8246494: introduce vm.flagless at-requires property

Reviewed-by: mseledtsov, sspitsyn

test/hotspot/jtreg/TEST.ROOT

@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2005, 2020, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2005, 2021, Oracle and/or its affiliates. All rights reserved.
 # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 #
 # This code is free software; you can redistribute it and/or modify it
@@ -75,6 +75,7 @@ requires.properties= \
     vm.compiler1.enabled \
     vm.compiler2.enabled \
     vm.musl \
+    vm.flagless \
     docker.support \
     jdk.containerized
 

test/hotspot/jtreg/applications/scimark/Scimark.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -24,6 +24,7 @@
 /*
  * @test
  * @library /test/lib
+ * @requires vm.flagless
  * @run driver Scimark
  */
 

test/hotspot/jtreg/gtest/GTestWrapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -26,6 +26,7 @@
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
+ * @requires vm.flagless
  * @run main/native GTestWrapper
  */
 

test/hotspot/jtreg/gtest/LargePageGtests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 2021, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2020 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -39,6 +39,7 @@
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
+ * @requires vm.flagless
  * @run main/native GTestWrapper --gtest_filter=os* -XX:+UseLargePages
  */
 
@@ -49,6 +50,7 @@
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
+ * @requires vm.flagless
  * @run main/native GTestWrapper --gtest_filter=os* -XX:+UseLargePages -XX:LargePageSizeInBytes=1G
  */
 
@@ -58,5 +60,6 @@
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
+ * @requires vm.flagless
  * @run main/native GTestWrapper --gtest_filter=os* -XX:+UseLargePages -XX:+UseSHM
  */

test/hotspot/jtreg/gtest/MetaspaceGtests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 2021, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2020 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -36,6 +36,7 @@
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
+ * @requires vm.flagless
  * @run main/native GTestWrapper --gtest_filter=metaspace* -XX:MetaspaceReclaimPolicy=none -XX:+UnlockDiagnosticVMOptions -XX:VerifyMetaspaceInterval=3
  */
 
@@ -45,6 +46,7 @@
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
+ * @requires vm.flagless
  * @run main/native GTestWrapper --gtest_filter=metaspace* -XX:MetaspaceReclaimPolicy=none
  */
 
@@ -58,6 +60,7 @@
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
+ * @requires vm.flagless
  * @run main/native GTestWrapper --gtest_filter=metaspace* -XX:MetaspaceReclaimPolicy=aggressive -XX:+UnlockDiagnosticVMOptions -XX:VerifyMetaspaceInterval=3
  */
 
@@ -67,6 +70,7 @@
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
+ * @requires vm.flagless
  * @run main/native GTestWrapper --gtest_filter=metaspace* -XX:MetaspaceReclaimPolicy=aggressive
  */
 
@@ -79,6 +83,7 @@
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
+ * @requires vm.flagless
  * @run main/native GTestWrapper --gtest_filter=metaspace* -XX:+UnlockDiagnosticVMOptions -XX:VerifyMetaspaceInterval=3 -XX:+MetaspaceGuardAllocations
  */
 
@@ -91,5 +96,6 @@
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
+ * @requires vm.flagless
  * @run main/native GTestWrapper --gtest_filter=metaspace* -XX:MetaspaceReclaimPolicy=balanced -XX:-UseCompressedClassPointers
  */

test/jtreg-ext/requires/VMProps.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -20,6 +20,7 @@
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
+
 package requires;
 
 import java.io.BufferedInputStream;
@@ -31,10 +32,12 @@ import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.nio.file.StandardOpenOption;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
+import java.util.Set;
 import java.util.concurrent.Callable;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Supplier;
@@ -118,6 +121,7 @@ public class VMProps implements Callable<Map<String, String>> {
         map.put("vm.musl", this::isMusl);
         map.put("release.implementor", this::implementor);
         map.put("jdk.containerized", this::jdkContainerized);
+        map.put("vm.flagless", this::isFlagless);
         vmGC(map); // vm.gc.X = true/false
         vmOptFinalFlags(map);
 
@@ -529,6 +533,65 @@ public class VMProps implements Callable<Map<String, String>> {
         return "" + "true".equalsIgnoreCase(isEnabled);
     }
 
+    /**
+     * Checks if we are in <i>almost</i> out-of-box configuration, i.e. the flags
+     * which JVM is started with don't affect its behavior "significantly".
+     * {@code TEST_VM_FLAGLESS} enviroment variable can be used to force this
+     * method to return true and allow any flags.
+     *
+     * @return true if there are no JVM flags
+     */
+    private String isFlagless() {
+        boolean result = true;
+        if (System.getenv("TEST_VM_FLAGLESS") != null) {
+            return "" + result;
+        }
+
+        List<String> allFlags = new ArrayList<String>();
+        Collections.addAll(allFlags, System.getProperty("test.vm.opts", "").trim().split("\\s+"));
+        Collections.addAll(allFlags, System.getProperty("test.java.opts", "").trim().split("\\s+"));
+
+        // check -XX flags
+        var ignoredXXFlags = Set.of(
+                // added by run-test framework
+                "MaxRAMPercentage",
+                // added by test environment
+                "CreateCoredumpOnCrash"
+        );
+        result &= allFlags.stream()
+                          .filter(s -> s.startsWith("-XX:"))
+                          // map to names:
+                              // remove -XX:
+                              .map(s -> s.substring(4))
+                              // remove +/- from bool flags
+                              .map(s -> s.charAt(0) == '+' || s.charAt(0) == '-' ? s.substring(1) : s)
+                              // remove =.* from others
+                              .map(s -> s.contains("=") ? s.substring(0, s.indexOf('=')) : s)
+                          // skip known-to-be-there flags
+                          .filter(s -> !ignoredXXFlags.contains(s))
+                          .findAny()
+                          .isEmpty();
+
+        // check -X flags
+        var ignoredXFlags = Set.of(
+                // default, yet still seen to be explicitly set
+                "mixed"
+        );
+        result &= allFlags.stream()
+                          .filter(s -> s.startsWith("-X") && !s.startsWith("-XX:"))
+                          // map to names:
+                              // remove -X
+                              .map(s -> s.substring(2))
+                              // remove :.* from flags with values
+                              .map(s -> s.contains(":") ? s.substring(0, s.indexOf(':')) : s)
+                          // skip known-to-be-there flags
+                          .filter(s -> !ignoredXFlags.contains(s))
+                          .findAny()
+                          .isEmpty();
+
+        return "" + result;
+    }
+
     /**
      * Dumps the map to the file if the file name is given as the property.
      * This functionality could be helpful to know context in the real