diff mbox series

[bpf-next,v6,2/2] selftests/bpf: Add testcase for bpf_task_under_cgroup

Message ID 20230505060818.60037-3-zhoufeng.zf@bytedance.com
State Superseded
Headers show
Series Introduce a new kfunc of bpf_task_under_cgroup | expand

Commit Message

Feng Zhou May 5, 2023, 6:08 a.m. UTC 
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>
Acked-by: Yonghong Song <yhs@fb.com>
---
 tools/testing/selftests/bpf/DENYLIST.s390x    |  1 +
 .../bpf/prog_tests/task_under_cgroup.c        | 53 +++++++++++++++++++
 .../bpf/progs/test_task_under_cgroup.c        | 51 ++++++++++++++++++
 3 files changed, 105 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

Comments

Yonghong Song May 5, 2023, 6:46 p.m. UTC | #1 
On 5/5/23 12:24 AM, Feng Zhou wrote:
> 在 2023/5/5 15:13, Hao Luo 写道:
>> On Thu, May 4, 2023 at 11:08 PM Feng zhou <zhoufeng.zf@bytedance.com> 
>> 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>
>>> Acked-by: Yonghong Song <yhs@fb.com>
>>> ---
>>
>> Hi Feng,
>>
>> I have a comment about the methodology of the test, but the patch
>> looks ok to me. Why do we have to test via a tracing program? I think
>> what we need is just a task and a cgroup. Since we have the kfunc
>> bpf_task_from_pid() and bpf_cgroup_from_id(), we can write a syscall
>> program which takes a pid and a cgroup id as input and get the task
>> and cgroup objects directly in the program.
>>
>> I like testing via a syscall program because it doesn't depend on the
>> newtask tracepoint and it should be simpler. But I'm ok with the
>> current version of the patch, just have some thoughts.
>>
>> Hao
> 
> Yes, your method is also very good. The reason why I did this is because 
> of Song's suggestion before, hope that the parameter of the hook point 
> will have a task, so I chose this to test.

The motivation of this patch is:
   Trace sched related functions, such as enqueue_task_fair, it is 
necessary to
   specify a task instead of the current task which within a given cgroup.

So I think it is okay to have a test related to sched.
diff mbox series

Patch

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..4224727fb364
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c
@@ -0,0 +1,53 @@ 
+// 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;
+	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:
+	test_task_under_cgroup__destroy(skel);
+	close(foo);
+}
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..56cdc0a553f0
--- /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 (cgrp)
+		bpf_cgroup_release(cgrp);
+	bpf_task_release(acquired);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";