1 /*
2 * Copyright (c) 2017, 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 */
25 package java.lang.invoke;
26
27 import sun.invoke.util.Wrapper;
28
29 import java.lang.invoke.AbstractConstantGroup.BSCIWithCache;
30 import java.util.Arrays;
31
32 import static java.lang.invoke.BootstrapCallInfo.makeBootstrapCallInfo;
33 import static java.lang.invoke.ConstantGroup.makeConstantGroup;
34 import static java.lang.invoke.MethodHandleNatives.*;
35 import static java.lang.invoke.MethodHandleStatics.TRACE_METHOD_LINKAGE;
36 import static java.lang.invoke.MethodHandles.Lookup;
37 import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
38
39 final class BootstrapMethodInvoker {
40 /**
41 * Factored code for invoking a bootstrap method for invokedynamic
42 * or a dynamic constant.
43 * @param resultType the expected return type (either CallSite or a constant type)
44 * @param bootstrapMethod the BSM to call
45 * @param name the method name or constant name
46 * @param type the method type or constant type
47 * @param info information passed up from the JVM, to derive static arguments
48 * @param callerClass the class containing the resolved method call or constant load
49 * @param <T> the expected return type
50 * @return the expected value, either a CallSite or a constant value
51 */
52 static <T> T invoke(Class<T> resultType,
53 MethodHandle bootstrapMethod,
54 // Callee information:
55 String name, Object type,
56 // Extra arguments for BSM, if any:
57 Object info,
58 // Caller information:
59 Class<?> callerClass) {
60 MethodHandles.Lookup caller = IMPL_LOOKUP.in(callerClass);
61 Object result;
62 boolean pullMode = isPullModeBSM(bootstrapMethod); // default value is false
63 boolean vmIsPushing = !staticArgumentsPulled(info); // default value is true
64 MethodHandle pullModeBSM;
65 // match the VM with the BSM
66 if (vmIsPushing) {
67 // VM is pushing arguments at us
68 pullModeBSM = null;
69 if (pullMode) {
70 bootstrapMethod = Adapters.pushMePullYou(bootstrapMethod, true);
71 }
72 } else {
73 // VM wants us to pull args from it
74 pullModeBSM = pullMode ? bootstrapMethod :
75 Adapters.pushMePullYou(bootstrapMethod, false);
76 bootstrapMethod = null;
77 }
78 try {
79 info = maybeReBox(info);
80 if (info == null) {
81 // VM is allowed to pass up a null meaning no BSM args
82 result = bootstrapMethod.invoke(caller, name, type);
83 }
84 else if (!info.getClass().isArray()) {
85 // VM is allowed to pass up a single BSM arg directly
86 result = bootstrapMethod.invoke(caller, name, type, info);
87 }
88 else if (info.getClass() == int[].class) {
89 // VM is allowed to pass up a pair {argc, index}
90 // referring to 'argc' BSM args at some place 'index'
91 // in the guts of the VM (associated with callerClass).
92 // The format of this index pair is private to the
93 // handshake between the VM and this class only.
94 // This supports "pulling" of arguments.
95 // The VM is allowed to do this for any reason.
96 // The code in this method makes up for any mismatches.
97 BootstrapCallInfo<Object> bsci
98 = new VM_BSCI<>(bootstrapMethod, name, type, caller, (int[])info);
99 // Pull-mode API is (Lookup, BootstrapCallInfo) -> Object
100 result = pullModeBSM.invoke(caller, bsci);
101 }
102 else {
103 // VM is allowed to pass up a full array of resolved BSM args
104 Object[] argv = (Object[]) info;
105 maybeReBoxElements(argv);
106 switch (argv.length) {
107 case 0:
108 result = bootstrapMethod.invoke(caller, name, type);
109 break;
110 case 1:
111 result = bootstrapMethod.invoke(caller, name, type,
112 argv[0]);
113 break;
114 case 2:
115 result = bootstrapMethod.invoke(caller, name, type,
116 argv[0], argv[1]);
117 break;
118 case 3:
119 result = bootstrapMethod.invoke(caller, name, type,
120 argv[0], argv[1], argv[2]);
121 break;
122 case 4:
123 result = bootstrapMethod.invoke(caller, name, type,
124 argv[0], argv[1], argv[2], argv[3]);
125 break;
126 case 5:
127 result = bootstrapMethod.invoke(caller, name, type,
128 argv[0], argv[1], argv[2], argv[3], argv[4]);
129 break;
130 case 6:
131 result = bootstrapMethod.invoke(caller, name, type,
132 argv[0], argv[1], argv[2], argv[3], argv[4], argv[5]);
133 break;
134 default:
135 final int NON_SPREAD_ARG_COUNT = 3; // (caller, name, type)
136 final int MAX_SAFE_SIZE = MethodType.MAX_MH_ARITY / 2 - NON_SPREAD_ARG_COUNT;
137 if (argv.length >= MAX_SAFE_SIZE) {
138 // to be on the safe side, use invokeWithArguments which handles jumbo lists
139 Object[] newargv = new Object[NON_SPREAD_ARG_COUNT + argv.length];
140 newargv[0] = caller;
141 newargv[1] = name;
142 newargv[2] = type;
143 System.arraycopy(argv, 0, newargv, NON_SPREAD_ARG_COUNT, argv.length);
144 result = bootstrapMethod.invokeWithArguments(newargv);
145 break;
146 }
147 MethodType invocationType = MethodType.genericMethodType(NON_SPREAD_ARG_COUNT + argv.length);
148 MethodHandle typedBSM = bootstrapMethod.asType(invocationType);
149 MethodHandle spreader = invocationType.invokers().spreadInvoker(NON_SPREAD_ARG_COUNT);
150 result = spreader.invokeExact(typedBSM, (Object) caller, (Object) name, type, argv);
151 }
152 }
153 if (resultType.isPrimitive()) {
154 // Non-reference conversions are more than just plain casts.
