BPF Instruction Set Architecture (ISA)
Redmond 98052 United States of America WA dave.thaler.ietf@gmail.com
INT bdf eBPF virtual machine extensibility eBPF (which is no longer an acronym for anything), also commonly referred to as BPF, is a technology with origins in the Linux kernel that can run untrusted programs in a privileged context such as an operating system kernel. This document specifies the BPF instruction set architecture (ISA).
Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at .
Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents () in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.
Table of Contents
  • .  Introduction
  • .  Documentation Conventions
    • .  Types
    • .  Functions
    • .  Definitions
    • .  Conformance Groups
  • .  Instruction Encoding
    • .  Basic Instruction Encoding
    • .  Wide Instruction Encoding
    • .  Instruction Classes
  • .  Arithmetic and Jump Instructions
    • .  Arithmetic Instructions
    • .  Byte Swap Instructions
    • .  Jump Instructions
      • .  Helper Functions
      • .  Program-Local Functions
  • .  Load and Store Instructions
    • .  Regular Load and Store Operations
    • .  Sign-Extension Load Operations
    • .  Atomic Operations
    • .  64-bit Immediate Instructions
      • .  Maps
      • .  Platform Variables
    • .  Legacy BPF Packet Access Instructions
  • .  Security Considerations
  • .  IANA Considerations
    • .  BPF Instruction Conformance Groups Registry
      • .  BPF Instruction Conformance Groups Registration Template
    • .  BPF Instruction Set Registry
      • .  BPF Instruction Registration Template
    • .  Adding Instructions
    • .  Deprecating Instructions
    • .  Change Control
    • .  Expert Review Instructions
  • .  References
    • .  Normative References
    • .  Informative References
  • .  Initial BPF Instruction Set Values
  • Acknowledgements
  • Author's Address
Introduction eBPF, also commonly referred to as BPF, is a technology with origins in the Linux kernel that can run untrusted programs in a privileged context such as an operating system kernel. This document specifies the BPF instruction set architecture (ISA). As a historical note, BPF originally stood for Berkeley Packet Filter, but now that it can do so much more than packet filtering, the acronym no longer makes sense. BPF is now considered a standalone term that does not stand for anything. The original BPF is sometimes referred to as cBPF (classic BPF) to distinguish it from the now widely deployed eBPF (extended BPF).
Documentation Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here. For brevity and consistency, this document refers to families of types using a shorthand syntax and refers to several expository, mnemonic functions when describing the semantics of instructions. The range of valid values for those types and the semantics of those functions are defined in the following subsections.
Types This document refers to integer types with the notation SN to specify a type's signedness (S) and bit width (N), respectively. Meaning of Signedness Notation
S Meaning
u unsigned
s signed
Meaning of Bit-Width Notation
N Bit Width
8 8 bits
16 16 bits
32 32 bits
64 64 bits
128 128 bits
For example, u32 is a type whose valid values are all the 32-bit unsigned numbers and s16 is a type whose valid values are all the 16-bit signed numbers.
Functions The following byte swap functions are direction agnostic. That is, the same function is used for conversion in either direction discussed below.
  • be16: Takes an unsigned 16-bit number and converts it between host byte order and big-endian byte order .
  • be32: Takes an unsigned 32-bit number and converts it between host byte order and big-endian byte order.
  • be64: Takes an unsigned 64-bit number and converts it between host byte order and big-endian byte order.
  • bswap16: Takes an unsigned 16-bit number in either big- or little-endian format and returns the equivalent number with the same bit width but opposite endianness.
  • bswap32: Takes an unsigned 32-bit number in either big- or little-endian format and returns the equivalent number with the same bit width but opposite endianness.
  • bswap64: Takes an unsigned 64-bit number in either big- or little-endian format and returns the equivalent number with the same bit width but opposite endianness.
  • le16: Takes an unsigned 16-bit number and converts it between host byte order and little-endian byte order.
  • le32: Takes an unsigned 32-bit number and converts it between host byte order and little-endian byte order.
  • le64: Takes an unsigned 64-bit number and converts it between host byte order and little-endian byte order.
Definitions
Sign Extend:
To sign extend an X-bit number, A, to a Y-bit number, B, means to
  1. Copy all X bits from A to the lower X bits of B.
  2. Set the value of the remaining Y - X bits of B to the value of the most significant bit of A.
Conformance Groups An implementation does not need to support all instructions specified in this document (e.g., deprecated instructions). Instead, a number of conformance groups are specified. An implementation MUST support the base32 conformance group and MAY support additional conformance groups, where supporting a conformance group means it MUST support all instructions in that conformance group. The use of named conformance groups enables interoperability between a runtime that executes instructions, and tools such as compilers that generate instructions for the runtime. Thus, capability discovery in terms of conformance groups might be done manually by users or automatically by tools. Each conformance group has a short ASCII label (e.g., "base32") that corresponds to a set of instructions that are mandatory. That is, each instruction has one or more conformance groups of which it is a member. This document defines the following conformance groups:
base32:
includes all instructions defined in this specification unless otherwise noted.
base64:
includes base32, plus instructions explicitly noted as being in the base64 conformance group.
atomic32:
includes 32-bit atomic operation instructions (see ).
atomic64:
includes atomic32, plus 64-bit atomic operation instructions.
divmul32:
includes 32-bit division, multiplication, and modulo instructions.
divmul64:
includes divmul32, plus 64-bit division, multiplication, and modulo instructions.
packet:
deprecated packet access instructions.
Instruction Encoding BPF 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 bits after the basic instruction for a total of 128 bits.
