8058575: IllegalAccessError trying to access package-private class from VM anonymous class

Put anonymous classes in unnamed package into host class's package.  Throw exception if host class's package differs from anonymous class.

Reviewed-by: coleenp, acorn

hotspot/src/share/vm/prims/unsafe.cpp

@@ -783,6 +783,7 @@ UNSAFE_ENTRY(jclass, Unsafe_DefineClass0(JNIEnv *env, jobject unsafe, jstring na
 
 // define a class but do not make it known to the class loader or system dictionary
 // - host_class:  supplies context for linkage, access control, protection domain, and class loader
+//                if host_class is itself anonymous then it is replaced with its host class.
 // - data:  bytes of a class file, a raw memory address (length gives the number of bytes)
 // - cp_patches:  where non-null entries exist, they replace corresponding CP entries in data
 
@@ -791,8 +792,12 @@ UNSAFE_ENTRY(jclass, Unsafe_DefineClass0(JNIEnv *env, jobject unsafe, jstring na
 // link to any member of U.  Just after U is loaded, the only way to use it is reflectively,
 // through java.lang.Class methods like Class.newInstance.
 
+// The package of an anonymous class must either match its host's class's package or be in the
+// unnamed package.  If it is in the unnamed package then it will be put in its host class's
+// package.
+//
+
 // Access checks for linkage sites within U continue to follow the same rules as for named classes.
-// The package of an anonymous class is given by the package qualifier on the name under which it was loaded.
 // An anonymous class also has special privileges to access any member of its host class.
 // This is the main reason why this loading operation is unsafe.  The purpose of this is to
 // allow language implementations to simulate "open classes"; a host class in effect gets
@@ -874,9 +879,11 @@ Unsafe_DefineAnonymousClass_impl(JNIEnv *env,
 
   // Primitive types have NULL Klass* fields in their java.lang.Class instances.
   if (host_klass == NULL) {
-    THROW_0(vmSymbols::java_lang_IllegalArgumentException());
+    THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), "Host class is null");
   }
 
+  assert(host_klass->is_instance_klass(), "Host class must be an instance class");
+
   const char* host_source = host_klass->external_name();
   Handle      host_loader(THREAD, host_klass->class_loader());
   Handle      host_domain(THREAD, host_klass->protection_domain());
@@ -907,7 +914,7 @@ Unsafe_DefineAnonymousClass_impl(JNIEnv *env,
                                                 host_loader,
                                                 host_domain,
                                                 &st,
-                                                host_klass,
+                                                InstanceKlass::cast(host_klass),
                                                 cp_patches,
                                                 CHECK_NULL);
   if (anonk == NULL) {