am c1398d50: am 8e99dfe1: am a1f6b095: FileSystemPermissionTest: assert /system mounted RO

* commit 'c1398d50':
  FileSystemPermissionTest: assert /system mounted RO

tests/tests/permission/src/android/permission/cts/FileSystemPermissionTest.java

@@ -23,10 +23,12 @@ import android.test.AndroidTestCase;
 import android.test.suitebuilder.annotation.MediumTest;
 import android.test.suitebuilder.annotation.LargeTest;
 
+import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileFilter;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
+import java.io.FileReader;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.HashSet;
@@ -583,6 +585,34 @@ public class FileSystemPermissionTest extends AndroidTestCase {
         return retval;
     }
 
+    /**
+     * Scan through /proc/self/mounts, looking for the /system line. If the line
+     * has "ro" in the 4th column, then we know the filesystem is mounted read-only.
+     */
+    public void testSystemMountedRO() throws IOException {
+        BufferedReader br = new BufferedReader(new FileReader("/proc/self/mounts"));
+        String line;
+        boolean foundSystem = false;
+        while((line = br.readLine()) != null) {
+            String[] fields = line.split(" ");
+            String mountPoint = fields[1];
+            if ("/system".equals(mountPoint)) {
+                foundSystem = true;
+                String all_options = fields[3];
+                boolean foundRo = false;
+                String[] options = all_options.split(",");
+                for (String option : options) {
+                    if ("ro".equals(option)) {
+                        foundRo = true;
+                        break;
+                    }
+                }
+                assertTrue(mountPoint + " is not mounted read-only", foundRo);
+            }
+        }
+        assertTrue("Cannot find /system partition", foundSystem);
+    }
+
     public void testAllBlockDevicesAreSecure() throws Exception {
         Set<File> insecure = getAllInsecureBlockDevicesInDirAndSubdir(new File("/dev"));
         assertTrue("Found insecure: " + insecure.toString(),