--- a/jdk/src/java.base/share/classes/java/lang/reflect/Module.java	Mon Jan 16 16:18:04 2017 +0100
+++ b/jdk/src/java.base/share/classes/java/lang/reflect/Module.java	Thu Jan 19 11:27:03 2017 +0100
@@ -128,14 +128,8 @@
         Version version = descriptor.version().orElse(null);
         String vs = Objects.toString(version, null);
         String loc = Objects.toString(uri, null);
-        Set<String> packages = descriptor.packages();
-        int n = packages.size();
-        String[] array = new String[n];
-        int i = 0;
-        for (String pn : packages) {
-            array[i++] = pn.replace('.', '/');
-        }
-        defineModule0(this, isOpen, vs, loc, array);
+        String[] packages = descriptor.packages().toArray(new String[0]);
+        defineModule0(this, isOpen, vs, loc, packages);
     }
 
 
@@ -789,13 +783,12 @@
 
         // update VM first, just in case it fails
         if (syncVM) {
-            String pkgInternalForm = pn.replace('.', '/');
             if (other == EVERYONE_MODULE) {
-                addExportsToAll0(this, pkgInternalForm);
+                addExportsToAll0(this, pn);
             } else if (other == ALL_UNNAMED_MODULE) {
-                addExportsToAllUnnamed0(this, pkgInternalForm);
+                addExportsToAllUnnamed0(this, pn);
             } else {
-                addExports0(this, pkgInternalForm, other);
+                addExports0(this, pn, other);
             }
         }
 
@@ -1021,7 +1014,7 @@
 
             // update VM first, just in case it fails
             if (syncVM)
-                addPackage0(this, pn.replace('.', '/'));
+                addPackage0(this, pn);
 
             // replace with new set
             this.extraPackages = extraPackages; // volatile write
@@ -1180,8 +1173,7 @@
         if (descriptor.isOpen()) {
             assert descriptor.opens().isEmpty();
             for (String source : descriptor.packages()) {
-                String sourceInternalForm = source.replace('.', '/');
-                addExportsToAll0(m, sourceInternalForm);
+                addExportsToAll0(m, source);
             }
             return;
         }
@@ -1192,7 +1184,6 @@
         // process the open packages first
         for (Opens opens : descriptor.opens()) {
             String source = opens.source();
-            String sourceInternalForm = source.replace('.', '/');
 
             if (opens.isQualified()) {
                 // qualified opens
@@ -1201,7 +1192,7 @@
                     // only open to modules that are in this configuration
                     Module m2 = nameToModule.get(target);
                     if (m2 != null) {
-                        addExports0(m, sourceInternalForm, m2);
+                        addExports0(m, source, m2);
                         targets.add(m2);
                     }
                 }
@@ -1210,7 +1201,7 @@
                 }
             } else {
                 // unqualified opens
-                addExportsToAll0(m, sourceInternalForm);
+                addExportsToAll0(m, source);
                 openPackages.put(source, EVERYONE_SET);
             }
         }
@@ -1218,7 +1209,6 @@
         // next the exports, skipping exports when the package is open
         for (Exports exports : descriptor.exports()) {
             String source = exports.source();
-            String sourceInternalForm = source.replace('.', '/');
 
             // skip export if package is already open to everyone
             Set<Module> openToTargets = openPackages.get(source);
@@ -1234,7 +1224,7 @@
                     if (m2 != null) {
                         // skip qualified export if already open to m2
                         if (openToTargets == null || !openToTargets.contains(m2)) {
-                            addExports0(m, sourceInternalForm, m2);
+                            addExports0(m, source, m2);
                             targets.add(m2);
                         }
                     }
@@ -1245,7 +1235,7 @@
 
             } else {
                 // unqualified exports
-                addExportsToAll0(m, sourceInternalForm);
+                addExportsToAll0(m, source);
                 exportedPackages.put(source, EVERYONE_SET);
             }
         }

--- a/jdk/src/java.base/share/native/include/jvm.h	Mon Jan 16 16:18:04 2017 +0100
+++ b/jdk/src/java.base/share/native/include/jvm.h	Thu Jan 19 11:27:03 2017 +0100
@@ -401,30 +401,67 @@
  * Module support funcions
  */
 
