Mon, 21 Nov 2016 23:13:27 -0800
Merge
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
23 * questions.
24 */
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
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.
40 You may not use this file except in compliance with either the Apache
41 License or the BSD License.
43 If you choose to use this file in compliance with the Apache License, the
44 following notice applies to you:
46 You may obtain a copy of the Apache License at
48 http://www.apache.org/licenses/LICENSE-2.0
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.
56 If you choose to use this file in compliance with the BSD License, the
57 following notice applies to you:
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.
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 */
84 package jdk.internal.dynalink;
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;
101 /**
102 * The linker for {@link RelinkableCallSite} objects. Users of it (scripting
103 * frameworks and language runtimes) have to create a linker using the
104 * {@link DynamicLinkerFactory} and invoke its link method from the invokedynamic
105 * bootstrap methods to set the target of all the call sites in the code they
106 * generate. Usual usage would be to create one class per language runtime to
107 * contain one linker instance as:
108 *
109 * <pre>
110 * class MyLanguageRuntime {
111 * private static final GuardingDynamicLinker myLanguageLinker = new MyLanguageLinker();
112 * private static final DynamicLinker dynamicLinker = createDynamicLinker();
113 *
114 * private static DynamicLinker createDynamicLinker() {
115 * final DynamicLinkerFactory factory = new DynamicLinkerFactory();
116 * factory.setPrioritizedLinker(myLanguageLinker);
117 * return factory.createLinker();
118 * }
119 *
120 * public static CallSite bootstrap(MethodHandles.Lookup lookup, String name, MethodType type) {
121 * return dynamicLinker.link(new MonomorphicCallSite(CallSiteDescriptorFactory.create(lookup, name, type)));
122 * }
123 * }
124 * </pre>
125 *
126 * Note how there are three components you will need to provide here:
127 * <ul>
128 *
129 * <li>You're expected to provide a {@link GuardingDynamicLinker} for your own
130 * language. If your runtime doesn't have its own language and/or object model
131 * (i.e., it's a generic scripting shell), you don't need to implement a dynamic
132 * linker; you would simply not invoke the {@code setPrioritizedLinker} method
133 * on the factory, or even better, simply use {@link DefaultBootstrapper}.</li>
134 *
135 * <li>The performance of the programs can depend on your choice of the class to
136 * represent call sites. The above example used {@link MonomorphicCallSite}, but
137 * you might want to use {@link ChainedCallSite} instead. You'll need to
138 * experiment and decide what fits your language runtime the best. You can
139 * subclass either of these or roll your own if you need to.</li>
140 *
141 * <li>You also need to provide {@link CallSiteDescriptor}s to your call sites.
142 * They are immutable objects that contain all the information about the call
143 * site: the class performing the lookups, the name of the method being invoked,
144 * and the method signature. The library has a default {@link CallSiteDescriptorFactory}
145 * for descriptors that you can use, or you can create your own descriptor
146 * classes, especially if you need to add further information (values passed in
147 * additional parameters to the bootstrap method) to them.</li>
148 *
149 * </ul>
150 *
151 * @author Attila Szegedi
152 */
153 public class DynamicLinker {
154 private static final String CLASS_NAME = DynamicLinker.class.getName();
155 private static final String RELINK_METHOD_NAME = "relink";
157 private static final String INITIAL_LINK_CLASS_NAME = "java.lang.invoke.MethodHandleNatives";
158 private static final String INITIAL_LINK_METHOD_NAME = "linkCallSite";
160 private final LinkerServices linkerServices;
161 private final GuardedInvocationFilter prelinkFilter;
162 private final int runtimeContextArgCount;
163 private final boolean syncOnRelink;
164 private final int unstableRelinkThreshold;
166 /**
167 * Creates a new dynamic linker.
168 *
169 * @param linkerServices the linkerServices used by the linker, created by the factory.
