This patch elaborates on the use of PC by expanding the PC acronym, explaining the units, and the relative position to which the offset applies. v1->v2: reword per feedback from Alexei v2->v3: reword per feedback from David Vernet Signed-off-by: Dave Thaler <dthaler1968@xxxxxxxxxxxxxx> --- Documentation/bpf/standardization/instruction-set.rst | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst index b44bdacd0..997560aba 100644 --- a/Documentation/bpf/standardization/instruction-set.rst +++ b/Documentation/bpf/standardization/instruction-set.rst @@ -469,6 +469,12 @@ 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. + The BPF program needs to store the return value into register R0 before doing an ``EXIT``. -- 2.40.1
