Android: add usage instructions for tracing zygote applications

Signed-off-by: Imre Deak <imre.deak@intel.com>

diff --git a/README.markdown b/README.markdown
index d5c4aedb148623e82c2792e4807c13d0c35213d9..9702ba0739294d14c41c8c7eb1264c3491d1391a 100644 (file)
--- a/README.markdown
+++ b/README.markdown
@@ -141,6 +141,67 @@ To trace the application inside gdb, invoke gdb as:
 
     gdb --ex 'set exec-wrapper env LD_PRELOAD=/path/to/glxtrace.so' --args /path/to/application
 
+### Android ###
+
+The following instructions should work at least for Android Ice Scream
+Sandwitch:
+
+For standalone applications the instructions above for Linux should
+work. To trace applications started from within the Android VM process
+(app_process aka zygote) you'll have to wrap this process and enable
+tracing dynamically for the application to be traced.
+
+- Wrapping the android main VM process:
+
+  In the Android root /init.rc add the LD_PRELOAD setting to zygote's
+  environment in the 'service zygote' section:
+
+  """
+  service zygote ...
+     setenv LD_PRELOAD /data/egltrace.so
+     ...
+  """
+
+  Note that ICS will overwrite the /init.rc during each boot with the
+  version in the recovery image. So you'll have to change the file in
+  your ICS source tree, rebuild and reflash the device.
+  Rebuilding/reflashing only the recovery image should be sufficient.
+
+
+- Copy egltrace.so to /data
+
+  On the host:
+  $ adb push /path/to/apitrace/build/wrappers/egltrace.so /data
+
+
+- Adjust file permissions to store the trace file:
+
+  By default egltrace.so will store the trace in
+  /data/app_process.trace. For this to work for applications running
+  with a uid other than 0, you have to allow writes to the /data
+  directory on the device:
+
+  # chmod 0777 /data
+
+
+- Enable tracing for a specific process name:
+
+  To trace for example the Settings application:
+  # setprop debug.apitrace.procname com.android.settings
+
+  In general this name will match what 'ps' reports.
+
+
+- Start the application:
+
+  If the application was already running, for example due to ICS's way
+  of pre-starting the apps, you might have to kill the application
+  first:
+
+  # kill <pid of app>
+
+  Launch the application for example from the application menu.
+
 ### Mac OS X ###
 
 Run the application you want to trace as