Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 340 insertions, 0 deletions

diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst
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+.. contents::
+.. sectnum::
+
+========================================
+eBPF Instruction Set Specification, v1.0
+========================================
+
+This document specifies version 1.0 of the eBPF instruction set.
+
+
+Registers and calling convention
+================================
+
+eBPF has 10 general purpose registers and a read-only frame pointer register,
+all of which are 64-bits wide.
+
+The eBPF calling convention is defined as:
+
+* R0: return value from function calls, and exit value for eBPF programs
+* R1 - R5: arguments for function calls
+* R6 - R9: callee saved registers that function calls will preserve
+* R10: read-only frame pointer to access stack
+
+R0 - R5 are scratch registers and eBPF programs needs to spill/fill them if
+necessary across calls.
+
+Instruction encoding
+====================
+
+eBPF has two instruction encodings:
+
+* the basic instruction encoding, which uses 64 bits to encode an instruction
+* the wide instruction encoding, which appends a second 64-bit immediate value
+  (imm64) after the basic instruction for a total of 128 bits.
+
+The basic instruction encoding looks as follows:
+
+=============  =======  ===============  ====================  ============
+32 bits (MSB)  16 bits  4 bits           4 bits                8 bits (LSB)
+=============  =======  ===============  ====================  ============
+immediate      offset   source register  destination register  opcode
+=============  =======  ===============  ====================  ============
+
+Note that most instructions do not use all of the fields.
+Unused fields shall be cleared to zero.
+
+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`_
+=========  =====  ===============================  ===================================
+
+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:
+
+==============  ======  =================
+4 bits (MSB)    1 bit   3 bits (LSB)
+==============  ======  =================
+operation code  source  instruction class
+==============  ======  =================
+
+The 4th bit encodes the source operand:
+
+  ======  =====  ========================================
+  source  value  description
+  ======  =====  ========================================
+  BPF_K   0x00   use 32-bit immediate as source operand
+  BPF_X   0x08   use 'src_reg' register as source operand
+  ======  =====  ========================================
+
+The four MSB bits store the operation code.
+
+
+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:
+
+========  =====  ==========================================================
+code      value  description
+========  =====  ==========================================================
+BPF_ADD   0x00   dst += src
+BPF_SUB   0x10   dst -= src
+BPF_MUL   0x20   dst \*= src
+BPF_DIV   0x30   dst = (src != 0) ? (dst / src) : 0
+BPF_OR    0x40   dst \|= src
+BPF_AND   0x50   dst &= src
+BPF_LSH   0x60   dst <<= src
+BPF_RSH   0x70   dst >>= src
+BPF_NEG   0x80   dst = ~src
+BPF_MOD   0x90   dst = (src != 0) ? (dst % src) : dst
+BPF_XOR   0xa0   dst ^= src
+BPF_MOV   0xb0   dst = src
+BPF_ARSH  0xc0   sign extending shift right
+BPF_END   0xd0   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 eBPF 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.
+
+``BPF_ADD | BPF_X | BPF_ALU`` means::
+
+  dst_reg = (u32) dst_reg + (u32) src_reg;
+
+``BPF_ADD | BPF_X | BPF_ALU64`` means::
+
+  dst_reg = dst_reg + src_reg
+
+``BPF_XOR | BPF_K | BPF_ALU`` means::
+
+  src_reg = (u32) src_reg ^ (u32) imm32
+
+``BPF_XOR | BPF_K | BPF_ALU64`` means::
+
+  src_reg = src_reg ^ imm32
+
+Also note that the division and modulo operations are unsigned. Thus, for
+``BPF_ALU``, 'imm' is first interpreted as an unsigned 32-bit value, whereas
+for ``BPF_ALU64``, 'imm' is first sign extended to 64 bits and the result
+interpreted as an unsigned 64-bit value. There are no instructions for
+signed division or modulo.
+
+Byte swap instructions
+~~~~~~~~~~~~~~~~~~~~~~
+
+The byte swap instructions use an instruction class of ``BPF_ALU`` and a 4-bit
+'code' field of ``BPF_END``.
+
+The byte swap instructions operate on the destination register
+only and do not use a separate source register or immediate value.
+
+The 1-bit source operand field in the opcode is used to select what byte
+order the operation convert from or to:
+
+=========  =====  =================================================
+source     value  description
+=========  =====  =================================================
+BPF_TO_LE  0x00   convert between host byte order and little endian
+BPF_TO_BE  0x08   convert between host byte order and big endian
+=========  =====  =================================================
+
+The 'imm' field encodes the width of the swap operations.  The following widths
+are supported: 16, 32 and 64.
