diff options
| author | Dave Thaler | 2023-03-08 20:53:03 +0000 |
|---|---|---|
| committer | Alexei Starovoitov | 2023-03-10 13:02:00 -0800 |
| commit | c1f9e14e3b676eb88fe1c9488c0b5f4fc9108a1c (patch) | |
| tree | c895db124ca1ed63b2683c3136c3a83f2fd7de0a /Documentation/bpf/instruction-set.rst | |
| parent | 74843b57ec70af7b67b7e6153374834ee18d139f (diff) | |
bpf, docs: Explain helper functions
Add brief text about existence of helper functions, with details to go in
separate psABI text.
Note that text about runtime functions (kfuncs) is part of a separate patch,
not this one.
Signed-off-by: Dave Thaler <dthaler@microsoft.com>
Link: https://lore.kernel.org/r/20230308205303.1308-1-dthaler1968@googlemail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'Documentation/bpf/instruction-set.rst')
| -rw-r--r-- | Documentation/bpf/instruction-set.rst | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst index db8789e6969e..5e43e14abe80 100644 --- a/Documentation/bpf/instruction-set.rst +++ b/Documentation/bpf/instruction-set.rst @@ -253,7 +253,7 @@ BPF_JSET 0x40 PC += off if dst & src BPF_JNE 0x50 PC += off if dst != src BPF_JSGT 0x60 PC += off if dst > src signed BPF_JSGE 0x70 PC += off if dst >= src signed -BPF_CALL 0x80 function call +BPF_CALL 0x80 function call see `Helper functions`_ BPF_EXIT 0x90 function / program return BPF_JMP only BPF_JLT 0xa0 PC += off if dst < src unsigned BPF_JLE 0xb0 PC += off if dst <= src unsigned @@ -264,6 +264,13 @@ BPF_JSLE 0xd0 PC += off if dst <= src signed The eBPF program needs to store the return value into register R0 before doing a BPF_EXIT. +Helper functions +~~~~~~~~~~~~~~~~ + +Helper functions are a concept whereby BPF programs can call into a +set of function calls exposed by the runtime. Each helper +function is identified by an integer used in a ``BPF_CALL`` instruction. +The available helper functions may differ for each program type. Load and store instructions =========================== |