diff options
Diffstat (limited to 'Documentation/bpf')
| -rw-r--r-- | Documentation/bpf/bpf_design_QA.rst | 15 | ||||
| -rw-r--r-- | Documentation/bpf/bpf_devel_QA.rst | 30 | ||||
| -rw-r--r-- | Documentation/bpf/btf.rst | 17 | ||||
| -rw-r--r-- | Documentation/bpf/index.rst | 9 |
4 files changed, 57 insertions, 14 deletions
diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst index 0e15f9b05c9d..437de2a7a5de 100644 --- a/Documentation/bpf/bpf_design_QA.rst +++ b/Documentation/bpf/bpf_design_QA.rst @@ -258,3 +258,18 @@ Q: Can BPF functionality such as new program or map types, new helpers, etc be added out of kernel module code? A: NO. + +Q: Directly calling kernel function is an ABI? +---------------------------------------------- +Q: Some kernel functions (e.g. tcp_slow_start) can be called +by BPF programs. Do these kernel functions become an ABI? + +A: NO. + +The kernel function protos will change and the bpf programs will be +rejected by the verifier. Also, for example, some of the bpf-callable +kernel functions have already been used by other kernel tcp +cc (congestion-control) implementations. If any of these kernel +functions has changed, both the in-tree and out-of-tree kernel tcp cc +implementations have to be changed. The same goes for the bpf +programs and they have to be adjusted accordingly. diff --git a/Documentation/bpf/bpf_devel_QA.rst b/Documentation/bpf/bpf_devel_QA.rst index 2ed89abbf9a4..253496af8fef 100644 --- a/Documentation/bpf/bpf_devel_QA.rst +++ b/Documentation/bpf/bpf_devel_QA.rst @@ -29,7 +29,7 @@ list: 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> @@ -234,11 +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 @@ -246,9 +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 @@ -449,6 +449,19 @@ 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. @@ -645,10 +658,9 @@ 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/ +.. _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 diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst index 44dc789de2b4..846354cd2d69 100644 --- a/Documentation/bpf/btf.rst +++ b/Documentation/bpf/btf.rst @@ -84,6 +84,7 @@ sequentially and type id is assigned to each recognized type starting from id #define BTF_KIND_FUNC_PROTO 13 /* Function Proto */ #define BTF_KIND_VAR 14 /* Variable */ #define BTF_KIND_DATASEC 15 /* Section */ + #define BTF_KIND_FLOAT 16 /* Floating point */ Note that the type section encodes debug info, not just pure types. ``BTF_KIND_FUNC`` is not a type, and it represents a defined subprogram. @@ -95,8 +96,8 @@ Each type contains the following common data:: /* "info" bits arrangement * bits 0-15: vlen (e.g. # of struct's members) * bits 16-23: unused - * bits 24-27: kind (e.g. int, ptr, array...etc) - * bits 28-30: unused + * bits 24-28: kind (e.g. int, ptr, array...etc) + * bits 29-30: unused * bit 31: kind_flag, currently used by * struct, union and fwd */ @@ -452,6 +453,18 @@ map definition. * ``offset``: the in-section offset of the variable * ``size``: the size of the variable in bytes +2.2.16 BTF_KIND_FLOAT +~~~~~~~~~~~~~~~~~~~~~ + +``struct btf_type`` encoding requirement: + * ``name_off``: any valid offset + * ``info.kind_flag``: 0 + * ``info.kind``: BTF_KIND_FLOAT + * ``info.vlen``: 0 + * ``size``: the size of the float type in bytes: 2, 4, 8, 12 or 16. + +No additional type data follow ``btf_type``. + 3. BTF Kernel API ***************** diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst index 4f2874b729c3..a702f67dd45f 100644 --- a/Documentation/bpf/index.rst +++ b/Documentation/bpf/index.rst @@ -12,9 +12,6 @@ BPF instruction-set. The Cilium project also maintains a `BPF and XDP Reference Guide`_ that goes into great technical depth about the BPF Architecture. -The primary info for the bpf syscall is available in the `man-pages`_ -for `bpf(2)`_. - BPF Type Format (BTF) ===================== @@ -35,6 +32,12 @@ Two sets of Questions and Answers (Q&A) are maintained. bpf_design_QA bpf_devel_QA +Syscall API +=========== + +The primary info for the bpf syscall is available in the `man-pages`_ +for `bpf(2)`_. For more information about the userspace API, see +Documentation/userspace-api/ebpf/index.rst. Helper functions ================ |