155 // By pushing the value through a funnel of the form (T x)->x,
156 // the boxed result can be widened as needed. See MH::asType.
157 MethodHandle funnel = MethodHandles.identity(resultType);
158 result = funnel.invoke(result);
159 // Now it is the wrapper type for resultType.
160 resultType = Wrapper.asWrapperType(resultType);
161 }
162 return resultType.cast(result);
163 }
164 catch (Error e) {
165 // Pass through an Error, including BootstrapMethodError, any other
166 // form of linkage error, such as IllegalAccessError if the bootstrap
167 // method is inaccessible, or say ThreadDeath/OutOfMemoryError
168 // See the "Linking Exceptions" section for the invokedynamic
169 // instruction in JVMS 6.5.
170 throw e;
171 }
172 catch (Throwable ex) {
173 // Wrap anything else in BootstrapMethodError
174 throw new BootstrapMethodError("bootstrap method initialization exception", ex);
175 }
176 }
177
178 /** The JVM produces java.lang.Integer values to box
179 * CONSTANT_Integer boxes but does not intern them.
180 * Let's intern them. This is slightly wrong for
181 * a {@code CONSTANT_Dynamic} which produces an
182 * un-interned integer (e.g., {@code new Integer(0)}).
183 */
184 private static Object maybeReBox(Object x) {
185 if (x instanceof Integer) {
186 int xi = (int) x;
187 if (xi == (byte) xi)
188 x = xi; // must rebox; see JLS 5.1.7
189 }
190 return x;
191 }
192
193 private static void maybeReBoxElements(Object[] xa) {
194 for (int i = 0; i < xa.length; i++) {
195 xa[i] = maybeReBox(xa[i]);
196 }
197 }
198
199 /** Canonical VM-aware implementation of BootstrapCallInfo.
200 * Knows how to dig into the JVM for lazily resolved (pull-mode) constants.
201 */
202 private static final class VM_BSCI<T> extends BSCIWithCache<T> {
203 private final int[] indexInfo;
204 private final Class<?> caller; // for index resolution only
205
206 VM_BSCI(MethodHandle bsm, String name, T type,
207 Lookup lookup, int[] indexInfo) {
208 super(bsm, name, type, indexInfo[0]);
209 if (!lookup.hasPrivateAccess()) //D.I.D.
210 throw new AssertionError("bad Lookup object");
211 this.caller = lookup.lookupClass();
212 this.indexInfo = indexInfo;
213 // scoop up all the easy stuff right away:
214 prefetchIntoCache(0, size());
215 }
216
217 @Override Object fillCache(int i) {
218 Object[] buf = { null };
219 copyConstants(i, i+1, buf, 0);
220 Object res = wrapNull(buf[0]);
221 cache[i] = res;
222 int next = i + 1;
223 if (next < cache.length && cache[next] == null)
224 maybePrefetchIntoCache(next, false); // try to prefetch
225 return res;
226 }
227
228 @Override public int copyConstants(int start, int end,
229 Object[] buf, int pos) {
230 int i = start, bufi = pos;
231 while (i < end) {
232 Object x = cache[i];
233 if (x == null) break;
234 buf[bufi++] = unwrapNull(x);
235 i++;
236 }
237 // give up at first null and grab the rest in one big block
238 if (i >= end) return i;
239 Object[] temp = new Object[end - i];
240 if (TRACE_METHOD_LINKAGE)
241 System.out.println("resolving more BSM arguments: "+
242 Arrays.asList(caller.getSimpleName(), Arrays.toString(indexInfo), i, end));
243 copyOutBootstrapArguments(caller, indexInfo,
244 i, end, temp, 0,
245 true, null);
246 for (Object x : temp) {
247 x = maybeReBox(x);
248 buf[bufi++] = x;
249 cache[i++] = wrapNull(x);
250 }
251 if (end < cache.length && cache[end] == null)
252 maybePrefetchIntoCache(end, true); // try to prefetch
253 return i;
254 }
255
256 private static final int MIN_PF = 4;
257 private void maybePrefetchIntoCache(int i, boolean bulk) {
258 int len = cache.length;
259 assert(0 <= i && i <= len);
260 int pfLimit = i;
261 if (bulk) pfLimit += i; // exponential prefetch expansion
262 // try to prefetch at least MIN_PF elements
263 if (pfLimit < i + MIN_PF) pfLimit = i + MIN_PF;
264 if (pfLimit > len || pfLimit < 0) pfLimit = len;
