The eBPF instruction set document does not currently document the basic instruction encoding. Add a section to do that. Signed-off-by: Christoph Hellwig <hch@xxxxxx> --- Documentation/bpf/instruction-set.rst | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst index 1af51143ff9f6..80f42984b5942 100644 --- a/Documentation/bpf/instruction-set.rst +++ b/Documentation/bpf/instruction-set.rst @@ -19,8 +19,22 @@ The eBPF calling convention is defined as: R0 - R5 are scratch registers and eBPF programs needs to spill/fill them if necessary across calls. +Instruction encoding +==================== + +eBPF uses 64-bit instructions with the following encoding: + + ============= ======= =============== ==================== ============ + 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: -- 2.30.2
