tests: Add checkpoint.py to fs tests directory

The configs directory for the fs tests was missing the
checkpoint.py file, causing some of the CI tests to fail.

Change-Id: Ifbd775ad658f96d06bea7bee554fe3bedcf5a5b5

tests/gem5/fs/linux/arm/configs/checkpoint.py

@@ -0,0 +1,133 @@
+# Copyright (c) 2015, 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.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met: redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer;
+# redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution;
+# neither the name of the copyright holders nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+from multiprocessing import Process
+import sys
+import os
+
+import m5
+
+_exit_normal = ("target called exit()", "m5_exit instruction encountered")
+
+_exit_limit = ("simulate() limit reached",)
+
+_exitcode_done = 0
+_exitcode_fail = 1
+_exitcode_checkpoint = 42
+
+
+def _run_step(name, restore=None, interval=0.5):
+    """
+    Instantiate (optionally from a checkpoint if restore is set to the
+    checkpoitn name) the system and run for interval seconds of
+    simulated time. At the end of the simulation interval, create a
+    checkpoint and exit.
+
+    As this function is intended to run in its own process using the
+    multiprocessing framework, the exit is a true call to exit which
+    terminates the process. Exit codes are used to pass information to
+    the parent.
+    """
+    if restore is not None:
+        m5.instantiate(restore)
+    else:
+        m5.instantiate()
+
+    e = m5.simulate(m5.ticks.fromSeconds(interval))
+    cause = e.getCause()
+    if cause in _exit_limit:
+        m5.checkpoint(name)
+        sys.exit(_exitcode_checkpoint)
+    elif cause in _exit_normal:
+        sys.exit(_exitcode_done)
+    else:
+        print(f"Test failed: Unknown exit cause: {cause}")
+        sys.exit(_exitcode_fail)
+
+
+def run_test(root, interval=0.5, max_checkpoints=5):
+    """
+    Run the simulated system for a fixed amount of time and take a
+    checkpoint, then restore from the same checkpoint and run until
+    the system calls m5 exit.
+    """
+
+    cpt_name = os.path.join(m5.options.outdir, "test.cpt")
+    restore = None
+    checkpointed = False
+
+    for cpt_no in range(max_checkpoints):
+        # Create a checkpoint from a separate child process. This enables
+        # us to get back to a (mostly) pristine state and restart
+        # simulation from the checkpoint.
+        p = Process(
+            target=_run_step,
+            args=(cpt_name,),
+            kwargs={"restore": restore, "interval": interval},
+        )
+        p.start()
+
+        # Wait for the child to return
+        p.join()
+
+        # Restore from the checkpoint next iteration
+        restore = cpt_name
+
+        if p.exitcode == _exitcode_done:
+            if checkpointed:
+                print("Test done.", file=sys.stderr)
+                sys.exit(0)
+            else:
+                print(
+                    "Test done, but no checkpoint was created.",
+                    file=sys.stderr,
+                )
+                sys.exit(1)
+        elif p.exitcode == _exitcode_checkpoint:
+            checkpointed = True
+        else:
+            print("Test failed.", file=sys.stderr)
+            sys.exit(1)
+
+    # Maximum number of checkpoints reached. Just run full-speed from
+    # now on.
+    m5.instantiate()
+    e = m5.simulate()
+    cause = e.getCause()
+    if cause in _exit_normal:
+        sys.exit(0)
+    else:
+        print(f"Test failed: Unknown exit cause: {cause}")
+        sys.exit(1)