|author||Martin KaFai Lau <email@example.com>||2021-03-29 22:41:50 -0700|
|committer||Alexei Starovoitov <firstname.lastname@example.org>||2021-03-30 07:31:01 -0700|
bpf: Update bpf_design_QA.rst to clarify the kfunc call is not ABI
This patch updates bpf_design_QA.rst to clarify that the kernel function callable by bpf program is not an ABI. Signed-off-by: Martin KaFai Lau <email@example.com> Signed-off-by: Alexei Starovoitov <firstname.lastname@example.org> Acked-by: Song Liu <email@example.com> Link: https://firstname.lastname@example.org
Diffstat (limited to 'Documentation/bpf')
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
@@ -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?
+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?
+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.