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OpenCloudOS-Kernel/Documentation/bpf/instruction-set.rst

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bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
====================
eBPF Instruction Set
====================
bpf, docs: Split the comparism to classic BPF from instruction-set.rst Split the introductory that explain eBPF vs classic BPF and how it maps to hardware from the instruction set specification into a standalone document. This duplicates a little bit of information but gives us a useful reference for the eBPF instrution set that is not encumbered by classic BPF. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-3-hch@lst.de
2021-12-23 18:19:04 +08:00
Registers and calling convention
================================
eBPF has 10 general purpose registers and a read-only frame pointer register,
all of which are 64-bits wide.
The eBPF calling convention is defined as:
* R0: return value from function calls, and exit value for eBPF programs
* R1 - R5: arguments for function calls
* R6 - R9: callee saved registers that function calls will preserve
* R10: read-only frame pointer to access stack
R0 - R5 are scratch registers and eBPF programs needs to spill/fill them if
necessary across calls.
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Add a setion to explain the basic instruction encoding The eBPF instruction set document does not currently document the basic instruction encoding. Add a section to do that. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-2-hch@lst.de
2022-01-04 02:35:51 +08:00
Instruction encoding
====================
bpf, docs: Better document the extended instruction format In addition to the normal 64-bit instruction encoding, eBPF also has a single instruction that uses a second 64-bit bits for a second immediate value. Instead of only documenting this format deep down in the document mention it in the instruction encoding section. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-5-hch@lst.de
2022-02-01 02:36:37 +08:00
eBPF has two instruction encodings:
* the basic instruction encoding, which uses 64 bits to encode an instruction
* the wide instruction encoding, which appends a second 64-bit immediate value
(imm64) after the basic instruction for a total of 128 bits.
The basic instruction encoding looks as follows:
bpf, docs: Add a setion to explain the basic instruction encoding The eBPF instruction set document does not currently document the basic instruction encoding. Add a section to do that. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-2-hch@lst.de
2022-01-04 02:35:51 +08:00
============= ======= =============== ==================== ============
32 bits (MSB) 16 bits 4 bits 4 bits 8 bits (LSB)
============= ======= =============== ==================== ============
immediate offset source register destination register opcode
============= ======= =============== ==================== ============
Note that most instructions do not use all of the fields.
Unused fields shall be cleared to zero.
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
Instruction classes
bpf, docs: Add a setion to explain the basic instruction encoding The eBPF instruction set document does not currently document the basic instruction encoding. Add a section to do that. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-2-hch@lst.de
2022-01-04 02:35:51 +08:00
-------------------
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
The three LSB bits of the 'opcode' field store the instruction class:
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Document the opcode classes Add a description for each opcode class. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-4-hch@lst.de
2022-01-04 02:35:53 +08:00
========= ===== ===============================
class value description
========= ===== ===============================
BPF_LD 0x00 non-standard load operations
BPF_LDX 0x01 load into register operations
BPF_ST 0x02 store from immediate operations
BPF_STX 0x03 store from register operations
BPF_ALU 0x04 32-bit arithmetic operations
BPF_JMP 0x05 64-bit jump operations
BPF_JMP32 0x06 32-bit jump operations
BPF_ALU64 0x07 64-bit arithmetic operations
========= ===== ===============================
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
Arithmetic and jump instructions
================================
For arithmetic and jump instructions (BPF_ALU, BPF_ALU64, BPF_JMP and
BPF_JMP32), the 8-bit 'opcode' field is divided into three parts:
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
============== ====== =================
4 bits (MSB) 1 bit 3 bits (LSB)
============== ====== =================
operation code source instruction class
============== ====== =================
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
The 4th bit encodes the source operand:
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
====== ===== ========================================
source value description
====== ===== ========================================
BPF_K 0x00 use 32-bit immediate as source operand
BPF_X 0x08 use 'src_reg' register as source operand
====== ===== ========================================
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
The four MSB bits store the operation code.
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Add subsections for ALU and JMP instructions Add a little more stucture to the ALU/JMP documentation with sections and improve the example text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-3-hch@lst.de
2022-01-04 02:35:52 +08:00
Arithmetic instructions
-----------------------
BPF_ALU uses 32-bit wide operands while BPF_ALU64 uses 64-bit wide operands for
otherwise identical operations.
