初阶技能：Android 应用异常如何丰富线索

在我们容器虚拟化产品开发过程中，时常会遇到某些应用无法启动或运行时异常崩溃的问题；让应用行为信息丰富，则能还原应用异常发生过程，对我们快速分析问题至关重要。

在这里需要用到以下几个开源工具：

• ByteHook： github.com/bytedance/b...
• ShadowHook： github.com/bytedance/a...
• Binderceptor： www.github.com/iofomo/bind...

01. 举个栗子

我们在做应用容器时，尝尝会遇到应用进程崩溃，通过adb抓取的日志，却只有很少的几行日志，没有其他任何信息，因此通过一些简单的方式让应用行为的痕迹还原，是我们第一步要做的事情。

9402 9402 D AndroidRuntime: Shutting down VM  
9402 9402 I Process : Sending signal. PID: 9402 SIG: 9  

02. 打印退出痕迹

通过拦截native函数，打印Java层的异常退出：

import android.os;  
  
public class Process {  
  
/**  
* Returns the identifier of this process, which can be used with  
* {@link #killProcess} and {@link #sendSignal}.  
*/  
public static final native void sendSignal(int pid, int signal);  
  
/**  
* @hide  
* Private impl for avoiding a log message... DO NOT USE without doing  
* your own log, or the Android Illuminati will find you some night and  
* beat you up.  
*/  
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)  
public static final native void sendSignalQuiet(int pid, int signal);  
  
}  
  
public class Runtime {  
private static native void nativeExit(int code);  
}  

通过拦截以下函数，打印Native层的异常退出：

void exit(int status);  
int kill(pid_t pid, int sig);  

打印调用栈：

// 非 JNI 环境获取从当前线程获取 JNIEnv（AttachCurrentThread）  
void jni_thread_dump(JNIEnv* env) {  
jclass jcls = env->FindClass("java/lang/Thread");  
if (!jcls) return;  
jmethodID jm = env->GetStaticMethodID(jcls, "dumpStack", "()V");  
if (!jm) return;  
env->CallStaticVoidMethod(jcls, jm);  
env->ExceptionClear();  
}  

输出结果：

5511 5511 W System.err: java.lang.Exception: Stack trace  
5511 5511 W System.err: at java.lang.Thread.dumpStack(Thread.java:1527)  
5511 5511 W System.err: at android.os.Process.sendSignal(Native Method)  
5511 5511 W System.err: at android.os.Process.killProcess(Process.java:1295)  
5511 5511 W System.err: at com.android.internal.os.RuntimeInit$KillApplicationHandler.uncaughtException(RuntimeInit.java:207)  
5511 5511 W System.err: at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:1073)  
5511 5511 W System.err: at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:1068)  
5511 5511 W System.err: at java.lang.Thread.dispatchUncaughtException(Thread.java:2211)  

03. 追踪Throwable异常调用栈

在我们常用的try ... catch语句中，异常时打印调用栈是常规操作，在这里可以拦截并打印栈日志信息。

import java.lang;  
  
public class Throwable implements Serializable {  
  
private static native StackTraceElement[] nativeGetStackTrace(Object stackState);  
  
private static native Object nativeFillInStackTrace();  
  
}  

04. 打印VM异常调用栈

package dalvik.system;  
  
/**  
* Provides a limited interface to the Dalvik VM stack. This class is mostly  
* used for implementing security checks.  
*/  
public final class VMStack {  
/**  
* Retrieves the stack trace from the specified thread.  
*  
* @param t  
* thread of interest  
* @return an array of stack trace elements, or null if the thread  
* doesn't have a stack trace (e.g. because it exited)  
*/  
native public static StackTraceElement[] getThreadStackTrace(Thread t);  
  
/**  
* Retrieves an annotated stack trace from the specified thread.  
*  
* @param t  
* thread of interest  
* @return an array of annotated stack frames, or null if the thread  
* doesn't have a stack trace (e.g. because it exited)  
*/  
native public static AnnotatedStackTraceElement[] getAnnotatedThreadStackTrace(Thread t);  
  
/**  
* Retrieves a partial stack trace from the specified thread into  
* the provided array.  
*  
* @param t  
* thread of interest  
* @param stackTraceElements  
* preallocated array for use when only the top of stack is  
* desired. Unused elements will be filled with null values.  
* @return the number of elements filled  
*/  
native public static int fillStackTraceElements(Thread t, StackTraceElement[] stackTraceElements);  
}  

