Add library to use OverlayFS to make read-only partitions writable. am: f198453ca8 am: f131819dfc

Original change: https://googleplex-android-review.googlesource.com/c/platform/platform_testing/+/16740299

Change-Id: I74dbfc24d1fb5b159ed44e763374884eff2e84bf

1 files changed, 94 insertions, 0 deletions

diff --git a/libraries/sts-common-util/host-side/src/com/android/sts/common/OverlayFsUtils.java b/libraries/sts-common-util/host-side/src/com/android/sts/common/OverlayFsUtils.java
new file mode 100644
index 000000000..f523fb7a4
--- /dev/null
+++ b/libraries/sts-common-util/host-side/src/com/android/sts/common/OverlayFsUtils.java
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.sts.common;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.regex.Pattern;
+import java.util.regex.Matcher;
+
+import com.android.tradefed.device.ITestDevice;
+import com.android.tradefed.device.DeviceNotAvailableException;
+import com.android.tradefed.util.CommandResult;
+import com.android.tradefed.util.CommandStatus;
+
+public class OverlayFsUtils {
+    // output of `stat`, e.g. "root shell 755 u:object_r:vendor_file:s0"
+    static final Pattern PERM_PATTERN =
+            Pattern.compile(
+                    "^(?<user>[a-zA-Z0-9_-]+) (?<group>[a-zA-Z0-9_-]+) (?<perm>[0-7]+)"
+                            + " (?<secontext>.*)$");
+
+    /**
+     * Mounts an OverlayFS dir over the top most common dir in the list.
+     *
+     * <p>The directory should be writable after this returns successfully. To cleanup, reboot the
+     * device as unfortunately unmounting overlayfs is complicated.
+     *
+     * @param device The test device to setup overlayfs for.
+     * @param dir The directory to make writable. Directories with single quotes are not supported.
+     */
+    public static void makeWritable(ITestDevice device, String dir)
+            throws DeviceNotAvailableException, IOException {
+        // TODO(duytruong): This should ideally be made into a TestRule that also handles cleanups
+        // However, test devices initiation is done in one of the @Before, after a rule's setup.
+        assertTrue("Can't acquire root for " + device.getSerialNumber(), device.enableAdbRoot());
+
+        String statOut = runAndCheck(device, "stat -c '%U %G %a %C' '" + dir + "'");
+        Matcher m = PERM_PATTERN.matcher(statOut);
+        assertTrue("Bad stats output: " + statOut, m.find());
+        String user = m.group("user");
+        String group = m.group("group");
+        String unixPerm = m.group("perm");
+        String seContext = m.group("secontext");
+
+        Path tempdir = Paths.get("/mnt", "stsoverlayfs", dir);
+        String upperdir = tempdir.resolve("upper").toString();
+        String workdir = tempdir.resolve("workdir").toString();
+
+        runAndCheck(device, String.format("mkdir -p '%s' '%s'", upperdir, workdir));
+        runAndCheck(device, String.format("chown %s:%s '%s'", user, group, upperdir));
+        runAndCheck(device, String.format("chcon '%s' '%s'", seContext, upperdir));
+        runAndCheck(device, String.format("chmod %s '%s'", unixPerm, upperdir));
+
+        String mountCmd =
+                String.format(
+                        "mount -t overlay overlay -o lowerdir='%s',upperdir='%s',workdir='%s' '%s'",
+                        dir, upperdir, workdir, dir);
+        runAndCheck(device, mountCmd);
+    }
+
+    /**
+     * Execute shell command on device, throws AssumptionViolatedException upon failure.
+     *
+     * @return stdout.
+     */
+    private static String runAndCheck(ITestDevice device, String cmd)
+            throws DeviceNotAvailableException {
+        CommandResult res = device.executeShellV2Command(cmd);
+        String failMsg =
+                String.format(
+                        "cmd failed: %s\ncode: %s\nstdout:\n%s\nstderr:\n%s",
+                        cmd, res.getExitCode(), res.getStdout(), res.getStderr());
+        assertEquals(failMsg, res.getStatus(), CommandStatus.SUCCESS);
+        return res.getStdout();
+    }
+}