changeset 2305:d6cd0d55d0b5

6987812: 2/3 SAJDI: "gHotSpotVMTypes was not initialized properly in the remote process" Summary: Change ExportDirectoryTableImpl to return the 'Export RVA' field without modification. Read 'Base Of Data' field in optional header when PE32 format COFF file is read. Refine search for dbgeng.dll and dbghelp.dll. Other cleanups. Reviewed-by: swamyv, poonam
author dcubed
date Thu, 23 Dec 2010 07:58:35 -0800
parents 07c62ff47437
children dbf8dcf069d1
files agent/src/share/classes/sun/jvm/hotspot/HotSpotTypeDataBase.java agent/src/share/classes/sun/jvm/hotspot/debugger/win32/coff/COFFFileParser.java agent/src/share/classes/sun/jvm/hotspot/debugger/win32/coff/DumpExports.java agent/src/share/classes/sun/jvm/hotspot/debugger/win32/coff/TestParser.java agent/src/share/classes/sun/jvm/hotspot/debugger/windbg/WindbgDebuggerLocal.java
diffstat 5 files changed, 219 insertions(+), 115 deletions(-) [+]
line wrap: on
line diff
--- a/agent/src/share/classes/sun/jvm/hotspot/HotSpotTypeDataBase.java	Wed Dec 22 16:52:02 2010 -0500
+++ b/agent/src/share/classes/sun/jvm/hotspot/HotSpotTypeDataBase.java	Thu Dec 23 07:58:35 2010 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2009, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2010, 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
@@ -99,15 +99,8 @@
     long typeEntrySizeOffset;
     long typeEntryArrayStride;
 
-    typeEntryTypeNameOffset       = getLongValueFromProcess("gHotSpotVMTypeEntryTypeNameOffset");
-    typeEntrySuperclassNameOffset = getLongValueFromProcess("gHotSpotVMTypeEntrySuperclassNameOffset");
-    typeEntryIsOopTypeOffset      = getLongValueFromProcess("gHotSpotVMTypeEntryIsOopTypeOffset");
-    typeEntryIsIntegerTypeOffset  = getLongValueFromProcess("gHotSpotVMTypeEntryIsIntegerTypeOffset");
-    typeEntryIsUnsignedOffset     = getLongValueFromProcess("gHotSpotVMTypeEntryIsUnsignedOffset");
-    typeEntrySizeOffset           = getLongValueFromProcess("gHotSpotVMTypeEntrySizeOffset");
-    typeEntryArrayStride          = getLongValueFromProcess("gHotSpotVMTypeEntryArrayStride");
-
-    // Fetch the address of the VMTypeEntry*
+    // Fetch the address of the VMTypeEntry*. We get this symbol first
+    // and try to use it to make sure that symbol lookup is working.
     Address entryAddr = lookupInProcess("gHotSpotVMTypes");
     //    System.err.println("gHotSpotVMTypes address = " + entryAddr);
     // Dereference this once to get the pointer to the first VMTypeEntry
@@ -118,6 +111,14 @@
       throw new RuntimeException("gHotSpotVMTypes was not initialized properly in the remote process; can not continue");
     }
 
+    typeEntryTypeNameOffset       = getLongValueFromProcess("gHotSpotVMTypeEntryTypeNameOffset");
+    typeEntrySuperclassNameOffset = getLongValueFromProcess("gHotSpotVMTypeEntrySuperclassNameOffset");
+    typeEntryIsOopTypeOffset      = getLongValueFromProcess("gHotSpotVMTypeEntryIsOopTypeOffset");
+    typeEntryIsIntegerTypeOffset  = getLongValueFromProcess("gHotSpotVMTypeEntryIsIntegerTypeOffset");
+    typeEntryIsUnsignedOffset     = getLongValueFromProcess("gHotSpotVMTypeEntryIsUnsignedOffset");
+    typeEntrySizeOffset           = getLongValueFromProcess("gHotSpotVMTypeEntrySizeOffset");
+    typeEntryArrayStride          = getLongValueFromProcess("gHotSpotVMTypeEntryArrayStride");
+
     // Start iterating down it until we find an entry with no name
     Address typeNameAddr = null;
     do {
--- a/agent/src/share/classes/sun/jvm/hotspot/debugger/win32/coff/COFFFileParser.java	Wed Dec 22 16:52:02 2010 -0500
+++ b/agent/src/share/classes/sun/jvm/hotspot/debugger/win32/coff/COFFFileParser.java	Thu Dec 23 07:58:35 2010 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2004, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2010, 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
@@ -122,10 +122,14 @@
       private MemoizedObject[] sectionHeaders;
       private MemoizedObject[] symbols;
 