The code field encodes the operation as below:
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
bpf, docs: Document the byte swapping instructions Add a section to document the byte swapping instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-2-hch@lst.de
2022-02-01 02:36:34 +08:00
======== ===== =================================================
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
code value description
bpf, docs: Document the byte swapping instructions Add a section to document the byte swapping instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-2-hch@lst.de
2022-02-01 02:36:34 +08:00
======== ===== =================================================
bpf, docs: Fully document the ALU opcodes Add pseudo-code to document all the different BPF_ALU / BPF_ALU64 opcodes. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-5-hch@lst.de
2022-01-04 02:35:54 +08:00
BPF_ADD 0x00 dst += src
BPF_SUB 0x10 dst -= src
BPF_MUL 0x20 dst \*= src
BPF_DIV 0x30 dst /= src
BPF_OR 0x40 dst \|= src
BPF_AND 0x50 dst &= src
BPF_LSH 0x60 dst <<= src
BPF_RSH 0x70 dst >>= src
BPF_NEG 0x80 dst = ~src
BPF_MOD 0x90 dst %= src
BPF_XOR 0xa0 dst ^= src
BPF_MOV 0xb0 dst = src
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
BPF_ARSH 0xc0 sign extending shift right
bpf, docs: Document the byte swapping instructions Add a section to document the byte swapping instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-2-hch@lst.de
2022-02-01 02:36:34 +08:00
BPF_END 0xd0 byte swap operations (see separate section below)
======== ===== =================================================
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Add subsections for ALU and JMP instructions Add a little more stucture to the ALU/JMP documentation with sections and improve the example text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-3-hch@lst.de
2022-01-04 02:35:52 +08:00
BPF_ADD | BPF_X | BPF_ALU means::
dst_reg = (u32) dst_reg + (u32) src_reg;
BPF_ADD | BPF_X | BPF_ALU64 means::
dst_reg = dst_reg + src_reg
BPF_XOR | BPF_K | BPF_ALU means::
src_reg = (u32) src_reg ^ (u32) imm32
BPF_XOR | BPF_K | BPF_ALU64 means::
src_reg = src_reg ^ imm32
bpf, docs: Document the byte swapping instructions Add a section to document the byte swapping instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-2-hch@lst.de
2022-02-01 02:36:34 +08:00
Byte swap instructions
----------------------
bpf, docs: Fix typo "BFP_ALU" to "BPF_ALU" "BFP" should be "BPF" Signed-off-by: Kosuke Fujimoto <fujimotokosuke0@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20220609083937.245749-1-fujimotoksouke0@gmail.com
2022-06-09 16:39:37 +08:00
The byte swap instructions use an instruction class of ``BPF_ALU`` and a 4-bit
bpf, docs: Document the byte swapping instructions Add a section to document the byte swapping instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-2-hch@lst.de
2022-02-01 02:36:34 +08:00
code field of ``BPF_END``.
bpf, docs: Remove duplicated word "instructions" The word "instructions" is duplicated, remove it. Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/1651139754-4838-2-git-send-email-yangtiezhu@loongson.cn
2022-04-28 17:55:52 +08:00
The byte swap instructions operate on the destination register
bpf, docs: Document the byte swapping instructions Add a section to document the byte swapping instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-2-hch@lst.de
2022-02-01 02:36:34 +08:00
only and do not use a separate source register or immediate value.
The 1-bit source operand field in the opcode is used to to select what byte
order the operation convert from or to:
========= ===== =================================================
source value description
========= ===== =================================================
BPF_TO_LE 0x00 convert between host byte order and little endian
BPF_TO_BE 0x08 convert between host byte order and big endian
========= ===== =================================================
The imm field encodes the width of the swap operations. The following widths
are supported: 16, 32 and 64.
