selftests/bpf: Add tracing multi attach benchmark test

Adding benchmark test that attaches to (almost) all allowed tracing
functions and display attach/detach times.

  # ./test_progs -t tracing_multi_bench_attach -v
  bpf_testmod.ko is already unloaded.
  Loading bpf_testmod.ko...
  Successfully loaded bpf_testmod.ko.
  serial_test_tracing_multi_bench_attach:PASS:btf__load_vmlinux_btf 0 nsec
  serial_test_tracing_multi_bench_attach:PASS:tracing_multi_bench__open_and_load 0 nsec
  serial_test_tracing_multi_bench_attach:PASS:get_syms 0 nsec
  serial_test_tracing_multi_bench_attach:PASS:bpf_program__attach_tracing_multi 0 nsec
  serial_test_tracing_multi_bench_attach: found 51186 functions
  serial_test_tracing_multi_bench_attach: attached in   1.295s
  serial_test_tracing_multi_bench_attach: detached in   0.243s
  #507     tracing_multi_bench_attach:OK
  Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
  Successfully unloaded bpf_testmod.ko.

Exporting skip_entry as is_unsafe_function and using it in the test.

Also updating trace_blacklist with ___migrate_enable to be in sync
with kernel functions deny list.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-29-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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

@@ -10,6 +10,7 @@
 #include "tracing_multi_session.skel.h"
 #include "tracing_multi_fail.skel.h"
 #include "tracing_multi_verifier.skel.h"
+#include "tracing_multi_bench.skel.h"
 #include "trace_helpers.h"
 
 static __u64 bpf_fentry_test_cookies[] = {
@@ -593,6 +594,129 @@ static void test_attach_api_fails(void)
 	free(ids2);
 }
 
+void serial_test_tracing_multi_bench_attach(void)
+{
+	LIBBPF_OPTS(bpf_tracing_multi_opts, opts);
+	struct tracing_multi_bench *skel = NULL;
+	long attach_start_ns, attach_end_ns;
+	long detach_start_ns, detach_end_ns;
+	double attach_delta, detach_delta;
+	struct bpf_link *link = NULL;
+	size_t i, cap = 0, cnt = 0;
+	struct ksyms *ksyms = NULL;
+	void *root = NULL;
+	void *dups = NULL;
+	__u32 *ids = NULL;
+	__u32 nr, type_id;
+	struct btf *btf;
+	int err;
+
+#ifndef __x86_64__
+	test__skip();
+	return;
+#endif
+
+	btf = btf__load_vmlinux_btf();
+	if (!ASSERT_OK_PTR(btf, "btf__load_vmlinux_btf"))
+		return;
+
+	skel = tracing_multi_bench__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "tracing_multi_bench__open_and_load"))
+		goto cleanup;
+
+	if (!ASSERT_OK(bpf_get_ksyms(&ksyms, true), "get_syms"))
+		goto cleanup;
+
+	/* Get all ftrace 'safe' symbols.. */
+	for (i = 0; i < ksyms->filtered_cnt; i++) {
+		if (!tsearch(&ksyms->filtered_syms[i], &root, compare)) {
+			ASSERT_FAIL("tsearch failed");
+			goto cleanup;
+		}
+	}
+
+	/*
+	 * Collect names that are not unique in kallsyms. The kernel resolves a
+	 * tracing-multi BTF id to an address with kallsyms_lookup_name(), which
+	 * returns the first symbol of that name. For a duplicate name that may
+	 * be a different (non-ftrace-able) instance than the ftrace-able one in
+	 * available_filter_functions, so attaching to it by BTF id fails with
+	 * -ENOENT (e.g. t_start/t_next/t_stop). ksyms->syms is sorted by name,
+	 * so equal names are adjacent.
+	 */
+	for (i = 1; i < ksyms->sym_cnt; i++) {
+		if (strcmp(ksyms->syms[i].name, ksyms->syms[i - 1].name))
+			continue;
+		if (!tsearch(&ksyms->syms[i].name, &dups, compare)) {
+			ASSERT_FAIL("tsearch failed");
+			goto cleanup;
+		}
+	}
+
+	/* ..and filter them through BTF and btf_type_is_traceable_func. */
+	nr = btf__type_cnt(btf);
+	for (type_id = 1; type_id < nr; type_id++) {
+		const struct btf_type *type;
+		const char *str;
+
+		type = btf__type_by_id(btf, type_id);
+		if (!type)
+			break;
+
+		if (BTF_INFO_KIND(type->info) != BTF_KIND_FUNC)
+			continue;
+
+		str = btf__name_by_offset(btf, type->name_off);
+		if (!str)
+			break;
+
+		if (!tfind(&str, &root, compare))
+			continue;
+
+		/* Skip names that are not unique in kallsyms, see above. */
+		if (tfind(&str, &dups, compare))
+			continue;
+
+		if (!btf_type_is_traceable_func(btf, type))
+			continue;
+
+		err = libbpf_ensure_mem((void **) &ids, &cap, sizeof(*ids), cnt + 1);
+		if (err)
+			goto cleanup;
+
+		ids[cnt++] = type_id;
+	}
+
+	opts.ids = ids;
+	opts.cnt = cnt;
+
+	attach_start_ns = get_time_ns();
+	link = bpf_program__attach_tracing_multi(skel->progs.bench, NULL, &opts);
+	attach_end_ns = get_time_ns();
+
+	if (!ASSERT_OK_PTR(link, "bpf_program__attach_tracing_multi"))
+		goto cleanup;
+
+	detach_start_ns = get_time_ns();
+	bpf_link__destroy(link);
+	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: found %lu functions\n", __func__, cnt);
+	printf("%s: attached in %7.3lfs\n", __func__, attach_delta);
+	printf("%s: detached in %7.3lfs\n", __func__, detach_delta);
+
+cleanup:
+	tracing_multi_bench__destroy(skel);
+	tdestroy(root, tdestroy_free_nop);
+	tdestroy(dups, tdestroy_free_nop);
+	free_kallsyms_local(ksyms);
+	free(ids);
+	btf__free(btf);
+}
+
 void test_tracing_multi_test(void)
 {
 #ifndef __x86_64__

