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

[Yonghong Song]

On 1/8/21 3:19 PM, Song Liu wrote:
> Task local storage is enabled for tracing programs. Add a test for it
> without CONFIG_BPF_LSM.
>
> Signed-off-by: Song Liu <songliubraving@xxxxxx>
> ---
>   .../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

> +
> +#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.

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

ditto.

> +	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.

> +	CHECK(skel->bss->value < count, "task_local_storage_value",
> +	      "task local value too small\n");
> +
> +out:
> +	task_local_storage__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/task_local_storage.c b/tools/testing/selftests/bpf/progs/task_local_storage.c
> new file mode 100644
> index 0000000000000..807255c5c162d
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/task_local_storage.c
> @@ -0,0 +1,37 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2020 Facebook */

2020 -> 2021

> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +struct local_data {
> +	__u64 val;
> +};
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
> +	__uint(map_flags, BPF_F_NO_PREALLOC);
> +	__type(key, int);
> +	__type(value, struct local_data);
> +} task_storage_map SEC(".maps");
> +
> +int value = 0;
> +
> +SEC("tp_btf/sched_switch")
> +int BPF_PROG(on_switch, bool preempt, struct task_struct *prev,
> +	     struct task_struct *next)
> +{
> +	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.

> +
> +	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;
> +}