selftests/bpf: Test multi-split BTF

Extend split BTF test to cover case where we create split BTF on top of
existing split BTF and add info to it; ensure that such BTF can be
created and handled by searching within it, dumping/comparing to expected.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250519165935.261614-3-alan.maguire@oracle.com

diff --git a/tools/testing/selftests/bpf/prog_tests/btf_split.c b/tools/testing/selftests/bpf/prog_tests/btf_split.c
index eef1158..3696fb9 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/btf_split.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf_split.c
@@ -12,10 +12,11 @@ static void btf_dump_printf(void *ctx, const char *fmt, va_list args)
        vfprintf(ctx, fmt, args);
 }
 
-void test_btf_split() {
+static void __test_btf_split(bool multi)
+{
        struct btf_dump *d = NULL;
        const struct btf_type *t;
-       struct btf *btf1, *btf2;
+       struct btf *btf1, *btf2, *btf3 = NULL;
        int str_off, i, err;
 
        btf1 = btf__new_empty();
@@ -63,14 +64,46 @@ void test_btf_split() {
        ASSERT_EQ(btf_vlen(t), 3, "split_struct_vlen");
        ASSERT_STREQ(btf__str_by_offset(btf2, t->name_off), "s2", "split_struct_name");
 
+       if (multi) {
+               btf3 = btf__new_empty_split(btf2);
+               if (!ASSERT_OK_PTR(btf3, "multi_split_btf"))
+                       goto cleanup;
+       } else {
+               btf3 = btf2;
+       }
+
+       btf__add_union(btf3, "u1", 16);                 /* [5] union u1 {       */
+       btf__add_field(btf3, "f1", 4, 0, 0);            /*      struct s2 f1;   */
+       btf__add_field(btf3, "uf2", 1, 0, 0);           /*      int f2;         */
+                                                       /* } */
+
+       if (multi) {
+               t = btf__type_by_id(btf2, 5);
+               ASSERT_NULL(t, "multisplit_type_in_first_split");
+       }
+
+       t = btf__type_by_id(btf3, 5);
+       if (!ASSERT_OK_PTR(t, "split_union_type"))
+               goto cleanup;
+       ASSERT_EQ(btf_is_union(t), true, "split_union_kind");
+       ASSERT_EQ(btf_vlen(t), 2, "split_union_vlen");
+       ASSERT_STREQ(btf__str_by_offset(btf3, t->name_off), "u1", "split_union_name");
+       ASSERT_EQ(btf__type_cnt(btf3), 6, "split_type_cnt");
+
+       t = btf__type_by_id(btf3, 1);
+       if (!ASSERT_OK_PTR(t, "split_base_type"))
+               goto cleanup;
+       ASSERT_EQ(btf_is_int(t), true, "split_base_int");
+       ASSERT_STREQ(btf__str_by_offset(btf3, t->name_off), "int", "split_base_type_name");
+
        /* BTF-to-C dump of split BTF */
        dump_buf_file = open_memstream(&dump_buf, &dump_buf_sz);
        if (!ASSERT_OK_PTR(dump_buf_file, "dump_memstream"))
                return;
-       d = btf_dump__new(btf2, btf_dump_printf, dump_buf_file, NULL);
+       d = btf_dump__new(btf3, btf_dump_printf, dump_buf_file, NULL);
        if (!ASSERT_OK_PTR(d, "btf_dump__new"))
                goto cleanup;
-       for (i = 1; i < btf__type_cnt(btf2); i++) {
+       for (i = 1; i < btf__type_cnt(btf3); i++) {
                err = btf_dump__dump_type(d, i);
                ASSERT_OK(err, "dump_type_ok");
        }
@@ -79,12 +112,15 @@ void test_btf_split() {
        ASSERT_STREQ(dump_buf,
 "struct s1 {\n"
 "      int f1;\n"
-"};\n"
-"\n"
+"};\n\n"
 "struct s2 {\n"
 "      struct s1 f1;\n"
 "      int f2;\n"
 "      int *f3;\n"
+"};\n\n"
+"union u1 {\n"
+"      struct s2 f1;\n"
+"      int uf2;\n"
 "};\n\n", "c_dump");
 
 cleanup:
@@ -94,4 +130,14 @@ cleanup:
        btf_dump__free(d);
        btf__free(btf1);
        btf__free(btf2);
+       if (btf2 != btf3)
+               btf__free(btf3);
+}
+
+void test_btf_split(void)
+{
+       if (test__start_subtest("single_split"))
+               __test_btf_split(false);
+       if (test__start_subtest("multi_split"))
+               __test_btf_split(true);
 }