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

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("fentry.multi")
+int BPF_PROG(bench)
+{
+	return 0;
+}

tools/testing/selftests/bpf/trace_helpers.c

@@ -546,9 +546,10 @@ static const char * const trace_blacklist[] = {
 	"__rcu_read_lock",
 	"__rcu_read_unlock",
 	"bpf_get_numa_node_id",
+	"___migrate_enable",
 };
 
-static bool skip_entry(char *name)
+bool is_unsafe_function(const char *name)
 {
 	int i;
 
@@ -651,7 +652,7 @@ int bpf_get_ksyms(struct ksyms **ksymsp, bool kernel)
 		free(name);
 		if (sscanf(buf, "%ms$*[^\n]\n", &name) != 1)
 			continue;
-		if (skip_entry(name))
+		if (is_unsafe_function(name))
 			continue;
 
 		ks = search_kallsyms_custom_local(ksyms, name, search_kallsyms_compare);
@@ -728,7 +729,7 @@ int bpf_get_addrs(unsigned long **addrsp, size_t *cntp, bool kernel)
 		free(name);
 		if (sscanf(buf, "%p %ms$*[^\n]\n", &addr, &name) != 2)
 			continue;
-		if (skip_entry(name))
+		if (is_unsafe_function(name))
 			continue;
 
 		if (cnt == max_cnt) {

tools/testing/selftests/bpf/trace_helpers.h

@@ -63,4 +63,5 @@ int read_build_id(const char *path, char *build_id, size_t size);
 int bpf_get_ksyms(struct ksyms **ksymsp, bool kernel);
 int bpf_get_addrs(unsigned long **addrsp, size_t *cntp, bool kernel);
 
+bool is_unsafe_function(const char *name);
 #endif