diff options
Diffstat (limited to '')
| -rw-r--r-- | Documentation/bpf/bpf_devel_QA.rst | 109 |
1 files changed, 70 insertions, 39 deletions
diff --git a/Documentation/bpf/bpf_devel_QA.rst b/Documentation/bpf/bpf_devel_QA.rst index c9856b927055..761474bd7fe6 100644 --- a/Documentation/bpf/bpf_devel_QA.rst +++ b/Documentation/bpf/bpf_devel_QA.rst @@ -20,16 +20,16 @@ Reporting bugs Q: How do I report bugs for BPF kernel code? -------------------------------------------- A: Since all BPF kernel development as well as bpftool and iproute2 BPF -loader development happens through the netdev kernel mailing list, +loader development happens through the bpf kernel mailing list, please report any found issues around BPF to the following mailing list: - netdev@vger.kernel.org + bpf@vger.kernel.org This may also include issues related to XDP, BPF tracing, etc. Given netdev has a high volume of traffic, please also add the BPF -maintainers to Cc (from kernel MAINTAINERS_ file): +maintainers to Cc (from kernel ``MAINTAINERS`` file): * Alexei Starovoitov <ast@kernel.org> * Daniel Borkmann <daniel@iogearbox.net> @@ -46,17 +46,12 @@ Submitting patches Q: To which mailing list do I need to submit my BPF patches? ------------------------------------------------------------ -A: Please submit your BPF patches to the netdev kernel mailing list: +A: Please submit your BPF patches to the bpf kernel mailing list: - netdev@vger.kernel.org - -Historically, BPF came out of networking and has always been maintained -by the kernel networking community. Although these days BPF touches -many other subsystems as well, the patches are still routed mainly -through the networking community. + bpf@vger.kernel.org In case your patch has changes in various different subsystems (e.g. -tracing, security, etc), make sure to Cc the related kernel mailing +networking, tracing, security, etc), make sure to Cc the related kernel mailing lists and maintainers from there as well, so they are able to review the changes and provide their Acked-by's to the patches. @@ -65,13 +60,13 @@ Q: Where can I find patches currently under discussion for BPF subsystem? A: All patches that are Cc'ed to netdev are queued for review under netdev patchwork project: - http://patchwork.ozlabs.org/project/netdev/list/ + https://patchwork.kernel.org/project/netdevbpf/list/ Those patches which target BPF, are assigned to a 'bpf' delegate for further processing from BPF maintainers. The current queue with patches under review can be found at: - https://patchwork.ozlabs.org/project/netdev/list/?delegate=77147 + https://patchwork.kernel.org/project/netdevbpf/list/?delegate=121173 Once the patches have been reviewed by the BPF community as a whole and approved by the BPF maintainers, their status in patchwork will be @@ -154,7 +149,7 @@ In case the patch or patch series has to be reworked and sent out again in a second or later revision, it is also required to add a version number (``v2``, ``v3``, ...) into the subject prefix:: - git format-patch --subject-prefix='PATCH net-next v2' start..finish + git format-patch --subject-prefix='PATCH bpf-next v2' start..finish When changes have been requested to the patch series, always send the whole patch series again with the feedback incorporated (never send @@ -168,7 +163,7 @@ a BPF point of view. Be aware that this is not a final verdict that the patch will automatically get accepted into net or net-next trees eventually: -On the netdev kernel mailing list reviews can come in at any point +On the bpf kernel mailing list reviews can come in at any point in time. If discussions around a patch conclude that they cannot get included as-is, we will either apply a follow-up fix or drop them from the trees entirely. Therefore, we also reserve to rebase @@ -239,11 +234,11 @@ be subject to change. Q: samples/bpf preference vs selftests? --------------------------------------- -Q: When should I add code to `samples/bpf/`_ and when to BPF kernel -selftests_ ? +Q: When should I add code to ``samples/bpf/`` and when to BPF kernel +selftests_? A: In general, we prefer additions to BPF kernel selftests_ rather than -`samples/bpf/`_. The rationale is very simple: kernel selftests are +``samples/bpf/``. The rationale is very simple: kernel selftests are regularly run by various bots to test for kernel regressions. The more test cases we add to BPF selftests, the better the coverage @@ -251,9 +246,9 @@ and the less likely it is that those could accidentally break. It is not that BPF kernel selftests cannot demo how a specific feature can be used. -That said, `samples/bpf/`_ may be a good place for people to get started, +That said, ``samples/bpf/`` may be a good place for people to get started, so it might be advisable that simple demos of features could go into -`samples/bpf/`_, but advanced functional and corner-case testing rather +``samples/bpf/``, but advanced functional and corner-case testing rather into kernel selftests. If your sample looks like a test case, then go for BPF kernel selftests @@ -442,6 +437,34 @@ needed:: See the kernels selftest `Documentation/dev-tools/kselftest.rst`_ document for further documentation. +To maximize the number of tests passing, the .config of the kernel +under test should match the config file fragment in +tools/testing/selftests/bpf as closely as possible. + +Finally to ensure support for latest BPF Type Format features - +discussed in `Documentation/bpf/btf.rst`_ - pahole version 1.16 +is required for kernels built with CONFIG_DEBUG_INFO_BTF=y. +pahole is delivered in the dwarves package or can be built +from source at + +https://github.com/acmel/dwarves + +pahole starts to use libbpf definitions and APIs since v1.13 after the +commit 21507cd3e97b ("pahole: add libbpf as submodule under lib/bpf"). +It works well with the git repository because the libbpf submodule will +use "git submodule update --init --recursive" to update. + +Unfortunately, the default github release source code does not contain +libbpf submodule source code and this will cause build issues, the tarball +from https://git.kernel.org/pub/scm/devel/pahole/pahole.git/ is same with +github, you can get the source tarball with corresponding libbpf submodule +codes from + +https://fedorapeople.org/~acme/dwarves + +Some distros have pahole version 1.16 packaged already, e.g. +Fedora, Gentoo. + Q: Which BPF kernel selftests version should I run my kernel against? --------------------------------------------------------------------- A: If you run a kernel ``xyz``, then always run the BPF kernel selftests @@ -469,17 +492,18 @@ LLVM's static compiler lists the supported targets through $ llc --version LLVM (http://llvm.org/): - LLVM version 6.0.0svn + LLVM version 10.0.0 Optimized build. Default target: x86_64-unknown-linux-gnu Host CPU: skylake Registered Targets: - bpf - BPF (host endian) - bpfeb - BPF (big endian) - bpfel - BPF (little endian) - x86 - 32-bit X86: Pentium-Pro and above - x86-64 - 64-bit X86: EM64T and AMD64 + aarch64 - AArch64 (little endian) + bpf - BPF (host endian) + bpfeb - BPF (big endian) + bpfel - BPF (little endian) + x86 - 32-bit X86: Pentium-Pro and above + x86-64 - 64-bit X86: EM64T and AMD64 For developers in order to utilize the latest features added to LLVM's BPF back end, it is advisable to run the latest LLVM releases. Support @@ -490,23 +514,30 @@ All LLVM releases can be found at: http://releases.llvm.org/ Q: Got it, so how do I build LLVM manually anyway? -------------------------------------------------- -A: You need cmake and gcc-c++ as build requisites for LLVM. Once you have -that set up, proceed with building the latest LLVM and clang version +A: We recommend that developers who want the fastest incremental builds +use the Ninja build system, you can find it in your system's package +manager, usually the package is ninja or ninja-build. + +You need ninja, cmake and gcc-c++ as build requisites for LLVM. Once you +have that set up, proceed with building the latest LLVM and clang version from the git repositories:: - $ git clone http://llvm.org/git/llvm.git - $ cd llvm/tools - $ git clone --depth 1 http://llvm.org/git/clang.git - $ cd ..; mkdir build; cd build - $ cmake .. -DLLVM_TARGETS_TO_BUILD="BPF;X86" \ - -DBUILD_SHARED_LIBS=OFF \ + $ git clone https://github.com/llvm/llvm-project.git + $ mkdir -p llvm-project/llvm/build + $ cd llvm-project/llvm/build + $ cmake .. -G "Ninja" -DLLVM_TARGETS_TO_BUILD="BPF;X86" \ + -DLLVM_ENABLE_PROJECTS="clang" \ -DCMAKE_BUILD_TYPE=Release \ -DLLVM_BUILD_RUNTIME=OFF - $ make -j $(getconf _NPROCESSORS_ONLN) + $ ninja The built binaries can then be found in the build/bin/ directory, where you can point the PATH variable to. +Set ``-DLLVM_TARGETS_TO_BUILD`` equal to the target you wish to build, you +will find a full list of targets within the llvm-project/llvm/lib/Target +directory. + Q: Reporting LLVM BPF issues ---------------------------- Q: Should I notify BPF kernel maintainers about issues in LLVM's BPF code @@ -627,11 +658,11 @@ when: .. Links .. _Documentation/process/: https://www.kernel.org/doc/html/latest/process/ -.. _MAINTAINERS: ../../MAINTAINERS -.. _netdev-FAQ: ../networking/netdev-FAQ.rst -.. _samples/bpf/: ../../samples/bpf/ -.. _selftests: ../../tools/testing/selftests/bpf/ +.. _netdev-FAQ: Documentation/process/maintainer-netdev.rst +.. _selftests: + https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/selftests/bpf/ .. _Documentation/dev-tools/kselftest.rst: https://www.kernel.org/doc/html/latest/dev-tools/kselftest.html +.. _Documentation/bpf/btf.rst: btf.rst Happy BPF hacking! |