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Message-ID: <f26d4f76-d932-576c-cbb9-31158d3a0e4b@bytedance.com>
Date:   Fri, 5 May 2023 11:20:54 +0800
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Subject: Re: Re: [PATCH bpf-next v5 2/2] selftests/bpf: Add testcase for
 bpf_task_under_cgroup
To:     Yonghong Song <yhs@meta.com>, martin.lau@linux.dev, ast@kernel.org,
        daniel@iogearbox.net, andrii@kernel.org, song@kernel.org,
        yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org,
        sdf@google.com, haoluo@google.com, jolsa@kernel.org,
        davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
        pabeni@redhat.com, mykolal@fb.com, shuah@kernel.org
Cc:     bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, linux-kselftest@vger.kernel.org,
        yangzhenze@bytedance.com, wangdongdong.6@bytedance.com
References: <20230504031513.13749-1-zhoufeng.zf@bytedance.com>
 <20230504031513.13749-3-zhoufeng.zf@bytedance.com>
 <63138022-e28f-a63c-6f4c-61b61e585641@meta.com>
From:   Feng Zhou <zhoufeng.zf@bytedance.com>
In-Reply-To: <63138022-e28f-a63c-6f4c-61b61e585641@meta.com>
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在 2023/5/4 22:46, Yonghong Song 写道:
> 
> 
> On 5/3/23 8:15 PM, Feng zhou wrote:
>> From: Feng Zhou <zhoufeng.zf@bytedance.com>
>>
>> test_progs:
>> Tests new kfunc bpf_task_under_cgroup().
>>
>> The bpf program saves the new task's pid within a given cgroup to
>> the remote_pid, which is convenient for the user-mode program to
>> verify the test correctness.
>>
>> The user-mode program creates its own mount namespace, and mounts the
>> cgroupsv2 hierarchy in there, call the fork syscall, then check if
>> remote_pid and local_pid are unequal.
>>
>> Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
> 
> Ack with a few nits below. You can carry my Ack in the
> next revision.
> 
> Acked-by: Yonghong Song <yhs@fb.com>
> 
> 

Will do

>> ---
>>   tools/testing/selftests/bpf/DENYLIST.s390x    |  1 +
>>   .../bpf/prog_tests/task_under_cgroup.c        | 54 +++++++++++++++++++
>>   .../bpf/progs/test_task_under_cgroup.c        | 51 ++++++++++++++++++
>>   3 files changed, 106 insertions(+)
>>   create mode 100644 
>> tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c
>>   create mode 100644 
>> tools/testing/selftests/bpf/progs/test_task_under_cgroup.c
>>
>> diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x 
>> b/tools/testing/selftests/bpf/DENYLIST.s390x
>> index c7463f3ec3c0..5061d9e24c16 100644
>> --- a/tools/testing/selftests/bpf/DENYLIST.s390x
>> +++ b/tools/testing/selftests/bpf/DENYLIST.s390x
>> @@ -26,3 +26,4 @@ user_ringbuf                             # failed to 
>> find kernel BTF type ID of
>>   verif_stats                              # 
>> trace_vprintk__open_and_load unexpected error: 
>> -9                           (?)
>>   xdp_bonding                              # failed to auto-attach 
>> program 'trace_on_entry': -524                        (trampoline)
>>   xdp_metadata                             # JIT does not support 
>> calling kernel function                                (kfunc)
>> +test_task_under_cgroup                   # JIT does not support 
>> calling kernel function                                (kfunc)
>> diff --git 
>> a/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c 
>> b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c
>> new file mode 100644
>> index 000000000000..fa3a98eae5ef
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c
>> @@ -0,0 +1,54 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (c) 2023 Bytedance */
>> +
>> +#include <sys/syscall.h>
>> +#include <test_progs.h>
>> +#include <cgroup_helpers.h>
>> +#include "test_task_under_cgroup.skel.h"
>> +
>> +#define FOO    "/foo"
>> +
>> +void test_task_under_cgroup(void)
>> +{
>> +    struct test_task_under_cgroup *skel;
>> +    int ret, foo = -1;
> 
> You do not need to initialize 'foo' here.
