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Diffstat (limited to 'Documentation/bpf/standardization/instruction-set.rst')
| -rw-r--r-- | Documentation/bpf/standardization/instruction-set.rst | 80 |
1 files changed, 54 insertions, 26 deletions
diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst index 245b6defc298..af43227b6ee4 100644 --- a/Documentation/bpf/standardization/instruction-set.rst +++ b/Documentation/bpf/standardization/instruction-set.rst @@ -97,6 +97,28 @@ 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 "basic" 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 as such 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., "basic") 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. + +The "basic" conformance group includes all instructions defined in this +specification unless otherwise noted. + Instruction encoding ==================== @@ -152,12 +174,12 @@ and imm containing the high 32 bits of the immediate value. This is depicted in the following figure:: basic_instruction - .-----------------------------. - | | - code:8 regs:8 offset:16 imm:32 unused:32 imm:32 - | | - '--------------' - pseudo instruction + .------------------------------. + | | + opcode:8 regs:8 offset:16 imm:32 unused:32 imm:32 + | | + '--------------' + pseudo instruction Thus the 64-bit immediate value is constructed as follows: @@ -295,7 +317,11 @@ 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. +operands into 64 bit operands. Unlike other arithmetic instructions, +``BPF_MOVSX`` is only defined for register source operands (``BPF_X``). + +The ``BPF_NEG`` instruction is only defined when the source bit is clear +(``BPF_K``). Shift operations use a mask of 0x3F (63) for 64-bit operations and 0x1F (31) for 32-bit operations. @@ -352,27 +378,27 @@ Jump instructions otherwise identical operations. 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 +======== ===== === =============================== ============================================= +code value src description notes +======== ===== === =============================== ============================================= +BPF_JA 0x0 0x0 PC += offset BPF_JMP | BPF_K only +BPF_JA 0x0 0x0 PC += imm BPF_JMP32 | BPF_K only 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_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 -======== ===== === =========================================== ========================================= +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 BPF_JMP | BPF_K only, see `Helper functions`_ +BPF_CALL 0x8 0x1 call PC += imm BPF_JMP | BPF_K only, see `Program-local functions`_ +BPF_CALL 0x8 0x2 call helper function by BTF ID BPF_JMP | BPF_K only, see `Helper functions`_ +BPF_EXIT 0x9 0x0 return BPF_JMP | BPF_K 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``. @@ -610,4 +636,6 @@ 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. +deprecated and should no longer be used. All legacy packet access +instructions belong to the "legacy" conformance group instead of the "basic" +conformance group. |