[PATCH 5.4 118/434] libbpf: Fix struct end padding in btf_dump

Greg Kroah-Hartman
2019-12-29T17:46:07Z

From: Andrii Nakryiko <andriin@fb.com>

[ Upstream commit b4099769f3321a8d258a47a8b4b9d278dad28a73 ]

Fix a case where explicit padding at the end of a struct is necessary
due to non-standart alignment requirements of fields (which BTF doesn't
capture explicitly).

Fixes: 351131b51c7a ("libbpf: add btf_dump API for BTF-to-C conversion")
Reported-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20191008231009.2991130-2-andriin@fb.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/lib/bpf/btf_dump.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index ede55fec3618..87f27e2664c5 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -876,7 +876,6 @@ static void btf_dump_emit_struct_def(struct btf_dump *d,
__u16 vlen = btf_vlen(t);

packed = is_struct ? btf_is_struct_packed(d->btf, id, t) : 0;
- align = packed ? 1 : btf_align_of(d->btf, id);

btf_dump_printf(d, "%s%s%s {",
is_struct ? "struct" : "union",
@@ -906,6 +905,13 @@ static void btf_dump_emit_struct_def(struct btf_dump *d,
btf_dump_printf(d, ";");
}

+ /* pad at the end, if necessary */
+ if (is_struct) {
+ align = packed ? 1 : btf_align_of(d->btf, id);
+ btf_dump_emit_bit_padding(d, off, t->size * 8, 0, align,
+ lvl + 1);
+ }
+
if (vlen)
btf_dump_printf(d, "\n");
btf_dump_printf(d, "%s}", pfx(lvl));
--
2.20.1