selftests/bpf: Add uprobe_multi usdt bench test

Adding test that attaches 50k usdt probes in usdt_multi binary.

After the attach is done we run the binary and make sure we get
proper amount of hits.

With current uprobes:

# perf stat --null ./test_progs -n 254/6
#254/6 uprobe_multi_test/bench_usdt:OK
#254 uprobe_multi_test:OK
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED

Performance counter stats for './test_progs -n 254/6':

1353.659680562 seconds time elapsed

With uprobe_multi link:

# perf stat --null ./test_progs -n 254/6
#254/6 uprobe_multi_test/bench_usdt:OK
#254 uprobe_multi_test:OK
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED

Performance counter stats for './test_progs -n 254/6':

0.322046364 seconds time elapsed

Signed-off-by: Jiri Olsa <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

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

···
 #include <test_progs.h>
 #include "uprobe_multi.skel.h"
 #include "uprobe_multi_bench.skel.h"
+#include "uprobe_multi_usdt.skel.h"
 #include "bpf/libbpf_internal.h"
 #include "testing_helpers.h"
 
···
 	printf("%s: detached in %7.3lfs\n", __func__, detach_delta);
 }
 
+static void test_bench_attach_usdt(void)
+{
+	long attach_start_ns = 0, attach_end_ns = 0;
+	struct uprobe_multi_usdt *skel = NULL;
+	long detach_start_ns, detach_end_ns;
+	double attach_delta, detach_delta;
+
+	skel = uprobe_multi_usdt__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "uprobe_multi__open"))
+		goto cleanup;
+
+	attach_start_ns = get_time_ns();
+
+	skel->links.usdt0 = bpf_program__attach_usdt(skel->progs.usdt0, -1, "./uprobe_multi",
+						     "test", "usdt", NULL);
+	if (!ASSERT_OK_PTR(skel->links.usdt0, "bpf_program__attach_usdt"))
+		goto cleanup;
+
+	attach_end_ns = get_time_ns();
+
+	system("./uprobe_multi usdt");
+
+	ASSERT_EQ(skel->bss->count, 50000, "usdt_count");
+
+cleanup:
+	detach_start_ns = get_time_ns();
+	uprobe_multi_usdt__destroy(skel);
+	detach_end_ns = get_time_ns();
+
+	attach_delta = (attach_end_ns - attach_start_ns) / 1000000000.0;
+	detach_delta = (detach_end_ns - detach_start_ns) / 1000000000.0;
+
+	printf("%s: attached in %7.3lfs\n", __func__, attach_delta);
+	printf("%s: detached in %7.3lfs\n", __func__, detach_delta);
+}
+
 void test_uprobe_multi_test(void)
 {
 	if (test__start_subtest("skel_api"))
···
 		test_link_api();
 	if (test__start_subtest("bench_uprobe"))
 		test_bench_attach_uprobe();
+	if (test__start_subtest("bench_usdt"))
+		test_bench_attach_usdt();
 }

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

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/usdt.bpf.h>
+
+char _license[] SEC("license") = "GPL";
+
+int count;
+
+SEC("usdt")
+int usdt0(struct pt_regs *ctx)
+{
+	count++;
+	return 0;
+}