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2023-10-19bpf, docs: Define signed modulo as using truncated divisionDave Thaler
There's different mathematical definitions (truncated, floored, rounded, etc.) and different languages have chosen different definitions [0][1]. E.g., languages/libraries that follow Knuth use a different mathematical definition than C uses. This patch specifies which definition BPF uses, as verified by Eduard [2] and others. [0] https://en.wikipedia.org/wiki/Modulo#Variants_of_the_definition [1] https://torstencurdt.com/tech/posts/modulo-of-negative-numbers/ [2] https://lore.kernel.org/bpf/57e6fefadaf3b2995bb259fa8e711c7220ce5290.camel@gmail.com/ Signed-off-by: Dave Thaler <dthaler@microsoft.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: David Vernet <void@manifault.com> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/bpf/20231017203020.1500-1-dthaler1968@googlemail.com
2023-08-30bpf, docs: s/eBPF/BPF in standards documentsDavid Vernet
There isn't really anything other than just "BPF" at this point, so referring to it as "eBPF" in our standards document just causes unnecessary confusion. Let's just be consistent and use "BPF". Suggested-by: Will Hawkins <hawkinsw@obs.cr> Signed-off-by: David Vernet <void@manifault.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20230828155948.123405-4-void@manifault.com
2023-08-30bpf, docs: Add abi.rst document to standardization subdirectoryDavid Vernet
As specified in the IETF BPF charter, the BPF working group has plans to add one or more informational documents that recommend conventions and guidelines for producing portable BPF program binaries. The instruction-set.rst document currently contains a "Registers and calling convention" subsection which dictates a calling convention that belongs in an ABI document, rather than an instruction set document. Let's move it to a new abi.rst document so we can clean it up. The abi.rst document will of course be significantly changed and expanded upon over time. For now, it's really just a placeholder which will contain ABI-specific language that doesn't belong in other documents. Signed-off-by: David Vernet <void@manifault.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20230828155948.123405-3-void@manifault.com
2023-08-30bpf, docs: Move linux-notes.rst to root bpf docs treeDavid Vernet
In commit 4d496be9ca05 ("bpf,docs: Create new standardization subdirectory"), I added a standardization/ directory to the BPF documentation, which will contain the docs that will be standardized as part of the effort with the IETF. I included linux-notes.rst in that directory, but I shouldn't have. It doesn't contain anything that will be standardized. Let's move it back to Documentation/bpf. Signed-off-by: David Vernet <void@manifault.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20230828155948.123405-2-void@manifault.com
2023-08-30bpf, docs: Correct source of offset for program-local callWill Hawkins
The offset to use when calculating the target of a program-local call is in the instruction's imm field, not its offset field. Signed-off-by: Will Hawkins <hawkinsw@obs.cr> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230826053258.1860167-1-hawkinsw@obs.cr
2023-08-08bpf, docs: Fix small typo and define semantics of sign extensionWill Hawkins
Add additional precision on the semantics of the sign extension operations in BPF. In addition, fix a very minor typo. Signed-off-by: Will Hawkins <hawkinsw@obs.cr> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230808212503.197834-1-hawkinsw@obs.cr Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
2023-08-07bpf, docs: Formalize type notation and function semantics in ISA standardWill Hawkins
Give a single place where the shorthand for types are defined and the semantics of helper functions are described. Signed-off-by: Will Hawkins <hawkinsw@obs.cr> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230807140651.122484-1-hawkinsw@obs.cr Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
2023-07-29docs/bpf: Fix malformed documentationYonghong Song
Two issues are fixed: 1. Malformed table due to newly-introduced BPF_MOVSX 2. Missing reference link for ``Sign-extension load operations`` Fixes: 245d4c40c09b ("docs/bpf: Add documentation for new instructions") Cc: bpf@ietf.org Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202307291840.Cqhj7uox-lkp@intel.com/ Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230730004251.381307-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2023-07-28docs/bpf: Improve documentation for cpu=v4 instructionsYonghong Song
Improve documentation for cpu=v4 instructions based on David's suggestions. Cc: bpf@ietf.org Suggested-by: David Vernet <void@manifault.com> Acked-by: David Vernet <void@manifault.com> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230728225105.919595-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2023-07-27docs/bpf: Add documentation for new instructionsYonghong Song
Add documentation in instruction-set.rst for new instruction encoding and their corresponding operations. Also removed the question related to 'no BPF_SDIV' in bpf_design_QA.rst since we have BPF_SDIV insn now. Cc: bpf@ietf.org Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230728011342.3724411-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2023-07-27bpf, docs: fix BPF_NEG entry in instruction-set.rstJose E. Marchesi
This patch fixes the documentation of the BPF_NEG instruction to denote that it does not use the source register operand. Signed-off-by: Jose E. Marchesi <jose.marchesi@oracle.com> Acked-by: Dave Thaler <dthaler@microsoft.com> Acked-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230726092543.6362-1-jose.marchesi@oracle.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2023-07-10bpf,docs: Create new standardization subdirectoryDavid Vernet
The BPF standardization effort is actively underway with the IETF. As described in the BPF Working Group (WG) charter in [0], there are a number of proposed documents, some informational and some proposed standards, that will be drafted as part of the standardization effort. [0]: https://datatracker.ietf.org/wg/bpf/about/ Though the specific documents that will formally be standardized will exist as Internet Drafts (I-D) and WG documents in the BPF WG datatracker page, the source of truth from where those documents will be generated will reside in the kernel documentation tree (originating in the bpf-next tree). Because these documents will be used to generate the I-D and WG documents which will be standardized with the IETF, they are a bit special as far as kernel-tree documentation goes: - They will be dual licensed with LGPL-2.1 OR BSD-2-Clause - IETF I-D and WG documents (the documents which will actually be standardized) will be auto-generated from these documents. In order to keep things clearly organized in the BPF documentation tree, and to make it abundantly clear where standards-related documentation needs to go, we should move standards-relevant documents into a separate standardization/ subdirectory. Signed-off-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230710183027.15132-1-void@manifault.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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