selftests/bpf: Add bpf_get_task_cmdline test case

Create a task, call bpf_get_task_cmdline to retrieve
the cmdline, and check if it succeeds.

Signed-off-by: Tao Chen <[email protected]>

Author: Tao Chen

tools/testing/selftests/bpf/prog_tests/task_kfunc.c

@@ -156,6 +156,10 @@ static const char * const vpid_success_tests[] = {
 	"test_task_from_vpid_invalid",
 };
 
+static const char * const cmdline_success_tests[] = {
+	"test_get_task_cmdline",
+};
+
 void test_task_kfunc(void)
 {
 	int i;
@@ -174,5 +178,12 @@ void test_task_kfunc(void)
 		run_vpid_success_test(vpid_success_tests[i]);
 	}
 
+	for (i = 0; i < ARRAY_SIZE(cmdline_success_tests); i++) {
+		if (!test__start_subtest(cmdline_success_tests[i]))
+			continue;
+
+		run_success_test(cmdline_success_tests[i]);
+	}
+
 	RUN_TESTS(task_kfunc_failure);
 }

tools/testing/selftests/bpf/progs/task_kfunc_success.c

@@ -367,6 +367,19 @@ int BPF_PROG(task_kfunc_acquire_trusted_walked, struct task_struct *task, u64 cl
 	return 0;
 }
 
+SEC("lsm.s/task_alloc")
+int BPF_PROG(test_get_task_cmdline, struct task_struct *task)
+{
+	char buf[64];
+	int ret;
+
+	ret = bpf_get_task_cmdline(task, buf, sizeof(buf));
+	if (ret < 0)
+		err = 1;
+
+	return 0;
+}
+
 SEC("syscall")
 int test_task_from_vpid_current(const void *ctx)
 {