selftests/bpf: add btf_dedup test for VOID equivalence check

This patch adds specific test exposing bug in btf_dedup_is_equiv() when
comparing candidate VOID type to a non-VOID canonical type. It's
important for canonical type to be anonymous, otherwise name equality
check will do the right thing and will exit early.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/test_btf.c b/tools/testing/selftests/bpf/test_btf.c
index 23e3b31..ec5794e 100644 (file)
--- a/tools/testing/selftests/bpf/test_btf.c
+++ b/tools/testing/selftests/bpf/test_btf.c
@@ -5777,6 +5777,53 @@ const struct btf_dedup_test dedup_tests[] = {
        },
 },
 {
+       .descr = "dedup: void equiv check",
+       /*
+        * // CU 1:
+        * struct s {
+        *      struct {} *x;
+        * };
+        * // CU 2:
+        * struct s {
+        *      int *x;
+        * };
+        */
+       .input = {
+               .raw_types = {
+                       /* CU 1 */
+                       BTF_STRUCT_ENC(0, 0, 1),                                /* [1] struct {}  */
+                       BTF_PTR_ENC(1),                                         /* [2] ptr -> [1] */
+                       BTF_STRUCT_ENC(NAME_NTH(1), 1, 8),                      /* [3] struct s   */
+                               BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+                       /* CU 2 */
+                       BTF_PTR_ENC(0),                                         /* [4] ptr -> void */
+                       BTF_STRUCT_ENC(NAME_NTH(1), 1, 8),                      /* [5] struct s   */
+                               BTF_MEMBER_ENC(NAME_NTH(2), 4, 0),
+                       BTF_END_RAW,
+               },
+               BTF_STR_SEC("\0s\0x"),
+       },
+       .expect = {
+               .raw_types = {
+                       /* CU 1 */
+                       BTF_STRUCT_ENC(0, 0, 1),                                /* [1] struct {}  */
+                       BTF_PTR_ENC(1),                                         /* [2] ptr -> [1] */
+                       BTF_STRUCT_ENC(NAME_NTH(1), 1, 8),                      /* [3] struct s   */
+                               BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+                       /* CU 2 */
+                       BTF_PTR_ENC(0),                                         /* [4] ptr -> void */
+                       BTF_STRUCT_ENC(NAME_NTH(1), 1, 8),                      /* [5] struct s   */
+                               BTF_MEMBER_ENC(NAME_NTH(2), 4, 0),
+                       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 = {
                .raw_types = {