selftests/bpf: Add uprobe session cookie test

Adding uprobe session test that verifies the cookie value
get properly propagated from entry to return program.

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_cookie.skel.h"
 #include "bpf/libbpf_internal.h"
 #include "testing_helpers.h"
 #include "../sdt.h"
···
 	uprobe_multi_session__destroy(skel);
 }
 
+static void test_session_cookie_skel_api(void)
+{
+	struct uprobe_multi_session_cookie *skel = NULL;
+	int err;
+
+	skel = uprobe_multi_session_cookie__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "uprobe_multi_session_cookie__open_and_load"))
+		goto cleanup;
+
+	skel->bss->pid = getpid();
+
+	err = uprobe_multi_session_cookie__attach(skel);
+	if (!ASSERT_OK(err, "uprobe_multi_session_cookie__attach"))
+		goto cleanup;
+
+	/* trigger all probes */
+	uprobe_multi_func_1();
+	uprobe_multi_func_2();
+	uprobe_multi_func_3();
+
+	ASSERT_EQ(skel->bss->test_uprobe_1_result, 1, "test_uprobe_1_result");
+	ASSERT_EQ(skel->bss->test_uprobe_2_result, 2, "test_uprobe_2_result");
+	ASSERT_EQ(skel->bss->test_uprobe_3_result, 3, "test_uprobe_3_result");
+
+cleanup:
+	uprobe_multi_session_cookie__destroy(skel);
+}
+
 static void test_bench_attach_uprobe(void)
 {
 	long attach_start_ns = 0, attach_end_ns = 0;
···
 		test_pid_filter_process(true);
 	if (test__start_subtest("session"))
 		test_session_skel_api();
+	if (test__start_subtest("session_cookie"))
+		test_session_cookie_skel_api();
 }

tools/testing/selftests/bpf/progs/uprobe_multi_session_cookie.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"
+
+char _license[] SEC("license") = "GPL";
+
+int pid = 0;
+
+__u64 test_uprobe_1_result = 0;
+__u64 test_uprobe_2_result = 0;
+__u64 test_uprobe_3_result = 0;
+
+static int check_cookie(__u64 val, __u64 *result)
+{
+	__u64 *cookie;
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 1;
+
+	cookie = bpf_session_cookie();
+
+	if (bpf_session_is_return())
+		*result = *cookie == val ? val : 0;
+	else
+		*cookie = val;
+	return 0;
+}
+
+SEC("uprobe.session//proc/self/exe:uprobe_multi_func_1")
+int uprobe_1(struct pt_regs *ctx)
+{
+	return check_cookie(1, &test_uprobe_1_result);
+}
+
+SEC("uprobe.session//proc/self/exe:uprobe_multi_func_2")
+int uprobe_2(struct pt_regs *ctx)
+{
+	return check_cookie(2, &test_uprobe_2_result);
+}
+
+SEC("uprobe.session//proc/self/exe:uprobe_multi_func_3")
+int uprobe_3(struct pt_regs *ctx)
+{
+	return check_cookie(3, &test_uprobe_3_result);
+}