libbpf: Fix struct end padding in btf_dump

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

diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index ede55fe..87f27e2 100644 (file)
--- 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));