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| author | Dave Thaler <dthaler1968@googlemail.com> | 2024-04-26 16:11:26 -0700 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2024-04-29 11:54:42 +0200 |
| commit | 07801a24e2f18624cd2400ce15f14569eb416c9a (patch) | |
| tree | 19e50ffbf18843caa1fee3e790f8a3b28ac5354d /Documentation/bpf | |
| parent | 6e25bcf06af0341691f7058e17e04800f6a19e26 (diff) | |
| download | linux-07801a24e2f18624cd2400ce15f14569eb416c9a.tar.gz linux-07801a24e2f18624cd2400ce15f14569eb416c9a.tar.bz2 linux-07801a24e2f18624cd2400ce15f14569eb416c9a.zip | |
bpf, docs: Clarify PC use in instruction-set.rst
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.
Signed-off-by: Dave Thaler <dthaler1968@googlemail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20240426231126.5130-1-dthaler1968@gmail.com
Diffstat (limited to 'Documentation/bpf')
| -rw-r--r-- | Documentation/bpf/standardization/instruction-set.rst | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst index b44bdacd0195..997560abadab 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``. |