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diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst index 245b6defc298..fbe975585236 100644 --- a/Documentation/bpf/standardization/instruction-set.rst +++ b/Documentation/bpf/standardization/instruction-set.rst @@ -1,15 +1,33 @@ .. contents:: .. sectnum:: -======================================= -BPF Instruction Set Specification, v1.0 -======================================= - -This document specifies version 1.0 of the BPF instruction set. +====================================== +BPF Instruction Set Architecture (ISA) +====================================== + +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 `<https://www.rfc-editor.org/info/rfc2119>`_ +`<https://www.rfc-editor.org/info/rfc8174>`_ +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. @@ -21,61 +39,60 @@ Types This document refers to integer types with the notation `SN` to specify a type's signedness (`S`) and bit width (`N`), respectively. -.. table:: Meaning of signedness notation. +.. table:: Meaning of signedness notation ==== ========= - `S` Meaning + S Meaning ==== ========= - `u` unsigned - `s` signed + u unsigned + s signed ==== ========= -.. table:: Meaning of bit-width notation. +.. table:: Meaning of bit-width notation ===== ========= - `N` Bit width + N Bit width ===== ========= - `8` 8 bits - `16` 16 bits - `32` 32 bits - `64` 64 bits - `128` 128 bits + 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 types whose valid values are all the 16-bit signed +numbers and `s16` is a type whose valid values are all the 16-bit signed numbers. Functions --------- -* `htobe16`: Takes an unsigned 16-bit number in host-endian format and - returns the equivalent number as an unsigned 16-bit number in big-endian - format. -* `htobe32`: Takes an unsigned 32-bit number in host-endian format and - returns the equivalent number as an unsigned 32-bit number in big-endian - format. -* `htobe64`: Takes an unsigned 64-bit number in host-endian format and - returns the equivalent number as an unsigned 64-bit number in big-endian - format. -* `htole16`: Takes an unsigned 16-bit number in host-endian format and - returns the equivalent number as an unsigned 16-bit number in little-endian - format. -* `htole32`: Takes an unsigned 32-bit number in host-endian format and - returns the equivalent number as an unsigned 32-bit number in little-endian - format. -* `htole64`: Takes an unsigned 64-bit number in host-endian format and - returns the equivalent number as an unsigned 64-bit number in little-endian - format. -* `bswap16`: Takes an unsigned 16-bit number in either big- or little-endian + +The following byteswap 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 + (`IEN137 <https://www.rfc-editor.org/ien/ien137.txt>`_) 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 +* 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 +* 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 ----------- @@ -97,40 +114,104 @@ Definitions A: 10000110 B: 11111111 10000110 +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 `Atomic operations`_). +* 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-bit immediate (i.e., - constant) value after the basic instruction for a total of 128 bits. +* the wide instruction encoding, which appends a second 64 bits + after the basic instruction for a total of 128 bits. -The fields conforming an encoded basic instruction are stored in the -following order:: +Basic instruction encoding +-------------------------- - opcode:8 src_reg:4 dst_reg:4 offset:16 imm:32 // In little-endian BPF. - opcode:8 dst_reg:4 src_reg:4 offset:16 imm:32 // In big-endian BPF. +A basic instruction is encoded as follows:: -**imm** - signed integer immediate value + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | opcode | regs | offset | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | imm | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -**offset** - signed integer offset used with pointer arithmetic +**opcode** + operation to perform, encoded as follows:: -**src_reg** - the source register number (0-10), except where otherwise specified - (`64-bit immediate instructions`_ reuse this field for other purposes) + +-+-+-+-+-+-+-+-+ + |specific |class| + +-+-+-+-+-+-+-+-+ -**dst_reg** - destination register number (0-10) + **specific** + The format of these bits varies by instruction class -**opcode** - operation to perform + **class** + The instruction class (see `Instruction classes`_) + +**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`_ reuse this field for other purposes) -Note that the contents of multi-byte fields ('imm' and 'offset') are -stored using big-endian byte ordering in big-endian BPF and -little-endian byte ordering in little-endian BPF. + **dst_reg** + 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:: @@ -141,74 +222,92 @@ For example:: 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. +Unused fields SHALL be cleared to zero. + +Wide instruction encoding +-------------------------- -As discussed below in `64-bit immediate instructions`_, a 64-bit immediate -instruction uses a 64-bit immediate value that is constructed as follows. -The 64 bits following the basic instruction contain a pseudo instruction -using the same format but with opcode, dst_reg, src_reg, and offset all set to zero, -and imm containing the high 32 bits of the immediate value. +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:: - basic_instruction - .-----------------------------. - | | - code:8 regs:8 offset:16 imm:32 unused:32 imm:32 - | | - '--------------' - pseudo instruction + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | opcode | regs | offset | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | imm | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | reserved | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | next_imm | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -Thus the 64-bit immediate value is constructed as follows: +**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 - imm64 = (next_imm << 32) | imm +**reserved** + unused, set to zero -where 'next_imm' refers to the imm value of the pseudo instruction -following the basic instruction. The unused bytes in the pseudo -instruction are reserved and shall be cleared to zero. +**next_imm** + second signed integer immediate value Instruction classes ------------------- -The three LSB bits of the 'opcode' field store the instruction class: - -========= ===== =============================== =================================== -class value description reference -========= ===== =============================== =================================== -BPF_LD 0x00 non-standard load operations `Load and store instructions`_ -BPF_LDX 0x01 load into register operations `Load and store instructions`_ -BPF_ST 0x02 store from immediate operations `Load and store instructions`_ -BPF_STX 0x03 store from register operations `Load and store instructions`_ -BPF_ALU 0x04 32-bit arithmetic operations `Arithmetic and jump instructions`_ -BPF_JMP 0x05 64-bit jump operations `Arithmetic and jump instructions`_ -BPF_JMP32 0x06 32-bit jump operations `Arithmetic and jump instructions`_ -BPF_ALU64 0x07 64-bit arithmetic operations `Arithmetic and jump instructions`_ -========= ===== =============================== =================================== +The three least significant bits of the 'opcode' field store the instruction class: + +.. table:: Instruction class + + ===== ===== =============================== =================================== + class value description reference + ===== ===== =============================== =================================== + LD 0x0 non-standard load operations `Load and store instructions`_ + LDX 0x1 load into register operations `Load and store instructions`_ + ST 0x2 store from immediate operations `Load and store instructions`_ + STX 0x3 store from register operations `Load and store instructions`_ + ALU 0x4 32-bit arithmetic operations `Arithmetic and jump instructions`_ + JMP 0x5 64-bit jump operations `Arithmetic and jump instructions`_ + JMP32 0x6 32-bit jump operations `Arithmetic and jump instructions`_ + ALU64 0x7 64-bit arithmetic operations `Arithmetic and jump instructions`_ + ===== ===== =============================== =================================== Arithmetic