--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.jcmd/linux/classes/sun/tools/common/ProcessHelper.java	Mon Sep 23 12:32:13 2019 +0200
@@ -0,0 +1,136 @@
+/*
+ * Copyright (c) 2019, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package sun.tools.common;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.stream.Stream;
+
+/**
+ * A helper class that retrieves the main class name for
+ * a running Java process using the proc filesystem (procfs)
+ */
+final class ProcessHelper {
+
+    private static final String CMD_PREFIX = "cmd:";
+
+    /**
+     * Gets the main class name for the given Java process by parsing the
+     * process command line. If the application was started with the <em>-jar</em>
+     * option this method returns the name of the jar file. If the application
+     * was started with <em>-m</em> or <em>--module</em> option, the method returns
+     * the module name and the main class name.
+     * @param pid - process ID (pid)
+     * @return the main class name or null if the process no longer exists or
+     * was started with a native launcher (e.g. jcmd etc)
+     */
+    static String getMainClass(String pid) {
+        String cmdLine = getCommandLine(pid);
+        if (cmdLine == null) {
+            return null;
+        }
+        if (cmdLine.startsWith(CMD_PREFIX)) {
+            cmdLine = cmdLine.substring(CMD_PREFIX.length());
+        }
+        String[] parts = cmdLine.split("\0");
+        String mainClass = null;
+
+        if (parts.length == 0) {
+            return null;
+        }
+
+        // Check the executable
+        String[] executablePath = parts[0].split("/");
+        if (executablePath.length > 0) {
+            String binaryName = executablePath[executablePath.length - 1];
+            if (!"java".equals(binaryName)) {
+                // Skip the process if it is not started with java launcher
+                return null;
+            }
+        }
+
+        // To be consistent with the behavior on other platforms, if -jar, -m, or --module
+        // options are used then just return the value (the path to the jar file or module
+        // name with a main class). Otherwise, the main class name is the first part that
+        // is not a Java option (doesn't start with '-' and is not a classpath or a module
+        // whitespace option).
+
+        for (int i = 1; i < parts.length && mainClass == null; i++) {
+            if (i < parts.length - 1) {
+                if (parts[i].equals("-m") || parts[i].equals("--module") || parts[i].equals("-jar")) {
+                    return parts[i + 1];
+                }
+            }
+
+            if (parts[i].startsWith("--module=")) {
+                return parts[i].substring("--module=".length());
+            }
+
+            // If this is a classpath or a module whitespace option then skip the next part
+            // (the classpath or the option value itself)
+            if (parts[i].equals("-cp") || parts[i].equals("-classpath") ||  parts[i].equals("--class-path") ||
+                    isModuleWhiteSpaceOption(parts[i])) {
+                i++;
+                continue;
+            }
+            // Skip all other Java options
+            if (parts[i].startsWith("-")) {
+                continue;
+            }
+
+            // If it is a source-file mode then return null
+            if (parts[i].endsWith(".java")) {
+                return null;
+            }
+
+            mainClass = parts[i];
+        }
+        return mainClass;
+    }
+
+    private static String getCommandLine(String pid) {
+        try (Stream<String> lines =
+                     Files.lines(Paths.get("/proc/" + pid + "/cmdline"))) {
+            return lines.findFirst().orElse(null);
+        } catch (IOException | UncheckedIOException e) {
+            return null;
+        }
+    }
+
+    private static boolean isModuleWhiteSpaceOption(String option) {
+        return option.equals("-p") ||
+               option.equals("--module-path") ||
+               option.equals("--upgrade-module-path") ||
+               option.equals("--add-modules") ||
+               option.equals("--limit-modules") ||
+               option.equals("--add-exports") ||
+               option.equals("--add-opens") ||
+               option.equals("--add-reads") ||
+               option.equals("--patch-module");
+    }
+}