Basic Instruction Encoding A basic instruction is encoded as follows: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | opcode | regs | offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | imm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
opcode:
operation to perform, encoded as follows: +-+-+-+-+-+-+-+-+ |specific |class| +-+-+-+-+-+-+-+-+
specific:
The format of these bits varies by instruction class
class:
the instruction class (see )
regs:
the source and destination register numbers, encoded as follows on a little-endian host: +-+-+-+-+-+-+-+-+ |src_reg|dst_reg| +-+-+-+-+-+-+-+-+ and as follows on a big-endian host: +-+-+-+-+-+-+-+-+ |dst_reg|src_reg| +-+-+-+-+-+-+-+-+
src_reg:
the source register number (0-10), except where otherwise specified (64-bit immediate instructions (see ) reuse this field for other purposes)
dst_reg:
the destination register number (0-10), unless otherwise specified (future instructions might reuse this field for other purposes)
offset:
signed integer offset used with pointer arithmetic, except where otherwise specified (some arithmetic instructions reuse this field for other purposes)
imm:
signed integer immediate value
Note that the contents of multi-byte fields ('offset' and 'imm') are stored using big-endian byte ordering on big-endian hosts and little-endian byte ordering on little-endian hosts. For example: opcode offset imm assembly src_reg dst_reg 07 0 1 00 00 44 33 22 11 r1 += 0x11223344 // little dst_reg src_reg 07 1 0 00 00 11 22 33 44 r1 += 0x11223344 // big Note that most instructions do not use all of the fields. Unused fields SHALL be cleared to zero.
Wide Instruction Encoding Some instructions are defined to use the wide instruction encoding, which uses two 32-bit immediate values. The 64 bits following the basic instruction format contain a pseudo instruction with 'opcode', 'dst_reg', 'src_reg', and 'offset' all set to zero. This is depicted in the following figure: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | opcode | regs | offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | imm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | next_imm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
opcode:
operation to perform, encoded as explained above
regs:
the source and destination register numbers (unless otherwise specified), encoded as explained above
offset:
signed integer offset used with pointer arithmetic, unless otherwise specified
imm:
signed integer immediate value
reserved:
unused, set to zero
next_imm:
second signed integer immediate value
Instruction Classes The three least significant bits of the 'opcode' field store the instruction class: Instruction Class
class Value Description Reference
LD 0x0 non-standard load operations
LDX 0x1 load into register operations
ST 0x2 store from immediate operations
STX 0x3 store from register operations
ALU 0x4 32-bit arithmetic operations
JMP 0x5 64-bit jump operations
JMP32 0x6 32-bit jump operations
ALU64 0x7 64-bit arithmetic operations
Arithmetic and Jump Instructions For arithmetic and jump instructions (ALU, ALU64, JMP, and JMP32), the 8-bit 'opcode' field is divided into three parts: +-+-+-+-+-+-+-+-+ | code |s|class| +-+-+-+-+-+-+-+-+
code:
the operation code, whose meaning varies by instruction class
s (source):
the source operand location, which unless otherwise specified is one of: Source Operand Location
source Value Description
K 0 use 32-bit 'imm' value as source operand
X 1 use 'src_reg' register value as source operand
class:
the instruction class (see )
Arithmetic Instructions ALU uses 32-bit wide operands while ALU64 uses 64-bit wide operands for otherwise identical operations. ALU64 instructions belong to the base64 conformance group unless noted otherwise. The 'code' field encodes the operation as below, where 'src' refers to the source operand and 'dst' refers to the value of the destination register. 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 sign extending () dst >>= (src & mask)
END 0xd 0 byte swap operations (see )
Underflow and overflow are allowed during arithmetic operations, meaning the 64-bit or 32-bit value will wrap. If BPF program execution would result in division by zero, the destination register is instead set to zero. If execution would result in modulo by zero, for ALU64 the value of the destination register is unchanged whereas for ALU the upper 32 bits of the destination register are zeroed. {ADD, X, ALU}, where 'code' = ADD, 'source' = X, and 'class' = ALU, means: dst = (u32) ((u32) dst + (u32) src) where '(u32)' indicates that the upper 32 bits are zeroed. {ADD, X, ALU64} means: dst = dst + src {XOR, K, ALU} means: dst = (u32) dst ^ (u32) imm {XOR, K, ALU64} means: dst = dst ^ imm Note that most arithmetic instructions have 'offset' set to 0. Only three instructions (SDIV, SMOD, MOVSX) have a non-zero 'offset'. Division, multiplication, and modulo operations for ALU are part of the "divmul32" conformance group, and division, multiplication, and modulo operations for ALU64 are part of the "divmul64" conformance group. The division and modulo operations support both unsigned and signed flavors. For unsigned operations (DIV and MOD), for ALU, 'imm' is interpreted as a 32-bit unsigned value. For ALU64, 'imm' is first sign extended () from 32 to 64 bits, and then interpreted as a 64-bit unsigned value. For signed operations (SDIV and SMOD), for ALU, 'imm' is interpreted as a 32-bit signed value. For ALU64, 'imm' is first sign extended () from 32 to 64 bits, and then interpreted as a 64-bit signed value. Note that there are varying definitions of the signed modulo operation when the dividend or divisor are negative, where implementations often vary by language such that Python, Ruby, etc. differ from C, Go, Java, etc. This specification requires that signed modulo MUST use truncated division (where -13 % 3 == -1) as implemented in C, Go, etc.: a % n = a - n * trunc(a / n) The MOVSX instruction does a move operation with sign extension. {MOVSX, X, ALU} sign extends () 8-bit and 16-bit operands into 32-bit operands, and zeroes the remaining upper 32 bits. {MOVSX, X, ALU64} sign extends () 8-bit, 16-bit, and 32-bit operands into 64-bit operands. Unlike other arithmetic instructions, MOVSX is only defined for register source operands (X). {MOV, K, ALU64} means: dst = (s64)imm {MOV, X, ALU} means: dst = (u32)src {MOVSX, X, ALU} with 'offset' 8 means: dst = (u32)(s32)(s8)src The NEG instruction is only defined when the source bit is clear (K). Shift operations use a mask of 0x3F (63) for 64-bit operations and 0x1F (31) for 32-bit operations.
