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| -rw-r--r-- | Documentation/bpf/bpf_design_QA.rst | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst index 0e15f9b05c9d..437de2a7a5de 100644 --- a/Documentation/bpf/bpf_design_QA.rst +++ b/Documentation/bpf/bpf_design_QA.rst @@ -258,3 +258,18 @@ Q: Can BPF functionality such as new program or map types, new helpers, etc be added out of kernel module code? A: NO. + +Q: Directly calling kernel function is an ABI? +---------------------------------------------- +Q: Some kernel functions (e.g. tcp_slow_start) can be called +by BPF programs. Do these kernel functions become an ABI? + +A: NO. + +The kernel function protos will change and the bpf programs will be +rejected by the verifier. Also, for example, some of the bpf-callable +kernel functions have already been used by other kernel tcp +cc (congestion-control) implementations. If any of these kernel +functions has changed, both the in-tree and out-of-tree kernel tcp cc +implementations have to be changed. The same goes for the bpf +programs and they have to be adjusted accordingly. |