170 * @param prelinkFilter see {@link DynamicLinkerFactory#setPrelinkFilter(GuardedInvocationFilter)}
171 * @param runtimeContextArgCount see {@link DynamicLinkerFactory#setRuntimeContextArgCount(int)}
172 */
173 DynamicLinker(final LinkerServices linkerServices, final GuardedInvocationFilter prelinkFilter, final int runtimeContextArgCount,
174 final boolean syncOnRelink, final int unstableRelinkThreshold) {
175 if(runtimeContextArgCount < 0) {
176 throw new IllegalArgumentException("runtimeContextArgCount < 0");
177 }
178 if(unstableRelinkThreshold < 0) {
179 throw new IllegalArgumentException("unstableRelinkThreshold < 0");
180 }
181 this.linkerServices = linkerServices;
182 this.prelinkFilter = prelinkFilter;
183 this.runtimeContextArgCount = runtimeContextArgCount;
184 this.syncOnRelink = syncOnRelink;
185 this.unstableRelinkThreshold = unstableRelinkThreshold;
186 }
188 /**
189 * Links an invokedynamic call site. It will install a method handle into
190 * the call site that invokes the relinking mechanism of this linker. Next
191 * time the call site is invoked, it will be linked for the actual arguments
192 * it was invoked with.
193 *
194 * @param <T> the particular subclass of {@link RelinkableCallSite} for
195 * which to create a link.
196 * @param callSite the call site to link.
197 *
198 * @return the callSite, for easy call chaining.
199 */
200 public <T extends RelinkableCallSite> T link(final T callSite) {
201 callSite.initialize(createRelinkAndInvokeMethod(callSite, 0));
202 return callSite;
203 }
205 /**
206 * Returns the object representing the lower level linker services of this
207 * class that are normally exposed to individual language-specific linkers.
208 * While as a user of this class you normally only care about the
209 * {@link #link(RelinkableCallSite)} method, in certain circumstances you
210 * might want to use the lower level services directly; either to lookup
211 * specific method handles, to access the type converters, and so on.
212 *
213 * @return the object representing the linker services of this class.
214 */
215 public LinkerServices getLinkerServices() {
216 return linkerServices;
217 }
219 private static final MethodHandle RELINK = Lookup.findOwnSpecial(MethodHandles.lookup(), RELINK_METHOD_NAME,
220 MethodHandle.class, RelinkableCallSite.class, int.class, Object[].class);
222 private MethodHandle createRelinkAndInvokeMethod(final RelinkableCallSite callSite, final int relinkCount) {
223 // Make a bound MH of invoke() for this linker and call site
224 final MethodHandle boundRelinker = MethodHandles.insertArguments(RELINK, 0, this, callSite, Integer.valueOf(
225 relinkCount));
226 // Make a MH that gathers all arguments to the invocation into an Object[]
227 final MethodType type = callSite.getDescriptor().getMethodType();
228 final MethodHandle collectingRelinker = boundRelinker.asCollector(Object[].class, type.parameterCount());
229 return MethodHandles.foldArguments(MethodHandles.exactInvoker(type), collectingRelinker.asType(
230 type.changeReturnType(MethodHandle.class)));
231 }
233 /**
234 * Relinks a call site conforming to the invocation arguments.
235 *
236 * @param callSite the call site itself
237 * @param arguments arguments to the invocation
238 *
239 * @return return the method handle for the invocation
240 *
241 * @throws Exception rethrows any exception thrown by the linkers
242 */
243 @SuppressWarnings("unused")
244 private MethodHandle relink(final RelinkableCallSite callSite, final int relinkCount, final Object... arguments) throws Exception {
245 final CallSiteDescriptor callSiteDescriptor = callSite.getDescriptor();
246 final boolean unstableDetectionEnabled = unstableRelinkThreshold > 0;
247 final boolean callSiteUnstable = unstableDetectionEnabled && relinkCount >= unstableRelinkThreshold;
248 final LinkRequest linkRequest =
249 runtimeContextArgCount == 0 ?
250 new LinkRequestImpl(callSiteDescriptor, callSite, relinkCount, callSiteUnstable, arguments) :
251 new RuntimeContextLinkRequestImpl(callSiteDescriptor, callSite, relinkCount, callSiteUnstable, arguments, runtimeContextArgCount);
253 GuardedInvocation guardedInvocation = linkerServices.getGuardedInvocation(linkRequest);
255 // None found - throw an exception
256 if(guardedInvocation == null) {
257 throw new NoSuchDynamicMethodException(callSiteDescriptor.toString());
258 }
260 // If our call sites have a runtime context, and the linker produced a context-stripped invocation, adapt the
261 // produced invocation into contextual invocation (by dropping the context...)
