1 /*
2 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
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24 */
25
26 /*
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file, and Oracle licenses the original version of this file under the BSD
31 * license:
32 */
33 /*
34 Copyright 2009-2013 Attila Szegedi
35
36 Licensed under both the Apache License, Version 2.0 (the "Apache License")
37 and the BSD License (the "BSD License"), with licensee being free to
38 choose either of the two at their discretion.
39
40 You may not use this file except in compliance with either the Apache
41 License or the BSD License.
42
43 If you choose to use this file in compliance with the Apache License, the
44 following notice applies to you:
45
46 You may obtain a copy of the Apache License at
47
48 http://www.apache.org/licenses/LICENSE-2.0
49
50 Unless required by applicable law or agreed to in writing, software
51 distributed under the License is distributed on an "AS IS" BASIS,
52 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
53 implied. See the License for the specific language governing
54 permissions and limitations under the License.
55
56 If you choose to use this file in compliance with the BSD License, the
57 following notice applies to you:
58
59 Redistribution and use in source and binary forms, with or without
60 modification, are permitted provided that the following conditions are
61 met:
62 * Redistributions of source code must retain the above copyright
63 notice, this list of conditions and the following disclaimer.
64 * Redistributions in binary form must reproduce the above copyright
65 notice, this list of conditions and the following disclaimer in the
66 documentation and/or other materials provided with the distribution.
67 * Neither the name of the copyright holder nor the names of
68 contributors may be used to endorse or promote products derived from
69 this software without specific prior written permission.
70
71 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
72 IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
73 TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
74 PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
75 BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
76 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
77 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
78 BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
79 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
80 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
81 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
82 */
83
84 package jdk.internal.dynalink;
85
86 import java.lang.invoke.MethodHandle;
87 import java.lang.invoke.MethodHandles;
88 import java.lang.invoke.MethodType;
89 import java.lang.invoke.MutableCallSite;
90 import java.util.List;
91 import java.util.Objects;
92 import jdk.internal.dynalink.linker.GuardedInvocation;
93 import jdk.internal.dynalink.linker.GuardingDynamicLinker;
94 import jdk.internal.dynalink.linker.LinkRequest;
95 import jdk.internal.dynalink.linker.LinkerServices;
96 import jdk.internal.dynalink.support.CallSiteDescriptorFactory;
97 import jdk.internal.dynalink.support.LinkRequestImpl;
98 import jdk.internal.dynalink.support.Lookup;
99 import jdk.internal.dynalink.support.RuntimeContextLinkRequestImpl;
100
101 /**
102 * The linker for {@link RelinkableCallSite} objects. Users of it (scripting frameworks and language runtimes) have to
103 * create a linker using the {@link DynamicLinkerFactory} and invoke its link method from the invokedynamic bootstrap
104 * methods to set the target of all the call sites in the code they generate. Usual usage would be to create one class
105 * per language runtime to contain one linker instance as:
106 *
107 * <pre>
108 * class MyLanguageRuntime {
109 * private static final GuardingDynamicLinker myLanguageLinker = new MyLanguageLinker();
110 * private static final DynamicLinker dynamicLinker = createDynamicLinker();
111 *
112 * private static DynamicLinker createDynamicLinker() {
113 * final DynamicLinkerFactory factory = new DynamicLinkerFactory();
114 * factory.setPrioritizedLinker(myLanguageLinker);
115 * return factory.createLinker();
116 * }
117 *
118 * public static CallSite bootstrap(MethodHandles.Lookup caller, String name, MethodType type) {
119 * return dynamicLinker.link(new MonomorphicCallSite(CallSiteDescriptorFactory.create(lookup, name, type)));
120 * }
121 * }
122 * </pre>
123 *
124 * Note how there are three components you will need to provide here:
125 * <ul>
126 * <li>You're expected to provide a {@link GuardingDynamicLinker} for your own language. If your runtime doesn't
127 * have its own language and/or object model (i.e. it's a generic scripting shell), you don't need to implement a
128 * dynamic linker; you would simply not invoke the {@code setPrioritizedLinker} method on the factory, or even better,
129 * simply use {@link DefaultBootstrapper}.</li>
130 * <li>The performance of the programs can depend on your choice of the class to represent call sites. The above
131 * example used {@link MonomorphicCallSite}, but you might want to use {@link ChainedCallSite} instead. You'll need to
132 * experiment and decide what fits your language runtime the best. You can subclass either of these or roll your own if
133 * you need to.</li>
134 * <li>You also need to provide {@link CallSiteDescriptor}s to your call sites. They are immutable objects that contain
135 * all the information about the call site: the class performing the lookups, the name of the method being invoked, and
136 * the method signature. The library has a default {@link CallSiteDescriptorFactory} for descriptors that you can use,
137 * or you can create your own descriptor classes, especially if you need to add further information (values passed in
138 * additional parameters to the bootstrap method) to them.</li>
139 * </ul>
140 *
141 * @author Attila Szegedi
142 */
143 public class DynamicLinker {
144 private static final String CLASS_NAME = DynamicLinker.class.getName();
145 private static final String RELINK_METHOD_NAME = "relink";
146
147 private static final String INITIAL_LINK_CLASS_NAME = "java.lang.invoke.MethodHandleNatives";
148 private static final String INITIAL_LINK_METHOD_NAME = "linkCallSite";
149
150 private final LinkerServices linkerServices;
151 private final GuardedInvocationFilter prelinkFilter;
152 private final int runtimeContextArgCount;
153 private final boolean syncOnRelink;
154 private final int unstableRelinkThreshold;
155
156 /**
157 * Creates a new dynamic linker.
