Enable coredumps on arm, assert for assumptions about sysctl coredump settings

tools/bots/fletch.py

Index: tools/bots/fletch.py
diff --git a/tools/bots/fletch.py b/tools/bots/fletch.py
index abc361de0e09119f91790319d7e026e17baefc51..ef4142729c4a75fbfb59a1d68c0ae3e51af5ce79 100644
--- a/tools/bots/fletch.py
+++ b/tools/bots/fletch.py
@@ -222,6 +222,7 @@ def StepsTargetRunner(debug_log, system, mode, arch):
     for snapshot_run in [True, False]:
       for configuration in configurations:
         if not ShouldSkipConfiguration(snapshot_run, configuration):
+          build_conf = configuration['build_conf']
           build_dir = configuration['build_dir']
 
           # Sanity check we got build artifacts which we expect.
@@ -234,15 +235,18 @@ def StepsTargetRunner(debug_log, system, mode, arch):
           shutil.copyfile(dart_arm, destination)
           shutil.copymode(dart_arm, destination)
 
-          StepTest(
-            configuration['build_conf'],
-            configuration['mode'],
-            configuration['arch'],
-            clang=configuration['clang'],
-            asan=configuration['asan'],
-            snapshot_run=snapshot_run,
-            debug_log=debug_log,
-            configuration=configuration)
+          def run():
+            StepTest(
+              build_conf,
+              configuration['mode'],
+              configuration['arch'],
+              clang=configuration['clang'],
+              asan=configuration['asan'],
+              snapshot_run=snapshot_run,
+              debug_log=debug_log,
+              configuration=configuration)
+
+          RunWithCoreDumpArchiving(run, build_dir, build_conf)
   finally:
     if os.path.exists(tarball):
       os.remove(tarball)
@@ -407,9 +411,12 @@ class CoredumpArchiver(object):
     self._conf = conf
 
   def __enter__(self):
-    # TODO(kustermann): Assert that the core pattern is correctly set (at least
-    # on linux)
-    pass
+    if utils.GuessOS() == 'linux':
+      core_pattern = open('/proc/sys/kernel/core_pattern').read()
+      core_pattern_uses_pid = open('/proc/sys/kernel/core_uses_pid').read()
+
+      assert core_pattern == 'core'

[kustermann, 2015/08/25 09:08:25]

I'm aware that the pattern could be made to include pid and more, but the Vms
are configured this way ATM.

[kustermann, 2015/08/25 11:14:48]

Also account for the newline in the file now.

+      assert core_pattern_uses_pid == '1'

[ricow1, 2015/08/25 09:10:09]

should we gracefully fail here, and just tell people that coredumps is not
available until the pattern is set?

[kustermann, 2015/08/25 11:14:48]

I thought about it as well, but
* users are not running this code, only bots are
* if a bot doesn't have it enabled, we really need to know and change that

That's why I decided against it so far.

[If we add a new VM it can easily happen it doesn't have the bit, and we'll
never notice, which is bad.]

 
   def __exit__(self, *_):
     coredumps = self._find_coredumps()