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Date: Thu, 4 May 2023 11:23:36 +0800
From: Feng Zhou <zhoufeng.zf@...edance.com>
To: Yonghong Song <yhs@...a.com>, martin.lau@...ux.dev, ast@...nel.org,
daniel@...earbox.net, andrii@...nel.org, song@...nel.org,
yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org,
sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org,
davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, mykolal@...com, shuah@...nel.org
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
yangzhenze@...edance.com, wangdongdong.6@...edance.com
Subject: Re: Re: [PATCH bpf-next v4 2/2] selftests/bpf: Add testcase for
bpf_task_under_cgroup
在 2023/4/29 00:32, Yonghong Song 写道:
>
>
> On 4/28/23 12:17 AM, Feng zhou wrote:
>> From: Feng Zhou <zhoufeng.zf@...edance.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@...edance.com>
>
> Ack with a few nits below.
>
> Acked-by: Yonghong Song <yhs@...com>
>
>> ---
>> tools/testing/selftests/bpf/DENYLIST.s390x | 1 +
>> .../bpf/prog_tests/task_under_cgroup.c | 55 +++++++++++++++++++
>> .../bpf/progs/test_task_under_cgroup.c | 51 +++++++++++++++++
>> 3 files changed, 107 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..5e79dff86dec
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c
>> @@ -0,0 +1,55 @@
>> +// 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;
>> + 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);
>> + else if (pid == -1)
>> + printf("Couldn't fork process!\n");
>
> ASSERT_* is preferred compared to 'printf'. Maybe ASSERT_TRUE(0,
> "Couldn't fork process")?
>
Will do.
>> +
>> + wait(NULL);
>> +
>> + test_task_under_cgroup__detach(skel);
>> +
>> + ASSERT_NEQ(skel->bss->remote_pid, skel->rodata->local_pid,
>> + "test task_under_cgroup");
>> +
>> +cleanup:
>> + if (foo >= 0)
>
> "if (foo >= 0)" is not needed. 'foo' is guaranteed ">= 0" as this point.
>
Yes
>> + close(foo);
>> +
>> + test_task_under_cgroup__destroy(skel);
>> +}
>> 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..5bcb726d6d0a
>> --- /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 long cgid;
>
> cgid cannot be a negative number. So let us do
> const volatile __u64 cgid;
>
Ok
>> +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 = NULL;
>
> "acquired = NULL" is not needed. Just do "struct task_struct *acquired;".
>
Ok
>> +
>> + 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);
>> + return 0;
>> +}
>> +
>> +char _license[] SEC("license") = "GPL";
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