selftests/bpf: Tests for btf_dedup_resolve_fwds

Tests to verify the following behavior of `btf_dedup_resolve_fwds`:
- remapping for struct forward declarations;
- remapping for union forward declarations;
- no remapping if forward declaration kind does not match similarly
  named struct or union declaration;
- no remapping if forward declaration name is ambiguous;
- base ids are considered for fwd resolution in split btf scenario.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Link: https://lore.kernel.org/bpf/20221109142611.879983-4-eddyz87@gmail.com

tools/testing/selftests/bpf/prog_tests/btf.c

@@ -7690,6 +7690,182 @@ static struct btf_dedup_test dedup_tests[] = {
 		BTF_STR_SEC("\0e1\0e1_val\0td"),
 	},
 },
+{
+	.descr = "dedup: standalone fwd declaration struct",
+	/*
+	 * Verify that CU1:foo and CU2:foo would be unified and that
+	 * typedef/ptr would be updated to point to CU1:foo.
+	 *
+	 * // CU 1:
+	 * struct foo { int x; };
+	 *
+	 * // CU 2:
+	 * struct foo;
+	 * typedef struct foo *foo_ptr;
+	 */
+	.input = {
+		.raw_types = {
+			/* CU 1 */
+			BTF_STRUCT_ENC(NAME_NTH(1), 1, 4),             /* [1] */
+			BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4), /* [2] */
+			/* CU 2 */
+			BTF_FWD_ENC(NAME_NTH(1), 0),                   /* [3] */
+			BTF_PTR_ENC(3),                                /* [4] */
+			BTF_TYPEDEF_ENC(NAME_NTH(3), 4),               /* [5] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0foo\0x\0foo_ptr"),
+	},
+	.expect = {
+		.raw_types = {
+			BTF_STRUCT_ENC(NAME_NTH(1), 1, 4),             /* [1] */
+			BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4), /* [2] */
+			BTF_PTR_ENC(1),                                /* [3] */
+			BTF_TYPEDEF_ENC(NAME_NTH(3), 3),               /* [4] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0foo\0x\0foo_ptr"),
+	},
+},
+{
+	.descr = "dedup: standalone fwd declaration union",
+	/*
+	 * Verify that CU1:foo and CU2:foo would be unified and that
+	 * typedef/ptr would be updated to point to CU1:foo.
+	 * Same as "dedup: standalone fwd declaration struct" but for unions.
+	 *
+	 * // CU 1:
+	 * union foo { int x; };
+	 *
+	 * // CU 2:
+	 * union foo;
+	 * typedef union foo *foo_ptr;
+	 */
+	.input = {
+		.raw_types = {
+			/* CU 1 */
+			BTF_UNION_ENC(NAME_NTH(1), 1, 4),              /* [1] */
+			BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4), /* [2] */
+			/* CU 2 */
+			BTF_FWD_ENC(NAME_TBD, 1),                      /* [3] */
+			BTF_PTR_ENC(3),                                /* [4] */
+			BTF_TYPEDEF_ENC(NAME_NTH(3), 4),               /* [5] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0foo\0x\0foo_ptr"),
+	},
+	.expect = {
+		.raw_types = {
+			BTF_UNION_ENC(NAME_NTH(1), 1, 4),              /* [1] */
+			BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4), /* [2] */
+			BTF_PTR_ENC(1),                                /* [3] */
+			BTF_TYPEDEF_ENC(NAME_NTH(3), 3),               /* [4] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0foo\0x\0foo_ptr"),
