--- /dev/null
+Tracing Dalvik VM (Java) applications on Android
+================================================
+
+Android's Java machine, DalvikVM, 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.
projects / apitrace / blobdiff