libbpf: Tighten BTF type ID rewriting with error checking

It should never fail, but if it does, it's better to know about this rather
than end up with nonsensical type IDs.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210423181348.1801389-11-andrii@kernel.org

diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index b0e0384..5505c85 100644 (file)
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -1429,6 +1429,13 @@ static int linker_fixup_btf(struct src_obj *obj)
 static int remap_type_id(__u32 *type_id, void *ctx)
 {
        int *id_map = ctx;
+       int new_id = id_map[*type_id];
+
+       /* Error out if the type wasn't remapped. Ignore VOID which stays VOID. */
+       if (new_id == 0 && *type_id != 0) {
+               pr_warn("failed to find new ID mapping for original BTF type ID %u\n", *type_id);
+               return -EINVAL;
+       }
 
        *type_id = id_map[*type_id];