Byte Swap Instructions The byte swap instructions use instruction classes of ALU and ALU64 and a 4-bit 'code' field of END. The byte swap instructions operate on the destination register only and do not use a separate source register or immediate value. For ALU, the 1-bit source operand field in the opcode is used to 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. Byte Swap Instructions
class source Value Description
ALU LE 0 convert between host byte order and little endian
ALU 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 conformance group and other swap operations belong to the base32 conformance group. Examples: {END, LE, ALU} with 'imm' = 16/32/64 means: dst = le16(dst) dst = le32(dst) dst = le64(dst) {END, BE, ALU} with 'imm' = 16/32/64 means: dst = be16(dst) dst = be32(dst) dst = be64(dst) {END, TO, ALU64} with 'imm' = 16/32/64 means: dst = bswap16(dst) dst = bswap32(dst) dst = bswap64(dst)
Jump Instructions JMP32 uses 32-bit wide operands and indicates the base32 conformance group; JMP uses 64-bit wide operands for otherwise identical operations and indicates the base64 conformance group unless otherwise specified. The 'code' field encodes the operation as below: 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
CALL 0x8 0x1 call PC += imm {CALL, K, JMP} only, see
CALL 0x8 0x2 call helper function by BTF ID {CALL, K, JMP} only, see
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 the jump instruction. Thus 'PC += 1' skips execution of the next instruction if it's a basic instruction or results in undefined behavior if the next instruction is a 128-bit wide instruction. Example: {JSGE, X, JMP32} means: if (s32)dst s>= (s32)src goto +offset where 's>=' indicates a signed '>=' comparison. {JLE, K, JMP} means: if dst <= (u64)(s64)imm goto +offset {JA, K, JMP32} means: gotol +imm where 'imm' means the branch offset comes from the 'imm' field. Note that there are two flavors of JA instructions. The JMP class permits a 16-bit jump offset specified by the 'offset' field, whereas the JMP32 class permits a 32-bit jump offset specified by the 'imm' field. A conditional jump greater than 16 bits may be converted to a conditional jump less than 16 bits plus a 32-bit unconditional jump. All CALL and JA instructions belong to the base32 conformance group.
Helper Functions Helper functions are a concept whereby BPF programs can call into a set of function calls exposed by the underlying platform. Historically, each helper function was identified by a static ID encoded in the 'imm' field. Further documentation of helper functions is outside the scope of this document and standardization is left for future work, but use is widely deployed and more information can be found in platform-specific documentation (e.g., Linux kernel documentation). Platforms that support the BPF Type Format (BTF) support identifying a helper function by a BTF ID encoded in the 'imm' field, where the BTF ID identifies the helper name and type. Further documentation of BTF is outside the scope of this document and standardization is left for future work, but use is widely deployed and more information can be found in platform-specific documentation (e.g., Linux kernel documentation).
Program-Local Functions Program-local functions are functions exposed by the same BPF program as the caller, and are referenced by offset from the instruction following the call instruction, similar to JA. The offset is encoded in the 'imm' field of the call instruction. An EXIT within the program-local function will return to the caller.
Load and Store Instructions For load and store instructions (LD, LDX, ST, and STX), the 8-bit 'opcode' field is divided as follows: +-+-+-+-+-+-+-+-+ |mode |sz |class| +-+-+-+-+-+-+-+-+
mode:
The mode modifier is one of: Mode Modifier
mode Value Description Reference
IMM 0 64-bit immediate instructions
ABS 1 legacy BPF packet access (absolute)
IND 2 legacy BPF packet access (indirect)
MEM 3 regular load and store operations
MEMSX 4 sign-extension load operations
ATOMIC 6 atomic operations
sz (size):
The size modifier is one of: Size Modifier
size Value Description
W 0 word (4 bytes)
H 1 half word (2 bytes)
B 2 byte
DW 3 double word (8 bytes)
Instructions using DW belong to the base64 conformance group.
class:
The instruction class (see )
Regular Load and Store Operations The MEM mode modifier is used to encode regular load and store instructions that transfer data between a register and memory. {MEM, <size>, STX} means: *(size *) (dst + offset) = src {MEM, <size>, ST} means: *(size *) (dst + offset) = imm {MEM, <size>, LDX} means: dst = *(unsigned size *) (src + offset) Where '<size>' is one of: B, H, W, or DW, and 'unsigned size' is one of: u8, u16, u32, or u64.
Sign-Extension Load Operations The MEMSX mode modifier is used to encode sign-extension load instructions () that transfer data between a register and memory. {MEMSX, <size>, LDX} means: dst = *(signed size *) (src + offset) Where '<size>' is one of: B, H, or W, and 'signed size' is one of: s8, s16, or s32.
Atomic Operations Atomic operations operate on memory and cannot be interrupted or corrupted by other access to the same memory region by other BPF programs or means outside of this specification. All atomic operations supported by BPF are encoded as store operations that use the ATOMIC mode modifier as follows:
  • {ATOMIC, W, STX} for 32-bit operations, which are part of the "atomic32" conformance group.
  • {ATOMIC, DW, STX} for 64-bit operations, which are part of the "atomic64" conformance group.
  • 8-bit and 16-bit wide atomic operations are not supported.
