bpf, docs: Rename legacy conformance group to packet

There could be other legacy conformance groups in the future,
so use a more descriptive name. The status of the conformance
group in the IANA registry is what designates it as legacy,
not the name of the group.

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Link: https://lore.kernel.org/r/20240302012229.16452-1-dthaler1968@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

bpf, docs: Use IETF format for field definitions in instruction-set.rst

In preparation for publication as an IETF RFC, the WG chairs asked me
to convert the document to use IETF packet format for field layout, so
this patch attempts to make it consistent with other IETF documents.

Some fields that are not byte aligned were previously inconsistent
in how values were defined. Some were defined as the value of the
byte containing the field (like 0x20 for a field holding the high
four bits of the byte), and others were defined as the value of the
field itself (like 0x2). This PR makes them be consistent in using
just the values of the field itself, which is IETF convention.

As a result, some of the defines that used BPF_* would no longer
match the value in the spec, and so this patch also drops the BPF_*
prefix to avoid confusion with the defines that are the full-byte
equivalent values. For consistency, BPF_* is then dropped from
other fields too. BPF_<foo> is thus the Linux implementation-specific
define for <foo> as it appears in the BPF ISA specification.

The syntax BPF_ADD | BPF_X | BPF_ALU only worked for full-byte
values so the convention {ADD, X, ALU} is proposed for referring
to field values instead.

Also replace the redundant "LSB bits" with "least significant bits".

A preview of what the resulting Internet Draft would look like can
be seen at:
https://htmlpreview.github.io/?https://raw.githubusercontent.com/dthaler/ebp
f-docs-1/format/draft-ietf-bpf-isa.html

v1->v2: Fix sphinx issue as recommended by David Vernet

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20240301222337.15931-1-dthaler1968@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

bpf, docs: specify which BPF_ABS and BPF_IND fields were zero

Specifying which fields were unused allows IANA to only list as deprecated
instructions that were actually used, leaving the rest as unassigned and
possibly available for future use for something else.

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20240221175419.16843-1-dthaler1968@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

bpf, docs: Fix typos in instruction-set.rst

* "BPF ADD" should be "BPF_ADD".
* "src" should be "src_reg" in several places. The latter is the field name
in the instruction. The former refers to the value of the register, or the
immediate.
* Add '' around field names in one sentence, for consistency with the rest
of the document.

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20240221173535.16601-1-dthaler1968@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

bpf, docs: Update ISA document title

* Use "Instruction Set Architecture (ISA)" instead of "Instruction Set
Specification"
* Remove version number

As previously discussed on the mailing list at
https://mailarchive.ietf.org/arch/msg/bpf/SEpn3OL9TabNRn-4rDX9A6XVbjM/

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20240208221449.12274-1-dthaler1968@gmail.com

bpf, docs: Fix typos in instructions-set.rst

* "imm32" should just be "imm"
* Add blank line to fix formatting error reported by Stephen Rothwell [0]

[0]: https://lore.kernel.org/bpf/20240206153301.4ead0bad@canb.auug.org.au/T/#u

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20240206045146.4965-1-dthaler1968@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

bpf, docs: Expand set of initial conformance groups

This patch attempts to update the ISA specification according
to the latest mailing list discussion about conformance groups,
in a way that is intended to be consistent with IANA registry
processes and IETF 118 WG meeting discussion.

It does the following:
* Split basic into base32 and base64 for 32-bit vs 64-bit base
instructions
* Split division/multiplication/modulo instructions out of base groups
* Split atomic instructions out of base groups

There may be additional changes as discussion continues,
but there seems to be consensus on the principles above.

v1->v2: fixed typo pointed out by David Vernet

v2->v3: Moved multiplication to same groups as division/modulo

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20240202221110.3872-1-dthaler1968@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

bpf, docs: Clarify which legacy packet instructions existed

As discussed on the BPF IETF mailing list (see link), this patch updates
the "Legacy BPF Packet access instructions" section to clarify which
instructions are deprecated (vs which were never defined and so are not
deprecated).

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: David Vernet <void@manifault.com>
Link: https://mailarchive.ietf.org/arch/msg/bpf/5LnnKm093cGpOmDI9TnLQLBXyys
Link: https://lore.kernel.org/bpf/20240131033759.3634-1-dthaler1968@gmail.com

docs/bpf: Improve documentation of 64-bit immediate instructions

For 64-bit immediate instruction, 'BPF_IMM | BPF_DW | BPF_LD' and
src_reg=[0-6], the current documentation describes the 64-bit
immediate is constructed by:

imm64 = (next_imm << 32) | imm

But actually imm64 is only used when src_reg=0. For all other
variants (src_reg != 0), 'imm' and 'next_imm' have separate special
encoding requirement and imm64 cannot be easily used to describe
instruction semantics.

This patch clarifies that 64-bit immediate instructions use
two 32-bit immediate values instead of a 64-bit immediate value,
so later describing individual 64-bit immediate instructions
becomes less confusing.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Dave Thaler <dthaler1968@gmail.com>
Link: https://lore.kernel.org/bpf/20240127194629.737589-1-yonghong.song@linux.dev

bpf, docs: Clarify definitions of various instructions

Clarify definitions of several instructions:

* BPF_NEG does not support BPF_X
* BPF_CALL does not support BPF_JMP32 or BPF_X
* BPF_EXIT does not support BPF_X
* BPF_JA does not support BPF_X (was implied but not explicitly stated)

Also fix a typo in the wide instruction figure where the field is
actually named "opcode" not "code".

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/bpf/20240126040050.8464-1-dthaler1968@gmail.com

bpf, docs: Clarify that MOVSX is only for BPF_X not BPF_K

Per discussion on the mailing list at
https://mailarchive.ietf.org/arch/msg/bpf/uQiqhURdtxV_ZQOTgjCdm-seh74/
the MOVSX operation is only defined to support register extension.

The document didn't previously state this and incorrectly implied
that one could use an immediate value.

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Acked-by: David Vernet <void@manifault.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240118232954.27206-1-dthaler1968@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Introduce concept of conformance groups

The discussion of what the actual conformance groups should be
is still in progress, so this is just part 1 which only uses
"legacy" for deprecated instructions and "basic" for everything
else. Subsequent patches will add more groups as discussion
continues.

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20240108214231.5280-1-dthaler1968@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

bpf, docs: Define signed modulo as using truncated division

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

bpf, docs: s/eBPF/BPF in standards documents

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

bpf, docs: Add abi.rst document to standardization subdirectory

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

bpf, docs: Correct source of offset for program-local call

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

bpf, docs: Fix small typo and define semantics of sign extension

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>

bpf, docs: Formalize type notation and function semantics in ISA standard

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>

docs/bpf: Fix malformed documentation

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>

docs/bpf: Improve documentation for cpu=v4 instructions

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>

docs/bpf: Add documentation for new instructions

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>

bpf, docs: fix BPF_NEG entry in instruction-set.rst

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>

bpf,docs: Create new standardization subdirectory

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>