+      // Init stringTable at decl time since other fields init'ed in the
+      // constructor need the String Table.
       private MemoizedObject stringTable = new MemoizedObject() {
           public Object computeValue() {
+            // the String Table follows the Symbol Table
             int ptr = getPointerToSymbolTable();
             if (ptr == 0) {
+              // no Symbol Table so no String Table
               return new StringTable(0);
             } else {
               return new StringTable(ptr + SYMBOL_SIZE * getNumberOfSymbols());
@@ -140,6 +144,8 @@
         timeDateStamp = readInt();
         pointerToSymbolTable = readInt();
         numberOfSymbols = readInt();
+        // String Table can be accessed at this point because
+        // pointerToSymbolTable and numberOfSymbols fields are set.
         sizeOfOptionalHeader = readShort();
         characteristics = readShort();
 
@@ -222,6 +228,8 @@
         private MemoizedObject windowsSpecificFields;
         private MemoizedObject dataDirectories;
 
+        // We use an offset of 2 because OptionalHeaderStandardFieldsImpl doesn't
+        // include the 'magic' field.
         private static final int STANDARD_FIELDS_OFFSET = 2;
         private static final int PE32_WINDOWS_SPECIFIC_FIELDS_OFFSET = 28;
         private static final int PE32_DATA_DIRECTORIES_OFFSET = 96;
@@ -288,7 +296,7 @@
         private int sizeOfUninitializedData;
         private int addressOfEntryPoint;
         private int baseOfCode;
-        private int baseOfData;
+        private int baseOfData;  // only set in PE32
 
         OptionalHeaderStandardFieldsImpl(int offset,
                                          boolean isPE32Plus) {
@@ -301,7 +309,8 @@
           sizeOfUninitializedData = readInt();
           addressOfEntryPoint = readInt();
           baseOfCode = readInt();
-          if (isPE32Plus) {
+          if (!isPE32Plus) {
+            // only available in PE32
             baseOfData = readInt();
           }
         }
@@ -433,7 +442,10 @@
                 if (dir.getRVA() == 0 || dir.getSize() == 0) {
                   return null;
                 }
-                return new ExportDirectoryTableImpl(rvaToFileOffset(dir.getRVA()), dir.getSize());
+                // ExportDirectoryTableImpl needs both the RVA and the
+                // RVA converted to a file offset.
+                return new
+                    ExportDirectoryTableImpl(dir.getRVA(), dir.getSize());
               }
             };
 
@@ -526,6 +538,7 @@
       }
 
       class ExportDirectoryTableImpl implements ExportDirectoryTable {
+        private int exportDataDirRVA;
         private int offset;
         private int size;
 
@@ -548,8 +561,9 @@
         private MemoizedObject exportOrdinalTable;
         private MemoizedObject exportAddressTable;
 
-        ExportDirectoryTableImpl(int offset, int size) {
-          this.offset = offset;
+        ExportDirectoryTableImpl(int exportDataDirRVA, int size) {
+          this.exportDataDirRVA = exportDataDirRVA;
+          offset = rvaToFileOffset(exportDataDirRVA);
           this.size   = size;
           seek(offset);
           exportFlags = readInt();
@@ -595,6 +609,7 @@
 
           exportOrdinalTable = new MemoizedObject() {
               public Object computeValue() {
+                // number of ordinals is same as the number of name pointers
                 short[] ordinals = new short[getNumberOfNamePointers()];
                 seek(rvaToFileOffset(getOrdinalTableRVA()));
                 for (int i = 0; i < ordinals.length; i++) {
@@ -608,14 +623,18 @@
               public Object computeValue() {
                 int[] addresses = new int[getNumberOfAddressTableEntries()];
                 seek(rvaToFileOffset(getExportAddressTableRVA()));
-                // Must make two passes to avoid rvaToFileOffset
-                // destroying seek() position
+                // The Export Address Table values are a union of two
+                // possible values:
+                //   Export RVA - The address of the exported symbol when
+                //       loaded into memory, relative to the image base.
+                //       This value doesn't get converted into a file offset.
+                //   Forwarder RVA - The pointer to a null-terminated ASCII
+                //       string in the export section. This value gets
+                //       converted into a file offset because we have to
+                //       fetch the string.
                 for (int i = 0; i < addresses.length; i++) {
                   addresses[i] = readInt();
                 }
-                for (int i = 0; i < addresses.length; i++) {
-                  addresses[i] = rvaToFileOffset(addresses[i]);
-                }
                 return addresses;
               }
             };
@@ -648,11 +667,12 @@
 