+	},
+},
+{
+	.descr = "dedup: standalone fwd declaration wrong kind",
+	/*
+	 * Negative test for btf_dedup_resolve_fwds:
+	 * - CU1:foo is a struct, C2:foo is a union, thus CU2:foo is not deduped;
+	 * - typedef/ptr should remain unchanged as well.
+	 *
+	 * // CU 1:
+	 * struct foo { int x; };
+	 *
+	 * // CU 2:
+	 * union foo;
+	 * typedef union foo *foo_ptr;
+	 */
+	.input = {
+		.raw_types = {
+			/* CU 1 */
+			BTF_STRUCT_ENC(NAME_NTH(1), 1, 4),             /* [1] */
+			BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4), /* [2] */
+			/* CU 2 */
+			BTF_FWD_ENC(NAME_NTH(3), 1),                   /* [3] */
+			BTF_PTR_ENC(3),                                /* [4] */
+			BTF_TYPEDEF_ENC(NAME_NTH(3), 4),               /* [5] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0foo\0x\0foo_ptr"),
+	},
+	.expect = {
+		.raw_types = {
+			/* CU 1 */
+			BTF_STRUCT_ENC(NAME_NTH(1), 1, 4),             /* [1] */
+			BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4), /* [2] */
+			/* CU 2 */
+			BTF_FWD_ENC(NAME_NTH(3), 1),                   /* [3] */
+			BTF_PTR_ENC(3),                                /* [4] */
+			BTF_TYPEDEF_ENC(NAME_NTH(3), 4),               /* [5] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0foo\0x\0foo_ptr"),
+	},
+},
+{
+	.descr = "dedup: standalone fwd declaration name conflict",
+	/*
+	 * Negative test for btf_dedup_resolve_fwds:
+	 * - two candidates for CU2:foo dedup, thus it is unchanged;
+	 * - typedef/ptr should remain unchanged as well.
+	 *
+	 * // CU 1:
+	 * struct foo { int x; };
+	 *
+	 * // CU 2:
+	 * struct foo;
+	 * typedef struct foo *foo_ptr;
+	 *
+	 * // CU 3:
+	 * struct foo { int x; int y; };
+	 */
+	.input = {
+		.raw_types = {
+			/* CU 1 */
+			BTF_STRUCT_ENC(NAME_NTH(1), 1, 4),             /* [1] */
+			BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4), /* [2] */
+			/* CU 2 */
+			BTF_FWD_ENC(NAME_NTH(1), 0),                   /* [3] */
+			BTF_PTR_ENC(3),                                /* [4] */
+			BTF_TYPEDEF_ENC(NAME_NTH(4), 4),               /* [5] */
+			/* CU 3 */
+			BTF_STRUCT_ENC(NAME_NTH(1), 2, 8),             /* [6] */
+			BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+			BTF_MEMBER_ENC(NAME_NTH(3), 2, 0),
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0foo\0x\0y\0foo_ptr"),
+	},
+	.expect = {
+		.raw_types = {
+			/* CU 1 */
+			BTF_STRUCT_ENC(NAME_NTH(1), 1, 4),             /* [1] */
+			BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4), /* [2] */
+			/* CU 2 */
+			BTF_FWD_ENC(NAME_NTH(1), 0),                   /* [3] */
+			BTF_PTR_ENC(3),                                /* [4] */
+			BTF_TYPEDEF_ENC(NAME_NTH(4), 4),               /* [5] */
+			/* CU 3 */
+			BTF_STRUCT_ENC(NAME_NTH(1), 2, 8),             /* [6] */
+			BTF_MEMBER_ENC(NAME_NTH(2), 2, 0),
+			BTF_MEMBER_ENC(NAME_NTH(3), 2, 0),
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0foo\0x\0y\0foo_ptr"),
+	},
+},
 };
 
