From: Eduard Zingerman <eddyz87@xxxxxxxxx>
[ Upstream commit 44a726c3f23cf762ef4ce3c1709aefbcbe97f62c ]
btf_dump_emit_struct_def attempts to print empty structures at a
single line, e.g. `struct empty {}`. However, it has to account for a
case when there are no regular but some padding fields in the struct.
In such case `vlen` would be zero, but size would be non-zero.
E.g. here is struct bpf_timer from vmlinux.h before this patch:
struct bpf_timer {
long: 64;
long: 64;};
And after this patch:
struct bpf_dynptr {
long: 64;
long: 64;
};
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20221001104425.415768-1-eddyz87@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
tools/lib/bpf/btf_dump.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 558d34fbd331c..6a8d8ed34b760 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -969,7 +969,11 @@ static void btf_dump_emit_struct_def(struct btf_dump *d,
if (is_struct)
btf_dump_emit_bit_padding(d, off, t->size * 8, align, false, lvl + 1);
- if (vlen)
+ /*
+ * Keep `struct empty {}` on a single line,
+ * only print newline when there are regular or padding fields.
+ */
+ if (vlen || t->size)
btf_dump_printf(d, "\n");
btf_dump_printf(d, "%s}", pfx(lvl));
if (packed)
--
2.39.2
