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com.google.inject.internal.aop.UnsafeClassDefiner Maven / Gradle / Ivy
/*
* Copyright (C) 2020 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.inject.internal.aop;
import static java.lang.reflect.Modifier.PUBLIC;
import static org.objectweb.asm.ClassWriter.COMPUTE_MAXS;
import static org.objectweb.asm.Opcodes.ACC_SUPER;
import static org.objectweb.asm.Opcodes.ACONST_NULL;
import static org.objectweb.asm.Opcodes.ALOAD;
import static org.objectweb.asm.Opcodes.ARETURN;
import static org.objectweb.asm.Opcodes.ARRAYLENGTH;
import static org.objectweb.asm.Opcodes.CHECKCAST;
import static org.objectweb.asm.Opcodes.ICONST_0;
import static org.objectweb.asm.Opcodes.INVOKESPECIAL;
import static org.objectweb.asm.Opcodes.INVOKEVIRTUAL;
import static org.objectweb.asm.Opcodes.RETURN;
import static org.objectweb.asm.Opcodes.V1_8;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.inject.internal.InternalFlags;
import com.google.inject.internal.InternalFlags.CustomClassLoadingOption;
import java.security.AccessController;
import java.security.PrivilegedExceptionAction;
import java.util.function.BiFunction;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Type;
/**
* {@link ClassDefiner} that defines classes using {@code sun.misc.Unsafe}.
*
* @author [email protected] (Stuart McCulloch)
*/
final class UnsafeClassDefiner implements ClassDefiner {
private static final Logger logger = Logger.getLogger(UnsafeClassDefiner.class.getName());
private static final ClassDefiner UNSAFE_DEFINER;
static {
ClassDefiner unsafeDefiner =
tryPrivileged(AnonymousClassDefiner::new, "Cannot bind Unsafe.defineAnonymousClass");
if (unsafeDefiner == null) {
unsafeDefiner =
tryPrivileged(
HiddenClassDefiner::new, "Cannot bind MethodHandles.Lookup.defineHiddenClass");
}
UNSAFE_DEFINER = unsafeDefiner;
}
private static final boolean ALWAYS_DEFINE_ANONYMOUSLY =
InternalFlags.getCustomClassLoadingOption() == CustomClassLoadingOption.ANONYMOUS;
private static final String DEFINEACCESS_BY_GUICE_MARKER = "$$DefineAccessByGuice$$";
private static final String[] DEFINEACCESS_API = {"java/util/function/BiFunction"};
private static final String CLASS_LOADER_TYPE = Type.getInternalName(ClassLoader.class);
private static final String BYTE_ARRAY_TYPE = Type.getInternalName(byte[].class);
// initialization-on-demand...
private static class ClassLoaderDefineClassHolder {
static final ClassDefiner CLASS_LOADER_DEFINE_CLASS =
tryPrivileged(
() -> accessDefineClass(ClassLoader.class), "Cannot access ClassLoader.defineClass");
}
// initialization-on-demand...
