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2022-11-14bpf: Remove local kptr references in documentationKumar Kartikeya Dwivedi1-5/+6
We don't want to commit to a specific name for these. Simply call them allocated objects coming from bpf_obj_new, which is completely clear in itself. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20221114191547.1694267-2-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-11-04Documentation: bpf: Escape underscore in BPF type name prefixBagas Sanjaya1-4/+4
Sphinx reported unknown target warning: Documentation/bpf/bpf_design_QA.rst:329: WARNING: Unknown target name: "bpf". The warning is caused by BPF type name prefix ("bpf_") which is written without escaping the trailing underscore. Escape the underscore to fix the warning. While at it, wrap the containing paragraph in less than 80 characters. Fixes: 9805af8d8a5b17 ("bpf: Document UAPI details for special BPF types") Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: KP Singh <kpsingh@kernel.org> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20221104123913.50610-1-bagasdotme@gmail.com
2022-11-03bpf: Document UAPI details for special BPF typesKumar Kartikeya Dwivedi1-0/+44
The kernel recognizes some special BPF types in map values or local kptrs. Document that only bpf_spin_lock and bpf_timer will preserve backwards compatibility, and kptr will preserve backwards compatibility for the operations on the pointer, not the types supported for such kptrs. For local kptrs, document that there are no stability guarantees at all. Finally, document that 'bpf_' namespace is reserved for adding future special fields, hence BPF programs must not declare types with such names in their programs and still expect backwards compatibility. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20221103191013.1236066-2-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-08-04bpf: Update bpf_design_QA.rst to clarify that BTF_ID does not ABIify a functionPaul E. McKenney1-0/+7
This patch updates bpf_design_QA.rst to clarify that mentioning a function to the BTF_ID macro does not make that function become part of the Linux kernel's ABI. Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Link: https://lore.kernel.org/r/20220802173913.4170192-3-paulmck@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-08-04bpf: Update bpf_design_QA.rst to clarify that attaching to functions is not ABIPaul E. McKenney1-0/+12
This patch updates bpf_design_QA.rst to clarify that the ability to attach a BPF program to an arbitrary function in the kernel does not make that function become part of the Linux kernel's ABI. [ paulmck: Apply Daniel Borkmann feedback. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Link: https://lore.kernel.org/r/20220802173913.4170192-2-paulmck@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-08-04bpf: Update bpf_design_QA.rst to clarify that kprobes is not ABIPaul E. McKenney1-0/+6
This patch updates bpf_design_QA.rst to clarify that the ability to attach a BPF program to a given point in the kernel code via kprobes does not make that attachment point be part of the Linux kernel's ABI. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Link: https://lore.kernel.org/r/20220802173913.4170192-1-paulmck@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2021-03-30bpf: Update bpf_design_QA.rst to clarify the kfunc call is not ABIMartin KaFai Lau1-0/+15
This patch updates bpf_design_QA.rst to clarify that the kernel function callable by bpf program is not an ABI. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20210330054150.2933542-1-kafai@fb.com
2021-01-20trace: bpf: Allow bpf to attach to bare tracepointsQais Yousef1-0/+6
Some subsystems only have bare tracepoints (a tracepoint with no associated trace event) to avoid the problem of trace events being an ABI that can't be changed. >From bpf presepective, bare tracepoints are what it calls RAW_TRACEPOINT(). Since bpf assumed there's 1:1 mapping, it relied on hooking to DEFINE_EVENT() macro to create bpf mapping of the tracepoints. Since bare tracepoints use DECLARE_TRACE() to create the tracepoint, bpf had no knowledge about their existence. By teaching bpf_probe.h to parse DECLARE_TRACE() in a similar fashion to DEFINE_EVENT(), bpf can find and attach to the new raw tracepoints. Enabling that comes with the contract that changes to raw tracepoints don't constitute a regression if they break existing bpf programs. We need the ability to continue to morph and modify these raw tracepoints without worrying about any ABI. Update Documentation/bpf/bpf_design_QA.rst to document this contract. Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20210119122237.2426878-2-qais.yousef@arm.com
2020-08-07bpf, doc: Remove references to warning message when using bpf_trace_printk()Alan Maguire1-11/+0
The BPF helper bpf_trace_printk() no longer uses trace_printk(); it is now triggers a dedicated trace event. Hence the described warning is no longer present, so remove the discussion of it as it may confuse people. Fixes: ac5a72ea5c89 ("bpf: Use dedicated bpf_trace_printk event instead of trace_printk()") Signed-off-by: Alan Maguire <alan.maguire@oracle.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/1596801029-32395-1-git-send-email-alan.maguire@oracle.com
2019-05-31bpf: doc: update answer for 32-bit subregister questionJiong Wang1-5/+25
There has been quite a few progress around the two steps mentioned in the answer to the following question: Q: BPF 32-bit subregister requirements This patch updates the answer to reflect what has been done. v2: - Add missing full stop. (Song Liu) - Minor tweak on one sentence. (Song Liu) v1: - Integrated rephrase from Quentin and Jakub Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com> Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: Jiong Wang <jiong.wang@netronome.com> Acked-by: Song Liu <songliubraving@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-04-23bpf: document the verifier limitsAlexei Starovoitov1-2/+27
Document the verifier limits. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2019-03-02docs/bpf: minor casing/punctuation fixesAndrii Nakryiko1-12/+12
Fix few casing and punctuation glitches. Signed-off-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2019-01-07bpf, doc: update design qa to reflect kern_version requirementDaniel Borkmann1-6/+5
Update the bpf_design_QA.rst to also reflect recent changes in 6c4fc209fcf9 ("bpf: remove useless version check for prog load"). Suggested-by: Quentin Monnet <quentin.monnet@netronome.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-05-14bpf, doc: convert bpf_design_QA.rst to use RST formattingJesper Dangaard Brouer1-79/+144
The RST formatting is done such that that when rendered or converted to different formats, an automatic index with links are created to the subsections. Thus, the questions are created as sections (or subsections), in-order to get the wanted auto-generated FAQ/QA index. Special thanks to Quentin Monnet <quentin.monnet@netronome.com> who have reviewed and corrected both RST formatting and GitHub rendering issues in this file. Those commits have been squashed. I've manually tested that this also renders nicely if included as part of the kernel 'make htmldocs'. As the end-goal is for this to become more integrated with kernel-doc project/movement. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-05-14bpf, doc: rename txt files to rst filesJesper Dangaard Brouer1-0/+156
This will cause them to get auto rendered, e.g. when viewing them on GitHub. Followup patches will correct the content to be RST compliant. Also adjust README.rst to point to the renamed files. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>