From: Andrii Nakryiko <andr...@fb.com>

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 <andr...@fb.com>
---
 tools/testing/selftests/bpf/test_btf.c | 47 ++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_btf.c 
b/tools/testing/selftests/bpf/test_btf.c
index 23e3b314ca60..ec5794e4205b 100644
--- a/tools/testing/selftests/bpf/test_btf.c
+++ b/tools/testing/selftests/bpf/test_btf.c
@@ -5776,6 +5776,53 @@ const struct btf_dedup_test dedup_tests[] = {
                .dedup_table_size = 1, /* force hash collisions */
        },
 },
+{
+       .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 = {
-- 
2.17.1

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