v0idmatr1x / bpftool

Automated upstream mirror for bpftool stand-alone build.

This is the official home for bpftool. Please use this Github repository for building and packaging bpftool and when using it in your projects through Git submodule.

The authoritative source code of bpftool is developed as part of the bpf-next Linux source tree under the tools/bpf/bpftool subdirectory and is periodically synced to https://github.com/libbpf/bpftool on Github. As such, all changes for bpftool should be sent to the BPF mailing list, please don't open PRs here unless you are changing some Github-specific components.

Questions on bpftool and BPF general usage

Check out the manual pages for documentation about bpftool. A number of example invocations are also displayed in this blog post.

All general BPF questions, including kernel functionality, bpftool features and usage, should be sent to [email protected] mailing list. You can subscribe to it here and search its archives here.

The mailing list is monitored by many more people than this repo and they will happily try to help you with whatever issue you encounter. This repository's PRs and issues should be opened only for dealing with issues related to components specific to the bpftool mirror repository (such as the synchronization script or the CI workflows). The project maintainers also use GitHub issues as a generic tracker for bpftool, but issues should first be reported on the mailing list nonetheless.

Dependencies

Required:

• libelf
• zlib

Optional:

• libbfd (for dumping JIT-compiled program instructions)
• libcap (for better feature probing)
• kernel BTF information (for profiling programs or showing PIDs of processes referencing BPF objects)
• clang/LLVM (idem)

Build

Initialize libbpf submodule

This repository uses libbpf as a submodule. You can initialize it when cloning bpftool:

$ git clone --recurse-submodules https://github.com/libbpf/bpftool.git

Alternatively, if you have already cloned the repository, you can initialize the submodule by running the following command from within the repository:

$ git submodule update --init

Build bpftool

To build bpftool:

$ cd src
$ make

To build and install bpftool on the system:

$ cd src
# make install

Building bpftool in a separate directory is supported via the OUTPUT variable:

$ mkdir /tmp/bpftool
$ cd src
$ OUTPUT=/tmp/bpftool make

Most of the output is suppressed by default, but detailed building logs can be displayed by passing V=1:

$ cd src
$ make V=1

Additional compilation flags can be passed to the command line if required. For example, we can create a static build with the following commands:

$ cd src
$ EXTRA_CFLAGS=--static make

Note that to use the LLVM disassembler with static builds, we need a static version of the LLVM library installed on the system:

1. Download a precompiled LLVM release or build it locally.

   • Download the appropriate release of LLVM for your platform, for example on x86_64 with LLVM 15.0.0:

     $ curl -LO https://github.com/llvm/llvm-project/releases/download/llvmorg-15.0.0/clang+llvm-15.0.0-x86_64-linux-gnu-rhel-8.4.tar.xz
     $ tar xvf clang+llvm-15.0.0-x86_64-linux-gnu-rhel-8.4.tar.xz
     $ mv clang+llvm-15.0.0-x86_64-linux-gnu-rhel-8.4 llvm_build

   • Alternatively, clone and build the LLVM libraries locally.

     $ git clone https://github.com/llvm/llvm-project.git
     $ mkdir llvm_build
     $ cmake -S llvm-project/llvm -B llvm_build -DCMAKE_BUILD_TYPE=Release
     $ make -j -C llvm_build llvm-config llvm-libraries

2. Build bpftool with EXTRA_CFLAGS set to --static, and by passing the path to the relevant llvm-config.

   $ cd bpftool
   $ LLVM_CONFIG=../../llvm_build/bin/llvm-config EXTRA_CFLAGS=--static make -j -C src

Build bpftool's man pages

The man pages for bpftool can be built with:

$ cd docs
$ make

They can be installed on the system with:

$ cd docs
# make install

bpf-next to GitHub sync

This repository mirrors bpf-next Linux source tree's tools/bpf/bpftool directory, plus its few dependencies from under kernel/bpf/, and its supporting header files. Some of these header files, include/linux/*.h on the current repository, are reduced versions of their counterpart files at bpf-next's tools/include/linux/*.h to make compilation successful.

Synchronization between the two repositories happens every few weeks or so. Given that bpftool remains aligned on libbpf's version, its repository tends to follow libbpf's. When the libbpf repo syncs up with bpf-next, bpftool's repo usually follows within the next few days.

The synchronization process is semi-automated: the script in scripts/sync-kernel.sh cherry-picks, adjusts and commits all changes from bpf-next to a local version of the bpftool repository. However, maintainers run this script manually and then create a pull request to merge the resulting commits.

Take a look at the script for the technical details of the process. See also the documentation in the accompanying README.md

License

This work is dual-licensed under the GNU GPL v2.0 (only) license and the BSD 2-clause license. You can select either of them if you reuse this work.

SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)