The 'imm' field is used to encode the actual atomic operation. Simple atomic operations use a subset of the values defined to encode arithmetic operations in the 'imm' field to encode the atomic operation: 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: *(u32 *)(dst + offset) += src {ATOMIC, DW, STX} with 'imm' = ADD means: *(u64 *)(dst + offset) += src In addition to the simple atomic operations, there is also a modifier and two complex atomic operations: Complex Atomic Operations and a Modifier
imm Value Description
FETCH 0x01 modifier: return old value
XCHG 0xe0 | FETCH atomic exchange
CMPXCHG 0xf0 | FETCH atomic compare and exchange
The FETCH modifier is optional for simple atomic operations and is always set for the complex atomic operations. If the FETCH flag is set, then the operation also overwrites src with the value that was in memory before it was modified. The XCHG operation atomically exchanges src with the value addressed by dst + offset. The CMPXCHG operation atomically compares the value addressed by dst + offset with R0. If they match, the value addressed by dst + offset is replaced with src. In either case, the value that was at dst + offset before the operation is zero-extended and loaded back to R0.
64-bit Immediate Instructions Instructions with the IMM 'mode' modifier use the wide instruction encoding defined in , and use the 'src_reg' field of the basic instruction to hold an opcode subtype. 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: 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
  • map_by_fd(imm) means to convert a 32-bit file descriptor into an address of a map (see )
  • map_by_idx(imm) means to convert a 32-bit index into an address of a map
  • map_val(map) gets the address of the first value in a given map
  • var_addr(imm) gets the address of a platform variable (see ) with a given id
  • code_addr(imm) gets the address of the instruction at a specified relative offset in number of (64-bit) instructions
  • the 'imm type' can be used by disassemblers for display
  • the 'dst type' can be used for verification and just-in-time compilation purposes
Maps Maps are shared memory regions accessible by BPF programs on some platforms. A map can have various semantics as defined in a separate document, and may or may not have a single contiguous memory region, but the 'map_val(map)' is currently only defined for maps that do have a single contiguous memory region. Each map can have a file descriptor (fd) if supported by the platform, where 'map_by_fd(imm)' means to get the map with the specified file descriptor. Each BPF program can also be defined to use a set of maps associated with the program at load time, and 'map_by_idx(imm)' means to get the map with the given index in the set associated with the BPF program containing the instruction.
Platform Variables Platform variables are memory regions, identified by integer ids, exposed by the runtime, and accessible by BPF programs on some platforms. The 'var_addr(imm)' operation means to get the address of the memory region identified by the given id.
Legacy BPF Packet Access Instructions BPF previously introduced special instructions for access to packet data that were carried over from classic BPF. These instructions used an instruction class of LD, a size modifier of W, H, or B, and a mode modifier of ABS or IND. The 'dst_reg' and 'offset' fields were set to zero, and 'src_reg' was set to zero for ABS. However, these instructions are deprecated and SHOULD no longer be used. All legacy packet access instructions belong to the "packet" conformance group.
Security Considerations BPF programs could use BPF instructions to do malicious things with memory, CPU, networking, or other system resources. This is not fundamentally different from any other type of software that may run on a device. Execution environments should be carefully designed to only run BPF programs that are trusted and verified, and sandboxing and privilege level separation are key strategies for limiting security and abuse impact. For example, BPF verifiers are well-known and widely deployed and are responsible for ensuring that BPF programs will terminate within a reasonable time, only interact with memory in safe ways, adhere to platform-specified API contracts, and don't use instructions with undefined behavior. This level of verification can often provide a stronger level of security assurance than for other software and operating system code. While the details are out of scope of this document, Linux and PREVAIL provide many details. Future IETF work will document verifier expectations and building blocks for allowing safe execution of untrusted BPF programs. Executing programs using the BPF instruction set also requires either an interpreter or a compiler to translate them to built-in hardware processor instructions. In general, interpreters are considered a source of insecurity (e.g., gadgets susceptible to side-channel attacks due to speculative execution) whenever one is used in the same memory address space as data with confidentiality concerns. As such, use of a compiler is recommended instead. Compilers should be audited carefully for vulnerabilities to ensure that compilation of a trusted and verified BPF program to built-in processor instructions does not introduce vulnerabilities. Exposing functionality via BPF extends the interface between the component executing the BPF program and the component submitting it. Careful consideration of what functionality is exposed and how that impacts the security properties desired is required.
IANA Considerations This document defines two registries.
BPF Instruction Conformance Groups Registry This document defines an IANA registry for BPF instruction conformance groups, as follows:
  • Name of the registry: BPF Instruction Conformance Groups
  • Name of the registry group: BPF Instructions
  • Required information for registrations: See the BPF Instruction Conformance Groups Registration Template ()
  • Syntax of registry entries: Each entry has the following fields: name, description, includes, excludes, status, change controller, and reference. See for more details.
  • Registration policy (see for details):
    • Permanent: Standards Action or IESG Approval
    • Provisional: Specification Required
    • Historical: Specification Required
  • Contact: BPF Working Group
  • Change Controller: IETF
Initial entries in this registry are as follows: Initial Conformance Groups
Name Description Includes Excludes Status Reference
atomic32 32-bit atomic instructions - - Permanent RFC 9669,
atomic64 64-bit atomic instructions atomic32 - Permanent RFC 9669,
base32 32-bit base instructions - - Permanent RFC 9669
base64 64-bit base instructions base32 - Permanent RFC 9669
divmul32 32-bit division and modulo - - Permanent RFC 9669,
divmul64 64-bit division and modulo divmul32 - Permanent RFC 9669,
packet Legacy packet instructions - - Historical RFC 9669,
BPF Instruction Conformance Groups Registration Template This template describes the fields that must be supplied in a registration request:
Name:
Alphanumeric label indicating the name of the conformance group.