and jump instructions ================================ -For arithmetic and jump instructions (``BPF_ALU``, ``BPF_ALU64``, ``BPF_JMP`` and -``BPF_JMP32``), the 8-bit 'opcode' field is divided into three parts: +For arithmetic and jump instructions (``ALU``, ``ALU64``, ``JMP`` and +``JMP32``), the 8-bit 'opcode' field is divided into three parts:: -============== ====== ================= -4 bits (MSB) 1 bit 3 bits (LSB) -============== ====== ================= -code source instruction class -============== ====== ================= + +-+-+-+-+-+-+-+-+ + | code |s|class| + +-+-+-+-+-+-+-+-+ **code** the operation code, whose meaning varies by instruction class -**source** +**s (source)** the source operand location, which unless otherwise specified is one of: - ====== ===== ============================================== - source value description - ====== ===== ============================================== - BPF_K 0x00 use 32-bit 'imm' value as source operand - BPF_X 0x08 use 'src_reg' register value as source operand - ====== ===== ============================================== + .. table:: 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 + ====== ===== ============================================== **instruction class** the instruction class (see `Instruction classes`_) @@ -216,86 +315,119 @@ code source instruction class 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, where 'src' and 'dst' refer -to the values of the source and destination registers, respectively. - -========= ===== ======= ========================================================== -code value offset description -========= ===== ======= ========================================================== -BPF_ADD 0x00 0 dst += src -BPF_SUB 0x10 0 dst -= src -BPF_MUL 0x20 0 dst \*= src -BPF_DIV 0x30 0 dst = (src != 0) ? (dst / src) : 0 -BPF_SDIV 0x30 1 dst = (src != 0) ? (dst s/ src) : 0 -BPF_OR 0x40 0 dst \|= src -BPF_AND 0x50 0 dst &= src -BPF_LSH 0x60 0 dst <<= (src & mask) -BPF_RSH 0x70 0 dst >>= (src & mask) -BPF_NEG 0x80 0 dst = -dst -BPF_MOD 0x90 0 dst = (src != 0) ? (dst % src) : dst -BPF_SMOD 0x90 1 dst = (src != 0) ? (dst s% src) : dst -BPF_XOR 0xa0 0 dst ^= src -BPF_MOV 0xb0 0 dst = src -BPF_MOVSX 0xb0 8/16/32 dst = (s8,s16,s32)src -BPF_ARSH 0xc0 0 :term:`sign extending<Sign Extend>` dst >>= (src & mask) -BPF_END 0xd0 0 byte swap operations (see `Byte swap instructions`_ below) -========= ===== ======= ========================================================== +``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 +the source operand and 'dst' refers to the value of the destination +register. + +.. table:: Arithmetic instructions + + ===== ===== ======= =================================================================================== + name code offset description + ===== ===== ======= =================================================================================== + ADD 0x0 0 dst += src + SUB 0x1 0 dst -= src + MUL 0x2 0 dst \*= src + DIV 0x3 0 dst = (src != 0) ? (dst / src) : 0 + SDIV 0x3 1 dst = (src == 0) ? 0 : ((src == -1 && dst == LLONG_MIN) ? LLONG_MIN : (dst s/ src)) + 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 : ((src == -1 && dst == LLONG_MIN) ? 0: (dst s% src)) + XOR 0xa 0 dst ^= src + MOV 0xb 0 dst = src + MOVSX 0xb 8/16/32 dst = (s8,s16,s32)src + ARSH 0xc 0 :term:`sign extending<Sign Extend>` dst >>= (src & mask) + END 0xd 0 byte swap operations (see `Byte swap instructions`_ below) + ===== ===== ======= =================================================================================== Underflow and overflow are allowed during arithmetic operations, meaning the 64-bit or 32-bit value will wrap. If BPF program execution would result in division by zero, the destination register is instead set to zero. -If execution would result in modulo by zero, for ``BPF_ALU64`` the value of -the destination register is unchanged whereas for ``BPF_ALU`` the upper -32 bits of the destination register are zeroed. +Otherwise, for ``ALU64``, if execution would result in ``LLONG_MIN`` +dividing -1, the desination register is instead set to ``LLONG_MIN``. For +``ALU``, if execution would result in ``INT_MIN`` dividing -1, the +desination register is instead set to ``INT_MIN``. + +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. Otherwise, for ``ALU64``, +if execution would resuslt in ``LLONG_MIN`` modulo -1, the destination +register is instead set to 0. For ``ALU``, if execution would result in +``INT_MIN`` modulo -1, the destination register is instead set to 0. -``BPF_ADD | BPF_X | BPF_ALU`` means:: +``{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. -``BPF_ADD | BPF_X | BPF_ALU64`` means:: +``{ADD, X, ALU64}`` means:: dst = dst + src -``BPF_XOR | BPF_K | BPF_ALU`` means:: +``{XOR, K, ALU}`` means:: - dst = (u32) dst ^ (u32) imm32 + dst = (u32) dst ^ (u32) imm -``BPF_XOR | BPF_K | BPF_ALU64`` means:: +``{XOR, K, ALU64}`` means:: - dst = dst ^ imm32 + dst = dst ^ imm -Note that most instructions have instruction offset of 0. Only three instructions -(``BPF_SDIV``, ``BPF_SMOD``, ``BPF_MOVSX``) have a non-zero offset. +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 (``BPF_DIV`` and ``BPF_MOD``), for ``BPF_ALU``, -'imm' is interpreted as a 32-bit unsigned value. For ``BPF_ALU64``, +For unsigned operations (``DIV`` and ``MOD``), for ``ALU``, +'imm' is interpreted as a 32-bit unsigned value. For ``ALU64``, 'imm' is first :term:`sign extended<Sign Extend>` from 32 to 64 bits, and then interpreted as a 64-bit unsigned value. -For signed operations (``BPF_SDIV`` and ``BPF_SMOD``), for ``BPF_ALU``, -'imm' is interpreted as a 32-bit signed value. For ``BPF_ALU64``, 'imm' +For signed operations (``SDIV`` and ``SMOD``), for ``ALU``, +'imm' is interpreted as a 32-bit signed value. For ``ALU64``, 'imm' is first :term:`sign extended<Sign Extend>` 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 use truncated division -(where -13 % 3 == -1) as implemented in C, Go, etc.: +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 ``BPF_MOVSX`` instruction does a move operation with sign extension. -``BPF_ALU | BPF_MOVSX`` :term:`sign extends<Sign Extend>` 8-bit and 16-bit operands into 32 -bit operands, and zeroes the remaining upper 32 bits. -``BPF_ALU64 | BPF_MOVSX`` :term:`sign extends<Sign Extend>` 8-bit, 16-bit, and 32-bit -operands into 64 bit operands. +The ``MOVSX`` instruction does a move operation with sign extension. +``{MOVSX, X, ALU}`` :term:`sign extends<Sign Extend>` 8-bit and 16-bit operands into +32-bit operands, and zeroes the remaining upper 32 bits. +``{MOVSX, X, ALU64}`` :term:`sign extends<Sign Extend>` 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. @@ -303,43 +435,47 @@ for 32-bit operations. Byte swap instructions ---------------------- -The byte swap instructions use instruction classes of ``BPF_ALU`` and ``BPF_ALU64`` -and a 4-bit 'code' field of ``BPF_END``. +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 ``BPF_ALU``, the 1-bit source operand field in the opcode is used to +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 -``BPF_ALU64``, the 1-bit source operand field in the opcode is reserved -and must be set to 0. +``ALU64``, the 1-bit source operand field in the opcode is reserved +and MUST be set to 0. + +.. table:: Byte swap instructions -========= ========= ===== ================================================= -class source value description -========= ========= ===== ================================================= -BPF_ALU BPF_TO_LE 0x00 convert between host byte order and little endian -BPF_ALU BPF_TO_BE 0x08 convert between host byte order and big endian -BPF_ALU64 Reserved 0x00 do byte swap unconditionally -========= ========= ===== ================================================= + ===== ======== ===== ================================================= + 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. +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: -``BPF_ALU | BPF_TO_LE | BPF_END`` with imm = 16/32/64 means:: +``{END, LE, ALU}`` with 'imm' = 16/32/64 means:: - dst = htole16(dst) - dst = htole32(dst) - dst = htole64(dst) + dst = le16(dst) + dst = le32(dst) + dst = le64(dst) -``BPF_ALU | BPF_TO_BE | BPF_END`` with imm = 16/32/64 means:: +``{END, BE, ALU}`` with 'imm' = 16/32/64 means:: - dst = htobe16(dst) - dst = htobe32(dst) - dst = htobe64(dst) + dst = be16(dst) + dst = be32(dst) + dst = be64(dst) -``BPF_ALU64 | BPF_TO_LE | BPF_END`` with imm = 16/32/64 means:: +``{END, TO, ALU64}`` with 'imm' = 16/32/64 means:: dst = bswap16(dst) dst = bswap32(dst) @@ -348,146 +484,175 @@ Examples: Jump instructions ----------------- -``BPF_JMP32`` uses 32-bit wide operands while ``BPF_JMP`` uses 64-bit wide operands for -otherwise identical operations. +``JMP32`` uses 32-bit wide operands and indicates the base32 +conformance group, while ``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: -======== ===== === =========================================== ========================================= -code value src description notes -======== ===== === =========================================== ========================================= -BPF_JA 0x0 0x0 PC += offset BPF_JMP class -BPF_JA 0x0 0x0 PC += imm BPF_JMP32 class -BPF_JEQ 0x1 any PC += offset if dst == src -BPF_JGT 0x2 any PC += offset if dst > src unsigned -BPF_JGE 0x3 any PC += offset if dst >= src unsigned -BPF_JSET 0x4 any PC += offset if dst & src -BPF_JNE 0x5 any PC += offset if dst != src -BPF_JSGT 0x6 any PC += offset if dst > src signed -BPF_JSGE 0x7 any PC += offset if dst >= src signed -BPF_CALL 0x8 0x0 call helper function by address see `Helper functions`_ -BPF_CALL 0x8 0x1 call PC += imm see `Program-local functions`_ -BPF_CALL 0x8 0x2 call helper function by BTF ID see `Helper functions`_ -BPF_EXIT 0x9 0x0 return BPF_JMP only -BPF_JLT 0xa any PC += offset if dst < src unsigned -BPF_JLE 0xb any PC += offset if dst <= src unsigned -BPF_JSLT 0xc any PC += offset if dst < src signed -BPF_JSLE 0xd any PC += offset if dst <= src signed -======== ===== === =========================================== ========================================= - -The BPF program needs to store the return value into register R0 before doing a -``BPF_EXIT``. +.. table:: Jump instructions + + ======== ===== ======= ================================= =================================================== + code value src_reg description notes + ======== ===== ======= ================================= =================================================== + JA 0x0 0x0 PC += offset {JA, K, JMP} only + JA 0x0 0x0 PC += imm {JA, K, JMP32} only + JEQ 0x1 any PC += offset if dst == src + JGT 0x2 any PC += offset if dst > src unsigned + JGE 0x3 any PC += offset if dst >= src unsigned + JSET 0x4 any PC += offset if dst & src + JNE 0x5 any PC += offset if dst != src + JSGT 0x6 any PC += offset if dst > src signed + JSGE 0x7 any PC += offset if dst >= src signed + CALL 0x8 0x0 call helper function by static ID {CALL, K, JMP} only, see `Helper functions`_ + CALL 0x8 0x1 call PC += imm {CALL, K, JMP} only, see `Program-local functions`_ + CALL 0x8 0x2 call helper function by BTF ID {CALL, K, JMP} only, see `Helper functions`_ + EXIT 0x9 0x0 return {CALL, K, JMP} only + JLT 0xa any PC += offset if dst < src unsigned + JLE 0xb any PC += offset if dst <= src unsigned + JSLT 0xc any PC += offset if dst < src signed + JSLE 0xd any PC += offset if dst <= src signed + ======== ===== ======= ================================= =================================================== + +where 'PC' denotes the program counter, and the offset to increment by +is in units of 64-bit instructions relative to the instruction following +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: -``BPF_JSGE | BPF_X | BPF_JMP32`` (0x7e) means:: +``{JSGE, X, JMP32}`` means:: if (s32)dst s>= (s32)src goto +offset where 's>=' indicates a signed '>=' comparison. -``BPF_JA | BPF_K | BPF_JMP32`` (0x06) means:: +``{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 insn 'imm' field. +where 'imm' means the branch offset comes from the 'imm' field. -Note that there are two flavors of ``BPF_JA`` instructions. The -``BPF_JMP`` class permits a 16-bit jump offset specified by the 'offset' -field, whereas the ``BPF_JMP32`` class permits a 32-bit jump offset +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 > 16-bit conditional jump may be converted to a < 16-bit conditional jump 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 an address -encoded in the imm field. The available helper