mirror of
https://gitee.com/openharmony/third_party_libbpf
synced 2024-10-07 22:43:33 +00:00
156 lines
6.4 KiB
Markdown
156 lines
6.4 KiB
Markdown
BPF/libbpf usage and questions
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==============================
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Please check out [libbpf-bootstrap](https://github.com/libbpf/libbpf-bootstrap)
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and [the companion blog post](https://nakryiko.com/posts/libbpf-bootstrap/) for
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the examples of building BPF applications with libbpf.
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[libbpf-tools](https://github.com/iovisor/bcc/tree/master/libbpf-tools) are also
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a good source of the real-world libbpf-based tracing tools.
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All general BPF questions, including kernel functionality, libbpf APIs and
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their application, should be sent to bpf@vger.kernel.org mailing list. You can
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subscribe to it [here](http://vger.kernel.org/vger-lists.html#bpf) and search
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its archive [here](https://lore.kernel.org/bpf/). Please search the archive
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before asking new questions. It very well might be that this was already
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addressed or answered before.
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bpf@vger.kernel.org is monitored by many more people and they will happily try
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to help you with whatever issue you have. This repository's PRs and issues
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should be opened only for dealing with issues pertaining to specific way this
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libbpf mirror repo is set up and organized.
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Build
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[](https://travis-ci.com/github/libbpf/libbpf)
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[](https://lgtm.com/projects/g/libbpf/libbpf/alerts/)
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[](https://scan.coverity.com/projects/libbpf)
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=====
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libelf is an internal dependency of libbpf and thus it is required to link
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against and must be installed on the system for applications to work.
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pkg-config is used by default to find libelf, and the program called can be
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overridden with `PKG_CONFIG`.
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If using `pkg-config` at build time is not desired, it can be disabled by
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setting `NO_PKG_CONFIG=1` when calling make.
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To build both static libbpf.a and shared libbpf.so:
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```bash
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$ cd src
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$ make
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```
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To build only static libbpf.a library in directory
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build/ and install them together with libbpf headers in a staging directory
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root/:
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```bash
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$ cd src
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$ mkdir build root
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$ BUILD_STATIC_ONLY=y OBJDIR=build DESTDIR=root make install
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```
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To build both static libbpf.a and shared libbpf.so against a custom libelf
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dependency installed in /build/root/ and install them together with libbpf
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headers in a build directory /build/root/:
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```bash
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$ cd src
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$ PKG_CONFIG_PATH=/build/root/lib64/pkgconfig DESTDIR=/build/root make install
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```
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Distributions
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=============
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Distributions packaging libbpf from this mirror:
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- [Fedora](https://src.fedoraproject.org/rpms/libbpf)
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- [Gentoo](https://packages.gentoo.org/packages/dev-libs/libbpf)
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- [Debian](https://packages.debian.org/source/sid/libbpf)
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- [Arch](https://www.archlinux.org/packages/extra/x86_64/libbpf/)
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- [Ubuntu](https://packages.ubuntu.com/source/groovy/libbpf)
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Benefits of packaging from the mirror over packaging from kernel sources:
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- Consistent versioning across distributions.
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- No ties to any specific kernel, transparent handling of older kernels.
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Libbpf is designed to be kernel-agnostic and work across multitude of
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kernel versions. It has built-in mechanisms to gracefully handle older
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kernels, that are missing some of the features, by working around or
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gracefully degrading functionality. Thus libbpf is not tied to a specific
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kernel version and can/should be packaged and versioned independently.
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- Continuous integration testing via
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[TravisCI](https://travis-ci.org/libbpf/libbpf).
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- Static code analysis via [LGTM](https://lgtm.com/projects/g/libbpf/libbpf)
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and [Coverity](https://scan.coverity.com/projects/libbpf).
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Package dependencies of libbpf, package names may vary across distros:
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- zlib
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- libelf
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BPF CO-RE (Compile Once – Run Everywhere)
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=========================================
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Libbpf supports building BPF CO-RE-enabled applications, which, in contrast to
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[BCC](https://github.com/iovisor/bcc/), do not require Clang/LLVM runtime
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being deployed to target servers and doesn't rely on kernel-devel headers
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being available.
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It does rely on kernel to be built with [BTF type
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information](https://www.kernel.org/doc/html/latest/bpf/btf.html), though.
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Some major Linux distributions come with kernel BTF already built in:
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- Fedora 31+
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- RHEL 8.2+
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- OpenSUSE Tumbleweed (in the next release, as of 2020-06-04)
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- Arch Linux (from kernel 5.7.1.arch1-1)
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- Ubuntu 20.10
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- Debian 11 (amd64/arm64)
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If your kernel doesn't come with BTF built-in, you'll need to build custom
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kernel. You'll need:
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- `pahole` 1.16+ tool (part of `dwarves` package), which performs DWARF to
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BTF conversion;
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- kernel built with `CONFIG_DEBUG_INFO_BTF=y` option;
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- you can check if your kernel has BTF built-in by looking for
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`/sys/kernel/btf/vmlinux` file:
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```shell
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$ ls -la /sys/kernel/btf/vmlinux
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-r--r--r--. 1 root root 3541561 Jun 2 18:16 /sys/kernel/btf/vmlinux
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```
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To develop and build BPF programs, you'll need Clang/LLVM 10+. The following
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distributions have Clang/LLVM 10+ packaged by default:
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- Fedora 32+
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- Ubuntu 20.04+
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- Arch Linux
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- Ubuntu 20.10 (LLVM 11)
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- Debian 11 (LLVM 11)
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Otherwise, please make sure to update it on your system.
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The following resources are useful to understand what BPF CO-RE is and how to
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use it:
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- [BPF Portability and CO-RE](https://facebookmicrosites.github.io/bpf/blog/2020/02/19/bpf-portability-and-co-re.html)
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- [HOWTO: BCC to libbpf conversion](https://facebookmicrosites.github.io/bpf/blog/2020/02/20/bcc-to-libbpf-howto-guide.html)
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- [libbpf-tools in BCC repo](https://github.com/iovisor/bcc/tree/master/libbpf-tools)
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contain lots of real-world tools converted from BCC to BPF CO-RE. Consider
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converting some more to both contribute to the BPF community and gain some
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more experience with it.
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Details
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=======
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This is a mirror of [bpf-next Linux source
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tree](https://kernel.googlesource.com/pub/scm/linux/kernel/git/bpf/bpf-next)'s
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`tools/lib/bpf` directory plus its supporting header files.
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All the gory details of syncing can be found in `scripts/sync-kernel.sh`
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script.
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Some header files in this repo (`include/linux/*.h`) are reduced versions of
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their counterpart files at
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[bpf-next](https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/)'s
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`tools/include/linux/*.h` to make compilation successful.
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License
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=======
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This work is dual-licensed under BSD 2-clause license and GNU LGPL v2.1 license.
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You can choose between one of them if you use this work.
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`SPDX-License-Identifier: BSD-2-Clause OR LGPL-2.1`
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