+/*
+ * Define a module with the specified packages and bind the module to the
+ * given class loader.
+ *  module:       module to define
+ *  is_open:      specifies if module is open (currently ignored)
+ *  version:      the module version
+ *  location:     the module location
+ *  packages:     list of packages in the module
+ *  num_packages: number of packages in the module
+ */
 JNIEXPORT void JNICALL
 JVM_DefineModule(JNIEnv *env, jobject module, jboolean is_open, jstring version,
-                 jstring location, jobjectArray packages);
+                 jstring location, const char* const* packages, jsize num_packages);
 
+/*
+ * Set the boot loader's unnamed module.
+ *  module: boot loader's unnamed module
+ */
 JNIEXPORT void JNICALL
 JVM_SetBootLoaderUnnamedModule(JNIEnv *env, jobject module);
 
-JNIEXPORT void JNICALL
-JVM_AddReadsModule(JNIEnv *env, jobject from_module, jobject to_module);
-
+/*
+ * Do a qualified export of a package.
+ *  from_module: module containing the package to export
+ *  package:     name of the package to export
+ *  to_module:   module to export the package to
+ */
 JNIEXPORT void JNICALL
-JVM_AddModuleExports(JNIEnv *env, jobject from_module, jstring package, jobject to_module);
+JVM_AddModuleExports(JNIEnv *env, jobject from_module, const char* package, jobject to_module);
 
+/*
+ * Do an export of a package to all unnamed modules.
+ *  from_module: module containing the package to export
+ *  package:     name of the package to export to all unnamed modules
+ */
 JNIEXPORT void JNICALL
-JVM_AddModuleExportsToAll(JNIEnv *env, jobject from_module, jstring package);
+JVM_AddModuleExportsToAllUnnamed(JNIEnv *env, jobject from_module, const char* package);
 
-JNIEXPORT void JNICALL
-JVM_AddModuleExportsToAllUnnamed(JNIEnv *env, jobject from_module, jstring package);
-
+/*
+ * Do an unqualified export of a package.
+ *  from_module: module containing the package to export
+ *  package:     name of the package to export
+ */
 JNIEXPORT void JNICALL
-JVM_AddModulePackage(JNIEnv* env,  jobject module, jstring package);
+JVM_AddModuleExportsToAll(JNIEnv *env, jobject from_module, const char* package);
 
-JNIEXPORT jobject JNICALL
-JVM_GetModuleByPackageName(JNIEnv *env, jobject cl, jstring pkg);
+/*
+ * Add a module to the list of modules that a given module can read.
+ *  from_module:   module requesting read access
+ *  source_module: module that from_module wants to read
+ */
+JNIEXPORT void JNICALL
+JVM_AddReadsModule(JNIEnv *env, jobject from_module, jobject source_module);
+
+/*
+ * Add a package to a module.
+ *  module:  module that will contain the package
+ *  package: package to add to the module
+ */
+JNIEXPORT void JNICALL
+JVM_AddModulePackage(JNIEnv* env,  jobject module, const char* package);
 
 /*
  * Reflection support functions

--- a/jdk/src/java.base/share/native/libjava/Module.c	Mon Jan 16 16:18:04 2017 +0100
+++ b/jdk/src/java.base/share/native/libjava/Module.c	Thu Jan 19 11:27:03 2017 +0100
@@ -22,18 +22,88 @@
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
+#include <stdlib.h>
+#include <string.h>
 
 #include "jni.h"
+#include "jni_util.h"
 #include "jvm.h"
 
 #include "java_lang_reflect_Module.h"
 