private static class DefineClassCacheHolder {
static final LoadingCache, ClassDefiner> DEFINE_CLASS_CACHE =
CacheBuilder.newBuilder()
.weakKeys()
.build(CacheLoader.from(UnsafeClassDefiner::tryAccessDefineClass));
}
/** Do we have access to {@code sun.misc.Unsafe}? */
public static boolean isAccessible() {
return UNSAFE_DEFINER != null;
}
/** Returns true if it's possible to load by name proxies defined from the given host. */
public static boolean canLoadProxyByName(Class hostClass) {
return findClassDefiner(hostClass.getClassLoader()) != UNSAFE_DEFINER;
}
/** Returns true if it's possible to downcast to proxies defined from the given host. */
public static boolean canDowncastToProxy(Class hostClass) {
return !(findClassDefiner(hostClass.getClassLoader()) instanceof AnonymousClassDefiner);
}
@Override
public Class define(Class hostClass, byte[] bytecode) throws Exception {
return findClassDefiner(hostClass.getClassLoader()).define(hostClass, bytecode);
}
/** Finds the appropriate class definer for the given class loader. */
private static ClassDefiner findClassDefiner(ClassLoader hostLoader) {
if (hostLoader == null || ALWAYS_DEFINE_ANONYMOUSLY) {
return UNSAFE_DEFINER;
} else if (ClassLoaderDefineClassHolder.CLASS_LOADER_DEFINE_CLASS != null) {
// we have access to the defineClass method of anything extending ClassLoader
return ClassLoaderDefineClassHolder.CLASS_LOADER_DEFINE_CLASS;
} else {
// can't access ClassLoader, try accessing the specific sub-class instead
return DefineClassCacheHolder.DEFINE_CLASS_CACHE.getUnchecked(hostLoader.getClass());
}
}
static T tryPrivileged(PrivilegedExceptionAction action, String errorMessage) {
try {
return AccessController.doPrivileged(action);
} catch (Throwable e) {
logger.log(Level.FINE, errorMessage, e);
return null;
}
}
static ClassDefiner tryAccessDefineClass(Class loaderClass) {
try {
logger.log(Level.FINE, "Accessing defineClass method in %s", loaderClass);
return AccessController.doPrivileged(
(PrivilegedExceptionAction) () -> accessDefineClass(loaderClass));
} catch (Throwable e) {
logger.log(Level.FINE, "Cannot access defineClass method in " + loaderClass, e);
return UNSAFE_DEFINER;
}
}
/** Generates helper in same package as the {@link ClassLoader} so it can access defineClass */
@SuppressWarnings("unchecked")
static ClassDefiner accessDefineClass(Class loaderClass) throws Exception {
byte[] bytecode = buildDefineClassAccess(loaderClass);
Class accessClass = UNSAFE_DEFINER.define(loaderClass, bytecode);
return new GeneratedClassDefiner(
(BiFunction>)
accessClass.getDeclaredConstructor().newInstance());
}
/** {@link ClassLoader} helper that sits in the same package and passes on defineClass requests */
private static byte[] buildDefineClassAccess(Class loaderClass) {
ClassWriter cw = new ClassWriter(COMPUTE_MAXS);
// target Java8 because that's all we need for the generated helper
cw.visit(
V1_8,
PUBLIC | ACC_SUPER,
loaderClass.getName().replace('.', '/') + DEFINEACCESS_BY_GUICE_MARKER,
null,
"java/lang/Object",
DEFINEACCESS_API);
MethodVisitor mv;
mv = cw.visitMethod(PUBLIC, "", "()V", null, null);
mv.visitCode();
mv.visitVarInsn(ALOAD, 0);
mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "", "()V", false);
mv.visitInsn(RETURN);
mv.visitMaxs(0, 0);
mv.visitEnd();
mv =
cw.visitMethod(
PUBLIC,
"apply",
"(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;",
null,
null);
mv.visitCode();
mv.visitVarInsn(ALOAD, 1);
mv.visitTypeInsn(CHECKCAST, CLASS_LOADER_TYPE);
mv.visitInsn(ACONST_NULL);
mv.visitVarInsn(ALOAD, 2);
mv.visitTypeInsn(CHECKCAST, BYTE_ARRAY_TYPE);
mv.visitInsn(ICONST_0);
mv.visitVarInsn(ALOAD, 2);
mv.visitTypeInsn(CHECKCAST, BYTE_ARRAY_TYPE);
mv.visitInsn(ARRAYLENGTH);
mv.visitMethodInsn(
INVOKEVIRTUAL,
"java/lang/ClassLoader",
"defineClass",
"(Ljava/lang/String;[BII)Ljava/lang/Class;",
false);
mv.visitInsn(ARETURN);
mv.visitMaxs(0, 0);
mv.visitEnd();
cw.visitEnd();
return cw.toByteArray();
}
}
