On Wed, Feb 27, 2019 at 2:48 PM Andrii Nakryiko <andriin@xxxxxx> wrote:
>
> This patch adds a btf_dedup test exercising logic of STRUCT<->FWD
> resolution and validating that STRUCT is not resolved to a FWD. It also
> forces hash collisions, forcing both FWD and STRUCT to be candidates for
> each other. Previously this condition caused infinite loop due to FWD
> pointing to STRUCT and STRUCT pointing to its FWD.
>
> Reported-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
> ---
> tools/testing/selftests/bpf/test_btf.c | 45 ++++++++++++++++++++++++++
> 1 file changed, 45 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/test_btf.c b/tools/testing/selftests/bpf/test_btf.c
> index 1426c0a905c8..38797aa627a7 100644
> --- a/tools/testing/selftests/bpf/test_btf.c
> +++ b/tools/testing/selftests/bpf/test_btf.c
> @@ -5731,6 +5731,51 @@ const struct btf_dedup_test dedup_tests[] = {
> .dont_resolve_fwds = false,
> },
> },
> +{
> + .descr = "dedup: struct <-> fwd resolution w/ hash collision",
> + /*
> + * // CU 1:
> + * struct x;
> + * struct s {
> + * struct x *x;
> + * };
> + * // CU 2:
> + * struct x {};
> + * struct s {
> + * struct x *x;
> + * };
> + */
> + .input = {
> + .raw_types = {
> + /* CU 1 */
> + BTF_FWD_ENC(NAME_TBD, 0 /* struct fwd */), /* [1] fwd x */
> + BTF_PTR_ENC(1), /* [2] ptr -> [1] */
> + BTF_STRUCT_ENC(NAME_TBD, 1, 8), /* [3] struct s */
> + BTF_MEMBER_ENC(NAME_TBD, 2, 0),
> + /* CU 2 */
> + BTF_STRUCT_ENC(NAME_TBD, 0, 0), /* [4] struct x */
> + BTF_PTR_ENC(4), /* [5] ptr -> [4] */
> + BTF_STRUCT_ENC(NAME_TBD, 1, 8), /* [6] struct s */
> + BTF_MEMBER_ENC(NAME_TBD, 5, 0),
> + BTF_END_RAW,
> + },
> + BTF_STR_SEC("\0x\0s\0x\0x\0s\0x\0"),
> + },
> + .expect = {
> + .raw_types = {
> + BTF_PTR_ENC(3), /* [1] ptr -> [3] */
> + BTF_STRUCT_ENC(NAME_TBD, 1, 8), /* [2] struct s */
> + BTF_MEMBER_ENC(NAME_TBD, 1, 0),
> + BTF_STRUCT_ENC(NAME_NTH(2), 0, 0), /* [3] struct x */
> + BTF_END_RAW,
> + },
> + BTF_STR_SEC("\0s\0x"),
> + },
> + .opts = {
> + .dont_resolve_fwds = false,
> + .dedup_table_size = 1, /* force hash collisions */
> + },
> +},
> {
> .descr = "dedup: all possible kinds (no duplicates)",
> .input = {
> --
> 2.17.1
>
