Re: [PATCH bpf-next v5 2/2] selftests/bpf: Add testcase for bpf_task_under_cgroup

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

---

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";