Examples:
``BPF_ALU | BPF_TO_LE | BPF_END`` with imm = 16 means::
dst_reg = htole16(dst_reg)
``BPF_ALU | BPF_TO_BE | BPF_END`` with imm = 64 means::
dst_reg = htobe64(dst_reg)
``BPF_FROM_LE`` and ``BPF_FROM_BE`` exist as aliases for ``BPF_TO_LE`` and
bpf, docs: Fix typo "respetively" to "respectively" "respetively" should be "respectively". Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/1651139754-4838-4-git-send-email-yangtiezhu@loongson.cn
2022-04-28 17:55:54 +08:00
``BPF_TO_BE`` respectively.
bpf, docs: Document the byte swapping instructions Add a section to document the byte swapping instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-2-hch@lst.de
2022-02-01 02:36:34 +08:00
bpf, docs: Add subsections for ALU and JMP instructions Add a little more stucture to the ALU/JMP documentation with sections and improve the example text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-3-hch@lst.de
2022-01-04 02:35:52 +08:00
Jump instructions
-----------------
BPF_JMP32 uses 32-bit wide operands while BPF_JMP uses 64-bit wide operands for
otherwise identical operations.
The code field encodes the operation as below:
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Fully document the JMP opcodes Add pseudo-code to document all the different BPF_JMP / BPF_JMP64 opcodes. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-6-hch@lst.de
2022-01-04 02:35:55 +08:00
======== ===== ========================= ============
code value description notes
======== ===== ========================= ============
BPF_JA 0x00 PC += off BPF_JMP only
BPF_JEQ 0x10 PC += off if dst == src
BPF_JGT 0x20 PC += off if dst > src unsigned
BPF_JGE 0x30 PC += off if dst >= src unsigned
BPF_JSET 0x40 PC += off if dst & src
BPF_JNE 0x50 PC += off if dst != src
BPF_JSGT 0x60 PC += off if dst > src signed
BPF_JSGE 0x70 PC += off if dst >= src signed
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
BPF_CALL 0x80 function call
bpf, docs: Fully document the JMP opcodes Add pseudo-code to document all the different BPF_JMP / BPF_JMP64 opcodes. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-6-hch@lst.de
2022-01-04 02:35:55 +08:00
BPF_EXIT 0x90 function / program return BPF_JMP only
BPF_JLT 0xa0 PC += off if dst < src unsigned
BPF_JLE 0xb0 PC += off if dst <= src unsigned
BPF_JSLT 0xc0 PC += off if dst < src signed
BPF_JSLE 0xd0 PC += off if dst <= src signed
======== ===== ========================= ============
bpf, docs: Split the comparism to classic BPF from instruction-set.rst Split the introductory that explain eBPF vs classic BPF and how it maps to hardware from the instruction set specification into a standalone document. This duplicates a little bit of information but gives us a useful reference for the eBPF instrution set that is not encumbered by classic BPF. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-3-hch@lst.de
2021-12-23 18:19:04 +08:00
bpf, docs: Add subsections for ALU and JMP instructions Add a little more stucture to the ALU/JMP documentation with sections and improve the example text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-3-hch@lst.de
2022-01-04 02:35:52 +08:00
The eBPF program needs to store the return value into register R0 before doing a
BPF_EXIT.
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
Load and store instructions
===========================
For load and store instructions (BPF_LD, BPF_LDX, BPF_ST and BPF_STX), the
8-bit 'opcode' field is divided as:
============ ====== =================
3 bits (MSB) 2 bits 3 bits (LSB)
============ ====== =================
mode size instruction class
============ ====== =================
The size modifier is one of:
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
============= ===== =====================
size modifier value description
============= ===== =====================
BPF_W 0x00 word (4 bytes)
BPF_H 0x08 half word (2 bytes)
BPF_B 0x10 byte
BPF_DW 0x18 double word (8 bytes)
============= ===== =====================
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
The mode modifier is one of:
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Fully document the JMP mode modifiers Add a description for all the modifiers. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-7-hch@lst.de
2022-01-04 02:35:56 +08:00
============= ===== ====================================
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
mode modifier value description
bpf, docs: Fully document the JMP mode modifiers Add a description for all the modifiers. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-7-hch@lst.de
2022-01-04 02:35:56 +08:00
============= ===== ====================================
bpf, docs: Better document the extended instruction format In addition to the normal 64-bit instruction encoding, eBPF also has a single instruction that uses a second 64-bit bits for a second immediate value. Instead of only documenting this format deep down in the document mention it in the instruction encoding section. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-5-hch@lst.de
2022-02-01 02:36:37 +08:00
BPF_IMM 0x00 64-bit immediate instructions
bpf, docs: Better document the legacy packet access instruction Use consistent terminology and structured RST elements to better document these two oddball instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-4-hch@lst.de
2022-02-01 02:36:36 +08:00
BPF_ABS 0x20 legacy BPF packet access (absolute)
BPF_IND 0x40 legacy BPF packet access (indirect)
bpf, docs: Better document the regular load and store instructions Add a separate section and a little intro blurb for the regular load and store instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-3-hch@lst.de
2022-02-01 02:36:35 +08:00
BPF_MEM 0x60 regular load and store operations
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
BPF_ATOMIC 0xc0 atomic operations
bpf, docs: Fully document the JMP mode modifiers Add a description for all the modifiers. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103183556.41040-7-hch@lst.de
2022-01-04 02:35:56 +08:00
============= ===== ====================================
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the regular load and store instructions Add a separate section and a little intro blurb for the regular load and store instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-3-hch@lst.de
2022-02-01 02:36:35 +08:00
Regular load and store operations
---------------------------------
The ``BPF_MEM`` mode modifier is used to encode regular load and store
instructions that transfer data between a register and memory.
