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, 31 insertions, 2 deletions

diff --git a/tools/testing/selftests/bpf/progs/uprobe_multi.c b/tools/testing/selftests/bpf/progs/uprobe_multi.c
index 86a7ff5d3726..44190efcdba2 100644
--- a/tools/testing/selftests/bpf/progs/uprobe_multi.c
+++ b/tools/testing/selftests/bpf/progs/uprobe_multi.c
@@ -1,8 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
-#include <linux/bpf.h>
+#include "vmlinux.h"
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
-#include <stdbool.h>
+#include <bpf/usdt.bpf.h>
 
 char _license[] SEC("license") = "GPL";
 
@@ -23,9 +23,12 @@ __u64 uprobe_multi_sleep_result = 0;
 int pid = 0;
 int child_pid = 0;
 int child_tid = 0;
+int child_pid_usdt = 0;
+int child_tid_usdt = 0;
 
 int expect_pid = 0;
 bool bad_pid_seen = false;
+bool bad_pid_seen_usdt = false;
 
 bool test_cookie = false;
 void *user_ptr = 0;
@@ -112,3 +115,29 @@ int uprobe_extra(struct pt_regs *ctx)
 	/* we need this one just to mix PID-filtered and global uprobes */
 	return 0;
 }
+
+SEC("usdt")
+int usdt_pid(struct pt_regs *ctx)
+{
+	__u64 cur_pid_tgid = bpf_get_current_pid_tgid();
+	__u32 cur_pid;
+
+	cur_pid = cur_pid_tgid >> 32;
+	if (pid && cur_pid != pid)
+		return 0;
+
+	if (expect_pid && cur_pid != expect_pid)
+		bad_pid_seen_usdt = true;
+
+	child_pid_usdt = cur_pid_tgid >> 32;
+	child_tid_usdt = (__u32)cur_pid_tgid;
+
+	return 0;
+}
+
+SEC("usdt")
+int usdt_extra(struct pt_regs *ctx)
+{
+	/* we need this one just to mix PID-filtered and global USDT probes */
+	return 0;
+}