Re: [PATCH bpf-next 8/8] selftests/bpf: add arraymap test for bpf_for_each_map_elem() helper

[Yonghong Song <yhs@fb.com>]

On 2/8/21 10:35 AM, Andrii Nakryiko wrote:
> On Thu, Feb 4, 2021 at 5:53 PM Yonghong Song <yhs@fb.com> wrote:
>>
>> A test is added for arraymap and percpu arraymap. The test also
>> exercises the early return for the helper which does not
>> traverse all elements.
>>      $ ./test_progs -n 44
>>      #44/1 hash_map:OK
>>      #44/2 array_map:OK
>>      #44 for_each:OK
>>      Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED
>>
>> Signed-off-by: Yonghong Song <yhs@fb.com>
>> ---
>>   .../selftests/bpf/prog_tests/for_each.c       | 54 ++++++++++++++
>>   .../bpf/progs/for_each_array_map_elem.c       | 71 +++++++++++++++++++
>>   2 files changed, 125 insertions(+)
>>   create mode 100644 tools/testing/selftests/bpf/progs/for_each_array_map_elem.c
>>
> 
> [...]
> 
>> +
>> +       arraymap_fd = bpf_map__fd(skel->maps.arraymap);
>> +       expected_total = 0;
>> +       max_entries = bpf_map__max_entries(skel->maps.arraymap);
>> +       for (i = 0; i < max_entries; i++) {
>> +               key = i;
>> +               val = i + 1;
>> +               /* skip the last iteration for expected total */
>> +               if (i != max_entries - 1)
>> +                       expected_total += val;
>> +               err = bpf_map_update_elem(arraymap_fd, &key, &val, BPF_ANY);
>> +               if (CHECK(err, "map_update", "map_update failed\n"))
>> +                       goto out;
>> +       }
>> +
>> +       num_cpus = bpf_num_possible_cpus();
>> +        percpu_map_fd = bpf_map__fd(skel->maps.percpu_map);
> 
> formatting is off, please check with checkfile.pl

Sure. will do.

> 
> 
>> +        percpu_valbuf = malloc(sizeof(__u64) * num_cpus);
>> +        if (CHECK_FAIL(!percpu_valbuf))
> 
> please don't use CHECK_FAIL, ASSERT_PTR_OK would work nicely here

Okay.

> 
>> +                goto out;
>> +
>> +       key = 0;
>> +        for (i = 0; i < num_cpus; i++)
>> +                percpu_valbuf[i] = i + 1;
>> +       err = bpf_map_update_elem(percpu_map_fd, &key, percpu_valbuf, BPF_ANY);
>> +       if (CHECK(err, "percpu_map_update", "map_update failed\n"))
>> +               goto out;
>> +
>> +       do_dummy_read(skel->progs.dump_task);
> 
> see previous patch, iter/tasks seems like an overkill for these tests

Yes, will use bpf_prog_test_run() in v2.

> 
>> +
>> +       ASSERT_EQ(skel->bss->called, 1, "called");
>> +       ASSERT_EQ(skel->bss->arraymap_output, expected_total, "array_output");
>> +       ASSERT_EQ(skel->bss->cpu + 1, skel->bss->percpu_val, "percpu_val");
>> +
>> +out:
>> +       free(percpu_valbuf);
>> +       for_each_array_map_elem__destroy(skel);
>> +}
>> +
> 
> [...]
> 
>> +SEC("iter/task")
>> +int dump_task(struct bpf_iter__task *ctx)
>> +{
>> +       struct seq_file *seq =  ctx->meta->seq;
>> +       struct task_struct *task = ctx->task;
>> +       struct callback_ctx data;
>> +
>> +       /* only call once */
>> +       if (called > 0)
>> +               return 0;
>> +
>> +       called++;
>> +
>> +       data.output = 0;
>> +       bpf_for_each_map_elem(&arraymap, check_array_elem, &data, 0);
>> +       arraymap_output = data.output;
>> +
>> +       bpf_for_each_map_elem(&percpu_map, check_percpu_elem, 0, 0);
> 
> nit: NULL, 0 ?

We do not NULL defined in vmlinux.h or bpf_helpers.h. Hence I am using
0, I should at least use (void *)0 here, I think.

> 
>> +
>> +       return 0;
>> +}
>> --
>> 2.24.1
>>