libbpf: Allow loading empty BTFs

[ Upstream commit b8d52264df85ec12f370c0a8b28d0ac59a05877a ]

Empty BTFs do come up (e.g., simple kernel modules with no new types and
strings, compared to the vmlinux BTF) and there is nothing technically wrong
with them. So remove unnecessary check preventing loading empty BTFs.

Fixes: d8123624506c ("libbpf: Fix BTF data layout checks and allow empty BTF")
Reported-by: Christopher William Snowhill <chris@kode54.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210110070341.1380086-2-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 987c151..c8c7512 100644 (file)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -210,11 +210,6 @@ static int btf_parse_hdr(struct btf *btf)
        }
 
        meta_left = btf->raw_size - sizeof(*hdr);
-       if (!meta_left) {
-               pr_debug("BTF has no data\n");
-               return -EINVAL;
-       }
-
        if (meta_left < hdr->str_off + hdr->str_len) {
                pr_debug("Invalid BTF total size:%u\n", btf->raw_size);
                return -EINVAL;