发表Android10 分钟读完 (大约1485个字)

Android Tinker源码分析(三):加载dex补丁流程

本系列 Tinker 源码解析基于 Tinker v1.9.12

加载dex补丁流程

TinkerDexLoader.loadTinkerJars

判断一下 dexList 和 classLoader

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if (loadDexList.isEmpty() && classNDexInfo.isEmpty()) {
    Log.w(TAG, "there is no dex to load");
    return true;
}

PathClassLoader classLoader = (PathClassLoader) TinkerDexLoader.class.getClassLoader();
if (classLoader != null) {
    Log.i(TAG, "classloader: " + classLoader.toString());
} else {
    Log.e(TAG, "classloader is null");
    ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_CLASSLOADER_NULL);
    return false;
}

如果 TinkerLoadVerifyFlag 为 true 的话，会对每个 dex 进行 md5 校验

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String dexPath = directory + "/" + DEX_PATH + "/";

ArrayList<File> legalFiles = new ArrayList<>();

for (ShareDexDiffPatchInfo info : loadDexList) {
    //for dalvik, ignore art support dex
    // 对于 dalvik 虚拟机，忽略 art support dex
    if (isJustArtSupportDex(info)) {
        continue;
    }

    String path = dexPath + info.realName;
    File file = new File(path);

    if (application.isTinkerLoadVerifyFlag()) {
        long start = System.currentTimeMillis();
        String checkMd5 = getInfoMd5(info);
        // 校验dex文件的 md5 值
        if (!SharePatchFileUtil.verifyDexFileMd5(file, checkMd5)) {
            //it is good to delete the mismatch file
            ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_MD5_MISMATCH);
            intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_MISMATCH_DEX_PATH,
                file.getAbsolutePath());
            return false;
        }
        Log.i(TAG, "verify dex file:" + file.getPath() + " md5, use time: " + (System.currentTimeMillis() - start));
    }
    // dex文件都通过的话，加入到 legalFiles 集合中 
    legalFiles.add(file);
}

如果是 art 虚拟机并且是 Android N 及以上的环境，会另外加上 tinker_classN.apk

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// verify merge classN.apk
if (isVmArt && !classNDexInfo.isEmpty()) {
    File classNFile = new File(dexPath + ShareConstants.CLASS_N_APK_NAME);
    long start = System.currentTimeMillis();

    if (application.isTinkerLoadVerifyFlag()) {
        for (ShareDexDiffPatchInfo info : classNDexInfo) {
            if (!SharePatchFileUtil.verifyDexFileMd5(classNFile, info.rawName, info.destMd5InArt)) {
                ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_MD5_MISMATCH);
                intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_MISMATCH_DEX_PATH,
                    classNFile.getAbsolutePath());
                return false;
            }
        }
    }
    Log.i(TAG, "verify dex file:" + classNFile.getPath() + " md5, use time: " + (System.currentTimeMillis() - start));

    legalFiles.add(classNFile);
}

如果用户是ART虚拟机并且做了OTA升级，那么在加载dex补丁的时候就会先把最近一次的补丁全部DexFile.loadDex一遍.这么做的原因是有些场景做了OTA后,oat的规则可能发生变化,在这种情况下去加载上个系统版本oat过的dex就会出现问题.

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File optimizeDir = new File(directory + "/" + oatDir);

        if (isSystemOTA) {
            final boolean[] parallelOTAResult = {true};
            final Throwable[] parallelOTAThrowable = new Throwable[1];
            String targetISA;
            try {
                targetISA = ShareTinkerInternals.getCurrentInstructionSet();
            } catch (Throwable throwable) {
                Log.i(TAG, "getCurrentInstructionSet fail:" + throwable);
//                try {
//                    targetISA = ShareOatUtil.getOatFileInstructionSet(testOptDexFile);
//                } catch (Throwable throwable) {
                // don't ota on the front
                deleteOutOfDateOATFile(directory);

                intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_INTERPRET_EXCEPTION, throwable);
                ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_GET_OTA_INSTRUCTION_SET_EXCEPTION);
                return false;
//                }
            }

            deleteOutOfDateOATFile(directory);