输出：

9402 9402 W stack : android.app.LoadedApk.makeApplication(LoadedApk.java:1554)  
9402 9402 W stack : android.app.ActivityThread.handleBindApplication(ActivityThread.java:8522)  
9402 9402 W stack : android.app.ActivityThread.access$2800(ActivityThread.java:311)  
9402 9402 W stack : android.app.ActivityThread$H.handleMessage(ActivityThread.java:2889)  
9402 9402 W stack : android.os.Handler.dispatchMessage(Handler.java:117)  
9402 9402 W stack : android.os.Looper.loopOnce(Looper.java:205)  
9402 9402 W stack : android.os.Looper.loop(Looper.java:293)  
9402 9402 W stack : android.app.ActivityThread.loopProcess(ActivityThread.java:9934)  
9402 9402 W stack : android.app.ActivityThread.main(ActivityThread.java:9923)  
9402 9402 W stack : java.lang.reflect.Method.invoke(Native Method)  
9402 9402 W stack : com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:586)  
9402 9402 W stack : com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1240)  
9402 9402 W stack : ohos.abilityshell.HarmonyLoader.tryLoadHarmony(HarmonyLoader.java:130)  
9402 9402 W stack : ohos.abilityshell.HarmonyApplication.tryLoadHarmony(HarmonyApplication.java:673)  
9402 9402 W stack : ohos.abilityshell.HarmonyApplication.attachBaseContext(HarmonyApplication.java:168)  
9402 9402 W stack : com.demo.app.DemoApp.attachBaseContext(SourceFile:1)  
9402 9402 W stack : android.app.Application.attach(Application.java:338)  
9402 9402 W stack : android.app.Instrumentation.newApplication(Instrumentation.java:1191)  
9402 9402 W stack : android.app.LoadedApk.makeApplication(LoadedApk.java:1546)  
9402 9402 W stack : android.app.ActivityThread.handleBindApplication(ActivityThread.java:8522)  
9402 9402 W stack : android.app.ActivityThread.access$2800(ActivityThread.java:311)  
9402 9402 W stack : android.app.ActivityThread$H.handleMessage(ActivityThread.java:2889)  
9402 9402 W stack : android.os.Handler.dispatchMessage(Handler.java:117)  
9402 9402 W stack : android.os.Looper.loopOnce(Looper.java:205)  
9402 9402 W stack : android.os.Looper.loop(Looper.java:293)  
9402 9402 W stack : android.app.ActivityThread.loopProcess(ActivityThread.java:9934)  
9402 9402 W stack : android.app.ActivityThread.main(ActivityThread.java:9923)  
9402 9402 W stack : java.lang.reflect.Method.invoke(Native Method)  
9402 9402 W stack : com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:586)  
9402 9402 W stack : com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1240)  

05. 打印异常信息

Android框架默认会为每个应用进程设置一个全局的异常Handler，我们可以替换掉输出打印更多内容。在这里要考虑应用自身也会设置的情况。

Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {  
@Override  
public void uncaughtException(Thread t, Throwable e) {  
// TODO  
}  
});  

06. 打印异常传送

Android在AMS服务中增加了一个应用向服务提交异常的接口，我们通过android.reflect.Proxy方式代理IActivityManager的实例，打印输出。

package android.app;  
  
// @source code: /frameworks/base/core/java/android/app/IActivityManager.aidl  
interface IActivityManager {  
void handleApplicationCrash(IBinder app, ApplicationErrorReport.ParcelableCrashInfo crashInfo);  
}  
  
// @source code: /frameworks/base/core/java/android/app/ApplicationErrorReport.java  
public class ApplicationErrorReport implements Parcelable {  
public static class CrashInfo {  
/**  
* Dump a CrashInfo instance to a Printer.  
*/  
public void dump(Printer pw, String prefix) {  
pw.println(prefix + "exceptionHandlerClassName: " + exceptionHandlerClassName);  
pw.println(prefix + "exceptionClassName: " + exceptionClassName);  
pw.println(prefix + "exceptionMessage: " + exceptionMessage);  
pw.println(prefix + "throwFileName: " + throwFileName);  
pw.println(prefix + "throwClassName: " + throwClassName);  
pw.println(prefix + "throwMethodName: " + throwMethodName);  
pw.println(prefix + "throwLineNumber: " + throwLineNumber);  
pw.println(prefix + "stackTrace: " + stackTrace);  
}  
}  
public static class ParcelableCrashInfo extends CrashInfo implements Parcelable {  
  
}  
}  

如输出结果为：

9402 9402 W Crash : exceptionClassName: java.lang.IllegalStateException  
9402 9402 W Crash : exceptionMessage: failed to attach Application, errorCode=30, errorInfo=bms service error, code is 8519969. 8519797  
9402 9402 W Crash : throwFileName: HarmonyLoader.java  
9402 9402 W Crash : throwClassName: ohos.abilityshell.HarmonyLoader  
9402 9402 W Crash : throwMethodName: tryLoadHarmony  
9402 9402 W Crash : throwLineNumber: 130  
9402 9402 W Crash : stackTrace: java.lang.RuntimeException: Unable to instantiate application com.demo.app.DemoApp package com.demo.app: java.lang.IllegalStateException: failed to attach Application, errorCode=30, errorInfo=bms service error, code is 8519969.  
9402 9402 W Crash : at android.app.LoadedApk.makeApplication(LoadedApk.java:1554)  
9402 9402 W Crash : at android.app.ActivityThread.handleBindApplication(ActivityThread.java:8522)  
9402 9402 W Crash : at android.app.ActivityThread.access$2800(ActivityThread.java:311)  
9402 9402 W Crash : at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2889)  
9402 9402 W Crash : at android.os.Handler.dispatchMessage(Handler.java:117)  
9402 9402 W Crash : at android.os.Looper.loopOnce(Looper.java:205)  
9402 9402 W Crash : at android.os.Looper.loop(Looper.java:293)  
9402 9402 W Crash : at android.app.ActivityThread.loopProcess(ActivityThread.java:9934)  
9402 9402 W Crash : at android.app.ActivityThread.main(ActivityThread.java:9923)  
9402 9402 W Crash : at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:586)  
9402 9402 W Crash : at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1240)  
9402 9402 W Crash : Caused by: java.lang.IllegalStateException: fail  