Description:
Brief description of the conformance group.
Includes:
Any other conformance groups that are included by this group.
Excludes:
Any other conformance groups that are excluded by this group.
Status:
This reflects the status requested and must be one of 'Permanent', 'Provisional', or 'Historical'.
Contact:
Person (including contact information) to contact for further information.
Change Controller:
Organization or person (often the author of the defining specification), including contact information, authorized to change this.
Reference:
A reference to the defining specification. Include full citations for all referenced documents. Registration requests for 'Provisional' registration can be included in an Internet-Draft; when the documents are approved for publication as an RFC, the registration will be updated to 'Permanent'.
BPF Instruction Set Registry This document defines an IANA registry for BPF instructions, as follows:
  • Name of the registry: BPF Instruction Set
  • Name of the registry group: BPF Instructions
  • Required information for registrations: See the BPF Instruction Registration Template ()
  • Syntax of registry entries: Each entry has the following fields: opcode, src, offset, imm, description, groups, change controller, and reference. See for more details.
  • Registration policy: New instructions require a new entry in the conformance group registry and the same registration policies apply.
  • Contact: BPF Working Group
  • Change Controller: IETF
  • Initial registrations: See . Instructions other than those listed as deprecated are Permanent. Any listed as deprecated are Historical.
BPF Instruction Registration Template This template describes the fields that must be supplied in a registration request:
Opcode:
A 1-byte value in hex format indicating the value of the opcode field.
Src_reg:
Either a numeric value indicating the value of the src_reg field, or "any".
Offset:
Either a numeric value indicating the value of the offset field, or "any".
Imm:
Either a value indicating the value of the imm field, or "any".
Description:
Description of what the instruction does, typically in pseudocode.
Groups:
A list of one or more comma-separated conformance groups to which the instruction belongs.
Contact:
Person (including contact information) to contact for further information.
Change Controller:
Organization or person (often the author), including contact information, authorized to change this.
Reference:
A reference to the defining specification. Include full citations for all referenced documents. Registration requests for 'Provisional' registration can be included in an Internet-Draft; when the documents are approved for publication as an RFC, the registration will be updated to 'Permanent'.
Adding Instructions A specification may add additional instructions to the BPF Instruction Set registry. Once a conformance group is registered with a set of instructions, no further instructions can be added to that conformance group. A specification should instead create a new conformance group that includes the original conformance group, plus any newly added instructions. Inclusion of the original conformance group is done via the "includes" column of the BPF Instruction Conformance Groups registry, and inclusion of newly added instructions is done via the "groups" column of the BPF Instruction Set registry. For example, consider an existing hypothetical group called "example" with two instructions in it. One might add two more instructions by first adding an "examplev2" group to the BPF Instruction Conformance Groups registry as follows: Conformance Group Example for Addition
Name Description Includes Excludes Status
example Original example instructions - - Permanent
examplev2 Newer set of example instructions example - Permanent
And then adding the new instructions into the BPF Instruction Set registry as follows: Instruction Addition Example
opcode ... Description Groups
aaa ... Original example instruction 1 example
bbb ... Original example instruction 2 example
ccc ... Added example instruction 3 examplev2
ddd ... Added example instruction 4 examplev2
Supporting the "examplev2" group thus requires supporting all four example instructions.
Deprecating Instructions Deprecating instructions that are part of an existing conformance group can be done by defining a new conformance group for the newly deprecated instructions, and defining a new conformance group that supersedes the existing conformance group containing the instructions, where the new conformance group includes the existing one and excludes the deprecated instruction group. For example, if deprecating an instruction in an existing hypothetical group called "example", two new groups ("legacyexample" and "examplev2") might be registered in the BPF Instruction Conformance Groups registry as follows: Conformance Group Example for Deprecation
Name Description Includes Excludes Status
example Original example instructions - - Permanent
legacyexample Legacy example instructions - - Historical
examplev2 Example instructions example legacyexample Permanent
The BPF Instruction Set registry entries for the deprecated instructions would then be updated to add "legacyexample" to the set of groups for those instructions, as follows: Instruction Deprecation Example
opcode ... Description Groups
aaa ... Good original instruction 1 example
bbb ... Good original instruction 2 example
ccc ... Bad original instruction 3 example, legacyexample
ddd ... Bad original instruction 4 example, legacyexample
Finally, updated implementations that dropped support for the deprecated instructions would then be able to claim conformance to "examplev2" rather than "example".
Change Control Registrations can be updated in a registry by the same mechanism as required for an initial registration. In cases where the original definition of an entry is contained in an IESG-approved document, in which case the IETF would be the change controller, update of the specification also requires IESG approval. 'Provisional' registrations can be updated by the change controller designated in the existing registration. In addition, the IESG can reassign responsibility for a 'Provisional' registration or can request specific changes to an entry. This will enable changes to be made to entries where the original registrant is out of contact or unwilling or unable to make changes. Transition from 'Provisional' to 'Permanent' status can be requested and approved in the same manner as a new 'Permanent' registration. Transition from 'Permanent' to 'Historical' status requires IESG approval. Transition from 'Provisional' to 'Historical' can be requested by anyone authorized to update the 'Provisional' registration.
Expert Review Instructions The IANA registries established by this document are informed by written specifications, which themselves are facilitated and approved by an Expert Review process (see ). Designated experts are expected to consult with the active BPF working group (e.g., via email to the working group's mailing list) if it exists, as well as other interested parties (e.g., via email to one or more active mailing list(s) for relevant BPF communities and platforms). The designated expert is expected to verify that the encoding and semantics for any new instructions are properly documented in a public-facing specification. In the event of future RFC documents for ISA extensions, experts may permit early assignment before the RFC document is available, as long as a specification that satisfies the above requirements exists.
