[PATCH bpf-next v5 15/16] selftests/bpf: Test the address space rendering of the arena type tag

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

Add an arena-tagged pointer member to the type tag dump test and expect
the address space attribute in front of the tag. The struct_ops test
that mirrors the previous rendering now describes it as the output of
an older libbpf.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 .../testing/selftests/bpf/prog_tests/btf_dump.c  | 16 +++++++++++++---
 .../bpf/progs/struct_ops_arena_member_render.c   |  8 ++++----
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dump.c b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
index 17fa44cb9c91..35f214e254da 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf_dump.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
@@ -604,8 +604,10 @@ static void test_btf_dump_type_tags(void)
 	 * struct s {
 	 *   void __attribute__((btf_type_tag(\"void_tag\"))) *p1;
 	 *   void __attribute__((void_attr)) *p2;
+	 *   void __arena *p3;
 	 * };
 	 *
+	 * The arena tag is rendered with the address space it denotes.
 	 */
 
 	id = btf__add_type_tag(btf, "void_tag", 0);
@@ -618,17 +620,25 @@ static void test_btf_dump_type_tags(void)
 	id = btf__add_ptr(btf, id);
 	ASSERT_EQ(id, 4, "void_ptr_id2");
 
-	id = btf__add_struct(btf, "s", 8);
-	ASSERT_EQ(id, 5, "struct_id");
+	id = btf__add_type_tag(btf, "arena", 0);
+	ASSERT_EQ(id, 5, "arena_tag_id");
+	id = btf__add_ptr(btf, id);
+	ASSERT_EQ(id, 6, "void_ptr_id3");
+
+	id = btf__add_struct(btf, "s", 24);
+	ASSERT_EQ(id, 7, "struct_id");
 	err = btf__add_field(btf, "p1", 2, 0, 0);
 	ASSERT_OK(err, "field_ok1");
-	err = btf__add_field(btf, "p2", 4, 0, 0);
+	err = btf__add_field(btf, "p2", 4, 64, 0);
 	ASSERT_OK(err, "field_ok2");
+	err = btf__add_field(btf, "p3", 6, 128, 0);
+	ASSERT_OK(err, "field_ok3");
 
 	test_ctx__dump_and_compare(&t,
 "struct s {\n"
 "	void __attribute__((btf_type_tag(\"void_tag\"))) *p1;\n"
 "	void __attribute__((void_attr)) *p2;\n"
+"	void __attribute__((address_space(1))) __attribute__((btf_type_tag(\"arena\"))) *p3;\n"
 "};\n\n", "dump_and_compare");
 
 	test_ctx__free(&t);
diff --git a/tools/testing/selftests/bpf/progs/struct_ops_arena_member_render.c b/tools/testing/selftests/bpf/progs/struct_ops_arena_member_render.c
index 23fc2b927793..09b4c740bdca 100644
--- a/tools/testing/selftests/bpf/progs/struct_ops_arena_member_render.c
+++ b/tools/testing/selftests/bpf/progs/struct_ops_arena_member_render.c
@@ -11,10 +11,10 @@
 char _license[] SEC("license") = "GPL";
 
 /*
- * The module types as vmlinux.h renders them: the tag is an attribute on a
- * pointer in the kernel address space, so the program has to cast the member
- * to the arena address space before using it. That is what a program built
- * against vmlinux.h sees for a kernel struct with an __arena member.
+ * The module types as a vmlinux.h generated by a libbpf that does not render
+ * the arena tag with its address space shows them: an attribute on a pointer
+ * in the kernel address space, so the program has to cast the member to the
+ * arena address space before using it.
  */
 #define __arena_tag	__attribute__((btf_type_tag("arena")))
 #define __nullable_tag	__attribute__((btf_type_tag("nullable")))
-- 
2.53.0-Meta