07. 打印Binder通信信息

可以打印应用访问了那些系统服务。可以通过Binderceptor项目来完成。

9402 9402 W Trace : Binder::tgt: 0x3887b52, 3, : android.content.pm.IPackageManager  
9402 9402 W Trace : Binder::tgt: 0xe45f2c2, 2, : android.os.IServiceManager  
9402 9402 W Trace : Binder::tgt: 0x76c2822, 56, : com.huawei.android.view.IHwWindowManager  
9402 9417 W Trace : Binder::tgt: 0x3887b52, 20, : android.content.pm.IPackageManager  
9402 9402 W Trace : Binder::tgt: 0x7db76a2, 30, : android.net.IConnectivityManager  
9402 9402 W Trace : Binder::tgt: 0x3887b52, 20, : android.content.pm.IPackageManager  
9402 9402 W Trace : Binder::tgt: 0x3887b52, 9, : android.content.pm.IPackageManager  
9402 9402 W Trace : Binder::tgt: 0x3887b52, 95, : android.content.pm.IPackageManager  
9402 9402 W Trace : Binder::tgt: 0x3887b52, 3, : android.content.pm.IPackageManager  
......  

binder code与aidl接口函数的对应关系：

public static void printStub(String clsName) {  
android.util.Log.w(TAG, ">>>>>> " + clsName);  
try {  
Class<?> nmClassStub = Class.findClass(clsName + "$Stub");  
Method[] mm = nmClassStub.getMethods();  
  
ArrayList<TRANSACTION_Item> list = new ArrayList<TRANSACTION_Item>();  
for (Method m : mm) {  
if (TextUtils.equals(m.getName(), "asBinder")) continue;  
try {  
funcName = m.toGenericString();  
funcName = funcName.replace("abstract ", "");  
funcName = funcName.replace(clsName + ".", "");  
  
fieldName = "TRANSACTION_" + m.getName();  
Field f = nmClassStub.getDeclaredField(fieldName);  
f.setAccessible(true);  
int val = f.getInt(null);  
// android.util.Log.w(TAG, fieldName + " " + val);  
list.add(new TRANSACTION_Item(val, funcName, fieldName));  
} catch (Exception e) {  
android.util.Log.e(TAG, e.toString());  
}  
}  
Collections.sort(list, new TRANSACTION_Comparator());  
} catch (Exception e) {  
android.util.Log.e(TAG, e.toString());  
}  
android.util.Log.w(TAG, "<<<<<< " + clsName);  
}  

排序后可以得到输出的结果：

package android.content.pm;  
  
interface IPackageManager {  
public void checkPackageStartable(java.lang.String,int) throws android.os.RemoteException;// 1  
public boolean isPackageAvailable(java.lang.String,int) throws android.os.RemoteException;// 2  
public android.content.pm.PackageInfo getPackageInfo(java.lang.String,int,int) throws android.os.RemoteException;// 3  
public android.content.pm.PackageInfo getPackageInfoVersioned(android.content.pm.VersionedPackage,int,int) throws android.os.RemoteException;// 4  
}  

08. 打印JNI调用轨迹

通过拦截JNIEnv层提供调用Java层方法的函数，打印调用信息。

env->FindClass(...);  
env->GetMethodID(...);  
env->GetStaticMethodID(...);  
env->RegisterNatives(...);  

09. 打印访问文件行为

通过拦截open系列函数（为什么是系列，因为libc.so经过多年迭代，衍生出来很多函数，所以说Android的兼容性让广大开发者开发Demo容易，做稳定则难上加难），打印文件访问记录。

int open(const char *fileName, int flags, ...);  
int open2(const char *fileName, int flags, ...);  
int _open(const char *fileName, int flags, ...);  
int openat(int dirfd, const char *fileName, int flags, ...);  
int _openat(int dirfd, const char *fileName, int flags, ...);  
...  

至此，通过以上基本的方法，可以快速的增加应用运行轨迹信息。

若还不够，则需要针对应用内部调试，动态库加载的进阶方法深一步剖析，后面会给大家整理进阶技能。