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| author | Dave Thaler <dthaler@microsoft.com> | 2023-03-08 20:53:03 +0000 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-03-10 13:02:00 -0800 |
| commit | c1f9e14e3b676eb88fe1c9488c0b5f4fc9108a1c (patch) | |
| tree | c895db124ca1ed63b2683c3136c3a83f2fd7de0a /Documentation/bpf/linux-notes.rst | |
| parent | 74843b57ec70af7b67b7e6153374834ee18d139f (diff) | |
| download | lwn-c1f9e14e3b676eb88fe1c9488c0b5f4fc9108a1c.tar.gz lwn-c1f9e14e3b676eb88fe1c9488c0b5f4fc9108a1c.zip | |
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/linux-notes.rst')
| -rw-r--r-- | Documentation/bpf/linux-notes.rst | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/Documentation/bpf/linux-notes.rst b/Documentation/bpf/linux-notes.rst index 956b0c86699d..f43b9c797bcb 100644 --- a/Documentation/bpf/linux-notes.rst +++ b/Documentation/bpf/linux-notes.rst @@ -12,6 +12,14 @@ Byte swap instructions ``BPF_FROM_LE`` and ``BPF_FROM_BE`` exist as aliases for ``BPF_TO_LE`` and ``BPF_TO_BE`` respectively. +Jump instructions +================= + +``BPF_CALL | BPF_X | BPF_JMP`` (0x8d), where the helper function +integer would be read from a specified register, is not currently supported +by the verifier. Any programs with this instruction will fail to load +until such support is added. + Legacy BPF Packet access instructions ===================================== |