``BPF_MEM | <size> | BPF_STX`` means::
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
*(size *) (dst_reg + off) = src_reg
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the regular load and store instructions Add a separate section and a little intro blurb for the regular load and store instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-3-hch@lst.de
2022-02-01 02:36:35 +08:00
``BPF_MEM | <size> | BPF_ST`` means::
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
*(size *) (dst_reg + off) = imm32
bpf, docs: Better document the regular load and store instructions Add a separate section and a little intro blurb for the regular load and store instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-3-hch@lst.de
2022-02-01 02:36:35 +08:00
``BPF_MEM | <size> | BPF_LDX`` means::
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
dst_reg = *(size *) (src_reg + off)
bpf, docs: Better document the regular load and store instructions Add a separate section and a little intro blurb for the regular load and store instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-3-hch@lst.de
2022-02-01 02:36:35 +08:00
Where size is one of: ``BPF_B``, ``BPF_H``, ``BPF_W``, or ``BPF_DW``.
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
Atomic operations
-----------------
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the atomic instructions Use proper tables and RST markup to document the atomic instructions in a structured way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-6-hch@lst.de
2022-02-01 02:36:38 +08:00
Atomic operations are operations that operate on memory and can not be
interrupted or corrupted by other access to the same memory region
by other eBPF programs or means outside of this specification.
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the atomic instructions Use proper tables and RST markup to document the atomic instructions in a structured way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-6-hch@lst.de
2022-02-01 02:36:38 +08:00
All atomic operations supported by eBPF are encoded as store operations
that use the ``BPF_ATOMIC`` mode modifier as follows:
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the atomic instructions Use proper tables and RST markup to document the atomic instructions in a structured way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-6-hch@lst.de
2022-02-01 02:36:38 +08:00
* ``BPF_ATOMIC | BPF_W | BPF_STX`` for 32-bit operations
* ``BPF_ATOMIC | BPF_DW | BPF_STX`` for 64-bit operations
* 8-bit and 16-bit wide atomic operations are not supported.
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the atomic instructions Use proper tables and RST markup to document the atomic instructions in a structured way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-6-hch@lst.de
2022-02-01 02:36:38 +08:00
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:
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the atomic instructions Use proper tables and RST markup to document the atomic instructions in a structured way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-6-hch@lst.de
2022-02-01 02:36:38 +08:00
======== ===== ===========
imm value description
======== ===== ===========
BPF_ADD 0x00 atomic add
BPF_OR 0x40 atomic or
BPF_AND 0x50 atomic and
BPF_XOR 0xa0 atomic xor
======== ===== ===========
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the atomic instructions Use proper tables and RST markup to document the atomic instructions in a structured way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-6-hch@lst.de
2022-02-01 02:36:38 +08:00
``BPF_ATOMIC | BPF_W | BPF_STX`` with imm = BPF_ADD means::
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the atomic instructions Use proper tables and RST markup to document the atomic instructions in a structured way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-6-hch@lst.de
2022-02-01 02:36:38 +08:00
*(u32 *)(dst_reg + off16) += src_reg
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the atomic instructions Use proper tables and RST markup to document the atomic instructions in a structured way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-6-hch@lst.de
2022-02-01 02:36:38 +08:00
``BPF_ATOMIC | BPF_DW | BPF_STX`` with imm = BPF ADD means::
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the atomic instructions Use proper tables and RST markup to document the atomic instructions in a structured way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-6-hch@lst.de
2022-02-01 02:36:38 +08:00
*(u64 *)(dst_reg + off16) += src_reg
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
bpf, docs: Better document the atomic instructions Use proper tables and RST markup to document the atomic instructions in a structured way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-6-hch@lst.de
2022-02-01 02:36:38 +08:00
``BPF_XADD`` is a deprecated name for ``BPF_ATOMIC | BPF_ADD``.
