Re: [RFC PATCH bpf-next/net v1 12/13] bpftool: Add support for dumping streams

[Eduard Zingerman <eddyz87@gmail.com>]

When I add a test as at the bottom of the email I get the following output:

    test_stream_cond_break:PASS:load 0 nsec
    test_stream_cond_break:PASS:run_opts 0 nsec
    test_stream_cond_break:PASS:info_by_fd 0 nsec
    ERROR: Timeout detected for may_goto instruction
    CPU: 6 UID: 0 PID: 206 Comm: test_progs
    Call trace:
     bpf_prog_stderr_dump_stack+0xde/0x160
     bpf_check_timed_may_goto+0x5d/0x90
     arch_bpf_timed_may_goto+0x21/0x40
     bpf_prog_34056decf3b2fb2f_long_loop+0x49/0x57: [stream_cond_break.c:8]
     bpf_prog_run_pin_on_cpu+0x5f/0x110
     bpf_prog_test_run_syscall+0x205/0x320
     bpf_prog_test_run+0x234/0x2a0
     __sys_bpf+0x2d7/0x570
     __x64_sys_bpf+0x7c/0x90
     do_syscall_64+0x79/0x120
     entry_SYSCALL_64_after_hwframe+0x76/0x7e
    
    prog_dump_stream: ret==-22
    test_stream_cond_break:FAIL:./tools/sbin/bpftool prog dump stderr id 8
     unexpected error: 59904 (errno 95)

Am I doing something wrong or EINVAL should not be returned from
prog_dump_stream in this case?

---

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index d0800fec9c3d..64386737a364 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -747,6 +747,7 @@ prog_dump_stream(struct bpf_prog_info *info, enum dump_mode mode, const char *fi
 		ret = -EINVAL;
 end:
 	stream_bpf__destroy(skel);
+	fprintf(stderr, "prog_dump_stream: ret==%d\n", ret);
 	return ret;
 }
 
diff --git a/tools/testing/selftests/bpf/prog_tests/stream_cond_break.c b/tools/testing/selftests/bpf/prog_tests/stream_cond_break.c
new file mode 100644
index 000000000000..7a29a45b0a04
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/stream_cond_break.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+#include <test_progs.h>
+#include "stream_cond_break.skel.h"
+
+static char log_buf[16 * 1024];
+
+void test_stream_cond_break(void)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts, .kernel_log_buf = log_buf,
+						.kernel_log_size = sizeof(log_buf),
+						.kernel_log_level = 1 | 2 | 4);
+	LIBBPF_OPTS(bpf_test_run_opts, run_opts);
+	struct stream_cond_break *skel = NULL;
+	struct bpf_prog_info prog_info;
+	__u32 prog_info_len;
+	int ret, fd;
+
+	skel = stream_cond_break__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "open_opts"))
+		goto out;
+	ret = stream_cond_break__load(skel);
+	if (env.verbosity >= VERBOSE_VERY) {
+		fprintf(stderr, "---- program load log ----\n");
+		fprintf(stderr, "%s", log_buf);
+		fprintf(stderr, "--------- end log --------\n");
+	}
+	if (!ASSERT_OK(ret, "load"))
+		return;
+	fd = bpf_program__fd(skel->progs.long_loop);
+	ret = bpf_prog_test_run_opts(fd, &run_opts);
+	if (!ASSERT_EQ(ret, 0, "run_opts"))
+		goto out;
+	memset(&prog_info, 0, sizeof(prog_info));
+	prog_info_len = sizeof(prog_info);
+	ret = bpf_prog_get_info_by_fd(fd, &prog_info, &prog_info_len);
+	if (!ASSERT_OK(ret, "info_by_fd"))
+		goto out;
+	SYS(out, "./tools/sbin/bpftool prog dump stderr id %i\n", prog_info.id);
+out:
+	stream_cond_break__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/stream_cond_break.c b/tools/testing/selftests/bpf/progs/stream_cond_break.c
new file mode 100644
index 000000000000..47c2e5f1b8fd
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/stream_cond_break.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "bpf_experimental.h"
+
+SEC("syscall")
+int long_loop(const void *ctx)
+{
+	for (;;)
+		cond_break;
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";