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

On Fri, Apr 21, 2023 at 05:04:03PM +0800, Feng zhou wrote:

From: Feng Zhou zhoufeng.zf@bytedance.com

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@bytedance.com

.../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) ?

• 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.

+int BPF_PROG(sysenter, struct pt_regs *regs, long id) +{

• struct cgroup *cgrp;
• if (id != __NR_getuid)

• return 0;
  

• if (local_pid != (bpf_get_current_pid_tgid() >> 32))

• return 0;
  

• cgrp = bpf_cgroup_from_id(cgid);
• if (!cgrp)

• return 0;
  

• if (!bpf_task_under_cgroup(cgrp, bpf_get_current_task_btf()))

• goto out;
  

• remote_pid = local_pid;

+out:

• bpf_cgroup_release(cgrp);
• return 0;

+}

+char _license[] SEC("license") = "GPL";

2.20.1