functions may differ -for each program type, but address values are unique across all program types. +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. +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 call instruction, similar to -``BPF_JA``. The offset is encoded in the imm field of the call instruction. -A ``BPF_EXIT`` within the program-local function will return to the caller. +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 (``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 mode modifier is one of: - - ============= ===== ==================================== ============= - mode modifier value description reference - ============= ===== ==================================== ============= - BPF_IMM 0x00 64-bit immediate instructions `64-bit immediate instructions`_ - BPF_ABS 0x20 legacy BPF packet access (absolute) `Legacy BPF Packet access instructions`_ - BPF_IND 0x40 legacy BPF packet access (indirect) `Legacy BPF Packet access instructions`_ - BPF_MEM 0x60 regular load and store operations `Regular load and store operations`_ - BPF_MEMSX 0x80 sign-extension load operations `Sign-extension load operations`_ - BPF_ATOMIC 0xc0 atomic operations `Atomic operations`_ - ============= ===== ==================================== ============= - -The size modifier is one of: - - ============= ===== ===================== - 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) - ============= ===== ===================== +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: + + .. table:: Mode modifier + + ============= ===== ==================================== ============= + mode modifier value description reference + ============= ===== ==================================== ============= + IMM 0 64-bit immediate instructions `64-bit immediate instructions`_ + ABS 1 legacy BPF packet access (absolute) `Legacy BPF Packet access instructions`_ + IND 2 legacy BPF packet access (indirect) `Legacy BPF Packet access instructions`_ + MEM 3 regular load and store operations `Regular load and store operations`_ + MEMSX 4 sign-extension load operations `Sign-extension load operations`_ + ATOMIC 6 atomic operations `Atomic operations`_ + ============= ===== ==================================== ============= + +**sz (size)** + The size modifier is one of: + + .. table:: 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 `Instruction classes`_) Regular load and store operations --------------------------------- -The ``BPF_MEM`` mode modifier is used to encode regular load and store +The ``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:: +``{MEM, <size>, STX}`` means:: *(size *) (dst + offset) = src -``BPF_MEM | <size> | BPF_ST`` means:: +``{MEM, <size>, ST}`` means:: - *(size *) (dst + offset) = imm32 + *(size *) (dst + offset) = imm -``BPF_MEM | <size> | BPF_LDX`` means:: +``{MEM, <size>, LDX}`` means:: dst = *(unsigned size *) (src + offset) -Where size is one of: ``BPF_B``, ``BPF_H``, ``BPF_W``, or ``BPF_DW`` and -'unsigned size' is one of u8, u16, u32 or u64. +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 ``BPF_MEMSX`` mode modifier is used to encode :term:`sign-extension<Sign Extend>` load +The ``MEMSX`` mode modifier is used to encode :term:`sign-extension<Sign Extend>` load instructions that transfer data between a register and memory. -``BPF_MEMSX | <size> | BPF_LDX`` means:: +``{MEMSX, <size>, LDX}`` means:: dst = *(signed size *) (src + offset) -Where size is one of: ``BPF_B``, ``BPF_H`` or ``BPF_W``, and -'signed size' is one of s8, s16 or s32. +Where '<size>' is one of: ``B``, ``H``, or ``W``, and +'signed size' is one of: s8, s16, or s32. Atomic operations ----------------- @@ -497,54 +662,60 @@ 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 ``BPF_ATOMIC`` mode modifier as follows: +that use the ``ATOMIC`` mode modifier as follows: -* ``BPF_ATOMIC | BPF_W | BPF_STX`` for 32-bit operations -* ``BPF_ATOMIC | BPF_DW | BPF_STX`` for 64-bit operations +* ``{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 operation use a subset of the values defined to encode arithmetic operations in the 'imm' field to encode the atomic operation: -======== ===== =========== -imm value