selftests/bpf: Add testcase for bpf_task_under_cgroup

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>
Link: https://lore.kernel.org/r/20230506031545.35991-3-zhoufeng.zf@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 53 insertions, 0 deletions

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);
+}