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bpf, docs: Add table captions

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As suggested by Ines Robles in his IETF GENART review at
https://datatracker.ietf.org/doc/review-ietf-bpf-isa-02-genart-lc-robles-2024-05-16/

Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Link: https://lore.kernel.org/r/20240524164618.18894-1-dthaler1968@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Dave Thaler 2024-05-24 09:46:18 -07:00 committed by Alexei Starovoitov
parent 4e1215d9a1
commit 6a6d8b6f00
1 changed files with 102 additions and 82 deletions
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184
Documentation/bpf/standardization/instruction-set.rst
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@ -32,7 +32,7 @@ Types
This document refers to integer types with the notation `SN` to specify
a type's signedness (`S`) and bit width (`N`), respectively.
.. table:: Meaning of signedness notation.
.. table:: Meaning of signedness notation
==== =========
S Meaning
@ -41,7 +41,7 @@ a type's signedness (`S`) and bit width (`N`), respectively.
s signed
==== =========
.. table:: Meaning of bit-width notation.
.. table:: Meaning of bit-width notation
===== =========
N Bit width
@ -263,18 +263,20 @@ Instruction classes
The three least significant bits of the 'opcode' field store the instruction class:
===== ===== =============================== ===================================
class value description reference
===== ===== =============================== ===================================
LD 0x0 non-standard load operations `Load and store instructions`_
LDX 0x1 load into register operations `Load and store instructions`_
ST 0x2 store from immediate operations `Load and store instructions`_
STX 0x3 store from register operations `Load and store instructions`_
ALU 0x4 32-bit arithmetic operations `Arithmetic and jump instructions`_
JMP 0x5 64-bit jump operations `Arithmetic and jump instructions`_
JMP32 0x6 32-bit jump operations `Arithmetic and jump instructions`_
ALU64 0x7 64-bit arithmetic operations `Arithmetic and jump instructions`_
===== ===== =============================== ===================================
.. table:: Instruction class
===== ===== =============================== ===================================
class value description reference
===== ===== =============================== ===================================
LD 0x0 non-standard load operations `Load and store instructions`_
LDX 0x1 load into register operations `Load and store instructions`_
ST 0x2 store from immediate operations `Load and store instructions`_
STX 0x3 store from register operations `Load and store instructions`_
ALU 0x4 32-bit arithmetic operations `Arithmetic and jump instructions`_
JMP 0x5 64-bit jump operations `Arithmetic and jump instructions`_
JMP32 0x6 32-bit jump operations `Arithmetic and jump instructions`_
ALU64 0x7 64-bit arithmetic operations `Arithmetic and jump instructions`_
===== ===== =============================== ===================================
Arithmetic and jump instructions
================================
@ -292,6 +294,8 @@ For arithmetic and jump instructions (``ALU``, ``ALU64``, ``JMP`` and
**s (source)**
the source operand location, which unless otherwise specified is one of:
.. table:: Source operand location
====== ===== ==============================================
source value description
====== ===== ==============================================
@ -312,27 +316,29 @@ The 'code' field encodes the operation as below, where 'src' refers to the
the source operand and 'dst' refers to the value of the destination
register.