 static int btf_type_size(const struct btf_type *t)

tools/testing/selftests/bpf/prog_tests/btf_dedup_split.c

@@ -141,6 +141,10 @@ static void test_split_fwd_resolve() {
 	btf__add_field(btf1, "f2", 3, 64, 0);		/*      struct s2 *f2; */
 							/* } */
 	btf__add_struct(btf1, "s2", 4);			/* [5] struct s2 { */
+	btf__add_field(btf1, "f1", 1, 0, 0);		/*      int f1; */
+							/* } */
+	/* keep this not a part of type the graph to test btf_dedup_resolve_fwds */
+	btf__add_struct(btf1, "s3", 4);                 /* [6] struct s3 { */
 	btf__add_field(btf1, "f1", 1, 0, 0);		/*      int f1; */
 							/* } */
 
@@ -153,20 +157,24 @@ static void test_split_fwd_resolve() {
 		"\t'f1' type_id=2 bits_offset=0\n"
 		"\t'f2' type_id=3 bits_offset=64",
 		"[5] STRUCT 's2' size=4 vlen=1\n"
+		"\t'f1' type_id=1 bits_offset=0",
+		"[6] STRUCT 's3' size=4 vlen=1\n"
 		"\t'f1' type_id=1 bits_offset=0");
 
 	btf2 = btf__new_empty_split(btf1);
 	if (!ASSERT_OK_PTR(btf2, "empty_split_btf"))
 		goto cleanup;
 
-	btf__add_int(btf2, "int", 4, BTF_INT_SIGNED);	/* [6] int */
-	btf__add_ptr(btf2, 10);				/* [7] ptr to struct s1 */
-	btf__add_fwd(btf2, "s2", BTF_FWD_STRUCT);	/* [8] fwd for struct s2 */
-	btf__add_ptr(btf2, 8);				/* [9] ptr to fwd struct s2 */
-	btf__add_struct(btf2, "s1", 16);		/* [10] struct s1 { */
-	btf__add_field(btf2, "f1", 7, 0, 0);		/*      struct s1 *f1; */
-	btf__add_field(btf2, "f2", 9, 64, 0);		/*      struct s2 *f2; */
+	btf__add_int(btf2, "int", 4, BTF_INT_SIGNED);	/* [7] int */
+	btf__add_ptr(btf2, 11);				/* [8] ptr to struct s1 */
+	btf__add_fwd(btf2, "s2", BTF_FWD_STRUCT);	/* [9] fwd for struct s2 */
+	btf__add_ptr(btf2, 9);				/* [10] ptr to fwd struct s2 */
+	btf__add_struct(btf2, "s1", 16);		/* [11] struct s1 { */
+	btf__add_field(btf2, "f1", 8, 0, 0);		/*      struct s1 *f1; */
+	btf__add_field(btf2, "f2", 10, 64, 0);		/*      struct s2 *f2; */
 							/* } */
+	btf__add_fwd(btf2, "s3", BTF_FWD_STRUCT);	/* [12] fwd for struct s3 */
+	btf__add_ptr(btf2, 12);				/* [13] ptr to struct s1 */
 
 	VALIDATE_RAW_BTF(
 		btf2,
@@ -178,13 +186,17 @@ static void test_split_fwd_resolve() {
 		"\t'f2' type_id=3 bits_offset=64",
 		"[5] STRUCT 's2' size=4 vlen=1\n"
 		"\t'f1' type_id=1 bits_offset=0",
-		"[6] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
-		"[7] PTR '(anon)' type_id=10",
-		"[8] FWD 's2' fwd_kind=struct",
-		"[9] PTR '(anon)' type_id=8",
-		"[10] STRUCT 's1' size=16 vlen=2\n"
-		"\t'f1' type_id=7 bits_offset=0\n"
-		"\t'f2' type_id=9 bits_offset=64");
+		"[6] STRUCT 's3' size=4 vlen=1\n"
+		"\t'f1' type_id=1 bits_offset=0",
+		"[7] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
+		"[8] PTR '(anon)' type_id=11",
+		"[9] FWD 's2' fwd_kind=struct",
+		"[10] PTR '(anon)' type_id=9",
+		"[11] STRUCT 's1' size=16 vlen=2\n"
+		"\t'f1' type_id=8 bits_offset=0\n"
+		"\t'f2' type_id=10 bits_offset=64",
+		"[12] FWD 's3' fwd_kind=struct",
+		"[13] PTR '(anon)' type_id=12");
 
 	err = btf__dedup(btf2, NULL);
 	if (!ASSERT_OK(err, "btf_dedup"))
@@ -199,7 +211,10 @@ static void test_split_fwd_resolve() {
 		"\t'f1' type_id=2 bits_offset=0\n"
 		"\t'f2' type_id=3 bits_offset=64",
 		"[5] STRUCT 's2' size=4 vlen=1\n"
-		"\t'f1' type_id=1 bits_offset=0");
+		"\t'f1' type_id=1 bits_offset=0",
+		"[6] STRUCT 's3' size=4 vlen=1\n"
+		"\t'f1' type_id=1 bits_offset=0",
+		"[7] PTR '(anon)' type_id=6");
 
 cleanup:
 	btf__free(btf2);