[Android] Workaround of an android platform bug.

base/android/java/src/org/chromium/base/library_loader/LibraryLoaderHelper.java

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+
+package org.chromium.base.library_loader;
+
+import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.os.Build;
+import android.util.Log;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
+
+/**
+ * The class provides helper functions to extract native libraries from APK,
+ * and load libraries from there.
+ *
+ * The class should be package-visible only, but made public for testing
+ * purpose.
+ */
+public class LibraryLoaderHelper {
+    private static final String TAG = "LibraryLoaderHelper";
+
+    private static final String LIB_DIR = "lib";
+
+    /**
+     * One-way switch becomes true if native libraries were unpacked
+     * from APK.
+     */
+    private static boolean sLibrariesWereUnpacked = false;
+
+    /**
+     * Loads native libraries using workaround only, skip the library in system
+     * lib path. The method exists only for testing purpose.
+     * Caller must ensure thread safety of this method.
+     * @param context
+     */
+    public static boolean loadNativeLibrariesUsingWorkaroundForTesting(Context context) {
+        // Although tryLoadLibraryUsingWorkaround might be called multiple times,
+        // libraries should only be unpacked once, this is guaranteed by
+        // sLibrariesWereUnpacked.
+        for (String library : NativeLibraries.LIBRARIES) {
+            if (!tryLoadLibraryUsingWorkaround(context, library)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /**
+     * Try to load a native library using a workaround of
+     *   http://b/13216167.
+     *
+     * Workaround for b/13216167 was adapted from code in
+     * https://googleplex-android-review.git.corp.google.com/#/c/433061
+     *
+     * More details about http://b/13216167:
+     *   PackageManager may fail to update shared library.
+     *
+     * Native library directory in an updated package is a symbolic link
+     * to a directory in /data/app-lib/<package name>, for example:
+     * /data/data/com.android.chrome/lib -> /data/app-lib/com.android.chrome[-1].
+     * When updating the application, the PackageManager create a new directory,
+     * e.g., /data/app-lib/com.android.chrome-2, and remove the old symlink and
+     * recreate one to the new directory. However, on some devices (e.g. Sony Xperia),
+     * the symlink was updated, but fails to extract new native libraries from
+     * the new apk.
+
+     * We make the following changes to alleviate the issue:
+     *  1) name the native library with apk version code, e.g.,
+     *     libchrome.1750.136.so, 1750.136 is Chrome version number;
+     *  2) first try to load the library using System.loadLibrary,
+     *     if that failed due to the library file was not found,
+     *     search the named library in a /data/data/com.android.chrome/app_lib
+     *     directory. Because of change 1), each version has a different native
+     *     library name, so avoid mistakenly using the old native library.
+     *
+     *  If named library is not in /data/data/com.android.chrome/app_lib directory,
+     *  extract native libraries from apk and cache in the directory.
+     *
+     * This function doesn't throw UnsatisfiedLinkError, the caller needs to
+     * check the return value.
+     */
+    static boolean tryLoadLibraryUsingWorkaround(Context context, String library) {
+        assert context != null;
+        File libFile = getWorkaroundLibFile(context, library);
+        if (!libFile.exists() && !unpackLibrariesOnce(context)) {
+            return false;
+        }
+        try {
+            System.load(libFile.getAbsolutePath());
+            return true;
+        } catch (UnsatisfiedLinkError e) {
+            return false;
+        }
+    }
+
+    /**
+     * Returns the directory for holding extracted native libraries.
+     * It may create the directory if it doesn't exist.
+     *
+     * @param context
+     * @return the directory file object
+     */
+    public static File getWorkaroundLibDir(Context context) {
+        return context.getDir(LIB_DIR, Context.MODE_PRIVATE);
+    }
+
+    private static File getWorkaroundLibFile(Context context, String library) {
+        String libName = System.mapLibraryName(library);
+        return new File(getWorkaroundLibDir(context), libName);
+    }
+
+    /**
+     * Unpack native libraries from the APK file. The method is supposed to
+     * be called only once. It deletes existing files in unpacked directory
+     * before unpacking.