         public boolean isExportAddressForwarder(short ordinal) {
           int addr = getExportAddress(ordinal);
-          return ((offset <= addr) && (addr < (offset + size)));
+          return ((exportDataDirRVA <= addr) &&
+              (addr < (exportDataDirRVA + size)));
         }
 
         public String getExportAddressForwarder(short ordinal) {
-          seek(getExportAddress(ordinal));
+          seek(rvaToFileOffset(getExportAddress(ordinal)));
           return readCString();
         }
 
@@ -3371,10 +3391,17 @@
               throw new COFFException(e);
             }
             // Look up in string table
+            // FIXME: this index value is assumed to be in the valid range
             name = getStringTable().get(index);
           } else {
             try {
-              name = new String(tmpName, US_ASCII);
+              int length = 0;
+              // find last non-NULL
+              for (; length < tmpName.length && tmpName[length] != '\0';) {
+                length++;
+              }
+              // don't include NULL chars in returned name String
+              name = new String(tmpName, 0, length, US_ASCII);
             } catch (UnsupportedEncodingException e) {
               throw new COFFException(e);
             }
@@ -3487,6 +3514,7 @@
                                 tmpName[5] << 16 |
                                 tmpName[6] <<  8 |
                                 tmpName[7]);
+            // FIXME: stringOffset is assumed to be in the valid range
             name = getStringTable().getAtOffset(stringOffset);
           }
 
@@ -3698,12 +3726,13 @@
 
         StringTable(int offset) {
           if (offset == 0) {
+            // no String Table
             strings = new COFFString[0];
             return;
           }
 
           seek(offset);
-          int length = readInt();
+          int length = readInt();  // length includes itself
           byte[] data = new byte[length - 4];
           int numBytesRead = readBytes(data);
           if (numBytesRead != data.length) {
--- a/agent/src/share/classes/sun/jvm/hotspot/debugger/win32/coff/DumpExports.java	Wed Dec 22 16:52:02 2010 -0500
+++ b/agent/src/share/classes/sun/jvm/hotspot/debugger/win32/coff/DumpExports.java	Thu Dec 23 07:58:35 2010 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2010, 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
@@ -37,35 +37,48 @@
 
