selftests/bpf: Test load and dump metadata with btftool and skel

This is a simple test to check that loading and dumping metadata
in btftool works, whether or not metadata contents are used by the
program.

A C test is also added to make sure the skeleton code can read the
metadata values.
Signed-off-by: YiFei Zhu <zhuyifei@google.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: YiFei Zhu <zhuyifei1999@gmail.com>
Link: https://lore.kernel.org/bpf/20200915234543.3220146-6-sdf@google.com

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 \

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

+// 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 int prog_holds_map(int prog_fd, int map_fd)
+{
+	struct bpf_prog_info prog_info = {};
+	struct bpf_prog_info map_info = {};
+	__u32 prog_info_len;
+	__u32 map_info_len;
+	__u32 *map_ids;
+	int nr_maps;
+	int ret;
+	int i;
+
+	map_info_len = sizeof(map_info);
+	ret = bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len);
+	if (ret)
+		return -errno;
+
+	prog_info_len = sizeof(prog_info);
+	ret = bpf_obj_get_info_by_fd(prog_fd, &prog_info, &prog_info_len);
+	if (ret)
+		return -errno;
+
+	map_ids = calloc(prog_info.nr_map_ids, sizeof(__u32));
+	if (!map_ids)
+		return -ENOMEM;
+
+	nr_maps = prog_info.nr_map_ids;
+	memset(&prog_info, 0, sizeof(prog_info));
+	prog_info.nr_map_ids = nr_maps;
+	prog_info.map_ids = ptr_to_u64(map_ids);
+	prog_info_len = sizeof(prog_info);
+
+	ret = bpf_obj_get_info_by_fd(prog_fd, &prog_info, &prog_info_len);
+	if (ret) {
+		ret = -errno;
+		goto free_map_ids;
+	}
+
+	ret = -ENOENT;
+	for (i = 0; i < prog_info.nr_map_ids; i++) {
+		if (map_ids[i] == map_info.id) {
+			ret = 0;
+			break;
+		}
+	}
+
+free_map_ids:
+	free(map_ids);
+	return ret;
+}
+
+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;
+
+	err = prog_holds_map(bpf_program__fd(obj->progs.prog),
+			     bpf_map__fd(obj->maps.rodata));
+	if (CHECK(err, "prog-holds-rodata", "errno: %d", err))
+		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;
+
+	err = prog_holds_map(bpf_program__fd(obj->progs.prog),
+			     bpf_map__fd(obj->maps.rodata));
+	if (CHECK(err, "prog-holds-rodata", "errno: %d", err))
+		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();
+}

tools/testing/selftests/bpf/progs/metadata_unused.c

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

tools/testing/selftests/bpf/progs/metadata_used.c

+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+volatile const char bpf_metadata_a[] SEC(".rodata") = "bar";
+volatile const int bpf_metadata_b SEC(".rodata") = 2;
+
+SEC("cgroup_skb/egress")
+int prog(struct xdp_md *ctx)
+{
+	return bpf_metadata_b ? 1 : 0;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/test_bpftool_metadata.sh

+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+TESTNAME=bpftool_metadata
+BPF_FS=$(awk '$3 == "bpf" {print $2; exit}' /proc/mounts)
+BPF_DIR=$BPF_FS/test_$TESTNAME
+
+_cleanup()
+{
+	set +e
+	rm -rf $BPF_DIR 2> /dev/null
+}
+
+cleanup_skip()
+{
+	echo "selftests: $TESTNAME [SKIP]"
+	_cleanup
+
+	exit $ksft_skip
+}
+
+cleanup()
+{
+	if [ "$?" = 0 ]; then
+		echo "selftests: $TESTNAME [PASS]"
+	else
+		echo "selftests: $TESTNAME [FAILED]"
+	fi
+	_cleanup
+}
+
+if [ $(id -u) -ne 0 ]; then
+	echo "selftests: $TESTNAME [SKIP] Need root privileges"
+	exit $ksft_skip
+fi
+
+if [ -z "$BPF_FS" ]; then
+	echo "selftests: $TESTNAME [SKIP] Could not run test without bpffs mounted"
+	exit $ksft_skip
+fi
+
+if ! bpftool version > /dev/null 2>&1; then
+	echo "selftests: $TESTNAME [SKIP] Could not run test without bpftool"
+	exit $ksft_skip
+fi
+
+set -e
+
+trap cleanup_skip EXIT
+
+mkdir $BPF_DIR
+
+trap cleanup EXIT
+
+bpftool prog load metadata_unused.o $BPF_DIR/unused
+
+METADATA_PLAIN="$(bpftool prog)"
+echo "$METADATA_PLAIN" | grep 'a = "foo"' > /dev/null
+echo "$METADATA_PLAIN" | grep 'b = 1' > /dev/null
+
+bpftool prog --json | grep '"metadata":{"a":"foo","b":1}' > /dev/null
+
+bpftool map | grep 'metadata.rodata' > /dev/null
+
+rm $BPF_DIR/unused
+
+bpftool prog load metadata_used.o $BPF_DIR/used
+
+METADATA_PLAIN="$(bpftool prog)"
+echo "$METADATA_PLAIN" | grep 'a = "bar"' > /dev/null
+echo "$METADATA_PLAIN" | grep 'b = 2' > /dev/null
+
+bpftool prog --json | grep '"metadata":{"a":"bar","b":2}' > /dev/null
+
+bpftool map | grep 'metadata.rodata' > /dev/null
+
+rm $BPF_DIR/used
+
+exit 0