            Log.w(TAG, "systemOTA, try parallel oat dexes, targetISA:" + targetISA);
            // change dir
            optimizeDir = new File(directory + "/" + INTERPRET_DEX_OPTIMIZE_PATH);

            // 对 dex 文件作 odex 处理
            TinkerDexOptimizer.optimizeAll(
                legalFiles, optimizeDir, true, targetISA,
                new TinkerDexOptimizer.ResultCallback() {
                    long start;

                    @Override
                    public void onStart(File dexFile, File optimizedDir) {
                        start = System.currentTimeMillis();
                        Log.i(TAG, "start to optimize dex:" + dexFile.getPath());
                    }

                    @Override
                    public void onSuccess(File dexFile, File optimizedDir, File optimizedFile) {
                        // Do nothing.
                        Log.i(TAG, "success to optimize dex " + dexFile.getPath() + ", use time " + (System.currentTimeMillis() - start));
                    }

                    @Override
                    public void onFailed(File dexFile, File optimizedDir, Throwable thr) {
                        parallelOTAResult[0] = false;
                        parallelOTAThrowable[0] = thr;
                        Log.i(TAG, "fail to optimize dex " + dexFile.getPath() + ", use time " + (System.currentTimeMillis() - start));
                    }
                }
            );


            if (!parallelOTAResult[0]) {
                Log.e(TAG, "parallel oat dexes failed");
                intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_INTERPRET_EXCEPTION, parallelOTAThrowable[0]);
                ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_OTA_INTERPRET_ONLY_EXCEPTION);
                return false;
            }
        }

加载dex

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try {
       SystemClassLoaderAdder.installDexes(application, classLoader, optimizeDir, legalFiles);
   } catch (Throwable e) {
       Log.e(TAG, "install dexes failed");
//            e.printStackTrace();
       intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_EXCEPTION, e);
       ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_LOAD_EXCEPTION);
       return false;
   }
	
   return true;

SystemClassLoaderAdder.installDexes

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public static void installDexes(Application application, PathClassLoader loader, File dexOptDir, List<File> files)
    throws Throwable {
    Log.i(TAG, "installDexes dexOptDir: " + dexOptDir.getAbsolutePath() + ", dex size:" + files.size());

    if (!files.isEmpty()) {
        files = createSortedAdditionalPathEntries(files);
        ClassLoader classLoader = loader;
        if (Build.VERSION.SDK_INT >= 24 && !checkIsProtectedApp(files)) {
            classLoader = AndroidNClassLoader.inject(loader, application);
        }
        //because in dalvik, if inner class is not the same classloader with it wrapper class.
        //it won't fail at dex2opt
        if (Build.VERSION.SDK_INT >= 23) {
            V23.install(classLoader, files, dexOptDir);
        } else if (Build.VERSION.SDK_INT >= 19) {
            V19.install(classLoader, files, dexOptDir);
        } else if (Build.VERSION.SDK_INT >= 14) {
            V14.install(classLoader, files, dexOptDir);
        } else {
            V4.install(classLoader, files, dexOptDir);
        }
        //install done
        sPatchDexCount = files.size();
        Log.i(TAG, "after loaded classloader: " + classLoader + ", dex size:" + sPatchDexCount);

        if (!checkDexInstall(classLoader)) {
            //reset patch dex
            SystemClassLoaderAdder.uninstallPatchDex(classLoader);
            throw new TinkerRuntimeException(ShareConstants.CHECK_DEX_INSTALL_FAIL);
        }
    }
}

可以看到，在加载 dex 的时候，分别分成了四个版本：

  • v4
  • v14
  • v19
  • v23

其中如果是 SDK 24 及以上，需要改造一下 classloder

针对每个版本不同的源码，进行 dex 插入

我们就来看其中一个版本 v19

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private static final class V19 {