262 if(runtimeContextArgCount > 0) {
263 final MethodType origType = callSiteDescriptor.getMethodType();
264 final MethodHandle invocation = guardedInvocation.getInvocation();
265 if(invocation.type().parameterCount() == origType.parameterCount() - runtimeContextArgCount) {
266 final List<Class<?>> prefix = origType.parameterList().subList(1, runtimeContextArgCount + 1);
267 final MethodHandle guard = guardedInvocation.getGuard();
268 guardedInvocation = guardedInvocation.dropArguments(1, prefix);
269 }
270 }
272 // Make sure we filter the invocation before linking it into the call site. This is typically used to match the
273 // return type of the invocation to the call site.
274 guardedInvocation = prelinkFilter.filter(guardedInvocation, linkRequest, linkerServices);
275 Objects.requireNonNull(guardedInvocation);
277 int newRelinkCount = relinkCount;
278 // Note that the short-circuited "&&" evaluation below ensures we'll increment the relinkCount until
279 // threshold + 1 but not beyond that. Threshold + 1 is treated as a special value to signal that resetAndRelink
280 // has already executed once for the unstable call site; we only want the call site to throw away its current
281 // linkage once, when it transitions to unstable.
282 if(unstableDetectionEnabled && newRelinkCount <= unstableRelinkThreshold && newRelinkCount++ == unstableRelinkThreshold) {
283 callSite.resetAndRelink(guardedInvocation, createRelinkAndInvokeMethod(callSite, newRelinkCount));
284 } else {
285 callSite.relink(guardedInvocation, createRelinkAndInvokeMethod(callSite, newRelinkCount));
286 }
287 if(syncOnRelink) {
288 MutableCallSite.syncAll(new MutableCallSite[] { (MutableCallSite)callSite });
289 }
290 return guardedInvocation.getInvocation();
291 }
293 /**
294 * Returns a stack trace element describing the location of the call site
295 * currently being linked on the current thread. The operation internally
296 * creates a Throwable object and inspects its stack trace, so it's
297 * potentially expensive. The recommended usage for it is in writing
298 * diagnostics code.
299 *
300 * @return a stack trace element describing the location of the call site
301 * currently being linked, or null if it is not invoked while a call
302 * site is being linked.
303 */
304 public static StackTraceElement getLinkedCallSiteLocation() {
305 final StackTraceElement[] trace = new Throwable().getStackTrace();
306 for(int i = 0; i < trace.length - 1; ++i) {
307 final StackTraceElement frame = trace[i];
308 if(isRelinkFrame(frame) || isInitialLinkFrame(frame)) {
309 return trace[i + 1];
310 }
311 }
312 return null;
313 }
315 /**
316 * Deprecated because of imprecise name.
317 *
318 * @deprecated Use {@link #getLinkedCallSiteLocation()} instead.
319 *
320 * @return see non-deprecated method
321 */
322 @Deprecated
323 public static StackTraceElement getRelinkedCallSiteLocation() {
324 return getLinkedCallSiteLocation();
325 }
327 /**
328 * Returns {@code true} if the frame represents {@code MethodHandleNatives.linkCallSite()},
329 * the frame immediately on top of the call site frame when the call site is
330 * being linked for the first time.
331 *
332 * @param frame the frame
333 *
334 * @return {@code true} if this frame represents {@code MethodHandleNatives.linkCallSite()}.
335 */
336 private static boolean isInitialLinkFrame(final StackTraceElement frame) {
337 return testFrame(frame, INITIAL_LINK_METHOD_NAME, INITIAL_LINK_CLASS_NAME);
338 }
340 /**
341 * Returns {@code true} if the frame represents {@code DynamicLinker.relink()},
342 * the frame immediately on top of the call site frame when the call site is
343 * being relinked (linked for second and subsequent times).
344 *
345 * @param frame the frame
346 *
347 * @return {@code true} if this frame represents {@code DynamicLinker.relink()}.
348 */
349 private static boolean isRelinkFrame(final StackTraceElement frame) {
350 return testFrame(frame, RELINK_METHOD_NAME, CLASS_NAME);
351 }
353 private static boolean testFrame(final StackTraceElement frame, final String methodName, final String className) {
354 return methodName.equals(frame.getMethodName()) && className.equals(frame.getClassName());
355 }
356 }