Re: [PATCH bpf-next 2/4] selftests/bpf: add non-BPF_LSM test for task local storage

On Mon, Jan 11, 2021 at 6:31 PM Yonghong Song [off-list ref] wrote:

On 1/8/21 3:19 PM, Song Liu wrote:

quoted

Task local storage is enabled for tracing programs. Add a test for it
without CONFIG_BPF_LSM.

Can you also explain what the test does in the commit log?

It would also be nicer to have a somewhat more realistic selftest which
represents a simple tracing + task local storage use case.

quoted

Signed-off-by: Song Liu <redacted>
---
  .../bpf/prog_tests/test_task_local_storage.c  | 34 +++++++++++++++++
  .../selftests/bpf/progs/task_local_storage.c  | 37 +++++++++++++++++++
  2 files changed, 71 insertions(+)
  create mode 100644 tools/testing/selftests/bpf/prog_tests/test_task_local_storage.c
  create mode 100644 tools/testing/selftests/bpf/progs/task_local_storage.c

diff --git a/tools/testing/selftests/bpf/prog_tests/test_task_local_storage.c b/tools/testing/selftests/bpf/prog_tests/test_task_local_storage.c
new file mode 100644
index 0000000000000..7de7a154ebbe6
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/test_task_local_storage.c

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */

2020 -> 2021

quoted

+
+#include <sys/types.h>
+#include <unistd.h>
+#include <test_progs.h>
+#include "task_local_storage.skel.h"
+
+static unsigned int duration;
+
+void test_test_task_local_storage(void)
+{
+     struct task_local_storage *skel;
+     const int count = 10;
+     int i, err;
+
+     skel = task_local_storage__open_and_load();
+

Extra line is unnecessary here.

quoted

+     if (CHECK(!skel, "skel_open_and_load", "skeleton open and load failed\n"))
+             return;
+
+     err = task_local_storage__attach(skel);
+

ditto.

quoted

+     if (CHECK(err, "skel_attach", "skeleton attach failed\n"))
+             goto out;
+
+     for (i = 0; i < count; i++)
+             usleep(1000);

Does a smaller usleep value will work? If it is, recommend to have a
smaller value here to reduce test_progs running time.

quoted

+     CHECK(skel->bss->value < count, "task_local_storage_value",
+           "task local value too small\n");

[...]

quoted

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */

2020 -> 2021

quoted

+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";

[...]

quoted

+{
+     struct local_data *storage;

If it possible that we do some filtering based on test_progs pid
so below bpf_task_storage_get is only called for test_progs process?
This is more targeted and can avoid counter contributions from
other unrelated processes and make test_task_local_storage.c result
comparison more meaningful.

Indeed, have a look at the monitored_pid approach some of the LSM programs
do.

quoted

+
+     storage = bpf_task_storage_get(&task_storage_map,
+                                    next, 0,
+                                    BPF_LOCAL_STORAGE_GET_F_CREATE);
+     if (storage) {
+             storage->val++;
+             value = storage->val;
+     }
+     return 0;
+}