binder添加log引起的不能开机问题分析

2018-9-18  9-19

为了观察binder的生命周期，添加了log

vi frameworks/base/core/java/android/os/Binder.java

vi frameworks/base/core/jni/android_util_Binder.cpp

vi frameworks/native/libs/binder/BpBinder.cpp

 

在Binder.java中添加

    public Binder() {

        init();

Log.d(TAG, "====binder, Binder() = " + this.getClass().getName() + ", this=" + this);

 

在android_util_Binder.cpp中打开log开关

55#define DEBUG_DEATH 0

56#if DEBUG_DEATH

57#define LOGDEATH ALOGD

58#else

59#define LOGDEATH ALOGV

60#endif

 

把#define DEBUG_DEATH 0修改为

#define DEBUG_DEATH 1

 

 

但是却导致系统不能开机，加了个log就导致不能开机？

这个log有毒？

 

使用user_debug版本抓到log

--------- beginning of crash

01-01 03:51:14.218   937   937 E AndroidRuntime: *** FATAL EXCEPTION IN SYSTEM PROCESS: main

01-01 03:51:14.218   937   937 E AndroidRuntime: java.lang.RuntimeException: Failed to boot service com.android.server.wifi.scanner.WifiScanningService: onBootPhase threw an exception during phase 500

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.server.SystemServiceManager.startBootPhase(SystemServiceManager.java:174)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.server.SystemServer.startOtherServices(SystemServer.java:1738)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.server.SystemServer.run(SystemServer.java:452)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.server.SystemServer.main(SystemServer.java:313)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at java.lang.reflect.Method.invoke(Native Method)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:845)

01-01 03:51:14.218   937   937 E AndroidRuntime: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Intent.getAction()' on a null object reference

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.server.am.BroadcastRecord.toString(BroadcastRecord.java:303)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at java.lang.String.valueOf(String.java:2827)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at java.lang.StringBuilder.append(StringBuilder.java:132)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at android.os.Binder.<init>(Binder.java:363)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.server.am.BroadcastRecord.<init>(BroadcastRecord.java:231)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.server.am.ActivityManagerService.registerReceiver(ActivityManagerService.java:19471)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at android.app.ContextImpl.registerReceiverInternal(ContextImpl.java:1417)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at android.app.ContextImpl.registerReceiver(ContextImpl.java:1378)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at android.app.ContextImpl.registerReceiver(ContextImpl.java:1366)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.server.wifi.scanner.WifiScanningServiceImpl.startService(WifiScanningServiceImpl.java:310)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.server.wifi.scanner.WifiScanningService.onBootPhase(WifiScanningService.java:53)

01-01 03:51:14.218   937   937 E AndroidRuntime:   at com.android.server.SystemServiceManager.startBootPhase(SystemServiceManager.java:165)

01-01 03:51:14.218   937   937 E AndroidRuntime:   ... 6 more

 

 

原来BroadcastRecord继承于Binder

final class BroadcastRecord extends Binder {

当构造BroadcastRecord对象的时候，就调用到了这里

public Binder() {

        init();

Log.d(TAG, "====binder, Binder() = " + this.getClass().getName() + ", this=" + this);

 

但是BroadcastRecord重写了toString方法，这里的 + this会调用到toString方法

    public String toString() {

        return "BroadcastRecord{"

            + Integer.toHexString(System.identityHashCode(this))

            + " u" + userId + " " + intent.getAction() + "}";

    }

这里的intent为null，就导致了空指针异常

 

为什么+ this会调用到toString方法呢？因为String的+操作会调用到String的valueOf方法

public static String valueOf(Object obj) {

        return (obj == null) ? "null" : obj.toString();

    }

里面调用了对象的toString方法