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分类: Android平台

2016-11-18 14:38:46

朴英敏,小米MIUI部门。从事嵌入式开发和调试工作8年多,擅长逆向分析方法,主要负责解决安卓系统稳定性问题。

实施hook

我们有了hook,但目前还不知道是哪个so中释放了functor

如果无法确定是哪个so,可以多hook几个so就行了。

当然对于特定的例子,也有技巧来确定so,比如我们这个例子:

被析构的对象是Functor类的对象,由于它的vtbl地址我们能够从log中获取到,

vtbl一般指向定义了该类的so中,所以用vtbl(0×73648de0)map表中找,就能确定是哪个so了。

...

  73635000-73646000 rw-p 00000000 00:00 0

  73646000-73648000 r-xp 00000000 b3:18 1287       /system/lib/libwebviewchromium_plat_support.so

=>73648000-73649000 r--p 00001000 b3:18 1287       /system/lib/libwebviewchromium_plat_support.so

  73649000-7364a000 rw-p 00002000 b3:18 1287       /system/lib/libwebviewchromium_plat_support.so

  7364a000-73684000 rw-p 00000000 00:00 0

  73684000-73696000 r-xp 00000000 b3:18 1034       /system/lib/libjavacrypto.so

  73696000-73697000 r--p 00011000 b3:18 1034       /system/lib/libjavacrypto.so

  73697000-73698000 rw-p 00012000 b3:18 1034       /system/lib/libjavacrypto.so

  ...

而需要注意的是,C++对象的释放是delete函数,

libwebviewchromium_plat_support.so不会直接调用libcfree函数,而是调用libc++.so中的delete函数,再由delete函数调用free函数,

所以我们得hook libc++.sofree函数,但打印调用栈的模块也依赖libc++.so,所以如果在hook函数中打印调用栈,也会遇到死循环问题。

所以我们得hook libwebviewchromium_plat_support.so中的delete函数,这样既减少log量,也能避免死循环。

 

先确认libwebviewchromium_plat_support.so是否依赖了delete函数:

 

$ readelf -s libwebviewchromium_plat_support.so |grep UND

     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND

     1: 00000000     0 FUNC    GLOBAL DEFAULT  UND __cxa_finalize

     2: 00000000     0 FUNC    GLOBAL DEFAULT  UND __cxa_atexit

     4: 00000000     0 FUNC    GLOBAL DEFAULT  UND __aeabi_unwind_cpp_pr0

     5: 00000000     0 FUNC    GLOBAL DEFAULT  UND __aeabi_unwind_cpp_pr1

     6: 00000000     0 FUNC    GLOBAL DEFAULT  UND getrlimit

     7: 00000000     0 FUNC    GLOBAL DEFAULT  UND setrlimit

     8: 00000000     0 FUNC    GLOBAL DEFAULT  UND __errno

     9: 00000000     0 FUNC    GLOBAL DEFAULT  UND strerror

    10: 00000000     0 FUNC    GLOBAL DEFAULT  UND __android_log_print

=>  11: 00000000     0 FUNC    GLOBAL DEFAULT  UND _Znwj

=>  12: 00000000     0 FUNC    GLOBAL DEFAULT  UND _ZdlPv

    14: 00000000     0 FUNC    GLOBAL DEFAULT  UND __android_log_assert

    ...

    51: 00000000     0 FUNC    GLOBAL DEFAULT  UND __aeabi_llsr

    52: 00000000     0 OBJECT  GLOBAL DEFAULT  UND __popcount_tab

其中11_Znwjnew的符号,_ZdlPvdelete的符号。

接下来就用工具hook libwebviewchromium_plat_support.sodelete函数:

 

extern void _ZdlPv(void *);

void inject__ZdlPv(void* ptr) {

    LOGD("delete %p",ptr);

    dumpNativeStack();

    dumpJavaStack();

    _ZdlPv(ptr);

