[PATCH 5.17 0619/1126] libbpf: Skip forward declaration when counting duplicated type names

Greg Kroah-Hartman
2022-04-05T10:08:13Z

From: Xu Kuohai <xukuohai@huawei.com>

[ Upstream commit 4226961b0019b2e1612029e8950a9e911affc995 ]

Currently if a declaration appears in the BTF before the definition, the
definition is dumped as a conflicting name, e.g.:

$ bpftool btf dump file vmlinux format raw | grep "'unix_sock'"
[81287] FWD 'unix_sock' fwd_kind=struct
[89336] STRUCT 'unix_sock' size=1024 vlen=14

$ bpftool btf dump file vmlinux format c | grep "struct unix_sock"
struct unix_sock;
struct unix_sock___2 { <--- conflict, the "___2" is unexpected
struct unix_sock___2 *unix_sk;

This causes a compilation error if the dump output is used as a header file.

Fix it by skipping declaration when counting duplicated type names.

Fixes: 351131b51c7a ("libbpf: add btf_dump API for BTF-to-C conversion")
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20220301053250.1464204-2-xukuohai@huawei.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/lib/bpf/btf_dump.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 07ebe70d3a30..6b1bc1f43728 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -1505,6 +1505,11 @@ static const char *btf_dump_resolve_name(struct btf_dump *d, __u32 id,
if (s->name_resolved)
return *cached_name ? *cached_name : orig_name;

+ if (btf_is_fwd(t) || (btf_is_enum(t) && btf_vlen(t) == 0)) {
+ s->name_resolved = 1;
+ return orig_name;
+ }
+
dup_cnt = btf_dump_name_dups(d, name_map, orig_name);
if (dup_cnt > 1) {
const size_t max_len = 256;
--
2.34.1