> 
>> +    pid_t pid;
>> +
>> +    foo = test__join_cgroup(FOO);
>> +    if (!ASSERT_OK(foo < 0, "cgroup_join_foo"))
>> +        return;
>> +
>> +    skel = test_task_under_cgroup__open();
>> +    if (!ASSERT_OK_PTR(skel, "test_task_under_cgroup__open"))
>> +        goto cleanup;
>> +
>> +    skel->rodata->local_pid = getpid();
>> +    skel->bss->remote_pid = getpid();
>> +    skel->rodata->cgid = get_cgroup_id(FOO);
>> +
>> +    ret = test_task_under_cgroup__load(skel);
>> +    if (!ASSERT_OK(ret, "test_task_under_cgroup__load"))
>> +        goto cleanup;
>> +
>> +    ret = test_task_under_cgroup__attach(skel);
>> +    if (!ASSERT_OK(ret, "test_task_under_cgroup__attach"))
>> +        goto cleanup;
>> +
>> +    pid = fork();
>> +    if (pid == 0)
>> +        exit(0);
>> +
>> +    ret = (pid == -1);
>> +    if (ASSERT_OK(ret, "fork process"))
>> +        wait(NULL);
>> +
>> +    test_task_under_cgroup__detach(skel);
>> +
>> +    ASSERT_NEQ(skel->bss->remote_pid, skel->rodata->local_pid,
>> +           "test task_under_cgroup");
>> +
>> +cleanup:
>> +    close(foo);
>> +
>> +    test_task_under_cgroup__destroy(skel);
> 
> Let us just do:
> cleanup:
>      test_task_under_cgroup__destroy(skel);
>      close(foo);
> 
> This is the reverse order of test__join_cgroup() and 
> test_task_under_cgroup__open().
> 
>> +}
>> diff --git 
>> a/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c 
>> b/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c
>> new file mode 100644
>> index 000000000000..79d98e65c7eb
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c
>> @@ -0,0 +1,51 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (c) 2023 Bytedance */
>> +
>> +#include <vmlinux.h>
>> +#include <bpf/bpf_tracing.h>
>> +#include <bpf/bpf_helpers.h>
>> +
>> +#include "bpf_misc.h"
>> +
>> +struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym;
>> +long bpf_task_under_cgroup(struct task_struct *task, struct cgroup 
>> *ancestor) __ksym;
>> +void bpf_cgroup_release(struct cgroup *p) __ksym;
>> +struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym;
>> +void bpf_task_release(struct task_struct *p) __ksym;
>> +
>> +const volatile int local_pid;
>> +const volatile __u64 cgid;
>> +int remote_pid;
>> +
>> +SEC("tp_btf/task_newtask")
>> +int BPF_PROG(handle__task_newtask, struct task_struct *task, u64 
>> clone_flags)
>> +{
>> +    struct cgroup *cgrp = NULL;
>> +    struct task_struct *acquired;
>> +
>> +    if (local_pid != (bpf_get_current_pid_tgid() >> 32))
>> +        return 0;
>> +
>> +    acquired = bpf_task_acquire(task);
>> +    if (!acquired)
>> +        return 0;
>> +
>> +    if (local_pid == acquired->tgid)
>> +        goto out;
>> +
>> +    cgrp = bpf_cgroup_from_id(cgid);
>> +    if (!cgrp)
>> +        goto out;
>> +
>> +    if (bpf_task_under_cgroup(acquired, cgrp))
>> +        remote_pid = acquired->tgid;
>> +
>> +out:
>> +    if (acquired)
>> +        bpf_task_release(acquired);
>> +    if (cgrp)
>> +        bpf_cgroup_release(cgrp);
> 
> Let us do:
> out:
>      if (cgrp)
>          bpf_cgroup_release(cgrp);
>      bpf_task_release(acquired);
> 
>> +    return 0;
>> +}
>> +
>> +char _license[] SEC("license") = "GPL";