}

hook后复现问题,抓到的log如下:

 

10-27 21:19:52.961  8027  8027 D ObserverLayout: onStop: clz=com.miui.player.display.view.DisplayFragmentLayout{45665838 V.E..... ........ 0,0-1080,1920 #7f080039 app:id/content}

10-27 21:19:52.965  8027  8027 I MusicBaseFragment: onDestroyView  the view is still attached, delay destroy

10-27 21:19:52.966  8027  8027 D INJECT  : delete 0x7a7b8530

10-27 21:19:52.986  8027  8027 D INJECT  : #00  pc 000015f6  /system/lib/libinject.so (inject__ZdlPv+21)

10-27 21:19:52.986  8027  8027 D INJECT  : #01  pc 00001134  /system/lib/libwebviewchromium_plat_supp

10-27 21:19:52.986  8027  8027 D INJECT  : #02  pc 00001088  /system/lib/libwebviewchromium_plat_supp

10-27 21:19:52.987  8027  8027 D INJECT  : #03  pc 0001d30c  /system/lib/libdvm.so (dvmPlatformInvoke+112)

10-27 21:19:52.987  8027  8027 D INJECT  : #04  pc 0004d8da  /system/lib/libdvm.so (dvmCallJNIMethod(unsigned int const*, JV+397)

10-27 21:19:52.987  8027  8027 D INJECT  : #05  pc 00026720  /system/lib/libdvm.so

10-27 21:19:52.987  8027  8027 D INJECT  : #06  pc 0002d790  /system/lib/libdvm.so (dvmMterpStd(Thread*)+76)

10-27 21:19:52.987  8027  8027 D INJECT  : #07  pc 0002adf4  /system/lib/libdvm.so (dvmInterpret(Thread*, Method const*, JVa+184)

10-27 21:19:52.988  8027  8027 D INJECT  : #08  pc 00060058  /system/lib/libdvm.so (dvmInvokeMethod(Object*, Method const*, +391)

10-27 21:19:52.988  8027  8027 D INJECT  : #09  pc 00067ff6  /system/lib/libdvm.so

10-27 21:19:52.988  8027  8027 D INJECT  : #10  pc 00026720  /system/lib/libdvm.so

10-27 21:19:52.988  8027  8027 D INJECT  : #11  pc 0002d790  /system/lib/libdvm.so (dvmMterpStd(Thread*)+76)

10-27 21:19:52.988  8027  8027 D INJECT  : #12  pc 0002adf4  /system/lib/libdvm.so (dvmInterpret(Thread*, Method const*, JVa+184)

10-27 21:19:52.988  8027  8027 D INJECT  : #13  pc 0005fd74  /system/lib/libdvm.so (dvmCallMethodV(Thread*, Method const*, O+335)

10-27 21:19:52.988  8027  8027 D INJECT  : #14  pc 000494c2  /system/lib/libdvm.so

10-27 21:19:52.989  8027  8027 D INJECT  :   at com.android.webview.chromium.DrawGLFunctor.nativeDestroyGLFunctor(Native Method)

10-27 21:19:52.989  8027  8027 D INJECT  :   at com.android.webview.chromium.DrawGLFunctor.access$000(DrawGLFunctor.java:31)

10-27 21:19:52.989  8027  8027 D INJECT  :   at com.android.webview.chromium.DrawGLFunctor$DestroyRunnable.run(DrawGLFunctor.java:91)

10-27 21:19:52.989  8027  8027 D INJECT  :   at com.android.org.chromium.content.common.CleanupReference.runCleanupTaskInternal(CleanupReference.java:159)

10-27 21:19:52.989  8027  8027 D INJECT  :   at com.android.org.chromium.content.common.CleanupReference.access$300(CleanupReference.java:32)

10-27 21:19:52.989  8027  8027 D INJECT  :   at com.android.org.chromium.content.common.CleanupReference$LazyHolder$1.handleMessage(CleanupReference.java:93)