158 *
159 * @param linkerServices the linkerServices used by the linker, created by the factory.
160 * @param prelinkFilter see {@link DynamicLinkerFactory#setPrelinkFilter(GuardedInvocationFilter)}
161 * @param runtimeContextArgCount see {@link DynamicLinkerFactory#setRuntimeContextArgCount(int)}
162 */
163 DynamicLinker(final LinkerServices linkerServices, final GuardedInvocationFilter prelinkFilter, final int runtimeContextArgCount,
164 final boolean syncOnRelink, final int unstableRelinkThreshold) {
165 if(runtimeContextArgCount < 0) {
166 throw new IllegalArgumentException("runtimeContextArgCount < 0");
167 }
168 if(unstableRelinkThreshold < 0) {
169 throw new IllegalArgumentException("unstableRelinkThreshold < 0");
170 }
171 this.linkerServices = linkerServices;
172 this.prelinkFilter = prelinkFilter;
173 this.runtimeContextArgCount = runtimeContextArgCount;
174 this.syncOnRelink = syncOnRelink;
175 this.unstableRelinkThreshold = unstableRelinkThreshold;
176 }
177
178 /**
179 * Links an invokedynamic call site. It will install a method handle into the call site that invokes the relinking
180 * mechanism of this linker. Next time the call site is invoked, it will be linked for the actual arguments it was
181 * invoked with.
182 *
183 * @param callSite the call site to link.
184 * @return the callSite, for easy call chaining.
185 */
186 public <T extends RelinkableCallSite> T link(final T callSite) {
187 callSite.initialize(createRelinkAndInvokeMethod(callSite, 0));
188 return callSite;
189 }
190
191 /**
192 * Returns the object representing the lower level linker services of this class that are normally exposed to
193 * individual language-specific linkers. While as a user of this class you normally only care about the
194 * {@link #link(RelinkableCallSite)} method, in certain circumstances you might want to use the lower level services
195 * directly; either to lookup specific method handles, to access the type converters, and so on.
196 * @return the object representing the linker services of this class.
197 */
198 public LinkerServices getLinkerServices() {
199 return linkerServices;
200 }
201
202 private static final MethodHandle RELINK = Lookup.findOwnSpecial(MethodHandles.lookup(), RELINK_METHOD_NAME,
203 MethodHandle.class, RelinkableCallSite.class, int.class, Object[].class);
204
205 private MethodHandle createRelinkAndInvokeMethod(final RelinkableCallSite callSite, final int relinkCount) {
206 // Make a bound MH of invoke() for this linker and call site
207 final MethodHandle boundRelinker = MethodHandles.insertArguments(RELINK, 0, this, callSite, Integer.valueOf(
208 relinkCount));
209 // Make a MH that gathers all arguments to the invocation into an Object[]
210 final MethodType type = callSite.getDescriptor().getMethodType();
211 final MethodHandle collectingRelinker = boundRelinker.asCollector(Object[].class, type.parameterCount());
212 return MethodHandles.foldArguments(MethodHandles.exactInvoker(type), collectingRelinker.asType(
213 type.changeReturnType(MethodHandle.class)));
214 }
215
216 /**
217 * Relinks a call site conforming to the invocation arguments.
218 *
219 * @param callSite the call site itself
220 * @param arguments arguments to the invocation
221 * @return return the method handle for the invocation
222 * @throws Exception rethrows any exception thrown by the linkers
223 */
224 @SuppressWarnings("unused")
225 private MethodHandle relink(final RelinkableCallSite callSite, final int relinkCount, final Object... arguments) throws Exception {
226 final CallSiteDescriptor callSiteDescriptor = callSite.getDescriptor();
227 final boolean unstableDetectionEnabled = unstableRelinkThreshold > 0;
228 final boolean callSiteUnstable = unstableDetectionEnabled && relinkCount >= unstableRelinkThreshold;
229 final LinkRequest linkRequest =
230 runtimeContextArgCount == 0 ?
