libbpf: Add explicit padding to btf_dump_emit_type_decl_opts

[ Upstream commit ea24b195 ]

Similar to
https://lore.kernel.org/bpf/20210313210920.1959628-2-andrii@kernel.org/



When DECLARE_LIBBPF_OPTS is used with inline field initialization, e.g:

  DECLARE_LIBBPF_OPTS(btf_dump_emit_type_decl_opts, opts,
    .field_name = var_ident,
    .indent_level = 2,
    .strip_mods = strip_mods,
  );

and compiled in debug mode, the compiler generates code which
leaves the padding uninitialized and triggers errors within libbpf APIs
which require strict zero initialization of OPTS structs.

Adding anonymous padding field fixes the issue.

Fixes: 9f81654e ("libbpf: Expose BTF-to-C type declaration emitting API")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210319192117.2310658-1-kpsingh@kernel.org


Signed-off-by: Sasha Levin <sashal@kernel.org>

tools/lib/bpf/btf.h

@@ -164,6 +164,7 @@ struct btf_dump_emit_type_decl_opts {
 	int indent_level;
 	/* strip all the const/volatile/restrict mods */
 	bool strip_mods;
+	size_t :0;
 };
 #define btf_dump_emit_type_decl_opts__last_field strip_mods