     String filename = args[0];
     COFFFile file   = COFFFileParser.getParser().parse(filename);
-    ExportDirectoryTable exports =
-      file.getHeader().
-        getOptionalHeader().
-          getDataDirectories().
-            getExportDirectoryTable();
+
+    // get common point for both things we want to dump
+    OptionalHeaderDataDirectories dataDirs = file.getHeader().getOptionalHeader().
+        getDataDirectories();
+
+    // dump the header data directory for the Export Table:
+    DataDirectory dir = dataDirs.getExportTable();
+    System.out.println("Export table: RVA = " + dir.getRVA() + "/0x" +
+        Integer.toHexString(dir.getRVA()) + ", size = " + dir.getSize() + "/0x" +
+        Integer.toHexString(dir.getSize()));
+
+    System.out.println(file.getHeader().getNumberOfSections() + " sections in file");
+    for (int i = 1; i <= file.getHeader().getNumberOfSections(); i++) {
+      SectionHeader sec = file.getHeader().getSectionHeader(i);
+      System.out.println("  Section " + i + ":");
+      System.out.println("    Name = '" + sec.getName() + "'");
+      System.out.println("    VirtualSize = " + sec.getSize() + "/0x" +
+          Integer.toHexString(sec.getSize()));
+      System.out.println("    VirtualAddress = " + sec.getVirtualAddress() + "/0x" +
+          Integer.toHexString(sec.getVirtualAddress()));
+      System.out.println("    SizeOfRawData = " + sec.getSizeOfRawData() + "/0x" +
+          Integer.toHexString(sec.getSizeOfRawData()));
+      System.out.println("    PointerToRawData = " + sec.getPointerToRawData() + "/0x" +
+          Integer.toHexString(sec.getPointerToRawData()));
+    }
+
+    ExportDirectoryTable exports = dataDirs.getExportDirectoryTable();
     if (exports == null) {
       System.out.println("No exports found.");
     } else {
-      System.out.println(file.getHeader().getNumberOfSections() + " sections in file");
-      for (int i = 0; i < file.getHeader().getNumberOfSections(); i++) {
-        System.out.println("  Section " + i + ": " + file.getHeader().getSectionHeader(1 + i).getName());
-      }
-
-      DataDirectory dir = file.getHeader().getOptionalHeader().getDataDirectories().getExportTable();
-      System.out.println("Export table: RVA = 0x" + Integer.toHexString(dir.getRVA()) +
-                         ", size = 0x" + Integer.toHexString(dir.getSize()));
-
       System.out.println("DLL name: " + exports.getDLLName());
       System.out.println("Time/date stamp 0x" + Integer.toHexString(exports.getTimeDateStamp()));
       System.out.println("Major version 0x" + Integer.toHexString(exports.getMajorVersion() & 0xFFFF));
       System.out.println("Minor version 0x" + Integer.toHexString(exports.getMinorVersion() & 0xFFFF));
-      System.out.println(exports.getNumberOfNamePointers() + " functions found");
+      System.out.println(exports.getNumberOfNamePointers() + " exports found");
       for (int i = 0; i < exports.getNumberOfNamePointers(); i++) {
-        System.out.println("  0x" +
-                           Integer.toHexString(exports.getExportAddress(exports.getExportOrdinal(i))) +
-                           "  " +
-                           (exports.isExportAddressForwarder(exports.getExportOrdinal(i))  ?
-                            ("Forwarded to " + exports.getExportAddressForwarder(exports.getExportOrdinal(i))) :
-                            exports.getExportName(i)));
+        short ordinal = exports.getExportOrdinal(i);
+        System.out.print("[" + i + "] '" + exports.getExportName(i) + "': [" +
+            ordinal + "] = 0x" + Integer.toHexString(exports.getExportAddress(ordinal)));
+        System.out.println(exports.isExportAddressForwarder(ordinal)
+            ? "  Forwarded to '" + exports.getExportAddressForwarder(ordinal) + "'"
+            : "");
       }
     }
   }
--- a/agent/src/share/classes/sun/jvm/hotspot/debugger/win32/coff/TestParser.java	Wed Dec 22 16:52:02 2010 -0500
+++ b/agent/src/share/classes/sun/jvm/hotspot/debugger/win32/coff/TestParser.java	Thu Dec 23 07:58:35 2010 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2010, 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
@@ -42,8 +42,8 @@
       COFFHeader header = file.getHeader();
       int numSections = header.getNumberOfSections();
       System.out.println(numSections + " sections detected.");
-      for (int i = 0; i < numSections; i++) {
-        SectionHeader secHeader = header.getSectionHeader(1 + i);
+      for (int i = 1; i <= numSections; i++) {
+        SectionHeader secHeader = header.getSectionHeader(i);
         System.out.println(secHeader.getName());
       }
 
--- a/agent/src/share/classes/sun/jvm/hotspot/debugger/windbg/WindbgDebuggerLocal.java	Wed Dec 22 16:52:02 2010 -0500
+++ b/agent/src/share/classes/sun/jvm/hotspot/debugger/windbg/WindbgDebuggerLocal.java	Thu Dec 23 07:58:35 2010 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2008, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2010, 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
@@ -506,7 +506,6 @@
     throw new DebuggerException("Unimplemented");
   }
 
-  private static String  DTFWHome;
   private static String  imagePath;
   private static String  symbolPath;
   private static boolean useNativeLookup;
@@ -514,81 +513,143 @@
     static {
 