    private static void install(ClassLoader loader, List<File> additionalClassPathEntries,
                                File optimizedDirectory)
        throws IllegalArgumentException, IllegalAccessException,
        NoSuchFieldException, InvocationTargetException, NoSuchMethodException, IOException {
        /* The patched class loader is expected to be a descendant of
         * dalvik.system.BaseDexClassLoader. We modify its
         * dalvik.system.DexPathList pathList field to append additional DEX
         * file entries.
         */
        Field pathListField = ShareReflectUtil.findField(loader, "pathList");
        Object dexPathList = pathListField.get(loader);
        ArrayList<IOException> suppressedExceptions = new ArrayList<IOException>();
        ShareReflectUtil.expandFieldArray(dexPathList, "dexElements", makeDexElements(dexPathList,
            new ArrayList<File>(additionalClassPathEntries), optimizedDirectory,
            suppressedExceptions));
        if (suppressedExceptions.size() > 0) {
            for (IOException e : suppressedExceptions) {
                Log.w(TAG, "Exception in makeDexElement", e);
                throw e;
            }
        }
    }

    /**
     * A wrapper around
     * {@code private static final dalvik.system.DexPathList#makeDexElements}.
     */
    private static Object[] makeDexElements(
        Object dexPathList, ArrayList<File> files, File optimizedDirectory,
        ArrayList<IOException> suppressedExceptions)
        throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {

        Method makeDexElements = null;
        try {
            makeDexElements = ShareReflectUtil.findMethod(dexPathList, "makeDexElements", ArrayList.class, File.class,
                ArrayList.class);
        } catch (NoSuchMethodException e) {
            Log.e(TAG, "NoSuchMethodException: makeDexElements(ArrayList,File,ArrayList) failure");
            // 对不同的 rom 做兼容，有的 rom 的 makeDexElements 方法参数类型是 List
            try {
                makeDexElements = ShareReflectUtil.findMethod(dexPathList, "makeDexElements", List.class, File.class, List.class);
            } catch (NoSuchMethodException e1) {
                Log.e(TAG, "NoSuchMethodException: makeDexElements(List,File,List) failure");
                throw e1;
            }
        }

        return (Object[]) makeDexElements.invoke(dexPathList, files, optimizedDirectory, suppressedExceptions);
    }
}

首先反射拿到反射得到 PathClassLoader 中的 pathList 对象,再将补丁文件通过反射调用makeDexElements 得到补丁文件的 Element[] ,再将补丁包的 Element[] 数组插入到 dexElements 中

另外，需要对 Android 7.0 及以上单独处理一下，具体看 Android N混合编译与对热补丁影响解析

加载补丁操作做好之后，最后还要检查一下，如果没加载成功就会执行卸载：

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if (!checkDexInstall(classLoader)) {
    //reset patch dex
    SystemClassLoaderAdder.uninstallPatchDex(classLoader);
    throw new TinkerRuntimeException(ShareConstants.CHECK_DEX_INSTALL_FAIL);
}

具体验证补丁是否加载成功的方法就是判断 TinkerTestDexLoad.isPatch 的值。

在没有补丁加载的情况下都是返回 false 的, 在补丁中修改 isPatch 属性为 true 。所以只要反射拿到isPatch 的属性为 true 就说明补丁已经成功加载进来了。否则就调用 SystemClassLoaderAdder.uninstallPatchDex 执行卸载

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public static void uninstallPatchDex(ClassLoader classLoader) throws Throwable {
    if (sPatchDexCount <= 0) {
        return;
    }
    if (Build.VERSION.SDK_INT >= 14) {
        Field pathListField = ShareReflectUtil.findField(classLoader, "pathList");
        Object dexPathList = pathListField.get(classLoader);
        ShareReflectUtil.reduceFieldArray(dexPathList, "dexElements", sPatchDexCount);
    } else {
        ShareReflectUtil.reduceFieldArray(classLoader, "mPaths", sPatchDexCount);
        ShareReflectUtil.reduceFieldArray(classLoader, "mFiles", sPatchDexCount);
        ShareReflectUtil.reduceFieldArray(classLoader, "mZips", sPatchDexCount);
        try {
            ShareReflectUtil.reduceFieldArray(classLoader, "mDexs", sPatchDexCount);
        } catch (Exception e) {
        }
    }
}

卸载补丁可以说是加载补丁的逆向操作，具体操作可以分成 v4 和 v14 两个版本

具体的内容就是把 dexElements 中的头部 element 去除了。

到这，dex 补丁加载的流程结束了。

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