The main BTFhub repository serves as a comprehensive resource, housing documentation, tools, and examples to guide users on how to leverage the BTF files effectively. However, the actual BTF files are stored separately in the BTFhub-Archive repository. This separation ensures a clean and organized structure, with each repository focusing on its designated role.

What is BTF ?

The Extended Berkeley Packet Filter (eBPF) is esteemed for its portability, a primary attribute of which is due to the BPF Type Format (BTF). More details about BTF can be discovered in this comprehensive guide.

Before the advent of Compile Once-Run Everywhere (CO-RE), developers working with eBPF had to compile an individual eBPF object for each kernel version they intended to support. This stipulation led toolkits, such as iovisor/bcc, to depend on runtime compilations to handle different kernel versions.

However, the introduction of CO-RE facilitated a significant shift in eBPF portability, allowing a single eBPF object to be loaded into multiple differing kernels. This is achieved by the libbpf loader, a component within the eBPF's loader and verification architecture. The libbpf loader arranges the necessary infrastructure for an eBPF object, including eBPF map creation, code relocation, setting up eBPF probes, managing links, handling their attachments, among others.

Here's the technical insight: both the eBPF object and the target kernel contain BTF information, generally embedded within their respective ELF (Executable and Linkable Format) files. The libbpf loader leverages this embedded BTF information to calculate the requisite changes such as relocations, map creations, probe attachments, and more for an eBPF object. As a result, this eBPF object can be loaded and have its programs executed across any kernel without the need for object modification, thus enhancing portability.

BTFHUB

Regrettably, the BPF Type Format (BTF) wasn't always readily available. This can be attributed to either a lack of kernel support or the absence of userland tools capable of interpreting the BTF format. As a result, certain Linux distributions ended up releasing kernels without embedded BTF information.

This is the precise reason behind the existence of BTFhub. BTFhub's primary function is to supply BTF information for those Linux kernels that were released by distributions without this information embedded. Instead of requiring you to recompile your eBPF code for each existing Linux kernel that lacks BTF support, your code will be relocated by libbpf based on the available BTF information fetched from BTFhub's files.

The libbpf's support for external (raw) BTF files, which started with this commit, enables us to supply libbpf with an external BTF file corresponding to the kernel you intend your eBPF code to run on. It's important to note that each kernel requires its unique BTF file.

Please note that BTFhub's use is not universally necessary. If your intent is to support your eBPF CO-RE application solely on the most recent kernels, you will not need BTFhub. However, if you aim to support all released kernels, which include versions from some Long Term Support Linux distributions, then BTFhub may prove to be an indispensable resource.

Supported Kernels and Distributions

This is a list of existing distributions and their current status on eBPF and BTF supportability over their kernel versions.

It is highly recommended that you update to your latest distribution's kernel version in order to use eBPF latest available features.

In the tables bellow you will find BPF, BTF and HUB columns:

• BPF - kernel has support for BPF programs (with or without embedded BTF info)
• BTF - kernel is compiled with DEBUG_INFO_BTF (/sys/kernel/btf/vmlinux avail)
• HUB - there is a 1:1 kernel <-> BTF file available in this hub

Alma

Alma	RHEL	Release Date	RHEL Date	Kernel	BPF	BTF	HUB
8.3	8.3	2021-03-30	2020-11-03	4.18.0-240	Y	Y	-
8.4	8.4	2021-05-26	2021-05-18	4.18.0-305	Y	Y	-
...	...	...	...	...	Y	Y	-

Note: ALL Alma releases have BPF & BTF support enabled!

Amazon Linux

Amazon Linux 1/2018

Amazon	Release Date	Kernel	BPF	BTF	HUB
2018	2018-03-01	4.14.26	Y	-	Y

Amazon Linux 2

Amazon	Release Date	Kernel	BPF	BTF	HUB
2	2018-09-25	4.14.33	Y	-	Y

CentOS and RHEL

CentOS 7 / RHEL 7

Centos	RHEL	Release Date	RHEL Date	Kernel	BPF	BTF	HUB
7.0.1406	7.0	2014-07	2014-06-09	3.10.0-123	-	-	Y
7.1.1503	7.1	2015-03	2015-03-05	3.10.0-229	-	-	Y
7.2.1511	7.2	2015-11	2015-11-19	3.10.0-327	-	-	Y
7.3.1611	7.3	2016-11	2016-11-03	3.10.0-514	-	-	Y
7.4.1708	7.4	2017-08	2017-07-31	3.10.0-693	-	-	Y
7.5.1804	7.5	2018-04	2018-04-10	3.10.0-862	-	-	Y
7.6.1810	7.6	2018-10	2018-10-30	3.10.0-957	Y	-	Y
7.7.1908	7.7	2019-08	2019-08-06	3.10.0-1062	Y	-	Y
7.8.2003	7.8	2020-03	2020-03-31	3.10.0-1127	Y	-	Y
7.9.2009	7.9	2020-09	2020-09-29	3.10.0-1160	Y	-	Y

Note: Latest centos7 kernels support BPF, and might support BTF, but they lack some eBPF features. With that, eBPF programs capable of running in those systems are very limited.