===== ===== ======= ==========================================================
name code offset description
===== ===== ======= ==========================================================
ADD 0x0 0 dst += src
SUB 0x1 0 dst -= src
MUL 0x2 0 dst \*= src
DIV 0x3 0 dst = (src != 0) ? (dst / src) : 0
SDIV 0x3 1 dst = (src != 0) ? (dst s/ src) : 0
OR 0x4 0 dst \|= src
AND 0x5 0 dst &= src
LSH 0x6 0 dst <<= (src & mask)
RSH 0x7 0 dst >>= (src & mask)
NEG 0x8 0 dst = -dst
MOD 0x9 0 dst = (src != 0) ? (dst % src) : dst
SMOD 0x9 1 dst = (src != 0) ? (dst s% src) : dst
XOR 0xa 0 dst ^= src
MOV 0xb 0 dst = src
MOVSX 0xb 8/16/32 dst = (s8,s16,s32)src
ARSH 0xc 0 :term:`sign extending<Sign Extend>` dst >>= (src & mask)
END 0xd 0 byte swap operations (see `Byte swap instructions`_ below)
===== ===== ======= ==========================================================
.. table:: Arithmetic instructions
===== ===== ======= ==========================================================
name code offset description
===== ===== ======= ==========================================================
ADD 0x0 0 dst += src
SUB 0x1 0 dst -= src
MUL 0x2 0 dst \*= src
DIV 0x3 0 dst = (src != 0) ? (dst / src) : 0
SDIV 0x3 1 dst = (src != 0) ? (dst s/ src) : 0
OR 0x4 0 dst \|= src
AND 0x5 0 dst &= src
LSH 0x6 0 dst <<= (src & mask)
RSH 0x7 0 dst >>= (src & mask)
NEG 0x8 0 dst = -dst
MOD 0x9 0 dst = (src != 0) ? (dst % src) : dst
SMOD 0x9 1 dst = (src != 0) ? (dst s% src) : dst
XOR 0xa 0 dst ^= src
MOV 0xb 0 dst = src
MOVSX 0xb 8/16/32 dst = (s8,s16,s32)src
ARSH 0xc 0 :term:`sign extending<Sign Extend>` dst >>= (src & mask)
END 0xd 0 byte swap operations (see `Byte swap instructions`_ below)
===== ===== ======= ==========================================================
Underflow and overflow are allowed during arithmetic operations, meaning
the 64-bit or 32-bit value will wrap. If BPF program execution would
@ -426,13 +432,15 @@ select what byte order the operation converts from or to. For
``ALU64``, the 1-bit source operand field in the opcode is reserved
and MUST be set to 0.
===== ======== ===== =================================================
class source value description
===== ======== ===== =================================================
ALU TO_LE 0 convert between host byte order and little endian
ALU TO_BE 1 convert between host byte order and big endian
ALU64 Reserved 0 do byte swap unconditionally
===== ======== ===== =================================================
.. table:: Byte swap instructions
===== ======== ===== =================================================
class source value description
===== ======== ===== =================================================
ALU TO_LE 0 convert between host byte order and little endian
ALU TO_BE 1 convert between host byte order and big endian
ALU64 Reserved 0 do byte swap unconditionally
===== ======== ===== =================================================
The 'imm' field encodes the width of the swap operations. The following widths
are supported: 16, 32 and 64. Width 64 operations belong to the base64
@ -468,27 +476,29 @@ otherwise identical operations, and indicates the base64 conformance
group unless otherwise specified.
The 'code' field encodes the operation as below:
======== ===== ======= ================================= ===================================================
code value src_reg description notes
======== ===== ======= ================================= ===================================================
JA 0x0 0x0 PC += offset {JA, K, JMP} only
JA 0x0 0x0 PC += imm {JA, K, JMP32} only
JEQ 0x1 any PC += offset if dst == src
JGT 0x2 any PC += offset if dst > src unsigned
JGE 0x3 any PC += offset if dst >= src unsigned
JSET 0x4 any PC += offset if dst & src
JNE 0x5 any PC += offset if dst != src
JSGT 0x6 any PC += offset if dst > src signed
JSGE 0x7 any PC += offset if dst >= src signed
CALL 0x8 0x0 call helper function by static ID {CALL, K, JMP} only, see `Helper functions`_
CALL 0x8 0x1 call PC += imm {CALL, K, JMP} only, see `Program-local functions`_
CALL 0x8 0x2 call helper function by BTF ID {CALL, K, JMP} only, see `Helper functions`_
EXIT 0x9 0x0 return {CALL, K, JMP} only
JLT 0xa any PC += offset if dst < src unsigned
JLE 0xb any PC += offset if dst <= src unsigned
JSLT 0xc any PC += offset if dst < src signed
JSLE 0xd any PC += offset if dst <= src signed
======== ===== ======= ================================= ===================================================
