From: Eduard Zingerman eddyz87@gmail.com
[ 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@gmail.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20221001104425.415768-1-eddyz87@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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)