      /*
-      * sawindbg.dll depends on dbgeng.dll which
-      * itself depends on dbghelp.dll. dbgeng.dll and dbghelp.dll.
-      * On systems newer than Windows 2000, these two .dlls are
-      * in the standard system directory so we will find them there.
-      * On Windows 2000 and earlier, these files do not exist.
-      * The user must download Debugging Tools For Windows (DTFW)
-      * and install it in order to use SA.
+      * sawindbg.dll depends on dbgeng.dll which itself depends on
+      * dbghelp.dll. We have to make sure that the dbgeng.dll and
+      * dbghelp.dll that we load are compatible with each other. We
+      * load both of those libraries from the same directory based
+      * on the theory that co-located libraries are compatible.
       *
-      * We have to make sure we use the two files from the same directory
-      * in case there are more than one copy on the system because
-      * one version of dbgeng.dll might not be compatible with a
-      * different version of dbghelp.dll.
-      * We first look for them in the directory pointed at by
-      * env. var. DEBUGGINGTOOLSFORWINDOWS, next in the default
-      * installation dir for DTFW, and lastly in the standard
-      * system directory.  We expect that that we will find
-      * them in the standard system directory on all systems
-      * newer than Windows 2000.
+      * On Windows 2000 and earlier, dbgeng.dll and dbghelp.dll were
+      * not included as part of the standard system directory. On
+      * systems newer than Windows 2000, dbgeng.dll and dbghelp.dll
+      * are included in the standard system directory. However, the
+      * versions included in the standard system directory may not
+      * be able to handle symbol information for the newer compilers.
+      *
+      * We search for and explicitly load the libraries using the
+      * following directory search order:
+      *
+      * - java.home/bin (same as $JAVA_HOME/jre/bin)
+      * - dir named by DEBUGGINGTOOLSFORWINDOWS environment variable
+      * - various "Debugging Tools For Windows" program directories
+      * - the system directory ($SYSROOT/system32)
+      *
+      * If SA is invoked with -Dsun.jvm.hotspot.loadLibrary.DEBUG=1,
+      * then debug messages about library loading are printed to
+      * System.err.
       */
-    String dirName = null;
-    DTFWHome = System.getenv("DEBUGGINGTOOLSFORWINDOWS");
 
-    if (DTFWHome == null) {
-      // See if we have the files in the default location.
+    String dbgengPath   = null;
+    String dbghelpPath  = null;
+    String sawindbgPath = null;
+    List   searchList   = new ArrayList();
+
+    boolean loadLibraryDEBUG =
+        System.getProperty("sun.jvm.hotspot.loadLibrary.DEBUG") != null;
+
+    {
+      // First place to search is co-located with sawindbg.dll in
+      // $JAVA_HOME/jre/bin (java.home property is set to $JAVA_HOME/jre):
+      searchList.add(System.getProperty("java.home") + File.separator + "bin");
+      sawindbgPath = (String) searchList.get(0) + File.separator +
+          "sawindbg.dll";
+
+      // second place to search is specified by an environment variable:
+      String DTFWHome = System.getenv("DEBUGGINGTOOLSFORWINDOWS");
+      if (DTFWHome != null) {
+        searchList.add(DTFWHome);
+      }
+
+      // The third place to search is the install directory for the
+      // "Debugging Tools For Windows" package; so far there are three
+      // name variations that we know of:
       String sysRoot = System.getenv("SYSTEMROOT");
-      DTFWHome = sysRoot + File.separator +
-          ".." + File.separator + "Program Files" +
-          File.separator + "Debugging Tools For Windows";
+      DTFWHome = sysRoot + File.separator + ".." + File.separator +
+          "Program Files" + File.separator + "Debugging Tools For Windows";
+      searchList.add(DTFWHome);
+      searchList.add(DTFWHome + " (x86)");
+      searchList.add(DTFWHome + " (x64)");
+
+      // The last place to search is the system directory:
+      searchList.add(sysRoot + File.separator + "system32");
     }
 
-    {
-      String dbghelp = DTFWHome + File.separator + "dbghelp.dll";
-      String dbgeng = DTFWHome + File.separator + "dbgeng.dll";
-      File fhelp = new File(dbghelp);
-      File feng = new File(dbgeng);
-      if (fhelp.exists() && feng.exists()) {
-        // found both, we are happy.
-        // NOTE: The order of loads is important! If we load dbgeng.dll
-        // first, then the dependency - dbghelp.dll - will be loaded
-        // from usual DLL search thereby defeating the purpose!
-        System.load(dbghelp);
-        System.load(dbgeng);
-      } else if (! fhelp.exists() && ! feng.exists()) {
-        // neither exist. We will ignore this dir and assume
-        // they are in the system dir.
-        DTFWHome = null;
-      } else {
-        // one exists but not the other
-        //System.err.println("Error: Both files dbghelp.dll and dbgeng.dll "
-        //                   "must exist in directory " + DTFWHome);
-        throw new UnsatisfiedLinkError("Both files dbghelp.dll and " +
-                                       "dbgeng.dll must exist in " +
-                                       "directory " + DTFWHome);
+    for (int i = 0; i < searchList.size(); i++) {
+      File dir = new File((String) searchList.get(i));
+      if (!dir.exists()) {
+        if (loadLibraryDEBUG) {
+          System.err.println("DEBUG: '" + searchList.get(i) +
+              "': directory does not exist.");
+        }
+        // this search directory doesn't exist so skip it
+        continue;
       }
-    }
-    if (DTFWHome == null) {
-      // The files better be in the system dir.
-      String sysDir = System.getenv("SYSTEMROOT") +
-          File.separator + "system32";
 