References Normative References ON HOLY WARS AND A PLEA FOR PEACE Key words for use in RFCs to Indicate Requirement Levels In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Guidelines for Writing an IANA Considerations Section in RFCs Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA). To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry. This is the third edition of this document; it obsoletes RFC 5226. Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References eBPF verifier Simple and Precise Static Analysis of Untrusted Linux Kernel Extensions
Initial BPF Instruction Set Values Initial values for the BPF Instruction Set registry are given below. The descriptions in this table are informative. In case of any discrepancy, the reference is authoritative. Initial BPF Instruction Set Values
opcode src_reg off-set imm Description Groups Ref
0x00 0x0 0 any (additional immediate value) base64 RFC 9669,
0x04 0x0 0 any dst = (u32)((u32)dst + (u32)imm) base32 RFC 9669,
0x05 0x0 any 0x00 goto +offset base32 RFC 9669,
0x06 0x0 0 any goto +imm base32 RFC 9669,
0x07 0x0 0 any dst += imm base64 RFC 9669,
0x0c any 0 0x00 dst = (u32)((u32)dst + (u32)src) base32 RFC 9669,
0x0f any 0 0x00 dst += src base64 RFC 9669,
0x14 0x0 0 any dst = (u32)((u32)dst - (u32)imm) base32 RFC 9669,
0x15 0x0 any any if dst == imm goto +offset base64 RFC 9669,
0x16 0x0 any any if (u32)dst == imm goto +offset base32 RFC 9669,
0x17 0x0 0 any dst -= imm base64 RFC 9669,
0x18 0x0 0 any dst = (next_imm << 32) | imm base64 RFC 9669,
0x18 0x1 0 any dst = map_by_fd(imm) base64 RFC 9669,
0x18 0x2 0 any dst = map_val(map_by_fd(imm)) + next_imm base64 RFC 9669,
0x18 0x3 0 any dst = var_addr(imm) base64 RFC 9669,
0x18 0x4 0 any dst = code_addr(imm) base64 RFC 9669,
0x18 0x5 0 any dst = map_by_idx(imm) base64 RFC 9669,
0x18 0x6 0 any dst = map_val(map_by_idx(imm)) + next_imm base64 RFC 9669,
0x1c any 0 0x00 dst = (u32)((u32)dst - (u32)src) base32 RFC 9669,
0x1d any any 0x00 if dst == src goto +offset base64 RFC 9669,
0x1e any any 0x00 if (u32)dst == (u32)src goto +offset base32 RFC 9669,
0x1f any 0 0x00 dst -= src base64 RFC 9669,
0x20 0x0 0 any (deprecated, implementation-specific) packet RFC 9669,
0x24 0x0 0 any dst = (u32)(dst * imm) divmul32 RFC 9669,
0x25 0x0 any any if dst > imm goto +offset base64 RFC 9669,
0x26 0x0 any any if (u32)dst > imm goto +offset base32 RFC 9669,
0x27 0x0 0 any dst *= imm divmul64 RFC 9669,
0x28 0x0 0 any (deprecated, implementation-specific) packet RFC 9669,
0x2c any 0 0x00 dst = (u32)(dst * src) divmul32 RFC 9669,
0x2d any any 0x00 if dst > src goto +offset base64 RFC 9669,
0x2e any any 0x00 if (u32)dst > (u32)src goto +offset base32 RFC 9669,
0x2f any 0 0x00 dst *= src divmul64 RFC 9669,
0x30 0x0 0 any (deprecated, implementation-specific) packet RFC 9669,
0x34 0x0 0 any dst = (u32)((imm != 0) ? ((u32)dst / (u32)imm) : 0) divmul32 RFC 9669,
0x34 0x0 1 any dst = (u32)((imm != 0) ? ((s32)dst s/ imm) : 0) divmul32 RFC 9669,
0x35 0x0 any any if dst >= imm goto +offset base64 RFC 9669,
0x36 0x0 any any if (u32)dst >= imm goto +offset base32 RFC 9669,
0x37 0x0 0 any dst = (imm != 0) ? (dst / (u32)imm) : 0 divmul64 RFC 9669,
0x37 0x0 1 any dst = (imm != 0) ? (dst s/ imm) : 0 divmul64 RFC 9669,
0x3c any 0 0x00 dst = (u32)((src != 0) ? ((u32)dst / (u32)src) : 0) divmul32 RFC 9669,
0x3c any 1 0x00 dst = (u32)((src != 0) ? ((s32)dst s/(s32)src) : 0) divmul32 RFC 9669,
0x3d any any 0x00 if dst >= src goto +offset base64 RFC 9669,
0x3e any any 0x00 if (u32)dst >= (u32)src goto +offset base32 RFC 9669,
0x3f any 0 0x00 dst = (src != 0) ? (dst / src) : 0 divmul64 RFC 9669,
0x3f any 1 0x00 dst = (src != 0) ? (dst s/ src) : 0 divmul64 RFC 9669,
0x40 any 0 any (deprecated, implementation-specific) packet RFC 9669,
0x44 0x0 0 any dst = (u32)(dst | imm) base32 RFC 9669,
0x45 0x0 any any if dst & imm goto +offset base64 RFC 9669,
0x46 0x0 any any if (u32)dst & imm goto +offset base32 RFC 9669,
