@@ -883,24 +883,24 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map,
if (btf_is_ptr(mtype)) {
struct bpf_program *prog;
- mtype = skip_mods_and_typedefs(btf, mtype->type, &mtype_id);
+ prog = st_ops->progs[i];
+ if (!prog)
+ continue;
+
kern_mtype = skip_mods_and_typedefs(kern_btf,
kern_mtype->type,
&kern_mtype_id);
- if (!btf_is_func_proto(mtype) ||
- !btf_is_func_proto(kern_mtype)) {
- pr_warn("struct_ops init_kern %s: non func ptr %s is not supported\n",
+
+ /* mtype->type must be a func_proto which was
+ * guaranteed in bpf_object__collect_st_ops_relos(),
+ * so only check kern_mtype for func_proto here.
+ */
+ if (!btf_is_func_proto(kern_mtype)) {
+ pr_warn("struct_ops init_kern %s: kernel member %s is not a func ptr\n",
map->name, mname);
return -ENOTSUP;
}
- prog = st_ops->progs[i];
- if (!prog) {
- pr_debug("struct_ops init_kern %s: func ptr %s is not set\n",
- map->name, mname);
- continue;
- }
-
prog->attach_btf_id = kern_type_id;
prog->expected_attach_type = kern_member_idx;
When libbpf initializes the kernel's struct_ops in "bpf_map__init_kern_struct_ops()", it enforces all pointer types must be a function pointer and rejects others. It turns out to be too strict. For example, when directly using "struct tcp_congestion_ops" from vmlinux.h, it has a "struct module *owner" member and it is set to NULL in a bpf_tcp_cc.o. Instead, it only needs to ensure the member is a function pointer if it has been set (relocated) to a bpf-prog. This patch moves the "btf_is_func_proto(kern_mtype)" check after the existing "if (!prog) { continue; }". The original debug message in "if (!prog) { continue; }" is also removed since it is no longer valid. Beside, there is a later debug message to tell which function pointer is set. The "btf_is_func_proto(mtype)" has already been guaranteed in "bpf_object__collect_st_ops_relos()" which has been run before "bpf_map__init_kern_struct_ops()". Thus, this check is removed. v2: - Remove outdated debug message (Andrii) Remove because there is a later debug message to tell which function pointer is set. - Following mtype->type is no longer needed. Remove: "skip_mods_and_typedefs(btf, mtype->type, &mtype_id)" - Do "if (!prog)" test before skip_mods_and_typedefs. Fixes: 590a00888250 ("bpf: libbpf: Add STRUCT_OPS support") Acked-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Martin KaFai Lau <kafai@fb.com> --- tools/lib/bpf/libbpf.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-)