selftests/bpf: extend multi-uprobe tests with USDTs

Validate libbpf's USDT-over-multi-uprobe logic by adding USDTs to
existing multi-uprobe tests. This checks correct libbpf fallback to
singular uprobes (when run on older kernels with buggy PID filtering).
We reuse already established child process and child thread testing
infrastructure, so additions are minimal. These test fail on either
older kernels or older version of libbpf that doesn't detect PID
filtering problems.

Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240521163401.3005045-6-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
index 677232d31432..bf6ca8e3eb13 100644
--- a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
@@ -8,6 +8,7 @@
 #include "uprobe_multi_usdt.skel.h"
 #include "bpf/libbpf_internal.h"
 #include "testing_helpers.h"
+#include "../sdt.h"
 
 static char test_data[] = "test_data";
 
@@ -26,6 +27,11 @@ noinline void uprobe_multi_func_3(void)
 	asm volatile ("");
 }
 
+noinline void usdt_trigger(void)
+{
+	STAP_PROBE(test, pid_filter_usdt);
+}
+
 struct child {
 	int go[2];
 	int c2p[2]; /* child -> parent channel */
@@ -90,6 +96,7 @@ static struct child *spawn_child(void)
 		uprobe_multi_func_1();
 		uprobe_multi_func_2();
 		uprobe_multi_func_3();
+		usdt_trigger();
 
 		exit(errno);
 	}
@@ -117,6 +124,7 @@ static void *child_thread(void *ctx)
 	uprobe_multi_func_1();
 	uprobe_multi_func_2();
 	uprobe_multi_func_3();
+	usdt_trigger();
 
 	err = 0;
 	pthread_exit(&err);
@@ -182,6 +190,7 @@ static void uprobe_multi_test_run(struct uprobe_multi *skel, struct child *child
 		uprobe_multi_func_1();
 		uprobe_multi_func_2();
 		uprobe_multi_func_3();
+		usdt_trigger();
 	}
 
 	if (child)
@@ -269,8 +278,24 @@ __test_attach_api(const char *binary, const char *pattern, struct bpf_uprobe_mul
 	if (!ASSERT_OK_PTR(skel->links.uprobe_extra, "bpf_program__attach_uprobe_multi"))
 		goto cleanup;
 
+	/* Attach (uprobe-backed) USDTs */
+	skel->links.usdt_pid = bpf_program__attach_usdt(skel->progs.usdt_pid, pid, binary,
+							"test", "pid_filter_usdt", NULL);
+	if (!ASSERT_OK_PTR(skel->links.usdt_pid, "attach_usdt_pid"))
+		goto cleanup;
+
+	skel->links.usdt_extra = bpf_program__attach_usdt(skel->progs.usdt_extra, -1, binary,
+							  "test", "pid_filter_usdt", NULL);
+	if (!ASSERT_OK_PTR(skel->links.usdt_extra, "attach_usdt_extra"))
+		goto cleanup;
+
 	uprobe_multi_test_run(skel, child);
 
+	ASSERT_FALSE(skel->bss->bad_pid_seen_usdt, "bad_pid_seen_usdt");
+	if (child) {
+		ASSERT_EQ(skel->bss->child_pid_usdt, child->pid, "usdt_multi_child_pid");
+		ASSERT_EQ(skel->bss->child_tid_usdt, child->tid, "usdt_multi_child_tid");
+	}
 cleanup:
 	uprobe_multi__destroy(skel);
 }