265 // stop prefetching where cache is more full than empty
266 int empty = 0, nonEmpty = 0, lastEmpty = i;
267 for (int j = i; j < pfLimit; j++) {
268 if (cache[j] == null) {
269 empty++;
270 lastEmpty = j;
271 } else {
272 nonEmpty++;
273 if (nonEmpty > empty) {
274 pfLimit = lastEmpty + 1;
275 break;
276 }
277 if (pfLimit < len) pfLimit++;
278 }
279 }
280 if (bulk && empty < MIN_PF && pfLimit < len)
281 return; // not worth the effort
282 prefetchIntoCache(i, pfLimit);
283 }
284
285 private void prefetchIntoCache(int i, int pfLimit) {
286 if (pfLimit <= i) return; // corner case
287 Object[] temp = new Object[pfLimit - i];
288 if (TRACE_METHOD_LINKAGE)
289 System.out.println("prefetching BSM arguments: "+
290 Arrays.asList(caller.getSimpleName(), Arrays.toString(indexInfo), i, pfLimit));
291 copyOutBootstrapArguments(caller, indexInfo,
292 i, pfLimit, temp, 0,
293 false, NOT_PRESENT);
294 for (Object x : temp) {
295 if (x != NOT_PRESENT && cache[i] == null) {
296 cache[i] = wrapNull(maybeReBox(x));
297 }
298 i++;
299 }
300 }
301 }
302
303 /*non-public*/ static final
304 class Adapters {
305 // skeleton for push-mode BSM which wraps a pull-mode BSM:
306 static Object pushToBootstrapMethod(MethodHandle pullModeBSM,
307 MethodHandles.Lookup lookup, String name, Object type,
308 Object... arguments) throws Throwable {
309 ConstantGroup cons = makeConstantGroup(Arrays.asList(arguments));
310 BootstrapCallInfo<?> bsci = makeBootstrapCallInfo(pullModeBSM, name, type, cons);
311 if (TRACE_METHOD_LINKAGE)
312 System.out.println("pull-mode BSM gets pushed arguments from fake BSCI");
313 return pullModeBSM.invoke(lookup, bsci);
314 }
315
316 // skeleton for pull-mode BSM which wraps a push-mode BSM:
317 static Object pullFromBootstrapMethod(MethodHandle pushModeBSM,
318 MethodHandles.Lookup lookup, BootstrapCallInfo<?> bsci)
319 throws Throwable {
320 int argc = bsci.size();
321 Object arguments[] = new Object[3 + argc];
322 arguments[0] = lookup;
323 arguments[1] = bsci.invocationName();
324 arguments[2] = bsci.invocationType();
325 bsci.copyConstants(0, argc, arguments, 3);
326 if (TRACE_METHOD_LINKAGE)
327 System.out.println("pulled arguments from VM for push-mode BSM");
328 return pushModeBSM.invokeWithArguments(arguments);
329 }
330 static final MethodHandle MH_pushToBootstrapMethod;
331 static final MethodHandle MH_pullFromBootstrapMethod;
332 static {
333 final Class<?> THIS_CLASS = Adapters.class;
334 try {
335 MH_pushToBootstrapMethod = IMPL_LOOKUP
336 .findStatic(THIS_CLASS, "pushToBootstrapMethod",
337 MethodType.methodType(Object.class, MethodHandle.class,
338 Lookup.class, String.class, Object.class, Object[].class));
339 MH_pullFromBootstrapMethod = IMPL_LOOKUP
340 .findStatic(THIS_CLASS, "pullFromBootstrapMethod",
341 MethodType.methodType(Object.class, MethodHandle.class,
342 Lookup.class, BootstrapCallInfo.class));
343 } catch (Throwable ex) {
344 throw new InternalError(ex);
345 }
346 }
347
348 /** Given a push-mode BSM (taking one argument) convert it to a
349 * pull-mode BSM (taking N pre-resolved arguments).
350 * This method is used when, in fact, the JVM is passing up
351 * pre-resolved arguments, but the BSM is expecting lazy stuff.
352 * Or, when goToPushMode is true, do the reverse transform.
353 * (The two transforms are exactly inverse.)
354 */
355 static MethodHandle pushMePullYou(MethodHandle bsm, boolean goToPushMode) {
356 if (TRACE_METHOD_LINKAGE)
357 System.out.println("converting BSM to "+(goToPushMode ? "push mode" : "pull mode"));
358 assert(isPullModeBSM(bsm) == goToPushMode); //there must be a change
359 if (goToPushMode) {
360 return Adapters.MH_pushToBootstrapMethod.bindTo(bsm).withVarargs(true);
361 } else {
362 return Adapters.MH_pullFromBootstrapMethod.bindTo(bsm).withVarargs(false);
363 }
364 }
365 }
366 }