1 /*
2 * Copyright 2008-2009 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.dyn;
27
28 import impl.java.dyn.util.MethodHandleInvoker;
29 import java.util.WeakHashMap;
30 import sun.reflect.Reflection;
31
32 /**
33 * Static methods which control the linkage of invokedynamic call sites.
34 * @author John Rose, JSR 292 EG
35 */
36 public class Linkage {
37 private Linkage() {} // do not instantiate
38
39 /**
40 * Register a bootstrap method for use for a given caller class.
41 * The method handle must be of a type equivalent to {@link Linkage#bootstrapInvokeDynamic}.
42 * <p>
43 * The operation will fail with an exception if any of the following conditions hold:
44 * <ul>
45 * <li>The caller of this method is in a different package than the {@code callerClass},
46 * and there is a security manager, and its {@code checkPermission} call throws
47 * when passed {@link LinkagePermission}("registerBootstrapMethod",callerClass).
48 * <li>The given class already has a bootstrap method, either from an embedded
49 * {@code BootstrapInvokeDynamic} classfile attribute, or from a previous
50 * call to this method.
51 * <li>The given class is already fully initialized.
52 * <li>The given class is in the process of initialization, in another thread.
53 * </ul>
54 * Because of these rules, a class may install its own bootstrap method in
55 * a static initializer.
56 */
57 public static
58 void registerBootstrapMethod(Class callerClass, MethodHandle mh) {
59 Class callc = Reflection.getCallerClass(2);
60 checkPackagePrivilege(callc, callerClass, "registerBootstrapMethod");
61 if (mh != null && mh.type() != BOOTSTRAP_METHOD_TYPE)
62 throw new WrongMethodTypeException(mh.type().toString());
63 synchronized (bootstrapMethods) {
64 if (bootstrapMethods.containsKey(callerClass))
65 throw new IllegalStateException("bootstrap method already declared in "+callerClass);
66 bootstrapMethods.put(callerClass, mh);
67 }
68 }
69
70 /**
71 * Report the bootstrap method registered for a given class.
72 * Returns null if the class has never yet registered a bootstrap method,
73 * or if the class has explicitly registered a null bootstrap method.
74 * Only callers privileged to set the bootstrap method may inquire
75 * about it, because a bootstrap method is potentially a back-door entry
76 * points to its class.
77 */
78 public static
79 MethodHandle getBootstrapMethod(Class callerClass) {
80 Class callc = Reflection.getCallerClass(2);
81 checkPackagePrivilege(callc, callerClass, "registerBootstrapMethod");
82 synchronized (bootstrapMethods) {
83 return bootstrapMethods.get(callerClass);
84 }
85 }
86
87 /** The type of any bootstrap method is (CallSite,Object...)Object.
88 * The varargs marker is required.
89 */
90 public static final MethodType BOOTSTRAP_METHOD_TYPE
91 = MethodType.make(Object.class,
92 CallSite.class, Object[].class).changeVarArgs(true);
93
94 private static MethodHandleInvoker bootstrapMethodInvoker;
95
96 private static final WeakHashMap<Class, MethodHandle> bootstrapMethods =
97 new WeakHashMap<Class, MethodHandle>();
98
99 /** Determine if the caller class has declared or registered its own bootstrap method.
100 * If so, delegate this call to it. Otherwise, throw an IncompatibleClassChangeError.
101 */
102 public static
103 Object bootstrapInvokeDynamic(CallSite site, Object... receiverAndArguments) {
104 Class callerClass = site.callerClass();
105 MethodHandle mh;
106 synchronized (bootstrapMethods) {
107 mh = bootstrapMethods.get(callerClass);
108 }
109 if (mh == null)
110 throw new IllegalStateException("no bootstrap method declared in "+callerClass);
111
112 System.out.println(site+": calling bootstrap "+mh);
113 if (bootstrapMethodInvoker == null)
114 bootstrapMethodInvoker = MethodHandleInvoker.make(BOOTSTRAP_METHOD_TYPE);
115 return bootstrapMethodInvoker.invoke(mh, site, receiverAndArguments);
116 }
117
118 /**
119 * Invalidate all <code>invokedynamic</code> call sites everywhere.