+     *
+     * @param context
+     * @return true when unpacking was successful, false when failed or called
+     *         more than once.
+     */
+    private static boolean unpackLibrariesOnce(Context context) {
+        if (sLibrariesWereUnpacked) {
+            return false;
+        }
+        sLibrariesWereUnpacked = true;
+
+        File libDir = getWorkaroundLibDir(context);
+        if (libDir.exists()) {
+            assert libDir.isDirectory();
+            deleteDirectorySync(libDir);
+        }
+
+        try {
+            ApplicationInfo appInfo = context.getApplicationInfo();
+            ZipFile file = new ZipFile(new File(appInfo.sourceDir), ZipFile.OPEN_READ);
+            for (String libName : NativeLibraries.LIBRARIES) {
+                String jniNameInApk = "lib/" + Build.CPU_ABI + "/" +
+                    System.mapLibraryName(libName);
+
+                final ZipEntry entry = file.getEntry(jniNameInApk);
+                if (entry == null) {
+                    Log.e(TAG, appInfo.sourceDir + " doesn't have file " + jniNameInApk);
+                    file.close();
+                    deleteDirectorySync(libDir);
+                    return false;
+                }
+
+                File outputFile = getWorkaroundLibFile(context, libName);
+
+                Log.i(TAG, "Extracting native libraries into " + outputFile.getAbsolutePath());
+
+                assert !outputFile.exists();
+
+                try {
+                    if (!outputFile.createNewFile()) {
+                        throw new IOException();
+                    }
+
+                    InputStream is = null;
+                    FileOutputStream os = null;
+                    try {
+                        is = file.getInputStream(entry);
+                        os = new FileOutputStream(outputFile);
+                        int count = 0;
+                        byte[] buffer = new byte[16 * 1024];
+                        while ((count = is.read(buffer)) > 0) {
+                            os.write(buffer, 0, count);
+                        }
+                    } finally {
+                        try {
+                            if (is != null) is.close();
+                        } finally {
+                            if (os != null) os.close();
+                        }
+                    }
+                    // Change permission to rwxr-xr-x
+                    outputFile.setReadable(true, false);
+                    outputFile.setExecutable(true, false);
+                    outputFile.setWritable(true);
+                } catch (IOException e) {
+                    if (outputFile.exists()) {
+                        if (!outputFile.delete()) {
+                            Log.e(TAG, "Failed to delete " + outputFile.getAbsolutePath());
+                        }
+                    }
+                    file.close();
+                    throw e;
+                }
+            }
+            file.close();
+            return true;
+        } catch (IOException e) {
+            Log.e(TAG, "Failed to unpack native libraries", e);
+            deleteDirectorySync(libDir);
+            return false;
+        }
+    }
+
+    /**
+     * Delete old library files in the backup directory.
+     *  The actual deletion is done in a background thread.
+     *
+     * @param context
+     */
+    static void deleteWorkaroundLibrariesAsynchronously(Context context) {
+        // Child process should not reach here.
+        final File libDir = getWorkaroundLibDir(context);
+        if (libDir.exists()) {
+            assert libDir.isDirectory();
+            // Async deletion
+            new Thread() {
+                @Override
+                public void run() {
+                    deleteDirectorySync(libDir);
+                }
+            }.start();
+        }
+    }
+
+    /**
+     * Delete the workaround libraries and directory synchronously.
+     * For testing purpose only.
+     * @param context
+     */
+    public static void deleteWorkaroundLibrariesSynchronously(Context context) {
+        File libDir = getWorkaroundLibDir(context);
+        if (libDir.exists()) {
+            deleteDirectorySync(libDir);
+        }
+    }
+
+    private static void deleteDirectorySync(File dir) {
+        try {
+            File[] files = dir.listFiles();
+            if (files != null) {
+                for (File file : files) {
+                    String fileName = file.getName();
+                    if (!file.delete()) {
+                      Log.e(TAG, "Failed to remove " + file.getAbsolutePath());
+                    }
+                }
+            }
+            if (!dir.delete()) {
+                Log.w(TAG, "Failed to remove " + dir.getAbsolutePath());
+            }
+            return;
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to remove old libs, ", e);
+        }
+    }
+}