用 jdb 追踪 Android
You may have debug Android in eclipse, Have you ever used jdb tracing Android. Since Dalvikvm support jdwp, we can use jdb to debug the program. there are 2 ways
Android as debug host
Steps
1) update libandroid_runtime
change below
frameworks/base/core/jni/AndroidRuntime.cpp
620 opt.optionString =
621 "-agentlib:jdwp=transport=dt_android_adb,suspend=n,server=y";
as
opt.optionString = "-agentlib:jdwp=transport=dt_socket,address=8011,server=y,suspend=y";
use "mmm frameworks/base/core/jni" to re-generate system/lib/libandroid_runtime.so, then copy to your runing env (system/lib)
2) change system/root/default.prop on your running env
change "ro.debuggable=0" to "ro.debuggable=1"
if you won not do it, you can specify AndroidManifest.xml
<application android:label="@string/app_name" android:icon="@drawable/plasma" android:debuggable="true">
Or the App can not be debugged
3) start the app
check stop you will see below
I/Zygote ( 6843/6843): Accepting command socket connections I/jdwp ( 7385/7385): JDWP will wait for debugger on port 8011
4) use jdb to attach the port
jdb -attach localhost:8011
--- you will see ---
Initializing jdb ... > VM Started: "thread=<1> main", dalvik.system.Zygote.nativeForkSystemServer(), line=-1 bci=-1 <1> main[1]
5) include source dirs by "use" command, you will see source code
<1> main[1] use /home/user/jb/frameworks/base/core/java:/home/user/jb/frameworks/base/packages/SettingsProvider/src/:/home/user/jb/frameworks/base/services/java
6) set break and trace
Use commands: stop in, cont, list, next, you will able to trace your code
<1> main[1] stop in com.android.server.InputMethodManagerService.getEnabledInputMethodSubtypeList
Deferring breakpoint com.android.server.InputMethodManagerService.getEnabledInputMethodSubtypeList.
<1> main[1] cont
> Ignoring cmd 268435570/199/1 from the VM
Set deferred breakpoint com.android.server.InputMethodManagerService.getEnabledInputMethodSubtypeList
Breakpoint hit: "thread=<12> android.server.ServerThread", com.android.server.InputMethodManagerService.getEnabledInputMethodSubtypeList(), line=845 bci=0
845 synchronized (mMethodMap) {
<12> android.server.ServerThread[1] list
841
842 @Override
843 public List<InputMethodSubtype> getEnabledInputMethodSubtypeList(InputMethodInfo imi,
844 boolean allowsImplicitlySelectedSubtypes) {
845 => synchronized (mMethodMap) {
846 return getEnabledInputMethodSubtypeListLocked(imi, allowsImplicitlySelectedSubtypes);
847 }
848 }
849
850 @Override
<12> android.server.ServerThread[1] next
Step completed: "thread=<12> android.server.ServerThread", com.android.server.InputMethodManagerService.getEnabledInputMethodSubtypeList(), line=846 bci=3
846 return getEnabledInputMethodSubtypeListLocked(imi, allowsImplicitlySelectedSubtypes);
<12> android.server.ServerThread[1]
Jdb as debug host
There are shortcomings in "Android as host", because every time the JavaVM starts up, it will move to listen status, So the SystemServer will listen, even we don't want to. so "Jdb as debug host" is a better idea.
1) update libandroid_runtime
change below
frameworks/base/core/jni/AndroidRuntime.cpp
620 opt.optionString =
621 "-agentlib:jdwp=transport=dt_android_adb,suspend=n,server=y";
as
opt.optionString = "-agentlib:jdwp=transport=dt_socket,address=localhost:8011,server=n,suspend=y";
if you won't run jdb on the same host, change "localhost" to other host/ip
2) change system/root/default.prop on your running env
change "ro.debuggable=0" to "ro.debuggable=1"
3) use jdb to listen the port
jdb -listen 8011
4) Start Android or APPs
when your Dalvik VM start, it will connect 8011
The good advantages of "Jdb as Host" is that when you need to debug, you let jdb listen; if you won't listen, Android will run as normal.
For example, when I want to debug the App, I run "jdb -listen 8011", then I click the App icon on the Launcher and start to debug.
Attention:
The Apps have launch timeout limits or It will be terminated by AM, when you enter jdb console, you need to quickly set breakpoint, and enter "cont" to run