.. table:: Jump instructions
======== ===== ======= ================================= ===================================================
code value src_reg description notes
======== ===== ======= ================================= ===================================================
JA 0x0 0x0 PC += offset {JA, K, JMP} only
JA 0x0 0x0 PC += imm {JA, K, JMP32} only
JEQ 0x1 any PC += offset if dst == src
JGT 0x2 any PC += offset if dst > src unsigned
JGE 0x3 any PC += offset if dst >= src unsigned
JSET 0x4 any PC += offset if dst & src
JNE 0x5 any PC += offset if dst != src
JSGT 0x6 any PC += offset if dst > src signed
JSGE 0x7 any PC += offset if dst >= src signed
CALL 0x8 0x0 call helper function by static ID {CALL, K, JMP} only, see `Helper functions`_
CALL 0x8 0x1 call PC += imm {CALL, K, JMP} only, see `Program-local functions`_
CALL 0x8 0x2 call helper function by BTF ID {CALL, K, JMP} only, see `Helper functions`_
EXIT 0x9 0x0 return {CALL, K, JMP} only
JLT 0xa any PC += offset if dst < src unsigned
JLE 0xb any PC += offset if dst <= src unsigned
JSLT 0xc any PC += offset if dst < src signed
JSLE 0xd any PC += offset if dst <= src signed
======== ===== ======= ================================= ===================================================
where 'PC' denotes the program counter, and the offset to increment by
is in units of 64-bit instructions relative to the instruction following
@ -559,6 +569,8 @@ For load and store instructions (``LD``, ``LDX``, ``ST``, and ``STX``), the
**mode**
The mode modifier is one of:
.. table:: Mode modifier
============= ===== ==================================== =============
mode modifier value description reference
============= ===== ==================================== =============
@ -573,6 +585,8 @@ For load and store instructions (``LD``, ``LDX``, ``ST``, and ``STX``), the
**sz (size)**
The size modifier is one of:
.. table:: Size modifier
==== ===== =====================
size value description
==== ===== =====================
@ -641,14 +655,16 @@ The 'imm' field is used to encode the actual atomic operation.
Simple atomic operation use a subset of the values defined to encode
arithmetic operations in the 'imm' field to encode the atomic operation:
======== ===== ===========
imm value description
======== ===== ===========
ADD 0x00 atomic add
OR 0x40 atomic or
AND 0x50 atomic and
XOR 0xa0 atomic xor
======== ===== ===========
.. table:: Simple atomic operations
======== ===== ===========
imm value description
======== ===== ===========
ADD 0x00 atomic add
OR 0x40 atomic or
AND 0x50 atomic and
XOR 0xa0 atomic xor
======== ===== ===========
``{ATOMIC, W, STX}`` with 'imm' = ADD means::
@ -662,6 +678,8 @@ XOR 0xa0 atomic xor
In addition to the simple atomic operations, there also is a modifier and
two complex atomic operations:
.. table:: Complex atomic operations
=========== ================ ===========================
imm value description
=========== ================ ===========================
@ -695,17 +713,19 @@ The following table defines a set of ``{IMM, DW, LD}`` instructions
with opcode subtypes in the 'src_reg' field, using new terms such as "map"
defined further below:
======= ========================================= =========== ==============
src_reg pseudocode imm type dst type
======= ========================================= =========== ==============
0x0 dst = (next_imm << 32) | imm integer integer
0x1 dst = map_by_fd(imm) map fd map
0x2 dst = map_val(map_by_fd(imm)) + next_imm map fd data address
0x3 dst = var_addr(imm) variable id data address
0x4 dst = code_addr(imm) integer code address
0x5 dst = map_by_idx(imm) map index map
0x6 dst = map_val(map_by_idx(imm)) + next_imm map index data address
======= ========================================= =========== ==============
.. table:: 64-bit immediate instructions
======= ========================================= =========== ==============
src_reg pseudocode imm type dst type
======= ========================================= =========== ==============
0x0 dst = (next_imm << 32) | imm integer integer
0x1 dst = map_by_fd(imm) map fd map
0x2 dst = map_val(map_by_fd(imm)) + next_imm map fd data address
0x3 dst = var_addr(imm) variable id data address
0x4 dst = code_addr(imm) integer code address
0x5 dst = map_by_idx(imm) map index map
0x6 dst = map_val(map_by_idx(imm)) + next_imm map index data address
======= ========================================= =========== ==============
where