Re: [PATCH bpf-next v4 5/5] selftests/bpf: Test load and dump metadata with btftool and skel

 tools/testing/selftests/bpf/Makefile          |  3 +-
 .../selftests/bpf/prog_tests/metadata.c       | 81 ++++++++++++++++++
 .../selftests/bpf/progs/metadata_unused.c     | 15 ++++
 .../selftests/bpf/progs/metadata_used.c       | 15 ++++
 .../selftests/bpf/test_bpftool_metadata.sh    | 82 +++++++++++++++++++
 5 files changed, 195 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/metadata.c
 create mode 100644 tools/testing/selftests/bpf/progs/metadata_unused.c
 create mode 100644 tools/testing/selftests/bpf/progs/metadata_used.c
 create mode 100755 tools/testing/selftests/bpf/test_bpftool_metadata.sh

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 65d3d9aaeb31..3c92db8a189a 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile

@@ -68,7 +68,8 @@ TEST_PROGS := test_kmod.sh \
        test_tc_edt.sh \
        test_xdping.sh \
        test_bpftool_build.sh \
-       test_bpftool.sh
+       test_bpftool.sh \
+       test_bpftool_metadata.sh \

 TEST_PROGS_EXTENDED := with_addr.sh \
        with_tunnels.sh \

diff --git a/tools/testing/selftests/bpf/prog_tests/metadata.c b/tools/testing/selftests/bpf/prog_tests/metadata.c
new file mode 100644
index 000000000000..dea8fa86b5fb
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/metadata.c

@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright 2020 Google LLC.
+ */
+
+#include <test_progs.h>
+#include <cgroup_helpers.h>
+#include <network_helpers.h>
+
+#include "metadata_unused.skel.h"
+#include "metadata_used.skel.h"
+
+static int duration;
+
+static void test_metadata_unused(void)
+{
+       struct metadata_unused *obj;
+       int err;
+
+       obj = metadata_unused__open_and_load();
+       if (CHECK(!obj, "skel-load", "errno %d", errno))
+               return;
+
+       /* Assert that we can access the metadata in skel and the values are
+        * what we expect.
+        */
+       if (CHECK(strncmp(obj->rodata->bpf_metadata_a, "foo",
+                         sizeof(obj->rodata->bpf_metadata_a)),
+                 "bpf_metadata_a", "expected \"foo\", value differ"))
+               goto close_bpf_object;
+       if (CHECK(obj->rodata->bpf_metadata_b != 1, "bpf_metadata_b",
+                 "expected 1, got %d", obj->rodata->bpf_metadata_b))
+               goto close_bpf_object;
+
+       /* Assert that binding metadata map to prog again succeeds. */
+       err = bpf_prog_bind_map(bpf_program__fd(obj->progs.prog),
+                               bpf_map__fd(obj->maps.rodata), NULL);
+       CHECK(err, "rebind_map", "errno %d, expected 0", errno);
+
+close_bpf_object:
+       metadata_unused__destroy(obj);
+}
+
+static void test_metadata_used(void)
+{
+       struct metadata_used *obj;
+       int err;
+
+       obj = metadata_used__open_and_load();
+       if (CHECK(!obj, "skel-load", "errno %d", errno))
+               return;
+
+       /* Assert that we can access the metadata in skel and the values are
+        * what we expect.
+        */
+       if (CHECK(strncmp(obj->rodata->bpf_metadata_a, "bar",
+                         sizeof(obj->rodata->bpf_metadata_a)),
+                 "metadata_a", "expected \"bar\", value differ"))
+               goto close_bpf_object;
+       if (CHECK(obj->rodata->bpf_metadata_b != 2, "metadata_b",
+                 "expected 2, got %d", obj->rodata->bpf_metadata_b))
+               goto close_bpf_object;
+
+       /* Assert that binding metadata map to prog again succeeds. */
+       err = bpf_prog_bind_map(bpf_program__fd(obj->progs.prog),
+                               bpf_map__fd(obj->maps.rodata), NULL);
+       CHECK(err, "rebind_map", "errno %d, expected 0", errno);
+
+close_bpf_object:
+       metadata_used__destroy(obj);
+}
+
+void test_metadata(void)
+{
+       if (test__start_subtest("unused"))
+               test_metadata_unused();
+
+       if (test__start_subtest("used"))
+               test_metadata_used();
+}

diff --git a/tools/testing/selftests/bpf/progs/metadata_unused.c b/tools/testing/selftests/bpf/progs/metadata_unused.c
new file mode 100644
index 000000000000..db5b804f6f4c
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/metadata_unused.c

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+const char bpf_metadata_a[] SEC(".rodata") = "foo";
+const int bpf_metadata_b SEC(".rodata") = 1;

+
+SEC("cgroup_skb/egress")
+int prog(struct xdp_md *ctx)
+{
+       return 0;
+}
+
+char _license[] SEC("license") = "GPL";

diff --git a/tools/testing/selftests/bpf/progs/metadata_used.c b/tools/testing/selftests/bpf/progs/metadata_used.c
new file mode 100644
index 000000000000..0dcb1ba2f0ae
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/metadata_used.c

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+const char bpf_metadata_a[] SEC(".rodata") = "bar";
+const int bpf_metadata_b SEC(".rodata") = 2;