.. contents::
.. sectnum::
-========================================
-eBPF Instruction Set Specification, v1.0
-========================================
+=======================================
+BPF Instruction Set Specification, v1.0
+=======================================
-This document specifies version 1.0 of the eBPF instruction set.
+This document specifies version 1.0 of the BPF instruction set.
Documentation conventions
=========================
A: 10000110
B: 11111111 10000110
-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:
+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.,
========= ===== ======= ==========================================================
Underflow and overflow are allowed during arithmetic operations, meaning
-the 64-bit or 32-bit value will wrap. If eBPF program execution would
+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
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 += offset see `Program-local 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_JSLE 0xd any PC += offset if dst <= src signed
======== ===== === =========================================== =========================================
-The eBPF program needs to store the return value into register R0 before doing a
+The BPF program needs to store the return value into register R0 before doing a
``BPF_EXIT``.
Example:
~~~~~~~~~~~~~~~~~~~~~~~
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``. A ``BPF_EXIT`` within the program-local function will return to
-the caller.
+``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.
Load and store instructions
===========================
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.
+by other BPF programs or means outside of this specification.
-All atomic operations supported by eBPF are encoded as store operations
+All atomic operations supported by BPF are encoded as store operations
that use the ``BPF_ATOMIC`` mode modifier as follows:
* ``BPF_ATOMIC | BPF_W | BPF_STX`` for 32-bit operations
Maps
~~~~
-Maps are shared memory regions accessible by eBPF programs on some platforms.
+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.
Legacy BPF Packet access instructions
-------------------------------------
-eBPF previously introduced special instructions for access to packet data that were
+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.
git.samba.org / sfrench / cifs-2.6.git / blobdiff