Check out eBPF features your code use HERE

CentOS 8 / RHEL 8

Centos	RHEL	Release Date	RHEL Date	Kernel	BPF	BTF	HUB
8.0.1905	8.0	2019-09-24	2019-05-07	4.18.0-80	-	-	Y
8.1.1911	8.1	2020-01-15	2019-11-05	4.18.0-147	-	-	Y
8.2.2004	8.2	2020-06-15	2020-04-28	4.18.0-193	Y	Y	Y
8.3.2011	8.3	2020-12-07	2020-11-03	4.18.0-240	Y	Y	Y
8.4.2105	8.4	2021-06-03	2021-05-18	4.18.0-305	Y	Y	Y
...	...	...	...	...	Y	Y	Y

Note: ALL latest CentOS 8 releases have BPF & BTF support enabled!

CentOS Stream 8 / RHEL Stream 8

Stream	RHEL	Release Date	RHEL Date	Kernel	BPF	BTF	HUB
8.3	8.3	2021-01-14	2020-11-03	4.18.0-240	Y	Y	-
8.4	8.4	2021-01-14	2020-11-03	4.18.0-240	Y	Y	-

Note: ALL CentOS Stream 8 releases have BPF & BTF support enabled

Debian

Debian	Release Date	Kernel	BPF	BTF	HUB
9 (Stretch)	2017-06-17	4.9.0	Y	-	Y
10 (Buster)	2019-07-06	4.19.0	Y	-	Y
11 (Bullseye)	2021-08-14	5.10.0	Y	Y	-

Fedora

Fedora	Release Date	Kernel	BPF	BTF	HUB
29	2018-10-30	4.18			Y
30	2019-05-07	5.0			Y
31	2019-10-29	5.3			Y
32	2020-04-28	5.6	Y	Y	-
33	2020-10-27	5.8	Y	Y	-
34	2021-04-27	5.11	Y	Y	-
...	-	-	Y	Y	-

Note: All supported future Fedora releases will have BPF & BTF support enabled.

OpenSUSE Leap

OpenSUSE Leap	Release Date	Kernel	BPF	BTF	HUB
15.0	2018-05-25	4.12.14	Y	-	Y
15.1	2019-05-22	4.12.14	Y	-	Y
15.2	2020-07-02	5.3.18	Y	-	Y
15.3	2021-06-02	5.3.18	Y	-	Y
15.4	2022-06-08	5.14.21	Y	Y	-
...	...	...	Y	Y	-

Oracle Linux

Oracle	Release Date	RH Kernel	UEK Kernel	BPF	BTF	HUB
7.8	2020-04-08	3.10.0-1127	4.14.35-1902.300.11	Y	-	Y
7.9	2020-10-07	3.10.0-1160	5.4.17-2011.6.2	Y	-	Y
8.2	2020-05-06	4.18.0-193	5.4.17-2011.1.2	Y	-	Y
8.3	2020-11-13	4.18.0-240	5.4.17-2011.7.4	Y	-	Y
8.4	2021-05-26	4.18.0-305	5.4.17-2102.201.3	Y	-	Y
...	...	...	...	Y	Y	-

SUSE Linux Enterprise Server (SLES)

SLES	Release Date	Kernel	BPF	BTF	HUB
12.3	2017-09-17	4.4.73-5	Y	-	Y
12.4	2018-12-11	4.12.14-94.41	Y	-	Y
12.5	2019-12-09	4.12.14-120	Y	-	Y
15.0	2018-07-16	4.12.14-23	Y	-	Y
15.1	2019-06-24	4.12.14-195	Y	-	Y
15.2	2020-07-21	5.3.18-22	Y	-	Y
15.3	2021-06-23	5.3.18-57	Y	-	Y
15.4	2022-06-24	5.14.21-150400.22	Y	Y	-
...	...	...	Y	Y	-

Ubuntu

Ubuntu Ver	Num	Release Date	Kernel	BPF	BTF	HUB
Xenial	16.04.2	2016-04-21	4.4.0	Y	-	Y
Xenial HWE	-	-	4.15.0	Y	-	Y
Bionic	18.04.2	2018-04-26	4.15.0	Y	-	Y
Bionic	-	-	4.18.0	Y	-	Y
Bionic HWE	-	-	5.4.0	Y	-	Y
Focal	20.04.2	2020-04-23	5.4.0	Y	-	Y
Focal HWE	-	-	5.8.0	Y	-	Y
Groovy	20.10	2020-10-22	5.8.0	Y	Y	-
Groovy HWE	20.10	-	5.11.0	Y	Y	-
Hirsute	21.04	2021-04-22	5.11.0	Y	Y	-
...	...	...	...	Y	Y	-

Notes: Bionic HWE, Focal and Focal HWE kernels need this HUB. All other future Ubuntu releases will have BPF & BTF support enabled.