selftests/bpf: Add uprobe session test

Adding uprobe session test and testing that the entry program
return value controls execution of the return probe 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_usdt.skel.h"
 #include "uprobe_multi_consumers.skel.h"
 #include "uprobe_multi_pid_filter.skel.h"
+#include "uprobe_multi_session.skel.h"
 #include "bpf/libbpf_internal.h"
 #include "testing_helpers.h"
 #include "../sdt.h"
···
 	uprobe_multi_pid_filter__destroy(skel);
 }
 
+static void test_session_skel_api(void)
+{
+	struct uprobe_multi_session *skel = NULL;
+	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
+	struct bpf_link *link = NULL;
+	int err;
+
+	skel = uprobe_multi_session__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "uprobe_multi_session__open_and_load"))
+		goto cleanup;
+
+	skel->bss->pid = getpid();
+	skel->bss->user_ptr = test_data;
+
+	err = uprobe_multi_session__attach(skel);
+	if (!ASSERT_OK(err, "uprobe_multi_session__attach"))
+		goto cleanup;
+
+	/* trigger all probes */
+	skel->bss->uprobe_multi_func_1_addr = (__u64) uprobe_multi_func_1;
+	skel->bss->uprobe_multi_func_2_addr = (__u64) uprobe_multi_func_2;
+	skel->bss->uprobe_multi_func_3_addr = (__u64) uprobe_multi_func_3;
+
+	uprobe_multi_func_1();
+	uprobe_multi_func_2();
+	uprobe_multi_func_3();
+
+	/*
+	 * We expect 2 for uprobe_multi_func_2 because it runs both entry/return probe,
+	 * uprobe_multi_func_[13] run just the entry probe. All expected numbers are
+	 * doubled, because we run extra test for sleepable session.
+	 */
+	ASSERT_EQ(skel->bss->uprobe_session_result[0], 2, "uprobe_multi_func_1_result");
+	ASSERT_EQ(skel->bss->uprobe_session_result[1], 4, "uprobe_multi_func_2_result");
+	ASSERT_EQ(skel->bss->uprobe_session_result[2], 2, "uprobe_multi_func_3_result");
+
+	/* We expect increase in 3 entry and 1 return session calls -> 4 */
+	ASSERT_EQ(skel->bss->uprobe_multi_sleep_result, 4, "uprobe_multi_sleep_result");
+
+cleanup:
+	bpf_link__destroy(link);
+	uprobe_multi_session__destroy(skel);
+}
+
 static void test_bench_attach_uprobe(void)
 {
 	long attach_start_ns = 0, attach_end_ns = 0;
···
 		test_pid_filter_process(false);
 	if (test__start_subtest("filter_clone_vm"))
 		test_pid_filter_process(true);
+	if (test__start_subtest("session"))
+		test_session_skel_api();
 }

tools/testing/selftests/bpf/progs/uprobe_multi_session.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_multi_func_1_addr = 0;
+__u64 uprobe_multi_func_2_addr = 0;
+__u64 uprobe_multi_func_3_addr = 0;
+
+__u64 uprobe_session_result[3] = {};
+__u64 uprobe_multi_sleep_result = 0;
+
+void *user_ptr = 0;
+int pid = 0;
+
+static int uprobe_multi_check(void *ctx, bool is_return)
+{
+	const __u64 funcs[] = {
+		uprobe_multi_func_1_addr,
+		uprobe_multi_func_2_addr,
+		uprobe_multi_func_3_addr,
+	};
+	unsigned int i;
+	__u64 addr;
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 1;
+
+	addr = bpf_get_func_ip(ctx);
+
+	for (i = 0; i < ARRAY_SIZE(funcs); i++) {
+		if (funcs[i] == addr) {
+			uprobe_session_result[i]++;
+			break;
+		}
+	}
+
+	/* only uprobe_multi_func_2 executes return probe */
+	if ((addr == uprobe_multi_func_1_addr) ||
+	    (addr == uprobe_multi_func_3_addr))
+		return 1;
+
+	return 0;
+}
+
+SEC("uprobe.session//proc/self/exe:uprobe_multi_func_*")
+int uprobe(struct pt_regs *ctx)
+{
+	return uprobe_multi_check(ctx, bpf_session_is_return());
+}
+
+static __always_inline bool verify_sleepable_user_copy(void)
+{
+	char data[9];
+
+	bpf_copy_from_user(data, sizeof(data), user_ptr);
+	return bpf_strncmp(data, sizeof(data), "test_data") == 0;
+}
+
+SEC("uprobe.session.s//proc/self/exe:uprobe_multi_func_*")
+int uprobe_sleepable(struct pt_regs *ctx)
+{
+	if (verify_sleepable_user_copy())
+		uprobe_multi_sleep_result++;
+	return uprobe_multi_check(ctx, bpf_session_is_return());
+}