When a struct_ops named xxx_ops was registered by a module, and
it will be used in both built-in modules and the module itself,
so that the btf_type of xxx_ops will be present in btf_vmlinux
instead of in btf_mod, which means that the btf_type of
bpf_struct_ops_xxx_ops and xxx_ops will not be in the same btf.
Here are four possible case:
+--------+---------------+-------------+---------------------------------+
| | st_ops_xxx_ops| xxx_ops | |
+--------+---------------+-------------+---------------------------------+
| case 0 | btf_vmlinux | bft_vmlinux | be used and reg only in vmlinux |
+--------+---------------+-------------+---------------------------------+
| case 1 | btf_vmlinux | bpf_mod | INVALID |
+--------+---------------+-------------+---------------------------------+
| case 2 | btf_mod | btf_vmlinux | reg in mod but be used both in |
| | | | vmlinux and mod. |
+--------+---------------+-------------+---------------------------------+
| case 3 | btf_mod | btf_mod | be used and reg only in mod |
+--------+---------------+-------------+---------------------------------+
At present, cases 0, 1, and 3 can be correctly identified, because
st_ops_xxx_ops is searched from the same btf with xxx_ops. In order to
handle case 2 correctly without affecting other cases, we cannot simply
change the search method for st_ops_xxx_ops from find_btf_by_prefix_kind()
to find_ksym_btf_id(), because in this way, case 1 will not be
recognized anymore.
To address the issue, we always look for st_ops_xxx_ops first,
figure out the btf, and then look for xxx_ops with the very btf to avoid
such issue.
Fixes: 590a00888250 ("bpf: libbpf: Add STRUCT_OPS support")
Signed-off-by: D. Wythe <alibuda@xxxxxxxxxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 41 +++++++++++++++++++++++------------------
1 file changed, 23 insertions(+), 18 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 66173ddb5a2d..202bc4c1001e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1005,14 +1005,33 @@ find_struct_ops_kern_types(struct bpf_object *obj, const char *tname_raw,
const struct btf_member *kern_data_member;
struct btf *btf = NULL;
__s32 kern_vtype_id, kern_type_id;
- char tname[256];
+ char tname[256], stname[256];
+ int ret;
__u32 i;
snprintf(tname, sizeof(tname), "%.*s",
(int)bpf_core_essential_name_len(tname_raw), tname_raw);
- kern_type_id = find_ksym_btf_id(obj, tname, BTF_KIND_STRUCT,
+ ret = snprintf(stname, sizeof(stname), "%s%s", STRUCT_OPS_VALUE_PREFIX,
+ tname);
+ if (ret < 0 || ret >= sizeof(stname))
+ return -ENAMETOOLONG;
+
+ /* Look for the corresponding "map_value" type that will be used
+ * in map_update(BPF_MAP_TYPE_STRUCT_OPS) first, figure out the btf
+ * and the mod_btf.
+ * For example, find "struct bpf_struct_ops_tcp_congestion_ops".
+ */
+ kern_vtype_id = find_ksym_btf_id(obj, stname, BTF_KIND_STRUCT,
&btf, mod_btf);
+ if (kern_vtype_id < 0) {
+ pr_warn("struct_ops init_kern: struct %s is not found in kernel BTF\n",
+ stname);
+ return kern_vtype_id;
+ }
+ kern_vtype = btf__type_by_id(btf, kern_vtype_id);
+
+ kern_type_id = btf__find_by_name_kind(btf, tname, BTF_KIND_STRUCT);
if (kern_type_id < 0) {
pr_warn("struct_ops init_kern: struct %s is not found in kernel BTF\n",
tname);
@@ -1020,20 +1039,6 @@ find_struct_ops_kern_types(struct bpf_object *obj, const char *tname_raw,
}
kern_type = btf__type_by_id(btf, kern_type_id);
- /* Find the corresponding "map_value" type that will be used
- * in map_update(BPF_MAP_TYPE_STRUCT_OPS). For example,
- * find "struct bpf_struct_ops_tcp_congestion_ops" from the
- * btf_vmlinux.
- */
- kern_vtype_id = find_btf_by_prefix_kind(btf, STRUCT_OPS_VALUE_PREFIX,
- tname, BTF_KIND_STRUCT);
- if (kern_vtype_id < 0) {
- pr_warn("struct_ops init_kern: struct %s%s is not found in kernel BTF\n",
- STRUCT_OPS_VALUE_PREFIX, tname);
- return kern_vtype_id;
- }
- kern_vtype = btf__type_by_id(btf, kern_vtype_id);
-
/* Find "struct tcp_congestion_ops" from
* struct bpf_struct_ops_tcp_congestion_ops {
* [ ... ]
@@ -1046,8 +1051,8 @@ find_struct_ops_kern_types(struct bpf_object *obj, const char *tname_raw,
break;
}
if (i == btf_vlen(kern_vtype)) {
- pr_warn("struct_ops init_kern: struct %s data is not found in struct %s%s\n",
- tname, STRUCT_OPS_VALUE_PREFIX, tname);
+ pr_warn("struct_ops init_kern: struct %s data is not found in struct %s\n",
+ tname, stname);
return -EINVAL;
}
--
2.45.0