10-27 21:19:52.990  8027  8027 D INJECT  :   at com.android.org.chromium.content.common.CleanupReference.handleOnUiThread(CleanupReference.java:147)

10-27 21:19:52.990  8027  8027 D INJECT  :   at com.android.org.chromium.content.common.CleanupReference.cleanupNow(CleanupReference.java:141)

10-27 21:19:52.990  8027  8027 D INJECT  :   at com.android.webview.chromium.DrawGLFunctor.destroy(DrawGLFunctor.java:46)

10-27 21:19:52.990  8027  8027 D INJECT  :   at com.android.webview.chromium.WebViewChromium.destroy(WebViewChromium.java:430)

10-27 21:19:52.990  8027  8027 D INJECT  :   at android.webkit.WebView.destroy(WebView.java:667)

10-27 21:19:52.990  8027  8027 D INJECT  :   at com.xiaomi.music.hybrid.HybridFragment.destroyHybridView(HybridFragment.java:64)

10-27 21:19:52.990  8027  8027 D INJECT  :   at com.xiaomi.music.hybrid.HybridFragment.onDestroyView(HybridFragment.java:115)

10-27 21:19:52.990  8027  8027 D INJECT  :   at com.miui.player.component.MusicBaseFragment.onDestroyView(MusicBaseFragment.java:216)

10-27 21:19:52.991  8027  8027 D INJECT  :   at android.app.Fragment.performDestroyView(Fragment.java:1898)

10-27 21:19:52.991  8027  8027 D INJECT  :   at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:954)

10-27 21:19:52.991  8027  8027 D INJECT  :   at android.app.FragmentManagerImpl.removeFragment(FragmentManager.java:1167)

10-27 21:19:52.991  8027  8027 D INJECT  :   at android.app.BackStackRecord.popFromBackStack(BackStackRecord.java:715)

10-27 21:19:52.991  8027  8027 D INJECT  :   at android.app.FragmentManagerImpl.popBackStackState(FragmentManager.java:1544)

10-27 21:19:52.992  8027  8027 D INJECT  :   at android.app.FragmentManagerImpl$3.run(FragmentManager.java:502)

10-27 21:19:52.992  8027  8027 D INJECT  :   at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1449)

10-27 21:19:52.992  8027  8027 D INJECT  :   at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)

10-27 21:19:52.992  8027  8027 D INJECT  :   at android.os.Handler.handleCallback(Handler.java:733)

10-27 21:19:52.992  8027  8027 D INJECT  :   at android.os.Handler.dispatchMessage(Handler.java:95)

10-27 21:19:52.992  8027  8027 D INJECT  :   at android.os.Looper.loop(Looper.java:136)

10-27 21:19:52.993  8027  8027 D INJECT  :   at android.app.ActivityThread.main(ActivityThread.java:5016)

10-27 21:19:52.993  8027  8027 D INJECT  :   at java.lang.reflect.Method.invokeNative(Native Method)

10-27 21:19:52.993  8027  8027 D INJECT  :   at java.lang.reflect.Method.invoke(Method.java:515)

10-27 21:19:52.993  8027  8027 D INJECT  :   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)

10-27 21:19:52.993  8027  8027 D INJECT  :   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)

10-27 21:19:52.993  8027  8027 D INJECT  :   at dalvik.system.NativeStart.main(Native Method)

10-27 21:19:53.020  8027  8027 I OpenGLRenderer: functor=0x7a7b8530,vtbl=0x400fc1b8

log中可以看到,确实是在distroy view的时候释放了Functor,而随后再Renderer中又使用了这个Functor

 

打印崩溃时的java调用栈如下:

 

10-27 21:19:53.274  8027  8027 I dalvikvm: "main" prio=5 tid=1 TIMED_WAIT10-27 21:19:53.279  8027  8027 I dalvikvm:   | group="main" sCount=0 dsCount=0 obj=0x41716ca8 self=0x415344f8

