From c1f9e14e3b676eb88fe1c9488c0b5f4fc9108a1c Mon Sep 17 00:00:00 2001 From: Dave Thaler Date: Wed, 8 Mar 2023 20:53:03 +0000 Subject: 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 Link: https://lore.kernel.org/r/20230308205303.1308-1-dthaler1968@googlemail.com Signed-off-by: Alexei Starovoitov --- Documentation/bpf/linux-notes.rst | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'Documentation/bpf/linux-notes.rst') 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 ===================================== -- cgit v1.2.3