print the process name and file path.

Measuring the overhead of eBPF programs is crucial to ensure they do not negatively impact system performance. The eBPF verifier enforces strict constraints on eBPF programs to ensure they are safe and efficient, including limitations on the number of instructions, memory access patterns, and use of kernel API calls. These constraints help prevent eBPF programs from causing kernel panics or other disruptive behavior. Developers can use tools like `bpftool prog test` to analyze the performance and resource usage of their eBPF programs before deploying them to production systems.

The eBPF Linux Security Module (LSM) hooks provide a powerful mechanism for integrating eBPF-based security and monitoring capabilities into the kernel. These hooks allow eBPF programs to intercept and inspect security-relevant events, such as file access, process execution, and network connections. By leveraging the eBPF LSM hooks, security teams can build advanced security monitoring and enforcement solutions that are deeply integrated with the Linux kernel, providing comprehensive visibility and control over system activities.The eBPF maps feature provides a flexible and efficient way for eBPF programs to store and share data. These in-kernel data structures come in various types, including hash tables, arrays, and ring buffers, each suited for different use cases. For example, a hash map can be used to track per-process metrics, while a ring buffer can be used to efficiently capture high-volume events for later analysis. eBPF programs can create, update, and query these maps using a dedicated set of system calls, allowing for powerful data-driven observability solutions.

The bpftool utility is a comprehensive command-line interface for managing eBPF programs and maps. With bpftool, users can list, load, and inspect eBPF programs, as well as create, update, and dump the contents of eBPF maps. This tool is essential for debugging, troubleshooting, and maintaining eBPF-based observability systems. For instance, the command `bpftool map dump name my_hash_map` can be used to inspect the contents of an eBPF hash map named "my_hash_map".

In addition to the built-in eBPF program types, the libbpf library provides a set of helper functions and abstractions that simplify the development of eBPF-based observability tools. The libbpf "skeleton" feature generates boilerplate code for eBPF programs, handling the complex details of program loading, map creation, and event handling. This allows developers to focus on the core functionality of their observability solutions, rather than the underlying eBPF mechanics. The libbpf library is actively maintained and provides comprehensive documentation, making it a popular choice for eBPF program development.