10-27 21:19:53.279  8027  8027 I dalvikvm:   | sysTid=6895 nice=-6 sched=0/0 cgrp=apps handle=1074409812

10-27 21:19:53.280  8027  8027 I dalvikvm:   | state=R schedstat=( 0 0 0 ) utm=184 stm=61 core=3

10-27 21:19:53.280  8027  8027 I dalvikvm:   at android.view.GLES20Canvas.nDrawDisplayList(Native Method)

10-27 21:19:53.281  8027  8027 I dalvikvm:   at android.view.GLES20Canvas.drawDisplayList(GLES20Canvas.java:420)

10-27 21:19:53.281  8027  8027 I dalvikvm:   at android.view.HardwareRenderer$GlRenderer.drawDisplayList(HardwareRenderer.java:1709)

10-27 21:19:53.281  8027  8027 I dalvikvm:   at android.view.HardwareRenderer$GlRenderer.draw(HardwareRenderer.java:1525)

10-27 21:19:53.282  8027  8027 I dalvikvm:   at android.view.ViewRootImpl.draw(ViewRootImpl.java:2475)

10-27 21:19:53.282  8027  8027 I dalvikvm:   at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:2347)

10-27 21:19:53.283  8027  8027 I dalvikvm:   at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1977)

10-27 21:19:53.284  8027  8027 I dalvikvm:   at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1094)

10-27 21:19:53.285  8027  8027 I dalvikvm:   at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5703)

10-27 21:19:53.285  8027  8027 I dalvikvm:   at android.view.Choreographer$CallbackRecord.run(Choreographer.java:764)

10-27 21:19:53.286  8027  8027 I dalvikvm:   at android.view.Choreographer.doCallbacks(Choreographer.java:577)

10-27 21:19:53.287  8027  8027 I dalvikvm:   at android.view.Choreographer.doFrame(Choreographer.java:547)

10-27 21:19:53.288  8027  8027 I dalvikvm:   at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:750)

10-27 21:19:53.289  8027  8027 I dalvikvm:   at android.os.Handler.handleCallback(Handler.java:733)

10-27 21:19:53.289  8027  8027 I dalvikvm:   at android.os.Handler.dispatchMessage(Handler.java:95)

10-27 21:19:53.290  8027  8027 I dalvikvm:   at android.os.Looper.loop(Looper.java:136)

10-27 21:19:53.291  8027  8027 I dalvikvm:   at android.app.ActivityThread.main(ActivityThread.java:5016)

10-27 21:19:53.291  8027  8027 I dalvikvm:   at java.lang.reflect.Method.invokeNative(Native Method)

10-27 21:19:53.292  8027  8027 I dalvikvm:   at java.lang.reflect.Method.invoke(Method.java:515)

10-27 21:19:53.293  8027  8027 I dalvikvm:   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)

10-27 21:19:53.293  8027  8027 I dalvikvm:   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)

10-27 21:19:53.293  8027  8027 I dalvikvm:   at dalvik.system.NativeStart.main(Native Method)

正常情况下,view在被destroy后不应该再被绘制,通过跟孙念沟通,得知这种情况可能是viewdestroy前没有remove导致的。

 

分析代码:

上面delete时的调用栈中有特别的两行:

 

10-27 21:19:52.990  8027  8027 D INJECT  :   at com.xiaomi.music.hybrid.HybridFragment.destroyHybridView(HybridFragment.java:64)

10-27 21:19:52.990  8027  8027 D INJECT  :   at com.xiaomi.music.hybrid.HybridFragment.onDestroyView(HybridFragment.java:115)

这个是应用的代码,而这个问题只有在这个应用上出现过,所以很可能是应用的代码引起的,

所以查了下opengrok中的代码,发现有两处destroyHybridView()的实现:

 