In addition to the simple atomic operations, there also is a modifier and
two complex atomic operations:
=========== ================ ===========================
imm value description
=========== ================ ===========================
BPF_FETCH 0x01 modifier: return old value
BPF_XCHG 0xe0 | BPF_FETCH atomic exchange
BPF_CMPXCHG 0xf0 | BPF_FETCH atomic compare and exchange
=========== ================ ===========================
The ``BPF_FETCH`` modifier is optional for simple atomic operations, and
always set for the complex atomic operations. If the ``BPF_FETCH`` flag
is set, then the operation also overwrites ``src_reg`` with the value that
was in memory before it was modified.
The ``BPF_XCHG`` operation atomically exchanges ``src_reg`` with the value
addressed by ``dst_reg + off``.
The ``BPF_CMPXCHG`` operation atomically compares the value addressed by
``dst_reg + off`` with ``R0``. If they match, the value addressed by
``dst_reg + off`` is replaced with ``src_reg``. In either case, the
value that was at ``dst_reg + off`` before the operation is zero-extended
and loaded back to ``R0``.
bpf, docs: Split general purpose eBPF documentation out of filter.rst filter.rst starts out documenting the classic BPF and then spills into introducing and documentating eBPF. Move the eBPF documentation into rwo new files under Documentation/bpf/ for the instruction set and the verifier and link to the BPF documentation from filter.rst. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de
2021-11-20 00:32:15 +08:00
Clang can generate atomic instructions by default when ``-mcpu=v3`` is
enabled. If a lower version for ``-mcpu`` is set, the only atomic instruction
Clang can generate is ``BPF_ADD`` *without* ``BPF_FETCH``. If you need to enable
the atomics features, while keeping a lower ``-mcpu`` version, you can use
``-Xclang -target-feature -Xclang +alu32``.
bpf, docs: Better document the extended instruction format In addition to the normal 64-bit instruction encoding, eBPF also has a single instruction that uses a second 64-bit bits for a second immediate value. Instead of only documenting this format deep down in the document mention it in the instruction encoding section. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-5-hch@lst.de
2022-02-01 02:36:37 +08:00
64-bit immediate instructions
-----------------------------
Instructions with the ``BPF_IMM`` mode modifier use the wide instruction
encoding for an extra imm64 value.
There is currently only one such instruction.
``BPF_LD | BPF_DW | BPF_IMM`` means::
dst_reg = imm64
bpf, docs: Generate nicer tables for instruction encodings Use RST tables that are nicely readable both in plain ascii as well as in html to render the instruction encodings, and add a few subheadings to better structure the text. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-4-hch@lst.de
2021-12-23 18:19:05 +08:00
bpf, docs: Move the packet access instructions last in instruction-set.rst The packet access instructions are a convoluted leftover from classic BPF. Move them last past the much more important atomic operations, and improve the rendering of the code example. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-5-hch@lst.de
2021-12-23 18:19:06 +08:00
bpf, docs: Better document the legacy packet access instruction Use consistent terminology and structured RST elements to better document these two oddball instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-4-hch@lst.de
2022-02-01 02:36:36 +08:00
Legacy BPF Packet access instructions
-------------------------------------
bpf, docs: Move the packet access instructions last in instruction-set.rst The packet access instructions are a convoluted leftover from classic BPF. Move them last past the much more important atomic operations, and improve the rendering of the code example. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-5-hch@lst.de
2021-12-23 18:19:06 +08:00
bpf, docs: Better document the legacy packet access instruction Use consistent terminology and structured RST elements to better document these two oddball instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-4-hch@lst.de
2022-02-01 02:36:36 +08:00
eBPF has special instructions for access to packet data that have been
carried over from classic BPF to retain the performance of legacy socket
filters running in the eBPF interpreter.