-      File feng = new File(sysDir + File.separator + "dbgeng.dll");
-      if (!feng.exists()) {
-        throw new UnsatisfiedLinkError("File dbgeng.dll does not exist in " +
-                                        sysDir + ".  Please search microsoft.com " +
-                                       "for Debugging Tools For Windows, and " +
-                                       "either download it to the default " +
-                                       "location, or download it to a custom " +
-                                       "location and set environment variable " +
-                                       "   DEBUGGINGTOOLSFORWINDOWS  "  +
-                                       "to the pathname of that location.");
+      dbgengPath = (String) searchList.get(i) + File.separator + "dbgeng.dll";
+      dbghelpPath = (String) searchList.get(i) + File.separator + "dbghelp.dll";
+
+      File feng = new File(dbgengPath);
+      File fhelp = new File(dbghelpPath);
+      if (feng.exists() && fhelp.exists()) {
+        // both files exist so we have a match
+        break;
       }
+
+      // At least one of the files does not exist; no warning if both
+      // don't exist. If just one doesn't exist then we don't check
+      // loadLibraryDEBUG because we have a mis-configured system.
+      if (feng.exists()) {
+        System.err.println("WARNING: found '" + dbgengPath +
+            "' but did not find '" + dbghelpPath + "'; ignoring '" +
+            dbgengPath + "'.");
+      } else if (fhelp.exists()) {
+        System.err.println("WARNING: found '" + dbghelpPath +
+            "' but did not find '" + dbgengPath + "'; ignoring '" +
+            dbghelpPath + "'.");
+      } else if (loadLibraryDEBUG) {
+        System.err.println("DEBUG: searched '" + searchList.get(i) +
+          "': dbgeng.dll and dbghelp.dll were not found.");
+      }
+      dbgengPath = null;
+      dbghelpPath = null;
     }
 
+    if (dbgengPath == null || dbghelpPath == null) {
+      // at least one of the files wasn't found anywhere we searched
+      String mesg = null;
+
+      if (dbgengPath == null && dbghelpPath == null) {
+        mesg = "dbgeng.dll and dbghelp.dll cannot be found. ";
+      } else if (dbgengPath == null) {
+        mesg = "dbgeng.dll cannot be found (dbghelp.dll was found). ";
+      } else {
+        mesg = "dbghelp.dll cannot be found (dbgeng.dll was found). ";
+      }
+      throw new UnsatisfiedLinkError(mesg +
+          "Please search microsoft.com for 'Debugging Tools For Windows', " +
+          "and either download it to the default location, or download it " +
+          "to a custom location and set environment variable " +
+          "'DEBUGGINGTOOLSFORWINDOWS' to the pathname of that location.");
+    }
+
+    // NOTE: The order of loads is important! If we load dbgeng.dll
+    // first, then the dependency - dbghelp.dll - will be loaded
+    // from usual DLL search thereby defeating the purpose!
+    if (loadLibraryDEBUG) {
+      System.err.println("DEBUG: loading '" + dbghelpPath + "'.");
+    }
+    System.load(dbghelpPath);
+    if (loadLibraryDEBUG) {
+      System.err.println("DEBUG: loading '" + dbgengPath + "'.");
+    }
+    System.load(dbgengPath);
+
     // Now, load sawindbg.dll
-    System.loadLibrary("sawindbg");
+    if (loadLibraryDEBUG) {
+      System.err.println("DEBUG: loading '" + sawindbgPath + "'.");
+    }
+    System.load(sawindbgPath);
+
     // where do I find '.exe', '.dll' files?
     imagePath = System.getProperty("sun.jvm.hotspot.debugger.windbg.imagePath");
     if (imagePath == null) {