core/java/android/webkit/WebViewFactory.java

/*
 * Copyright (C) 2012 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 android.webkit;

import android.os.Build;
import android.os.Process;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.os.StrictMode;
import android.util.AndroidRuntimeException;
import android.util.Log;
import dalvik.system.VMRuntime;

import java.io.File;

import com.android.internal.os.Zygote;

/**
 * Top level factory, used creating all the main WebView implementation classes.
 *
 * @hide
 */
public final class WebViewFactory {

    private static final String CHROMIUM_WEBVIEW_FACTORY =
            "com.android.webview.chromium.WebViewChromiumFactoryProvider";

    private static final String NULL_WEBVIEW_FACTORY =
            "com.android.webview.nullwebview.NullWebViewFactoryProvider";

    // TODO(torne): we need to use a system property instead of hardcoding the library paths to
    // enable it to be changed when a webview update apk is installed.
    private static final String CHROMIUM_WEBVIEW_NATIVE_LIB_32 =
            "/system/lib/libwebviewchromium.so";
    private static final String CHROMIUM_WEBVIEW_NATIVE_LIB_64 =
            "/system/lib64/libwebviewchromium.so";
    private static final String CHROMIUM_WEBVIEW_NATIVE_RELRO_32 =
            "/data/misc/shared_relro/libwebviewchromium32.relro";
    private static final String CHROMIUM_WEBVIEW_NATIVE_RELRO_64 =
            "/data/misc/shared_relro/libwebviewchromium64.relro";

    private static final String LOGTAG = "WebViewFactory";

    private static final boolean DEBUG = false;

    // Cache the factory both for efficiency, and ensure any one process gets all webviews from the
    // same provider.
    private static WebViewFactoryProvider sProviderInstance;
    private static final Object sProviderLock = new Object();
    private static boolean sAddressSpaceReserved = false;

    public static String getWebViewPackageName() {
        // TODO: Make this dynamic based on resource configuration.
        return "com.android.webview";
    }

    static WebViewFactoryProvider getProvider() {
        synchronized (sProviderLock) {
            // For now the main purpose of this function (and the factory abstraction) is to keep
            // us honest and minimize usage of WebView internals when binding the proxy.
            if (sProviderInstance != null) return sProviderInstance;

            loadNativeLibrary();

            Class<WebViewFactoryProvider> providerClass;
            try {
                providerClass = getFactoryClass();
            } catch (ClassNotFoundException e) {
                Log.e(LOGTAG, "error loading provider", e);
                throw new AndroidRuntimeException(e);
            }

            StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
            try {
                sProviderInstance = providerClass.newInstance();
                if (DEBUG) Log.v(LOGTAG, "Loaded provider: " + sProviderInstance);
                return sProviderInstance;
            } catch (Exception e) {
                Log.e(LOGTAG, "error instantiating provider", e);
                throw new AndroidRuntimeException(e);
            } finally {
                StrictMode.setThreadPolicy(oldPolicy);
            }
        }
    }

    private static Class<WebViewFactoryProvider> getFactoryClass() throws ClassNotFoundException {
        try {
            return (Class<WebViewFactoryProvider>) Class.forName(CHROMIUM_WEBVIEW_FACTORY);
        } catch (ClassNotFoundException e) {
            Log.e(LOGTAG, "Chromium WebView does not exist");
            return (Class<WebViewFactoryProvider>) Class.forName(NULL_WEBVIEW_FACTORY);
        }
    }

    /**
     * Perform any WebView loading preparations that must happen in the zygote.
     * Currently, this means allocating address space to load the real JNI library later.
     */
    public static void prepareWebViewInZygote() {
        try {
            System.loadLibrary("webviewchromium_loader");
            sAddressSpaceReserved = nativeReserveAddressSpace(CHROMIUM_WEBVIEW_NATIVE_LIB_32,
                                                              CHROMIUM_WEBVIEW_NATIVE_LIB_64);
            if (sAddressSpaceReserved) {
                if (DEBUG) Log.v(LOGTAG, "address space reserved");
            } else {
                Log.e(LOGTAG, "reserving address space failed");
            }
        } catch (Throwable e) {
            // Log and discard errors at this stage as we must not crash the zygote.
            Log.e(LOGTAG, "error preparing native loader", e);
        }
    }

