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| author |   Andrii Nakryiko <andrii@kernel.org> | 2022-04-08 11:14:23 -0700 |
|---|---|---|
| committer |   Daniel Borkmann <daniel@iogearbox.net> | 2022-04-08 22:24:15 +0200 |
| commit | e89d57d938c8fa80c457982154ed6110804814fe (patch) | |
| tree | a5a6b8b62931835354fc3ad34e1348a35895e5e5 /tools/lib/bpf | |
| parent | samples, bpf: Move routes monitor in xdp_router_ipv4 in a dedicated thread (diff) | |
| download | linux-dev-e89d57d938c8fa80c457982154ed6110804814fe.tar.xz linux-dev-e89d57d938c8fa80c457982154ed6110804814fe.zip | |
libbpf: Don't error out on CO-RE relos for overriden weak subprogs
During BPF static linking, all the ELF relocations and .BTF.ext
information (including CO-RE relocations) are preserved for __weak
subprograms that were logically overriden by either previous weak
subprogram instance or by corresponding "strong" (non-weak) subprogram.
This is just how native user-space linkers work, nothing new.
But libbpf is over-zealous when processing CO-RE relocation to error out
when CO-RE relocation belonging to such eliminated weak subprogram is
encountered. Instead of erroring out on this expected situation, log
debug-level message and skip the relocation.
Fixes: db2b8b06423c ("libbpf: Support CO-RE relocations for multi-prog sections")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220408181425.2287230-2-andrii@kernel.org
Diffstat (limited to 'tools/lib/bpf')
| -rw-r--r-- | tools/lib/bpf/libbpf.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 9deb1fc67f19..465b7c0996f1 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -5687,10 +5687,17 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path) insn_idx = rec->insn_off / BPF_INSN_SZ; prog = find_prog_by_sec_insn(obj, sec_idx, insn_idx); if (!prog) { - pr_warn("sec '%s': failed to find program at insn #%d for CO-RE offset relocation #%d\n", - sec_name, insn_idx, i); - err = -EINVAL; - goto out; + /* When __weak subprog is "overridden" by another instance + * of the subprog from a different object file, linker still + * appends all the .BTF.ext info that used to belong to that + * eliminated subprogram. + * This is similar to what x86-64 linker does for relocations. + * So just ignore such relocations just like we ignore + * subprog instructions when discovering subprograms. + */ + pr_debug("sec '%s': skipping CO-RE relocation #%d for insn #%d belonging to eliminated weak subprogram\n", + sec_name, i, insn_idx); + continue; } /* no need to apply CO-RE relocation if the program is * not going to be loaded |