0x47 0x0 0 any dst |= imm base64 RFC 9669,
0x48 any 0 any (deprecated, implementation-specific) packet RFC 9669,
0x4c any 0 0x00 dst = (u32)(dst | src) base32 RFC 9669,
0x4d any any 0x00 if dst & src goto +offset base64 RFC 9669,
0x4e any any 0x00 if (u32)dst & (u32)src goto +offset base32 RFC 9669,
0x4f any 0 0x00 dst |= src base64 RFC 9669,
0x50 any 0 any (deprecated, implementation-specific) packet RFC 9669,
0x54 0x0 0 any dst = (u32)(dst & imm) base32 RFC 9669,
0x55 0x0 any any if dst != imm goto +offset base64 RFC 9669,
0x56 0x0 any any if (u32)dst != imm goto +offset base32 RFC 9669,
0x57 0x0 0 any dst &= imm base64 RFC 9669,
0x5c any 0 0x00 dst = (u32)(dst & src) base32 RFC 9669,
0x5d any any 0x00 if dst != src goto +offset base64 RFC 9669,
0x5e any any 0x00 if (u32)dst != (u32)src goto +offset base32 RFC 9669,
0x5f any 0 0x00 dst &= src base64 RFC 9669,
0x61 any any 0x00 dst = *(u32 *)(src + offset) base32 RFC 9669,
0x62 0x0 any any *(u32 *)(dst + offset) = imm base32 RFC 9669,
0x63 any any 0x00 *(u32 *)(dst + offset) = src base32 RFC 9669,
0x64 0x0 0 any dst = (u32)(dst << imm) base32 RFC 9669,
0x65 0x0 any any if dst s> imm goto +offset base64 RFC 9669,
0x66 0x0 any any if (s32)dst s> (s32)imm goto +offset base32 RFC 9669,
0x67 0x0 0 any dst <<= imm base64 RFC 9669,
0x69 any any 0x00 dst = *(u16 *)(src + offset) base32 RFC 9669,
0x6a 0x0 any any *(u16 *)(dst + offset) = imm base32 RFC 9669,
0x6b any any 0x00 *(u16 *)(dst + offset) = src base32 RFC 9669,
0x6c any 0 0x00 dst = (u32)(dst << src) base32 RFC 9669,
0x6d any any 0x00 if dst s> src goto +offset base64 RFC 9669,
0x6e any any 0x00 if (s32)dst s> (s32)src goto +offset base32 RFC 9669,
0x6f any 0 0x00 dst <<= src base64 RFC 9669,
0x71 any any 0x00 dst = *(u8 *)(src + offset) base32 RFC 9669,
0x72 0x0 any any *(u8 *)(dst + offset) = imm base32 RFC 9669,
0x73 any any 0x00 *(u8 *)(dst + offset) = src base32 RFC 9669,
0x74 0x0 0 any dst = (u32)(dst >> imm) base32 RFC 9669,
0x75 0x0 any any if dst s>= imm goto +offset base64 RFC 9669,
0x76 0x0 any any if (s32)dst s>= (s32)imm goto +offset base32 RFC 9669,
0x77 0x0 0 any dst >>= imm base64 RFC 9669,
0x79 any any 0x00 dst = *(u64 *)(src + offset) base64 RFC 9669,
0x7a 0x0 any any *(u64 *)(dst + offset) = imm base64 RFC 9669,
0x7b any any 0x00 *(u64 *)(dst + offset) = src base64 RFC 9669,
0x7c any 0 0x00 dst = (u32)(dst >> src) base32 RFC 9669,
0x7d any any 0x00 if dst s>= src goto +offset base64 RFC 9669,
0x7e any any 0x00 if (s32)dst s>= (s32)src goto +offset base32 RFC 9669,
0x7f any 0 0x00 dst >>= src base64 RFC 9669,
0x84 0x0 0 0x00 dst = (u32)-dst base32 RFC 9669,
0x85 0x0 0 any call helper function by static ID base32 RFC 9669,
0x85 0x1 0 any call PC += imm base32 RFC 9669,
0x85 0x2 0 any call helper function by BTF ID base32 RFC 9669,
0x87 0x0 0 0x00 dst = -dst base64 RFC 9669,
0x94 0x0 0 any dst = (u32)((imm != 0)?((u32)dst % (u32)imm) : dst) divmul32 RFC 9669,
0x94 0x0 1 any dst = (u32)((imm != 0) ? ((s32)dst s% imm) : dst) divmul32 RFC 9669,
0x95 0x0 0 0x00 return base32 RFC 9669,
0x97 0x0 0 any dst = (imm != 0) ? (dst % (u32)imm) : dst divmul64 RFC 9669,
0x97 0x0 1 any dst = (imm != 0) ? (dst s% imm) : dst divmul64 RFC 9669,
0x9c any 0 0x00 dst = (u32)((src != 0)?((u32)dst % (u32)src) : dst) divmul32 RFC 9669,
0x9c any 1 0x00 dst = (u32)((src != 0)?((s32)dst s% (s32)src) :dst) divmul32 RFC 9669,
0x9f any 0 0x00 dst = (src != 0) ? (dst % src) : dst divmul64 RFC 9669,
0x9f any 1 0x00 dst = (src != 0) ? (dst s% src) : dst divmul64 RFC 9669,
0xa4 0x0 0 any dst = (u32)(dst ^ imm) base32 RFC 9669,
0xa5 0x0 any any if dst < imm goto +offset base64 RFC 9669,
0xa6 0x0 any any if (u32)dst < imm goto +offset base32 RFC 9669,
0xa7 0x0 0 any dst ^= imm base64 RFC 9669,
0xac any 0 0x00 dst = (u32)(dst ^ src) base32 RFC 9669,
0xad any any 0x00 if dst < src goto +offset base64 RFC 9669,
0xae any any 0x00 if (u32)dst < (u32)src goto +offset base32 RFC 9669,
0xaf any 0 0x00 dst ^= src base64 RFC 9669,