    /**
     * Perform any WebView loading preparations that must happen at boot from the system server,
     * after the package manager has started.
     * This must be called in the system server.
     * Currently, this means spawning the child processes which will create the relro files.
     */
    public static void prepareWebViewInSystemServer() {
        if (DEBUG) Log.v(LOGTAG, "creating relro files");
        if (new File(CHROMIUM_WEBVIEW_NATIVE_LIB_64).exists()) {
            createRelroFile(Build.SUPPORTED_64_BIT_ABIS[0]);
        }
        if (new File(CHROMIUM_WEBVIEW_NATIVE_LIB_32).exists()) {
            createRelroFile(Build.SUPPORTED_32_BIT_ABIS[0]);
        }
    }

    private static void createRelroFile(String abi) {
        try {
            Process.start("android.webkit.WebViewFactory$RelroFileCreator",
                          "WebViewLoader-" + abi,
                          Process.SHARED_RELRO_UID,
                          Process.SHARED_RELRO_UID,
                          null,
                          0,                 // TODO(torne): do we need to set debug flags?
                          Zygote.MOUNT_EXTERNAL_NONE,
                          Build.VERSION.SDK_INT,
                          null,
                          abi,
                          null);
        } catch (Throwable e) {
            // Log and discard errors as we must not crash the system server.
            Log.e(LOGTAG, "error starting relro file creator for abi " + abi, e);
        }
    }

    private static class RelroFileCreator {
        // Called in an unprivileged child process to create the relro file.
        public static void main(String[] args) {
            if (!sAddressSpaceReserved) {
                Log.e(LOGTAG, "can't create relro file; address space not reserved");
                return;
            }
            boolean result = nativeCreateRelroFile(CHROMIUM_WEBVIEW_NATIVE_LIB_32,
                                                   CHROMIUM_WEBVIEW_NATIVE_LIB_64,
                                                   CHROMIUM_WEBVIEW_NATIVE_RELRO_32,
                                                   CHROMIUM_WEBVIEW_NATIVE_RELRO_64);
            if (!result) {
                Log.e(LOGTAG, "failed to create relro file");
            } else if (DEBUG) {
                Log.v(LOGTAG, "created relro file");
            }
            try {
                getUpdateService().notifyRelroCreationCompleted(VMRuntime.getRuntime().is64Bit(),
                                                                result);
            } catch (RemoteException e) {
                Log.e(LOGTAG, "error notifying update service", e);
            }

            // Must explicitly exit or else this process will just sit around after we return.
            System.exit(0);
        }
    }

    private static void loadNativeLibrary() {
        if (!sAddressSpaceReserved) {
            Log.e(LOGTAG, "can't load with relro file; address space not reserved");
            return;
        }

        try {
            getUpdateService().waitForRelroCreationCompleted(VMRuntime.getRuntime().is64Bit());
        } catch (RemoteException e) {
            Log.e(LOGTAG, "error waiting for relro creation, proceeding without", e);
            return;
        }

        boolean result = nativeLoadWithRelroFile(CHROMIUM_WEBVIEW_NATIVE_LIB_32,
                                                 CHROMIUM_WEBVIEW_NATIVE_LIB_64,
                                                 CHROMIUM_WEBVIEW_NATIVE_RELRO_32,
                                                 CHROMIUM_WEBVIEW_NATIVE_RELRO_64);
        if (!result) {
            Log.w(LOGTAG, "failed to load with relro file, proceeding without");
        } else if (DEBUG) {
            Log.v(LOGTAG, "loaded with relro file");
        }
    }

    private static IWebViewUpdateService getUpdateService() {
        return IWebViewUpdateService.Stub.asInterface(ServiceManager.getService("webviewupdate"));
    }

    private static native boolean nativeReserveAddressSpace(String lib32, String lib64);
    private static native boolean nativeCreateRelroFile(String lib32, String lib64,
                                                        String relro32, String relro64);
    private static native boolean nativeLoadWithRelroFile(String lib32, String lib64,
                                                          String relro32, String relro64);
}