+/*
+ * Gets the UTF-8 chars for the string and translates '.' to '/'.  Does no
+ * further validation, assumption being that both calling code in
+ * java.lang.reflect.Module and VM will do deeper validation.
+ */
+static char*
+GetInternalPackageName(JNIEnv *env, jstring pkg, char* buf, jsize buf_size)
+{
+    jsize len;
+    jsize unicode_len;
+    char* p;
+    char* utf_str;
+
+    len = (*env)->GetStringUTFLength(env, pkg);
+    unicode_len = (*env)->GetStringLength(env, pkg);
+    if (len >= buf_size) {
+        utf_str = malloc(len + 1);
+        if (utf_str == NULL) {
+            JNU_ThrowOutOfMemoryError(env, NULL);
+            return NULL;
+        }
+    } else {
+        utf_str = buf;
+    }
+    (*env)->GetStringUTFRegion(env, pkg, 0, unicode_len, utf_str);
+
+    p = utf_str;
+    while (*p != '\0') {
+        if (*p == '.') {
+            *p = '/';
+        }
+        p++;
+    }
+    return utf_str;
+}
+
 JNIEXPORT void JNICALL
 Java_java_lang_reflect_Module_defineModule0(JNIEnv *env, jclass cls, jobject module,
                                             jboolean is_open, jstring version,
                                             jstring location, jobjectArray packages)
 {
-    JVM_DefineModule(env, module, is_open, version, location, packages);
+    char** pkgs = NULL;
+    jsize idx;
+    jsize num_packages = (*env)->GetArrayLength(env, packages);
+
+    if (num_packages != 0 && (pkgs = calloc(num_packages, sizeof(char*))) == NULL) {
+        JNU_ThrowOutOfMemoryError(env, NULL);
+        return;
+    } else {
+        int valid = 1;
+        for (idx = 0; idx < num_packages; idx++) {
+            jstring pkg = (*env)->GetObjectArrayElement(env, packages, idx);
+            pkgs[idx] = GetInternalPackageName(env, pkg, NULL, 0);
+            if (pkgs[idx] == NULL) {
+                valid = 0;
+                break;
+            }
+        }
+
+        if (valid != 0) {
+            JVM_DefineModule(env, module, is_open, version, location,
+                    (const char* const*)pkgs, num_packages);
+        }
+    }
+
+    if (num_packages > 0) {
+        for (idx = 0; idx < num_packages; idx++) {
+            if (pkgs[idx] != NULL) {
+                free(pkgs[idx]);
+            }
+        }
+        free(pkgs);
+    }
 }
 
 JNIEXPORT void JNICALL
@@ -46,25 +116,81 @@
 Java_java_lang_reflect_Module_addExports0(JNIEnv *env, jclass cls, jobject from,
                                           jstring pkg, jobject to)
 {
-    JVM_AddModuleExports(env, from, pkg, to);
+    char buf[128];
+    char* pkg_name;
+
+    if (pkg == NULL) {
+        JNU_ThrowNullPointerException(env, "package is null");
+        return;
+    }
+
+    pkg_name = GetInternalPackageName(env, pkg, buf, (jsize)sizeof(buf));
+    if (pkg_name != NULL) {
+        JVM_AddModuleExports(env, from, pkg_name, to);
+        if (pkg_name != buf) {
+            free(pkg_name);
+        }
+    }
 }
 
 JNIEXPORT void JNICALL
 Java_java_lang_reflect_Module_addExportsToAll0(JNIEnv *env, jclass cls, jobject from,
                                                jstring pkg)
 {
-    JVM_AddModuleExportsToAll(env, from, pkg);
+    char buf[128];
+    char* pkg_name;
+
+    if (pkg == NULL) {
+        JNU_ThrowNullPointerException(env, "package is null");
+        return;
+    }
+
+    pkg_name = GetInternalPackageName(env, pkg, buf, (jsize)sizeof(buf));
+    if (pkg_name != NULL) {
+        JVM_AddModuleExportsToAll(env, from, pkg_name);
+        if (pkg_name != buf) {
+            free(pkg_name);
+        }
+    }
 }
 
 JNIEXPORT void JNICALL
 Java_java_lang_reflect_Module_addExportsToAllUnnamed0(JNIEnv *env, jclass cls,
                                                       jobject from, jstring pkg)
 {
-    JVM_AddModuleExportsToAllUnnamed(env, from, pkg);
+    char buf[128];
+    char* pkg_name;
+
+    if (pkg == NULL) {
+        JNU_ThrowNullPointerException(env, "package is null");
+        return;
+    }
+
+    pkg_name = GetInternalPackageName(env, pkg, buf, (jsize)sizeof(buf));
+    if (pkg_name != NULL) {
+        JVM_AddModuleExportsToAllUnnamed(env, from, pkg_name);
+        if (pkg_name != buf) {
+            free(pkg_name);
+        }
+    }
 }
 
 JNIEXPORT void JNICALL
 Java_java_lang_reflect_Module_addPackage0(JNIEnv *env, jclass cls, jobject m, jstring pkg)
 {
-    JVM_AddModulePackage(env, m, pkg);
+    char buf[128];
+    char* pkg_name;
+
+    if (pkg == NULL) {
+        JNU_ThrowNullPointerException(env, "package is null");
+        return;
+    }
+
+    pkg_name = GetInternalPackageName(env, pkg, buf, (jsize)sizeof(buf));
+    if (pkg_name != NULL) {
+        JVM_AddModulePackage(env, m, pkg_name);
+        if (pkg_name != buf) {
+            free(pkg_name);
+        }
+    }
 }