d8d4713476
Add a bunch of getter for various aspects of BPF map. Some of these attribute (e.g., key_size, value_size, type, etc) are available right now in struct bpf_map_def, but this patch adds getter allowing to fetch them individually. bpf_map_def approach isn't very scalable, when ABI stability requirements are taken into account. It's much easier to extend libbpf and add support for new features, when each aspect of BPF map has separate getter/setter. Getters follow the common naming convention of not explicitly having "get" in its name: bpf_map__type() returns map type, bpf_map__key_size() returns key_size. Setters, though, explicitly have set in their name: bpf_map__set_type(), bpf_map__set_key_size(). This patch ensures we now have a getter and a setter for the following map attributes: - type; - max_entries; - map_flags; - numa_node; - key_size; - value_size; - ifindex. bpf_map__resize() enforces unnecessary restriction of max_entries > 0. It is unnecessary, because libbpf actually supports zero max_entries for some cases (e.g., for PERF_EVENT_ARRAY map) and treats it specially during map creation time. To allow setting max_entries=0, new bpf_map__set_max_entries() setter is added. bpf_map__resize()'s behavior is preserved for backwards compatibility reasons. Map ifindex getter is added as well. There is a setter already, but no corresponding getter. Fix this assymetry as well. bpf_map__set_ifindex() itself is converted from void function into error-returning one, similar to other setters. The only error returned right now is -EBUSY, if BPF map is already loaded and has corresponding FD. One lacking attribute with no ability to get/set or even specify it declaratively is numa_node. This patch fixes this gap and both adds programmatic getter/setter, as well as adds support for numa_node field in BTF-defined map. Signed-off-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Toke Høiland-Jørgensen <toke@redhat.com> Link: https://lore.kernel.org/bpf/20200621062112.3006313-1-andriin@fb.com
This is a mirror of bpf-next linux tree's
tools/lib/bpf directory plus its supporting header files.
The following files will by sync'ed with bpf-next repo:
src/<->bpf-next/tools/lib/bpf/include/uapi/linux/bpf_common.h<->bpf-next/tools/include/uapi/linux/bpf_common.hinclude/uapi/linux/bpf.h<->bpf-next/tools/include/uapi/linux/bpf.hinclude/uapi/linux/btf.h<->bpf-next/tools/include/uapi/linux/btf.hinclude/uapi/linux/if_link.h<->bpf-next/tools/include/uapi/linux/if_link.hinclude/uapi/linux/if_xdp.h<->bpf-next/tools/include/uapi/linux/if_xdp.hinclude/uapi/linux/netlink.h<->bpf-next/tools/include/uapi/linux/netlink.hinclude/tools/libc_compat.h<->bpf-next/tools/include/tools/libc_compat.h
Other header files at this repo (include/linux/*.h) are reduced versions of
their counterpart files at bpf-next's tools/include/linux/*.h to make compilation
successful.
Build
libelf is an internal dependency of libbpf and thus it is required to link
against and must be installed on the system for applications to work.
pkg-config is used by default to find libelf, and the program called can be
overridden with PKG_CONFIG.
If using pkg-config at build time is not desired, it can be disabled by setting
NO_PKG_CONFIG=1 when calling make.
To build both static libbpf.a and shared libbpf.so:
$ cd src
$ make
To build only static libbpf.a library in directory build/ and install them together with libbpf headers in a staging directory root/:
$ cd src
$ mkdir build root
$ BUILD_STATIC_ONLY=y OBJDIR=build DESTDIR=root make install
To build both static libbpf.a and shared libbpf.so against a custom libelf dependency installed in /build/root/ and install them together with libbpf headers in a build directory /build/root/:
$ cd src
$ PKG_CONFIG_PATH=/build/root/lib64/pkgconfig DESTDIR=/build/root make install
Distributions
Distributions packaging libbpf from this mirror:
Benefits of packaging from the mirror over packaging from kernel sources:
- Consistent versioning across distributions.
- No ties to any specific kernel, transparent handling of older kernels. Libbpf is designed to be kernel-agnostic and work across multitude of kernel versions. It has built-in mechanisms to gracefully handle older kernels, that are missing some of the features, by working around or gracefully degrading functionality. Thus libbpf is not tied to a specific kernel version and can/should be packaged and versioned independently.
- Continuous integration testing via TravisCI.
- Static code analysis via LGTM and Coverity.
Package dependencies of libbpf, package names may vary across distros:
- zlib
- libelf
BPF CO-RE (Compile Once – Run Everywhere)
Libbpf supports building BPF CO-RE-enabled applications, which, in contrast to BCC, do not require Clang/LLVM runtime being deployed to target servers and doesn't rely on kernel-devel headers being available.
It does rely on kernel to be built with BTF type information, though. Some major Linux distributions come with kernel BTF already built in:
- Fedora 31+
- RHEL 8.2+
- OpenSUSE Tumbleweed (in the next release, as of 2020-06-04)
- Arch Linux (from kernel 5.7.1.arch1-1)
If your kernel doesn't come with BTF built-in, you'll need to build custom kernel. You'll need:
pahole1.16+ tool (part ofdwarvespackage), which performs DWARF to BTF conversion;- kernel built with
CONFIG_DEBUG_INFO_BTF=yoption; - you can check if your kernel has BTF built-in by looking for
/sys/kernel/btf/vmlinuxfile:
$ ls -la /sys/kernel/btf/vmlinux
-r--r--r--. 1 root root 3541561 Jun 2 18:16 /sys/kernel/btf/vmlinux
To develop and build BPF programs, you'll need Clang/LLVM 10+. The following distributions have Clang/LLVM 10+ packaged by default:
- Fedora 32+
- Ubuntu 20.04+
- Arch Linux
Otherwise, please make sure to update it on your system.
The following resources are useful to understand what BPF CO-RE is and how to use it:
- BPF Portability and CO-RE
- HOWTO: BCC to libbpf conversion
- libbpf-tools in BCC repo contain lots of real-world tools converted from BCC to BPF CO-RE. Consider converting some more to both contribute to the BPF community and gain some more experience with it.
License
This work is dual-licensed under BSD 2-clause license and GNU LGPL v2.1 license. You can choose between one of them if you use this work.
SPDX-License-Identifier: BSD-2-Clause OR LGPL-2.1