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Wythe" To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, pabeni@redhat.com, song@kernel.org, sdf@google.com, haoluo@google.com, yhs@fb.com, edumazet@google.com, john.fastabend@gmail.com, kpsingh@kernel.org, jolsa@kernel.org, mjambigi@linux.ibm.com, wenjia@linux.ibm.com, wintera@linux.ibm.com, dust.li@linux.alibaba.com, tonylu@linux.alibaba.com, guwen@linux.alibaba.com Cc: bpf@vger.kernel.org, davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org, sidraya@linux.ibm.com, jaka@linux.ibm.com Subject: [PATCH bpf-next v2 3/4] libbpf: fix error when st-prefix_ops and ops from differ btf Date: Thu, 18 Sep 2025 16:03:40 +0800 Message-ID: <20250918080342.25041-4-alibuda@linux.alibaba.com> X-Mailer: git-send-email 2.45.0 In-Reply-To: <20250918080342.25041-1-alibuda@linux.alibaba.com> References: <20250918080342.25041-1-alibuda@linux.alibaba.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Acked-by: Andrii Nakryiko --- tools/lib/bpf/libbpf.c | 37 ++++++++++++++++++------------------- 1 file changed, 18 insertions(+), 19 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index fe4fc5438678..50ca13833511 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1013,35 +1013,34 @@ 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]; __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, + (int)strlen(tname), 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 +1053,8 @@ 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