Re: Re: [PATCH bpf-next v4 2/2] selftests/bpf: Add testcase for bpf_task_under_cgroup

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在 2023/4/29 00:32, Yonghong Song 写道:


On 4/28/23 12:17 AM, Feng zhou wrote:
From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>

Ack with a few nits below.

Acked-by: Yonghong Song <yhs@xxxxxx>

---
  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")?


Will do.

+
+    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.


Yes

+        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;


Ok

+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;".


Ok

+
+    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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