Workaround for JDK 14 EA FileChannel.map issue (#50523)

FileChannel.map provokes static initialization of ExtendedMapMode in
JDK14 EA, which needs elevated privileges.

Relates #50512

server/src/main/java/org/elasticsearch/bootstrap/Bootstrap.java

@@ -160,6 +160,24 @@ final class Bootstrap {
         JvmInfo.jvmInfo();
     }
 
+    /**
+     * JDK 14 bug:
+     * https://github.com/elastic/elasticsearch/issues/50512
+     * We circumvent it here by loading the offending class before installing security manager.
+     *
+     * To be removed once the JDK is fixed.
+     */
+    static void fixJDK14EAFileChannelMap() {
+        // minor time-bomb here to ensure that we reevaluate if final 14 version does not include fix.
+        if (System.getProperty("java.version").equals("14-ea")) {
+            try {
+                Class.forName("jdk.internal.misc.ExtendedMapMode", true, Bootstrap.class.getClassLoader());
+            } catch (ClassNotFoundException e) {
+                throw new RuntimeException("Unable to lookup ExtendedMapMode class", e);
+            }
+        }
+    }
+
     private void setup(boolean addShutdownHook, Environment environment) throws BootstrapException {
         Settings settings = environment.settings();
 
@@ -211,6 +229,8 @@ final class Bootstrap {
         // Log ifconfig output before SecurityManager is installed
         IfConfig.logIfNecessary();
 
+        fixJDK14EAFileChannelMap();
+
         // install SM after natives, shutdown hooks, etc.
         try {
             Security.configure(environment, BootstrapSettings.SECURITY_FILTER_BAD_DEFAULTS_SETTING.get(settings));

test/framework/src/main/java/org/elasticsearch/bootstrap/BootstrapForTesting.java

@@ -102,6 +102,8 @@ public class BootstrapForTesting {
         // Log ifconfig output before SecurityManager is installed
         IfConfig.logIfNecessary();
 
+        Bootstrap.fixJDK14EAFileChannelMap();
+
         // install security manager if requested
         if (systemPropertyAsBoolean("tests.security.manager", true)) {
             try {