libbpf: Skip CO-RE relocations for not loaded BPF programs

Bypass CO-RE relocations step for BPF programs that are not going to be
loaded. This allows to have BPF programs compiled in and disabled dynamically
if kernel is not supposed to provide enough relocation information. In such
case, there won't be unnecessary warnings about failed relocations.

Fixes: d929758101fc ("libbpf: Support disabling auto-loading BPF programs")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201008001025.292064-2-andrii@kernel.org

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index faec389c48494046491c4a7f048f7428187e1ac9..07d62771472fce3353f9f4d51bc8325ccf96464a 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5765,6 +5765,11 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
                                err = -EINVAL;
                                goto out;
                        }
+                       /* no need to apply CO-RE relocation if the program is
+                        * not going to be loaded
+                        */
+                       if (!prog->load)
+                               continue;
 
                        err = bpf_core_apply_relo(prog, rec, i, obj->btf,
                                                  targ_btf, cand_cache);