[Android] Add PIE support for ICS devices.

build/android/pylib/device/device_utils.py

Index: build/android/pylib/device/device_utils.py
diff --git a/build/android/pylib/device/device_utils.py b/build/android/pylib/device/device_utils.py
index a1b4117f7b963887e8516526ec0fc878ba5c1c8a..8ae40c1714f34998ac36061dd3ebb0c8d4dd46a5 100644
--- a/build/android/pylib/device/device_utils.py
+++ b/build/android/pylib/device/device_utils.py
@@ -412,7 +412,7 @@ class DeviceUtils(object):
 
   @decorators.WithTimeoutAndRetriesFromInstance()
   def RunShellCommand(self, cmd, check_return=False, cwd=None, env=None,
-                      as_root=False, single_line=False,
+                      as_root=False, with_pie=False, single_line=False,

[perezju, 2015/02/16 10:25:23]

Do we expect many clients needing this option? If we don't expect that many, I
think I would rather have clients calling GetDevicePieWrapper and building the
command themselves.

[jbudorick, 2015/02/17 15:15:10]

I don't, though I do anticipate it being more than one. I chose to include it as
an option since that's how we handle most wrappers.

[perezju, 2015/02/17 16:04:26]

I'm not crazy about this. We're adding this option now, but there are no callers
requiring it yet. Already one of the potential clients (the md5sum tool), will
probably never use this option because it needs to build it's own script anyway.

That feels, to me, like the preferred approach: the helper for the tool
requiring a special wrapper to be run, should just create the appropriate
command as required by the tool itself. Why should RunShellCommand know about
all the different wrappers that different tools might need?

Anyway, I guess you've got more experience, and I might be missing some context,
so I won't press on this point.

[jbudorick, 2015/02/17 16:14:18]

I suppose it makes sense to hold off on adding this until we have a client. I
anticipate that happening soon, but since we don't need it now, I'll take it
out. We can discuss it further when it's relevant.

                       timeout=None, retries=None):
     """Run an ADB shell command.
 
@@ -479,6 +479,9 @@ class DeviceUtils(object):
 
     if not isinstance(cmd, basestring):
       cmd = ' '.join(cmd_helper.SingleQuote(s) for s in cmd)
+    if with_pie and (self.build_version_sdk <
+                     constants.ANDROID_SDK_VERSION_CODES.JELLY_BEAN):
+      cmd = '%s %s' % (self.GetDevicePieWrapper(), cmd)
     if env:
       env = ' '.join(env_quote(k, v) for k, v in env.iteritems())
       cmd = '%s %s' % (env, cmd)
@@ -512,6 +515,42 @@ class DeviceUtils(object):
       return output
 
   @decorators.WithTimeoutAndRetriesFromInstance()
+  def GetDevicePieWrapper(self, timeout=None, retries=None):

[jbudorick, 2015/02/14 00:48:54]

Maybe this should be done as a property, wdyt?

[perezju, 2015/02/16 10:25:23]

I would lean a bit towards "No". I would reserve properties to things which are
more or less quick to compute, and do not have many side-effects when reading.
Pushing a file to the device seems to break both of those criteria.

[jbudorick, 2015/02/17 15:15:10]

Acknowledged.

+    """Gets the absolute path to the run_pie wrapper on the device.
+
+    We have to build our device executables to be PIE, but they need to be able
+    to run on versions of android that don't support PIE (i.e. ICS and below).
+    To do so, we push a wrapper to the device that lets older android versions
+    run PIE executables. This method pushes that wrapper to the device if
+    necessary and returns the path to it.
+
+    This is exposed publicly to allow clients to write scripts using run_pie
+    (e.g. md5sum.CalculateDeviceMd5Sum). However, in most cases,
+    RunShellCommand(..., with_pie=True) should suffice.
+
+    Args:
+      timeout: timeout in seconds
+      retries: number of retries
+
+    Returns:
+      The path to the PIE wrapper on the device, or an empty string if the
+      device does not require the wrapper.
+    """
+    if 'run_pie' not in self._cache:
+      pie = ''
+      if (self.build_version_sdk <
+          constants.ANDROID_SDK_VERSION_CODES.JELLY_BEAN):
+        host_pie_path = os.path.join(constants.GetOutDirectory(), 'run_pie')
+        if not os.path.exists(host_pie_path):
+          raise device_errors.CommandFailedError('Please build run_pie')
+        pie = '%s/run_pie' % constants.TEST_EXECUTABLE_DIR
+        self.adb.Push(host_pie_path, pie)
+
+      self._cache['run_pie'] = pie
+
+    return self._cache['run_pie']
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
   def KillAll(self, process_name, signum=9, as_root=False, blocking=False,
               timeout=None, retries=None):
     """Kill all processes with the given name on the device.