@v8-kk-pisces-alpha/packages/apps/MiuiMusic/common/music_sdk/hybrid/src/com/xiaomi/music/hybrid/HybridFragment.java

    private void destroyHybridView() {

        for (HybridView view : mHybridViews) {

            if (view != null) {

                view.destroy();

            }

        }

        mHybridViews.clear();

    }

 

@v8-kk-pisces-alpha/packages/apps/MiuiSdk/library/src/java/miui/hybrid/HybridFragment.java

    private void destroyHybridView() {

        for (HybridView view : mHybridViews) {

            if (view != null) {

=>              if (view.getParent() != null) {

=>                  ((ViewGroup) view.getParent()).removeView(view);

=>              }

                view.destroy();

            }

        }

        mHybridViews.clear();

    }

跟应用的同事沟通后得知,音乐应用是用上面的代码,也就是没有removeView的代码。

将上面代码中添加removeView的逻辑后不再复现问题。

 

虽然问题得到解决,但还不清楚为什么没有removeView会导致野指针。

为了找到根源仔细阅读了相关代码,发现代码中Render中有detachFunctor的代码:

 

class GLES20Canvas extends HardwareCanvas {

    ...

    public void detachFunctor(int functor) {

        nDetachFunctor(mRenderer, functor);

    }

studio在这个代码中设置断点,得到如下调用栈:

 

 

java.lang.Thread.State: RUNNABLE

      at android.view.GLES20Canvas.detachFunctor(GLES20Canvas.java:321)

      at android.view.HardwareRenderer$GlRenderer.detachFunctor(HardwareRenderer.java:1791)

      at android.view.ViewRootImpl.detachFunctor(ViewRootImpl.java:744)

      at com.android.webview.chromium.DrawGLFunctor$DestroyRunnable.detachNativeFunctor(DrawGLFunctor.java:97)

      at com.android.webview.chromium.DrawGLFunctor.detach(DrawGLFunctor.java:53)

      at com.android.webview.chromium.WebViewChromium.onDetachedFromWindow(WebViewChromium.java:1718)

      at android.webkit.WebView.onDetachedFromWindow(WebView.java:2108)

      at android.view.View.dispatchDetachedFromWindow(View.java:12631)

      at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2587)

      at android.view.ViewGroup.removeViewInternal(ViewGroup.java:3845)

      at android.view.ViewGroup.removeViewInternal(ViewGroup.java:3818)

      at android.view.ViewGroup.removeView(ViewGroup.java:3750)

      at com.xiaomi.music.hybrid.HybridFragment.destroyHybridView(HybridFragment.java:66)

      at com.xiaomi.music.hybrid.HybridFragment.onDestroyView(HybridFragment.java:119)

      at com.miui.player.component.MusicBaseFragment.onDestroyView(MusicBaseFragment.java:216)

      at android.app.Fragment.performDestroyView(Fragment.java:1898)

      at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:954)

      at android.app.FragmentManagerImpl.removeFragment(FragmentManager.java:1167)

      at android.app.BackStackRecord.popFromBackStack(BackStackRecord.java:715)

      at android.app.FragmentManagerImpl.popBackStackState(FragmentManager.java:1544)

      at android.app.FragmentManagerImpl$3.run(FragmentManager.java:502)

      at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1449)

      at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)

      at android.os.Handler.handleCallback(Handler.java:733)

      at android.os.Handler.dispatchMessage(Handler.java:95)

      at android.os.Looper.loop(Looper.java:136)

      at android.app.ActivityThread.main(ActivityThread.java:5016)

      at java.lang.reflect.Method.invokeNative(Method.java:-1)

      at java.lang.reflect.Method.invoke(Method.java:515)

      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)

      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)

      at dalvik.system.NativeStart.main(NativeStart.java:-1)

加了removeView后,会从Render中删除Functor,这样Render在绘制时,不再调用这个Functor

 这个问题只会在KK上有,L以后对Render做的很大改动,即使不做removeView,也不会存在野指针问题。


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