bpf, docs: Move the packet access instructions last in instruction-set.rst The packet access instructions are a convoluted leftover from classic BPF. Move them last past the much more important atomic operations, and improve the rendering of the code example. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-5-hch@lst.de
2021-12-23 18:19:06 +08:00
bpf, docs: Better document the legacy packet access instruction Use consistent terminology and structured RST elements to better document these two oddball instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-4-hch@lst.de
2022-02-01 02:36:36 +08:00
The instructions come in two forms: ``BPF_ABS | <size> | BPF_LD`` and
``BPF_IND | <size> | BPF_LD``.
bpf, docs: Move the packet access instructions last in instruction-set.rst The packet access instructions are a convoluted leftover from classic BPF. Move them last past the much more important atomic operations, and improve the rendering of the code example. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-5-hch@lst.de
2021-12-23 18:19:06 +08:00
bpf, docs: Better document the legacy packet access instruction Use consistent terminology and structured RST elements to better document these two oddball instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-4-hch@lst.de
2022-02-01 02:36:36 +08:00
These instructions are used to access packet data and can only be used when
the program context is a pointer to networking packet. ``BPF_ABS``
accesses packet data at an absolute offset specified by the immediate data
and ``BPF_IND`` access packet data at an offset that includes the value of
a register in addition to the immediate data.
bpf, docs: Move the packet access instructions last in instruction-set.rst The packet access instructions are a convoluted leftover from classic BPF. Move them last past the much more important atomic operations, and improve the rendering of the code example. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-5-hch@lst.de
2021-12-23 18:19:06 +08:00
bpf, docs: Better document the legacy packet access instruction Use consistent terminology and structured RST elements to better document these two oddball instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-4-hch@lst.de
2022-02-01 02:36:36 +08:00
These instructions have seven implicit operands:
bpf, docs: Move the packet access instructions last in instruction-set.rst The packet access instructions are a convoluted leftover from classic BPF. Move them last past the much more important atomic operations, and improve the rendering of the code example. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-5-hch@lst.de
2021-12-23 18:19:06 +08:00
bpf, docs: Better document the legacy packet access instruction Use consistent terminology and structured RST elements to better document these two oddball instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-4-hch@lst.de
2022-02-01 02:36:36 +08:00
* Register R6 is an implicit input that must contain pointer to a
struct sk_buff.
* Register R0 is an implicit output which contains the data fetched from
the packet.
* Registers R1-R5 are scratch registers that are clobbered after a call to
bpf, docs: Fix the code formatting in instruction-set A minor typo fix to include "| BPF_LD" into its previous code phrase: ``BPF_IND`` | BPF_LD --> ``BPF_IND | BPF_LD`` Signed-off-by: Shahab Vahedi <shahab@synopsys.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/b6120b31-3d1d-bf2d-2f2a-aa768d91257b@synopsys.com
2022-06-24 22:14:11 +08:00
``BPF_ABS | BPF_LD`` or ``BPF_IND | BPF_LD`` instructions.
bpf, docs: Better document the legacy packet access instruction Use consistent terminology and structured RST elements to better document these two oddball instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-4-hch@lst.de
2022-02-01 02:36:36 +08:00
These instructions have an implicit program exit condition as well. When an
eBPF program is trying to access the data beyond the packet boundary, the
program execution will be aborted.
``BPF_ABS | BPF_W | BPF_LD`` means::
bpf, docs: Move the packet access instructions last in instruction-set.rst The packet access instructions are a convoluted leftover from classic BPF. Move them last past the much more important atomic operations, and improve the rendering of the code example. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211223101906.977624-5-hch@lst.de
2021-12-23 18:19:06 +08:00
bpf, docs: Better document the legacy packet access instruction Use consistent terminology and structured RST elements to better document these two oddball instructions. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220131183638.3934982-4-hch@lst.de
2022-02-01 02:36:36 +08:00
R0 = ntohl(*(u32 *) (((struct sk_buff *) R6)->data + imm32))
``BPF_IND | BPF_W | BPF_LD`` means::
R0 = ntohl(*(u32 *) (((struct sk_buff *) R6)->data + src_reg + imm32))