selftests/bpf: Add uprobe session single consumer test

Testing that the session ret_handler bypass works on single
uprobe with multiple consumers, each with different session
ignore return value.

Signed-off-by: Jiri Olsa <[e-mail]>
Signed-off-by: Andrii Nakryiko <[e-mail]>
Acked-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

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

···
 #include "uprobe_multi_consumers.skel.h"
 #include "uprobe_multi_pid_filter.skel.h"
 #include "uprobe_multi_session.skel.h"
+#include "uprobe_multi_session_single.skel.h"
 #include "uprobe_multi_session_cookie.skel.h"
 #include "uprobe_multi_session_recursive.skel.h"
 #include "uprobe_multi_verifier.skel.h"
···
 	uprobe_multi_session__destroy(skel);
 }
 
+static void test_session_single_skel_api(void)
+{
+	struct uprobe_multi_session_single *skel = NULL;
+	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
+	int err;
+
+	skel = uprobe_multi_session_single__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "uprobe_multi_session_single__open_and_load"))
+		goto cleanup;
+
+	skel->bss->pid = getpid();
+
+	err = uprobe_multi_session_single__attach(skel);
+	if (!ASSERT_OK(err, "uprobe_multi_session_single__attach"))
+		goto cleanup;
+
+	uprobe_multi_func_1();
+
+	/*
+	 * We expect consumer 0 and 2 to trigger just entry handler (value 1)
+	 * and consumer 1 to hit both (value 2).
+	 */
+	ASSERT_EQ(skel->bss->uprobe_session_result[0], 1, "uprobe_session_result_0");
+	ASSERT_EQ(skel->bss->uprobe_session_result[1], 2, "uprobe_session_result_1");
+	ASSERT_EQ(skel->bss->uprobe_session_result[2], 1, "uprobe_session_result_2");
+
+cleanup:
+	uprobe_multi_session_single__destroy(skel);
+}
+
 static void test_session_cookie_skel_api(void)
 {
 	struct uprobe_multi_session_cookie *skel = NULL;
···
 		test_pid_filter_process(true);
 	if (test__start_subtest("session"))
 		test_session_skel_api();
+	if (test__start_subtest("session_single"))
+		test_session_single_skel_api();
 	if (test__start_subtest("session_cookie"))
 		test_session_cookie_skel_api();
 	if (test__start_subtest("session_cookie_recursive"))

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

···
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <stdbool.h>
+#include "bpf_kfuncs.h"
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+__u64 uprobe_session_result[3] = {};
+int pid = 0;
+
+static int uprobe_multi_check(void *ctx, int idx)
+{
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 1;
+
+	uprobe_session_result[idx]++;
+
+	/* only consumer 1 executes return probe */
+	if (idx == 0 || idx == 2)
+		return 1;
+
+	return 0;
+}
+
+SEC("uprobe.session//proc/self/exe:uprobe_multi_func_1")
+int uprobe_0(struct pt_regs *ctx)
+{
+	return uprobe_multi_check(ctx, 0);
+}
+
+SEC("uprobe.session//proc/self/exe:uprobe_multi_func_1")
+int uprobe_1(struct pt_regs *ctx)
+{
+	return uprobe_multi_check(ctx, 1);
+}
+
+SEC("uprobe.session//proc/self/exe:uprobe_multi_func_1")
+int uprobe_2(struct pt_regs *ctx)
+{
+	return uprobe_multi_check(ctx, 2);
+}