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no longer valid.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- Remove outdated debug message (Andrii)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 <and...@kernel.org>
Signed-off-by: Martin KaFai Lau <ka...@fb.com>
---
tools/lib/bpf/libbpf.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 6ae748f6ea11..a0d4fc4de402 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -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;
--
2.24.1