0xb4 0x0 0 any dst = (u32) imm base32 RFC 9669,
0xb5 0x0 any any if dst <= imm goto +offset base64 RFC 9669,
0xb6 0x0 any any if (u32)dst <= imm goto +offset base32 RFC 9669,
0xb7 0x0 0 any dst = imm base64 RFC 9669,
0xbc any 0 0x00 dst = (u32) src base32 RFC 9669,
0xbc any 8 0x00 dst = (u32) (s32) (s8) src base32 RFC 9669,
0xbc any 16 0x00 dst = (u32) (s32) (s16) src base32 RFC 9669,
0xbd any any 0x00 if dst <= src goto +offset base64 RFC 9669,
0xbe any any 0x00 if (u32)dst <= (u32)src goto +offset base32 RFC 9669,
0xbf any 0 0x00 dst = src base64 RFC 9669,
0xbf any 8 0x00 dst = (s64) (s8) src base64 RFC 9669,
0xbf any 16 0x00 dst = (s64) (s16) src base64 RFC 9669,
0xbf any 32 0x00 dst = (s64) (s32) src base64 RFC 9669,
0xc3 any any 0x00 lock *(u32 *)(dst + offset) += src atomic32 RFC 9669,
0xc3 any any 0x01 src = atomic_fetch_add_32((u32 *)(dst + offset), src) atomic32 RFC 9669,
0xc3 any any 0x40 lock *(u32 *)(dst + offset) |= src atomic32 RFC 9669,
0xc3 any any 0x41 src = atomic_fetch_or_32((u32 *)(dst + offset), src) atomic32 RFC 9669,
0xc3 any any 0x50 lock *(u32 *)(dst + offset) &= src atomic32 RFC 9669,
0xc3 any any 0x51 src = atomic_fetch_and_32((u32 *)(dst + offset), src) atomic32 RFC 9669,
0xc3 any any 0xa0 lock *(u32 *)(dst + offset) ^= src atomic32 RFC 9669,
0xc3 any any 0xa1 src = atomic_fetch_xor_32((u32 *)(dst + offset), src) atomic32 RFC 9669,
0xc3 any any 0xe1 src = xchg_32((u32 *)(dst + offset), src) atomic32 RFC 9669,
0xc3 any any 0xf1 r0 = cmpxchg_32((u32 *)(dst + offset), r0, src) atomic32 RFC 9669,
0xc4 0x0 0 any dst = (u32)(dst s>> imm) base32 RFC 9669,
0xc5 0x0 any any if dst s< imm goto +offset base64 RFC 9669,
0xc6 0x0 any any if (s32)dst s< (s32)imm goto +offset base32 RFC 9669,
0xc7 0x0 0 any dst s>>= imm base64 RFC 9669,
0xcc any 0 0x00 dst = (u32)(dst s>> src) base32 RFC 9669,
0xcd any any 0x00 if dst s< src goto +offset base64 RFC 9669,
0xce any any 0x00 if (s32)dst s< (s32)src goto +offset base32 RFC 9669,
0xcf any 0 0x00 dst s>>= src base64 RFC 9669,
0xd4 0x0 0 0x10 dst = htole16(dst) base32 RFC 9669,
0xd4 0x0 0 0x20 dst = htole32(dst) base32 RFC 9669,
0xd4 0x0 0 0x40 dst = htole64(dst) base64 RFC 9669,
0xd5 0x0 any any if dst s<= imm goto +offset base64 RFC 9669,
0xd6 0x0 any any if (s32)dst s<= (s32)imm goto +offset base32 RFC 9669,
0xd7 0x0 0 0x10 dst = bswap16(dst) base32 RFC 9669,
0xd7 0x0 0 0x20 dst = bswap32(dst) base32 RFC 9669,
0xd7 0x0 0 0x40 dst = bswap64(dst) base64 RFC 9669,
0xdb any any 0x00 lock *(u64 *)(dst + offset) += src atomic64 RFC 9669,
0xdb any any 0x01 src = atomic_fetch_add_64((u64 *)(dst + offset), src) atomic64 RFC 9669,
0xdb any any 0x40 lock *(u64 *)(dst + offset) |= src atomic64 RFC 9669,
0xdb any any 0x41 src = atomic_fetch_or_64((u64 *)(dst + offset), src) atomic64 RFC 9669,
0xdb any any 0x50 lock *(u64 *)(dst + offset) &= src atomic64 RFC 9669,
0xdb any any 0x51 src = atomic_fetch_and_64((u64 *)(dst + offset), src) atomic64 RFC 9669,
0xdb any any 0xa0 lock *(u64 *)(dst + offset) ^= src atomic64 RFC 9669,
0xdb any any 0xa1 src = atomic_fetch_xor_64((u64 *)(dst + offset), src) atomic64 RFC 9669,
0xdb any any 0xe1 src = xchg_64((u64 *)(dst + offset), src) atomic64 RFC 9669,
0xdb any any 0xf1 r0 = cmpxchg_64((u64 *)(dst + offset), r0, src) atomic64 RFC 9669,
0xdc 0x0 0 0x10 dst = htobe16(dst) base32 RFC 9669,
0xdc 0x0 0 0x20 dst = htobe32(dst) base32 RFC 9669,
0xdc 0x0 0 0x40 dst = htobe64(dst) base64 RFC 9669,
0xdd any any 0x00 if dst s<= src goto +offset base64 RFC 9669,
0xde any any 0x00 if (s32)dst s<= (s32)src goto +offset base32 RFC 9669,
Acknowledgements This document was generated from instruction-set.rst in the Linux kernel repository, to which a number of other individuals have authored contributions over time, including , , , , , , , , , , , , and , with review and suggestions by many others including , , , , , , , , , and .
Author's Address
Redmond 98052 United States of America WA dave.thaler.ietf@gmail.com