X-Git-Url: https://git.notmuchmail.org/git?a=blobdiff_plain;f=Dalvik.markdown;fp=Dalvik.markdown;h=add486075c33538aaaae556c318f5a86937802a0;hb=646cb5061d6d7383fe8857facd3bd1a8723e5fc4;hp=0000000000000000000000000000000000000000;hpb=644352f611d0a09018e762b10e07d0e153430116;p=apitrace diff --git a/Dalvik.markdown b/Dalvik.markdown new file mode 100644 index 0000000..add4860 --- /dev/null +++ b/Dalvik.markdown @@ -0,0 +1,71 @@ +Tracing Dalvik VM (Java) applications on Android +================================================ + +Android's Java virtual machine, Dalvik, runs as a system service (started at +bootup by `init`) and Java applications are run by forks of the initial +resident process. Thus, injecting apitrace's tracing library is different from +other operating systems. + +The following discussion assumes that tracing library is copied to '/data': + + adb push /path/to/apitrace/build/wrappers/egltrace.so /data + +Tracing on Android 4.0 and newer +-------------------------------- + +Starting from Android 4.0 (Ice Cream Sandwich) release, Dalvik supports +running designated processes with wrappers, in which case a new Java VM is +started with 'system()' library call for that process. + +Obtain the process name of the application to be traced (the one reported in +`ps` output, such as `com.android.settings`), and set two system properties: + + PROCNAME=com.android.settings + adb shell setprop wrap.$PROCNAME LD_PRELOAD=/data/egltrace.so + adb shell setprop debug.apitrace.procname $PROCNAME + +(the former is read by Dalvik and specifies wrapping prefix, the latter is +read by apitrace itself and used in case apitrace is preloaded into Java VM +globally to specify which process should be traced). + +Make sure the process is not loaded before starting to trace it, for example +use `-S` flag to `am start`: + + adb shell am start -S $PROCNAME + +Use `adb logcat \*:S apitrace` to examine apitrace debug output. Trace files +are saved into '/data/' directory by default: + + adb pull /data/$PROCNAME.trace + adb shell rm /data/$PROCNAME.trace + +(you need to `chmod 0777 /data` beforehand). + + +Injecting tracing library globally +---------------------------------- + +If `LD_PRELOAD` is supported (Android 2.3 "Gingerbread" and newer), it is +possible to inject `egltrace.so` into the resident Java VM, in which case +`debug.apitrace.procname` system propery is used to control for which process +tracing will be active. + +Restarting 'zygote' (Java VM) service is not straightforward, since '/init.rc' +is read only once at system bootup, and restored from the recovery image on +reboots. Thus, you either need to augment '/init.rc' in the recovery image +with `setenv LD_PRELOAD /data/egltrace.so` in `service zygote` section, or you +can use a tool such as +[adjust-child-env](https://github.com/amonakov/adjust-child-env) to restart +the service with modified environment. + +Put `adjust-child-env` and a script with the following contents into `/data`: + + stop zygote + /data/adjust-child-env 1 /system/bin/app_process LD_PRELOAD=/data/egltrace.so & + sleep 1 + start zygote + +The scripts restarts the Java VM ('zygote') with modified environment. + +Invoke the script with `adb shell` to prepare for tracing, and then follow the +Android 4.0 directions.