linux-kernel - Re: [PATCH bpf-next 2/4] selftests/bpf: add non-BPF

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Date:   Mon, 11 Jan 2021 22:49:00 +0000
From:   Song Liu <songliubraving@...com>
To:     Yonghong Song <yhs@...com>
CC:     bpf <bpf@...r.kernel.org>, netdev <netdev@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Peter Ziljstra" <peterz@...radead.org>,
        Alexei Starovoitov <ast@...nel.org>,
        "Daniel Borkmann" <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        "john fastabend" <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        "Kernel Team" <Kernel-team@...com>,
        "haoluo@...gle.com" <haoluo@...gle.com>
Subject: Re: [PATCH bpf-next 2/4] selftests/bpf: add non-BPF_LSM test for task
 local storage



> On Jan 11, 2021, at 9:30 AM, Yonghong Song <yhs@...com> wrote:
> 
> 
> 
> 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@...com>
>> ---
>>  .../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.

I thought 10ms total was acceptable. But yeah, smaller value should still work. 

> 
>> +	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.

Make sense. Will fix in the next version. 

> 
>> +
>> +	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;
>> +}