1 /*
2 * Copyright (c) 2011, 2019, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23 package jdk.vm.ci.hotspot;
24
25 import static jdk.vm.ci.hotspot.CompilerToVM.compilerToVM;
26 import static jdk.vm.ci.services.Services.IS_IN_NATIVE_IMAGE;
27
28 import jdk.vm.ci.code.InstalledCode;
29 import jdk.vm.ci.code.InvalidInstalledCodeException;
30 import jdk.vm.ci.meta.JavaKind;
31 import jdk.vm.ci.meta.JavaType;
32 import jdk.vm.ci.meta.ResolvedJavaMethod;
33
34 /**
35 * Implementation of {@link InstalledCode} for code installed as an {@code nmethod}. The address of
36 * the {@code nmethod} is stored in {@link InstalledCode#address} and the value of
37 * {@code nmethod::verified_entry_point()} is in {@link InstalledCode#entryPoint}.
38 */
39 public class HotSpotNmethod extends HotSpotInstalledCode {
40
41 /**
42 * This (indirect) {@code Method*} reference is safe since class redefinition preserves all
43 * methods associated with nmethods in the code cache.
44 */
45 private final HotSpotResolvedJavaMethodImpl method;
46
47 /**
48 * Specifies whether the {@code nmethod} associated with this object is the code executed by
49 * default HotSpot linkage when a normal Java call to {@link #method} is made. That is, does
50 * {@code this.method.metadataHandle->_code} == {@code this.address}. If not, then the
51 * {@code nmethod} can only be invoked via a reference to this object. An example of this is the
52 * trampoline mechanism used by Truffle: https://goo.gl/LX88rZ.
53 */
54 private final boolean isDefault;
55
56 /**
57 * Determines whether this object is in the oops table of the nmethod.
58 * <p>
59 * If this object is in the oops table, the VM uses the oops table entry to update this object's
60 * {@link #address} and {@link #entryPoint} fields when the state of the nmethod changes. The
61 * nmethod will be unloadable when this object dies.
62 * <p>
63 * Otherwise, the nmethod's unloadability is not changed when this object dies.
64 */
65 boolean inOopsTable() {
66 return compileIdSnapshot != 0;
67 }
68
69 /**
70 * If this field is 0, this object is in the oops table of the nmethod. Otherwise, the value of
71 * the field records the nmethod's compile identifier. This value is used to confirm an entry in
72 * the code cache retrieved by {@link #address} is indeed the nmethod represented by this
73 * object.
74 *
75 * @see #inOopsTable
76 */
77 private final long compileIdSnapshot;
78
79 HotSpotNmethod(HotSpotResolvedJavaMethodImpl method, String name, boolean isDefault, long compileId) {
80 super(name);
81 this.method = method;
82 this.isDefault = isDefault;
83 boolean inOopsTable = !IS_IN_NATIVE_IMAGE && !isDefault;
84 this.compileIdSnapshot = inOopsTable ? 0L : compileId;
85 assert inOopsTable || compileId != 0L : this;
86 }
87
88 /**
89 * Determines if the nmethod associated with this object is the compiled entry point for
90 * {@link #getMethod()}.
91 */
92 public boolean isDefault() {
93 return isDefault;
94 }
95
96 @Override
97 public boolean isValid() {
98 if (compileIdSnapshot != 0L) {
99 compilerToVM().updateHotSpotNmethod(this);
100 }
101 return super.isValid();
102 }
103
104 public ResolvedJavaMethod getMethod() {
105 return method;
106 }
107
108 @Override
109 public void invalidate() {
110 compilerToVM().invalidateHotSpotNmethod(this);
111 }
112
113 @Override
114 public long getAddress() {
115 if (compileIdSnapshot != 0L) {
116 compilerToVM().updateHotSpotNmethod(this);
117 }
118 return super.getAddress();
119 }
120
121 @Override
122 public long getEntryPoint() {
123 if (compileIdSnapshot != 0L) {
124 return 0;
125 }
126 return super.getEntryPoint();
127 }
128
129 @Override
130 public String toString() {
131 return String.format("HotSpotNmethod[method=%s, codeBlob=0x%x, isDefault=%b, name=%s, inOopsTable=%s]",
132 method, getAddress(), isDefault, name, inOopsTable());
133 }
134
135 private boolean checkArgs(Object... args) {
136 JavaType[] sig = method.toParameterTypes();
137 assert args.length == sig.length : method.format("%H.%n(%p): expected ") + sig.length + " args, got " + args.length;
138 for (int i = 0; i < sig.length; i++) {
139 Object arg = args[i];
140 if (arg == null) {
141 assert sig[i].getJavaKind() == JavaKind.Object : method.format("%H.%n(%p): expected arg ") + i + " to be Object, not " + sig[i];
142 } else if (sig[i].getJavaKind() != JavaKind.Object) {
143 assert sig[i].getJavaKind().toBoxedJavaClass() == arg.getClass() : method.format("%H.%n(%p): expected arg ") + i + " to be " + sig[i] + ", not " + arg.getClass();
144 }
145 }
146 return true;
147 }
148
149 /**
150 * {@inheritDoc}
151 *
152 * It's possible for the HotSpot runtime to sweep nmethods at any point in time. As a result,
153 * there is no guarantee that calling this method will execute the wrapped nmethod. Instead, it
154 * may end up executing the bytecode of the associated {@link #getMethod() Java method}. Only if
155 * {@link #isValid()} is {@code true} after returning can the caller be sure that the nmethod
156 * was executed. If {@link #isValid()} is {@code false}, then the only way to determine if the
157 * nmethod was executed is to test for some side-effect specific to the nmethod (e.g., update to
158 * a field) that is not performed by the bytecode of the associated {@link #getMethod() Java
159 * method}.
160 */
161 @Override
162 public Object executeVarargs(Object... args) throws InvalidInstalledCodeException {
163 if (IS_IN_NATIVE_IMAGE) {
164 throw new HotSpotJVMCIUnsupportedOperationError("Cannot execute nmethod via mirror in native image");
165 }
166 assert checkArgs(args);
167 return compilerToVM().executeHotSpotNmethod(args, this);
168 }
169
170 @Override
171 public long getStart() {
172 return isValid() ? super.getStart() : 0;
173 }
174 }