description -======== ===== =========== -BPF_ADD 0x00 atomic add -BPF_OR 0x40 atomic or -BPF_AND 0x50 atomic and -BPF_XOR 0xa0 atomic xor -======== ===== =========== +.. table:: Simple atomic operations + ======== ===== =========== + imm value description + ======== ===== =========== + ADD 0x00 atomic add + OR 0x40 atomic or + AND 0x50 atomic and + XOR 0xa0 atomic xor + ======== ===== =========== -``BPF_ATOMIC | BPF_W | BPF_STX`` with 'imm' = BPF_ADD means:: + +``{ATOMIC, W, STX}`` with 'imm' = ADD means:: *(u32 *)(dst + offset) += src -``BPF_ATOMIC | BPF_DW | BPF_STX`` with 'imm' = BPF ADD means:: +``{ATOMIC, DW, STX}`` with 'imm' = ADD means:: *(u64 *)(dst + offset) += src 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 -=========== ================ =========================== +.. table:: Complex atomic operations + + =========== ================ =========================== + imm value description + =========== ================ =========================== + FETCH 0x01 modifier: return old value + XCHG 0xe0 | FETCH atomic exchange + CMPXCHG 0xf0 | 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 +The ``FETCH`` modifier is optional for simple atomic operations, and +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 ``BPF_XCHG`` operation atomically exchanges ``src`` with the value +The ``XCHG`` operation atomically exchanges ``src`` with the value addressed by ``dst + offset``. -The ``BPF_CMPXCHG`` operation atomically compares the value addressed by +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 @@ -553,25 +724,27 @@ and loaded back to ``R0``. 64-bit immediate instructions ----------------------------- -Instructions with the ``BPF_IMM`` 'mode' modifier use the wide instruction -encoding defined in `Instruction encoding`_, and use the 'src' field of the +Instructions with the ``IMM`` 'mode' modifier use the wide instruction +encoding defined in `Instruction encoding`_, and use the 'src_reg' field of the basic instruction to hold an opcode subtype. -The following table defines a set of ``BPF_IMM | BPF_DW | BPF_LD`` instructions -with opcode subtypes in the 'src' field, using new terms such as "map" +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: -========================= ====== === ========================================= =========== ============== -opcode construction opcode src pseudocode imm type dst type -========================= ====== === ========================================= =========== ============== -BPF_IMM | BPF_DW | BPF_LD 0x18 0x0 dst = imm64 integer integer -BPF_IMM | BPF_DW | BPF_LD 0x18 0x1 dst = map_by_fd(imm) map fd map -BPF_IMM | BPF_DW | BPF_LD 0x18 0x2 dst = map_val(map_by_fd(imm)) + next_imm map fd data pointer -BPF_IMM | BPF_DW | BPF_LD 0x18 0x3 dst = var_addr(imm) variable id data pointer -BPF_IMM | BPF_DW | BPF_LD 0x18 0x4 dst = code_addr(imm) integer code pointer -BPF_IMM | BPF_DW | BPF_LD 0x18 0x5 dst = map_by_idx(imm) map index map -BPF_IMM | BPF_DW | BPF_LD 0x18 0x6 dst = map_val(map_by_idx(imm)) + next_imm map index data pointer -========================= ====== === ========================================= =========== ============== +.. table:: 64-bit immediate instructions + + ======= ========================================= =========== ============== + src_reg pseudocode imm type dst type + ======= ========================================= =========== ============== + 0x0 dst = (next_imm << 32) | imm integer integer + 0x1 dst = map_by_fd(imm) map fd map + 0x2 dst = map_val(map_by_fd(imm)) + next_imm map fd data address + 0x3 dst = var_addr(imm) variable id data address + 0x4 dst = code_addr(imm) integer code address + 0x5 dst = map_by_idx(imm) map index map + 0x6 dst = map_val(map_by_idx(imm)) + next_imm map index data address + ======= ========================================= =========== ============== where @@ -609,5 +782,9 @@ Legacy BPF Packet access instructions ------------------------------------- BPF previously introduced special instructions for access to packet data that were -carried over from classic BPF. However, these instructions are -deprecated and should no longer be used. +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. |