selftests/bpf: add fwd enum resolution test for btf_dedup

This patch adds test verifying new btf_dedup logic of resolving
forward-declared enums.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/test_btf.c

@@ -5874,6 +5874,50 @@ const struct btf_dedup_test dedup_tests[] = {
 		.dont_resolve_fwds = false,
 	},
 },
+{
+	.descr = "dedup: enum fwd resolution",
+	.input = {
+		.raw_types = {
+			/* [1] fwd enum 'e1' before full enum */
+			BTF_TYPE_ENC(NAME_NTH(1), BTF_INFO_ENC(BTF_KIND_ENUM, 0, 0), 4),
+			/* [2] full enum 'e1' after fwd */
+			BTF_TYPE_ENC(NAME_NTH(1), BTF_INFO_ENC(BTF_KIND_ENUM, 0, 1), 4),
+				BTF_ENUM_ENC(NAME_NTH(2), 123),
+			/* [3] full enum 'e2' before fwd */
+			BTF_TYPE_ENC(NAME_NTH(3), BTF_INFO_ENC(BTF_KIND_ENUM, 0, 1), 4),
+				BTF_ENUM_ENC(NAME_NTH(4), 456),
+			/* [4] fwd enum 'e2' after full enum */
+			BTF_TYPE_ENC(NAME_NTH(3), BTF_INFO_ENC(BTF_KIND_ENUM, 0, 0), 4),
+			/* [5] incompatible fwd enum with different size */
+			BTF_TYPE_ENC(NAME_NTH(1), BTF_INFO_ENC(BTF_KIND_ENUM, 0, 0), 1),
+			/* [6] incompatible full enum with different value */
+			BTF_TYPE_ENC(NAME_NTH(1), BTF_INFO_ENC(BTF_KIND_ENUM, 0, 1), 4),
+				BTF_ENUM_ENC(NAME_NTH(2), 321),
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0e1\0e1_val\0e2\0e2_val"),
+	},
+	.expect = {
+		.raw_types = {
+			/* [1] full enum 'e1' */
+			BTF_TYPE_ENC(NAME_NTH(1), BTF_INFO_ENC(BTF_KIND_ENUM, 0, 1), 4),
+				BTF_ENUM_ENC(NAME_NTH(2), 123),
+			/* [2] full enum 'e2' */
+			BTF_TYPE_ENC(NAME_NTH(3), BTF_INFO_ENC(BTF_KIND_ENUM, 0, 1), 4),
+				BTF_ENUM_ENC(NAME_NTH(4), 456),
+			/* [3] incompatible fwd enum with different size */
+			BTF_TYPE_ENC(NAME_NTH(1), BTF_INFO_ENC(BTF_KIND_ENUM, 0, 0), 1),
+			/* [4] incompatible full enum with different value */
+			BTF_TYPE_ENC(NAME_NTH(1), BTF_INFO_ENC(BTF_KIND_ENUM, 0, 1), 4),
+				BTF_ENUM_ENC(NAME_NTH(2), 321),
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0e1\0e1_val\0e2\0e2_val"),
+	},
+	.opts = {
+		.dont_resolve_fwds = false,
+	},
+},
 
 };