Re: [External] Re: [PATCH bpf-next v2 2/2] selftests/bpf: Add testcase for bpf_task_under_cgroup

[Alexei Starovoitov]

On Sat, Apr 22, 2023 at 8:51 PM Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx> wrote:
>
> 在 2023/4/22 02:24, Alexei Starovoitov 写道:
>
> On Fri, Apr 21, 2023 at 05:04:03PM +0800, Feng zhou wrote:
>
> From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
>
> test_progs:
> Tests new kfunc bpf_task_under_cgroup().
>
> The bpf program saves the pid which call the getuid syscall 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 getuid syscall, then check if
> remote_pid and local_pid are equal.
>
> Signed-off-by: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
> ---
>  .../bpf/prog_tests/task_under_cgroup.c        | 46 +++++++++++++++++++
>  .../selftests/bpf/progs/cgrp_kfunc_common.h   |  1 +
>  .../bpf/progs/test_task_under_cgroup.c        | 40 ++++++++++++++++
>  3 files changed, 87 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/prog_tests/task_under_cgroup.c b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c
> new file mode 100644
> index 000000000000..bd3deb469938
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c
> @@ -0,0 +1,46 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2023 Bytedance */
> +
> +#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;
> +
> + 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->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;
> +
> + syscall(__NR_getuid);
> +
> + test_task_under_cgroup__detach(skel);
> +
> + ASSERT_EQ(skel->bss->remote_pid, skel->rodata->local_pid,
> +  "test task_under_cgroup");
> +
> +cleanup:
> + if (foo)
> + close(foo);
>
> Looks wrong. should be if (foo >= 0) ?
>
> Yes.
>
> +
> + test_task_under_cgroup__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h b/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h
> index 22914a70db54..41b3ea231698 100644
> --- a/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h
> +++ b/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h
> @@ -26,6 +26,7 @@ struct cgroup *bpf_cgroup_ancestor(struct cgroup *cgrp, int level) __ksym;
>  struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym;
>  void bpf_rcu_read_lock(void) __ksym;
>  void bpf_rcu_read_unlock(void) __ksym;
> +int bpf_task_under_cgroup(struct cgroup *cgrp, struct task_struct *task) __ksym;
>
>  static inline struct __cgrps_kfunc_map_value *cgrps_kfunc_map_value_lookup(struct cgroup *cgrp)
>  {
> 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..e2740f9b029d
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c
> @@ -0,0 +1,40 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2023 Bytedance */
> +
> +#include <vmlinux.h>
> +#include <asm/unistd.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +
> +#include "cgrp_kfunc_common.h"
> +
> +const volatile int local_pid;
> +const volatile long cgid;
> +int remote_pid;
> +
> +SEC("tp_btf/sys_enter")
>
> pls narrow down to specific syscall. Like you use in user space part: getuid
>
> Also add this test to denylist.s390. See BPF CI failure.
>
> bpf_task_under_cgroup is placed in generic_btf_ids, belongs to BPF_PROG_TYPE_TRACING,
>
> if narrow down to specific syscall and uses SEC ("tp/syscalls/sys_enter_getuid"),
>
> bpf prog type is TRACEPOINT, kfunc cannot be used, and reports
>
> "calls kernel function bpf_cgroup_from_id is not allowed".

sure, pls narrow it down. sys_enter is too broad.
In parallel test_progs the bpf prog will be way too many times.