netdev - [PATCH bpf 2/2] selftests/bpf: add btf_dedup test for VOID equivalence check

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Date:   Tue, 26 Mar 2019 22:00:07 -0700
From:   <andrii.nakryiko@...il.com>
To:     <andrii.nakryiko@...il.com>, <ast@...com>, <yhs@...com>,
        <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <acme@...nel.org>,
        <kernel-team@...com>, <daniel@...earbox.net>
CC:     Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf 2/2] selftests/bpf: add btf_dedup test for VOID equivalence check

From: Andrii Nakryiko <andriin@...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 <andriin@...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