6.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: D. Wythe alibuda@linux.alibaba.com
[ Upstream commit 0cc114dc358cf8da2ca23a366e761e89a46ca277 ]
When a module registers a struct_ops, the struct_ops type and its corresponding map_value type ("bpf_struct_ops_") may reside in different btf objects, here are four possible case:
+--------+---------------+-------------+---------------------------------+ | |bpf_struct_ops_| xxx_ops | | +--------+---------------+-------------+---------------------------------+ | case 0 | btf_vmlinux | btf_vmlinux | be used and reg only in vmlinux | +--------+---------------+-------------+---------------------------------+ | case 1 | btf_vmlinux | mod_btf | INVALID | +--------+---------------+-------------+---------------------------------+ | case 2 | mod_btf | btf_vmlinux | reg in mod but be used both in | | | | | vmlinux and mod. | +--------+---------------+-------------+---------------------------------+ | case 3 | mod_btf | mod_btf | be used and reg only in mod | +--------+---------------+-------------+---------------------------------+
Currently we figure out the mod_btf by searching with the struct_ops type, which makes it impossible to figure out the mod_btf when the struct_ops type is in btf_vmlinux while it's corresponding map_value type is in mod_btf (case 2).
The fix is to use the corresponding map_value type ("bpf_struct_ops_") as the lookup anchor instead of the struct_ops type to figure out the `btf` and `mod_btf` via find_ksym_btf_id(), and then we can locate the kern_type_id via btf__find_by_name_kind() with the `btf` we just obtained from find_ksym_btf_id().
With this change the lookup obtains the correct btf and mod_btf for case 2, preserves correct behavior for other valid cases, and still fails as expected for the invalid scenario (case 1).
Fixes: 590a00888250 ("bpf: libbpf: Add STRUCT_OPS support") Signed-off-by: D. Wythe alibuda@linux.alibaba.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Acked-by: Andrii Nakryiko andrii@kernel.org Acked-by: Martin KaFai Lau martin.lau@kernel.org Link: https://lore.kernel.org/bpf/20250926071751.108293-1-alibuda@linux.alibaba.co... Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/libbpf.c | 36 +++++++++++++++++------------------- 1 file changed, 17 insertions(+), 19 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index fe4fc5438678c..8f9261279b921 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1013,35 +1013,33 @@ 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[192], stname[256]; __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, - &btf, mod_btf); - if (kern_type_id < 0) { - pr_warn("struct_ops init_kern: struct %s is not found in kernel BTF\n", - tname); - return kern_type_id; - } - kern_type = btf__type_by_id(btf, kern_type_id); + snprintf(stname, sizeof(stname), "%s%s", STRUCT_OPS_VALUE_PREFIX, tname);
- /* 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. + /* 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_btf_by_prefix_kind(btf, STRUCT_OPS_VALUE_PREFIX, - tname, BTF_KIND_STRUCT); + 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%s is not found in kernel BTF\n", - STRUCT_OPS_VALUE_PREFIX, tname); + 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); + return kern_type_id; + } + kern_type = btf__type_by_id(btf, kern_type_id); + /* Find "struct tcp_congestion_ops" from * struct bpf_struct_ops_tcp_congestion_ops { * [ ... ] @@ -1054,8 +1052,8 @@ 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; }