231 new LinkRequestImpl(callSiteDescriptor, callSite, relinkCount, callSiteUnstable, arguments) :
232 new RuntimeContextLinkRequestImpl(callSiteDescriptor, callSite, relinkCount, callSiteUnstable, arguments, runtimeContextArgCount);
233
234 GuardedInvocation guardedInvocation = linkerServices.getGuardedInvocation(linkRequest);
235
236 // None found - throw an exception
237 if(guardedInvocation == null) {
238 throw new NoSuchDynamicMethodException(callSiteDescriptor.toString());
239 }
240
241 // If our call sites have a runtime context, and the linker produced a context-stripped invocation, adapt the
242 // produced invocation into contextual invocation (by dropping the context...)
243 if(runtimeContextArgCount > 0) {
244 final MethodType origType = callSiteDescriptor.getMethodType();
245 final MethodHandle invocation = guardedInvocation.getInvocation();
246 if(invocation.type().parameterCount() == origType.parameterCount() - runtimeContextArgCount) {
247 final List<Class<?>> prefix = origType.parameterList().subList(1, runtimeContextArgCount + 1);
248 final MethodHandle guard = guardedInvocation.getGuard();
249 guardedInvocation = guardedInvocation.dropArguments(1, prefix);
250 }
251 }
252
253 // Make sure we filter the invocation before linking it into the call site. This is typically used to match the
254 // return type of the invocation to the call site.
255 guardedInvocation = prelinkFilter.filter(guardedInvocation, linkRequest, linkerServices);
256 Objects.requireNonNull(guardedInvocation);
257
258 int newRelinkCount = relinkCount;
259 // Note that the short-circuited "&&" evaluation below ensures we'll increment the relinkCount until
260 // threshold + 1 but not beyond that. Threshold + 1 is treated as a special value to signal that resetAndRelink
261 // has already executed once for the unstable call site; we only want the call site to throw away its current
262 // linkage once, when it transitions to unstable.
263 if(unstableDetectionEnabled && newRelinkCount <= unstableRelinkThreshold && newRelinkCount++ == unstableRelinkThreshold) {
264 callSite.resetAndRelink(guardedInvocation, createRelinkAndInvokeMethod(callSite, newRelinkCount));
265 } else {
266 callSite.relink(guardedInvocation, createRelinkAndInvokeMethod(callSite, newRelinkCount));
267 }
268 if(syncOnRelink) {
269 MutableCallSite.syncAll(new MutableCallSite[] { (MutableCallSite)callSite });
270 }
271 return guardedInvocation.getInvocation();
272 }
273
274 /**
275 * Returns a stack trace element describing the location of the call site currently being linked on the current
276 * thread. The operation internally creates a Throwable object and inspects its stack trace, so it's potentially
277 * expensive. The recommended usage for it is in writing diagnostics code.
278 * @return a stack trace element describing the location of the call site currently being linked, or null if it is
279 * not invoked while a call site is being linked.
280 */
281 public static StackTraceElement getLinkedCallSiteLocation() {
282 final StackTraceElement[] trace = new Throwable().getStackTrace();
283 for(int i = 0; i < trace.length - 1; ++i) {
284 final StackTraceElement frame = trace[i];
285 if(isRelinkFrame(frame) || isInitialLinkFrame(frame)) {
286 return trace[i + 1];
287 }
288 }
289 return null;
290 }
291
292 /**
293 * Deprecated because of not precise name.
294 * @deprecated Use {@link #getLinkedCallSiteLocation()} instead.
295 * @return see non-deprecated method
296 */
297 @Deprecated
298 public static StackTraceElement getRelinkedCallSiteLocation() {
299 return getLinkedCallSiteLocation();
300 }
301
302 /**
303 * Returns true if the frame represents {@code MethodHandleNatives.linkCallSite()}, the frame immediately on top of
304 * the call site frame when the call site is being linked for the first time.
305 * @param frame the frame
306 * @return true if this frame represents {@code MethodHandleNatives.linkCallSite()}
307 */
308 private static boolean isInitialLinkFrame(final StackTraceElement frame) {
309 return testFrame(frame, INITIAL_LINK_METHOD_NAME, INITIAL_LINK_CLASS_NAME);
310 }
311
312 /**
313 * Returns true if the frame represents {@code DynamicLinker.relink()}, the frame immediately on top of the call
314 * site frame when the call site is being relinked (linked for second and subsequent times).
315 * @param frame the frame
316 * @return true if this frame represents {@code DynamicLinker.relink()}
317 */
318 private static boolean isRelinkFrame(final StackTraceElement frame) {
319 return testFrame(frame, RELINK_METHOD_NAME, CLASS_NAME);
320 }
321
322 private static boolean testFrame(final StackTraceElement frame, final String methodName, final String className) {
323 return methodName.equals(frame.getMethodName()) && className.equals(frame.getClassName());
324 }
325 }