+
+Examples:
+
+``BPF_ALU | BPF_TO_LE | BPF_END`` with imm = 16 means::
+
+  dst_reg = htole16(dst_reg)
+
+``BPF_ALU | BPF_TO_BE | BPF_END`` with imm = 64 means::
+
+  dst_reg = htobe64(dst_reg)
+
+Jump instructions
+-----------------
+
+``BPF_JMP32`` uses 32-bit wide operands while ``BPF_JMP`` uses 64-bit wide operands for
+otherwise identical operations.
+The 'code' field encodes the operation as below:
+
+========  =====  =========================  ============
+code      value  description                notes
+========  =====  =========================  ============
+BPF_JA    0x00   PC += off                  BPF_JMP only
+BPF_JEQ   0x10   PC += off if dst == src
+BPF_JGT   0x20   PC += off if dst > src     unsigned
+BPF_JGE   0x30   PC += off if dst >= src    unsigned
+BPF_JSET  0x40   PC += off if dst & src
+BPF_JNE   0x50   PC += off if dst != src
+BPF_JSGT  0x60   PC += off if dst > src     signed
+BPF_JSGE  0x70   PC += off if dst >= src    signed
+BPF_CALL  0x80   function call
+BPF_EXIT  0x90   function / program return  BPF_JMP only
+BPF_JLT   0xa0   PC += off if dst < src     unsigned
+BPF_JLE   0xb0   PC += off if dst <= src    unsigned
+BPF_JSLT  0xc0   PC += off if dst < src     signed
+BPF_JSLE  0xd0   PC += off if dst <= src    signed
+========  =====  =========================  ============
+
+The eBPF program needs to store the return value into register R0 before doing a
+BPF_EXIT.
+
+
+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_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)
+  =============  =====  =====================
+
+Regular load and store operations
+---------------------------------
+
+The ``BPF_MEM`` mode modifier is used to encode regular load and store
+instructions that transfer data between a register and memory.
+
+``BPF_MEM | <size> | BPF_STX`` means::
+
+  *(size *) (dst_reg + off) = src_reg
+
+``BPF_MEM | <size> | BPF_ST`` means::
+
+  *(size *) (dst_reg + off) = imm32
+
+``BPF_MEM | <size> | BPF_LDX`` means::
+
+  dst_reg = *(size *) (src_reg + off)
+
+Where size is one of: ``BPF_B``, ``BPF_H``, ``BPF_W``, or ``BPF_DW``.
+
+Atomic operations
+-----------------
+
+Atomic operations are operations that operate on memory and can not be
+interrupted or corrupted by other access to the same memory region
+by other eBPF programs or means outside of this specification.
+
+All atomic operations supported by eBPF are encoded as store operations
+that use the ``BPF_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
+* 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
+========  =====  ===========
+
+
+``BPF_ATOMIC | BPF_W  | BPF_STX`` with 'imm' = BPF_ADD means::
+
+  *(u32 *)(dst_reg + off16) += src_reg
+
+``BPF_ATOMIC | BPF_DW | BPF_STX`` with 'imm' = BPF ADD means::
+
+  *(u64 *)(dst_reg + off16) += src_reg
+
+In addition to the simple atomic operations, there also is a modifier and
+two complex atomic operations:
+
+===========  ================  ===========================
+imm          value             description
+===========  ================  ===========================
+BPF_FETCH    0x01              modifier: return old value
+BPF_XCHG     0xe0 | BPF_FETCH  atomic exchange
+BPF_CMPXCHG  0xf0 | BPF_FETCH  atomic compare and exchange
+===========  ================  ===========================
+
+The ``BPF_FETCH`` modifier is optional for simple atomic operations, and
+always set for the complex atomic operations.  If the ``BPF_FETCH`` flag
+is set, then the operation also overwrites ``src_reg`` with the value that
+was in memory before it was modified.
+
+The ``BPF_XCHG`` operation atomically exchanges ``src_reg`` with the value
+addressed by ``dst_reg + off``.
+
+The ``BPF_CMPXCHG`` operation atomically compares the value addressed by
+``dst_reg + off`` with ``R0``. If they match, the value addressed by
+``dst_reg + off`` is replaced with ``src_reg``. In either case, the
+value that was at ``dst_reg + off`` before the operation is zero-extended
+and loaded back to ``R0``.
+
+64-bit immediate instructions
+-----------------------------
+
+Instructions with the ``BPF_IMM`` 'mode' modifier use the wide instruction
+encoding for an extra imm64 value.
+
+There is currently only one such instruction.
+
+``BPF_LD | BPF_DW | BPF_IMM`` means::
+
+  dst_reg = imm64
+
+
+Legacy BPF Packet access instructions
+-------------------------------------
+
+eBPF 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.