libbpf: Allow loading empty BTFs

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

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 3c3f2bc6c6528e08fdaa913f1da43e2c02799b48..9970a288dda536768b5878f5f0a2c71dc0af8a97 100644 (file)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -240,11 +240,6 @@ 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;