android 9 如何讓 runtime.exec 執行

System.err: java.io.IOException: Cannot run program "su": error=13, Permission denied


1: android/system/core/libcutils/fs_config.cpp
改為
{ 04755, AID_ROOT,      AID_SHELL,     0, "system/xbin/su" },

2:  android selinux
    (1)透過adb:
             adb connect 192.168.1.13
             adb root
             adb shell setenforce 0
             adb shell getenforce
   (2)透過console:
            setenforce 0
            getenforce
   (3)source code:
            https://source.android.com/security/selinux/implement
            由上面網址中, 可以看出設定
            BOARD_KERNEL_CMDLINE := androidboot.selinux=permissive
            但是我在kernel找不到BOARD_KERNEL_CMDLINE?

             system/core/init/Android.mk
             -DALLOW_PERMISSIVE_SELINUX=1
         




         
import java.io.*;

Runtime runtime = Runtime.getRuntime();
try {
Process localProcess = runtime.exec("su");
OutputStream localOutputStream = localProcess.getOutputStream();
DataOutputStream localDataOutputStream = new DataOutputStream(localOutputStream);
localDataOutputStream.writeBytes("/vendor/bin/hostapd_cli status");
localDataOutputStream.flush();
} catch (IOException e) {
e.printStackTrace();
}