selftests/bpf: Test "incremental" btf_dump in C format

Add test validating that btf_dump works fine with BTFs that are modified and
incrementally generated.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200929232843.1249318-5-andriin@fb.com

diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dump.c b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
index 39fb81d..c60091e 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/btf_dump.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
@@ -129,6 +129,109 @@ done:
        return err;
 }
 
+static char *dump_buf;
+static size_t dump_buf_sz;
+static FILE *dump_buf_file;
+
+void test_btf_dump_incremental(void)
+{
+       struct btf *btf = NULL;
+       struct btf_dump *d = NULL;
+       struct btf_dump_opts opts;
+       int id, err, i;
+
+       dump_buf_file = open_memstream(&dump_buf, &dump_buf_sz);
+       if (!ASSERT_OK_PTR(dump_buf_file, "dump_memstream"))
+               return;
+       btf = btf__new_empty();
+       if (!ASSERT_OK_PTR(btf, "new_empty"))
+               goto err_out;
+       opts.ctx = dump_buf_file;
+       d = btf_dump__new(btf, NULL, &opts, btf_dump_printf);
+       if (!ASSERT_OK(libbpf_get_error(d), "btf_dump__new"))
+               goto err_out;
+
+       /* First, generate BTF corresponding to the following C code:
+        *
+        * enum { VAL = 1 };
+        *
+        * struct s { int x; };
+        *
+        */
+       id = btf__add_enum(btf, NULL, 4);
+       ASSERT_EQ(id, 1, "enum_id");
+       err = btf__add_enum_value(btf, "VAL", 1);
+       ASSERT_OK(err, "enum_val_ok");
+
+       id = btf__add_int(btf, "int", 4, BTF_INT_SIGNED);
+       ASSERT_EQ(id, 2, "int_id");
+
+       id = btf__add_struct(btf, "s", 4);
+       ASSERT_EQ(id, 3, "struct_id");
+       err = btf__add_field(btf, "x", 2, 0, 0);
+       ASSERT_OK(err, "field_ok");
+
+       for (i = 1; i <= btf__get_nr_types(btf); i++) {
+               err = btf_dump__dump_type(d, i);
+               ASSERT_OK(err, "dump_type_ok");
+       }
+
+       fflush(dump_buf_file);
+       dump_buf[dump_buf_sz] = 0; /* some libc implementations don't do this */
+       ASSERT_STREQ(dump_buf,
+"enum {\n"
+"      VAL = 1,\n"
+"};\n"
+"\n"
+"struct s {\n"
+"      int x;\n"
+"};\n\n", "c_dump1");
+
+       /* Now, after dumping original BTF, append another struct that embeds
+        * anonymous enum. It also has a name conflict with the first struct:
+        *
+        * struct s___2 {
+        *     enum { VAL___2 = 1 } x;
+        *     struct s s;
+        * };
+        *
+        * This will test that btf_dump'er maintains internal state properly.
+        * Note that VAL___2 enum value. It's because we've already emitted
+        * that enum as a global anonymous enum, so btf_dump will ensure that
+        * enum values don't conflict;
+        *
+        */
+       fseek(dump_buf_file, 0, SEEK_SET);
+
+       id = btf__add_struct(btf, "s", 4);
+       ASSERT_EQ(id, 4, "struct_id");
+       err = btf__add_field(btf, "x", 1, 0, 0);
+       ASSERT_OK(err, "field_ok");
+       err = btf__add_field(btf, "s", 3, 32, 0);
+       ASSERT_OK(err, "field_ok");
+
+       for (i = 1; i <= btf__get_nr_types(btf); i++) {
+               err = btf_dump__dump_type(d, i);
+               ASSERT_OK(err, "dump_type_ok");
+       }
+
+       fflush(dump_buf_file);
+       dump_buf[dump_buf_sz] = 0; /* some libc implementations don't do this */
+       ASSERT_STREQ(dump_buf,
+"struct s___2 {\n"
+"      enum {\n"
+"              VAL___2 = 1,\n"
+"      } x;\n"
+"      struct s s;\n"
+"};\n\n" , "c_dump1");
+
+err_out:
+       fclose(dump_buf_file);
+       free(dump_buf);
+       btf_dump__free(d);
+       btf__free(btf);
+}
+
 void test_btf_dump() {
        int i;
 
@@ -140,4 +243,6 @@ void test_btf_dump() {
 
                test_btf_dump_case(i, &btf_dump_test_cases[i]);
        }
+       if (test__start_subtest("btf_dump: incremental"))
+               test_btf_dump_incremental();
 }