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Date: Fri, 28 Apr 2023 09:32:01 -0700
From: Yonghong Song <yhs@...a.com>
To: Feng zhou <zhoufeng.zf@...edance.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: [PATCH bpf-next v4 2/2] selftests/bpf: Add testcase for
bpf_task_under_cgroup
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")?
> +
> + 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.
> + 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;
> +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;".
> +
> + 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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