120 * <p>
121 * When this method returns, every <code>invokedynamic</code> instruction
122 * will invoke its bootstrap method on next call.
123 * <p>
124 * It is unspecified whether call sites already known to the Java
125 * code will continue to be associated with <code>invokedynamic</code>
126 * instructions. If any call site is still so associated, its
127 * {@link CallSite#getTarget()} method is guaranteed to return null
128 * the invalidation operation completes.
129 * <p>
130 * Invalidation operations are likely to be slow. Use them sparingly.
131 */
132 public static
133 Object invalidateAll() {
134 SecurityManager security = System.getSecurityManager();
135 if (security != null) {
136 security.checkPermission(new LinkagePermission("invalidateAll"));
137 }
138 throw new UnsupportedOperationException("NYI");
139 }
140
141 /**
142 * Invalidate all <code>invokedynamic</code> call sites associated
143 * with the given class.
144 * (These are exactly those sites which report the given class
145 * via the {@link CallSite#callerClass()} method.)
146 * <p>
147 * When this method returns, every matching <code>invokedynamic</code>
148 * instruction will invoke its bootstrap method on next call.
149 * <p>
150 * For additional semantics of call site invalidation,
151 * see {@link #invalidateAll()}.
152 */
153 public static
154 Object invalidateCallerClass(Class<?> callerClass) {
155 SecurityManager security = System.getSecurityManager();
156 if (security != null) {
157 security.checkPermission(new LinkagePermission("invalidateAll", callerClass));
158 }
159 throw new UnsupportedOperationException("NYI");
160 }
161
162 /**
163 * Ensure the requesting class have privileges to perform invokedynamic
164 * linkage operations on subjectClass. True if requestingClass is
165 * null (meaning the request originates from the JVM) or if the
166 * classes are in the same package and have consistent class loaders.
167 * (The subject class loader must be identical with or be a child of
168 * the requesting class loader.)
169 * @param requestingClass
170 * @param subjectClass
171 * @return
172 */
173 static void checkPackagePrivilege(Class requestingClass, Class subjectClass,
174 String permissionName) {
175 if (requestingClass == null) return;
176 if (requestingClass == subjectClass) return;
177 SecurityManager security = System.getSecurityManager();
178 if (security == null) return; // open season
179 ClassLoader rcl = requestingClass.getClassLoader();
180 ClassLoader scl = subjectClass.getClassLoader();
181 if (isParent(rcl, scl)) {
182 String rn = requestingClass.getName();
183 if (rn.startsWith("java.dyn.")) return;
184 String sn = subjectClass.getName();
185 if (samePackage(rn, sn)) return;
186 }
187 security.checkPermission(new LinkagePermission(permissionName, requestingClass));
188 }
189
190 static
191 MethodHandle findBootstrapMethod(Class callerClass, Class searchBootstrapClass) {
192 if (searchBootstrapClass != null) throw new UnsupportedOperationException("NYI");
193 MethodHandle mh = getBootstrapMethod(callerClass);
194 System.out.println("reporting bootstrap method to JVM: "+mh);
195 return mh;
196 }
197
198 private static boolean isParent(ClassLoader rcl, ClassLoader scl) {
199 while (scl != null && scl != rcl)
200 scl = scl.getParent();
201 return (scl == rcl);
202 }
203
204 private static boolean samePackage(String rn, String sn) {
205 assert((rn.indexOf('/') & sn.indexOf('/')) < 0); // no bytecode names
206 int lastDot = rn.lastIndexOf('.');
207 if (lastDot != sn.lastIndexOf('.')) return false;
208 return rn.startsWith(sn.substring(0, lastDot+1));
209 }
210
211 }