diff --git a/ext/testlib/helper.py b/ext/testlib/helper.py
index ff83409866..01ca539dc3 100644
--- a/ext/testlib/helper.py
+++ b/ext/testlib/helper.py
@@ -1,3 +1,15 @@
+# Copyright (c) 2020 ARM Limited
+# All rights reserved
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
 # Copyright (c) 2017 Mark D. Hill and David A. Wood
 # All rights reserved.
 #
@@ -29,7 +41,7 @@
 '''
 Helper classes for writing tests with this test library.
 '''
-from collections import MutableSet
+from collections import MutableSet, namedtuple
 
 import difflib
 import errno
@@ -42,6 +54,83 @@ import tempfile
 import threading
 import time
 
+class TimedWaitPID(object):
+    """Utility to monkey-patch os.waitpid() with os.wait4().
+
+    This allows process usage time to be obtained directly from the OS
+    when used with APIs, such as `subprocess`, which use os.waitpid to
+    join child processes.
+
+    The resource usage data from os.wait4() is stored in a functor and
+    can be obtained using the get_time_for_pid() method.
+
+    To avoid unbounded memory usage, the time record is deleted after
+    it is read.
+
+    """
+    TimeRecord = namedtuple( "_TimeRecord", "user_time system_time" )
+
+    class Wrapper(object):
+        def __init__(self):
+            self._time_for_pid = {}
+            self._access_lock = threading.Lock()
+
+        def __call__(self, pid, options):
+            pid, status, resource_usage = os.wait4(pid, options)
+            with self._access_lock:
+                self._time_for_pid[pid] = (
+                    TimedWaitPID.TimeRecord(
+                        resource_usage.ru_utime,
+                        resource_usage.ru_stime
+                    )
+                )
+            return (pid, status)
+
+        def has_time_for_pid(self, pid):
+            with self._access_lock:
+                return pid in self._time_for_pid
+
+        def get_time_for_pid(self, pid):
+            with self._access_lock:
+                if pid not in self._time_for_pid:
+                    raise Exception("No resource usage for pid {}".format(pid))
+                time_for_pid = self._time_for_pid[pid]
+                del self._time_for_pid[pid]
+                return time_for_pid
+
+    _wrapper = None
+    _wrapper_lock = threading.Lock()
+    _original_os_waitpid = None
+
+    @staticmethod
+    def install():
+        with TimedWaitPID._wrapper_lock:
+            if TimedWaitPID._wrapper is None:
+                TimedWaitPID._wrapper = TimedWaitPID.Wrapper()
+            if TimedWaitPID._original_os_waitpid is None :
+                TimedWaitPID._original_os_waitpid = os.waitpid
+                os.waitpid = TimedWaitPID._wrapper
+
+    @staticmethod
+    def restore():
+        with TimedWaitPID._wrapper_lock:
+            if TimedWaitPID._original_os_waitpid is not None :
+                os.waitpid = TimedWaitPID._original_os_waitpid
+                TimedWaitPID._original_os_waitpid = None
+
+    @staticmethod
+    def has_time_for_pid(pid):
+        with TimedWaitPID._wrapper_lock:
+            return TimedWaitPID._wrapper.has_time_for_pid(pid)
+
+    @staticmethod
+    def get_time_for_pid(pid):
+        with TimedWaitPID._wrapper_lock:
+            return TimedWaitPID._wrapper.get_time_for_pid(pid)
+
+# Patch os.waitpid()
+TimedWaitPID.install()
+
 #TODO Tear out duplicate logic from the sandbox IOManager
 def log_call(logger, command, *popenargs, **kwargs):
     '''