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8359707: Add classfile modification code to RedefineClassHelper

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Reviewed-by: lmesnik, dholmes, sspitsyn
This commit is contained in:
Coleen Phillimore
2025-07-01 17:14:36 +00:00
parent 38f59f84c9
commit e7a450038a
2 changed files with 48 additions and 47 deletions
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49
test/hotspot/jtreg/serviceability/jvmti/RedefineClasses/ClassVersionAfterRedefine.java
View File

@@ -32,68 +32,27 @@
* @run main/othervm -javaagent:redefineagent.jar ClassVersionAfterRedefine
*/
import java.io.InputStream;
import java.lang.reflect.Method;
import static jdk.test.lib.Asserts.assertTrue;
public class ClassVersionAfterRedefine extends ClassLoader {
private static String myName = ClassVersionAfterRedefine.class.getName();
private static byte[] getBytecodes(String name) throws Exception {
InputStream is = ClassVersionAfterRedefine.class.getResourceAsStream(name + ".class");
byte[] buf = is.readAllBytes();
System.out.println("sizeof(" + name + ".class) == " + buf.length);
return buf;
}
private static int getStringIndex(String needle, byte[] buf) {
return getStringIndex(needle, buf, 0);
}
private static int getStringIndex(String needle, byte[] buf, int offset) {
outer:
for (int i = offset; i < buf.length - offset - needle.length(); i++) {
for (int j = 0; j < needle.length(); j++) {
if (buf[i + j] != (byte)needle.charAt(j)) continue outer;
}
return i;
}
return 0;
}
private static void replaceString(byte[] buf, String name, int index) {
for (int i = index; i < index + name.length(); i++) {
buf[i] = (byte)name.charAt(i - index);
}
}
private static void replaceAllStrings(byte[] buf, String oldString, String newString) throws Exception {
assertTrue(oldString.length() == newString.length(), "must have same length");
int index = -1;
while ((index = getStringIndex(oldString, buf, index + 1)) != 0) {
replaceString(buf, newString, index);
}
}
public static void main(String[] s) throws Exception {
byte[] buf = getBytecodes("TestClassOld");
// Poor man's renaming of class "TestClassOld" to "TestClassXXX"
replaceAllStrings(buf, "TestClassOld", "TestClassXXX");
ClassVersionAfterRedefine cvar = new ClassVersionAfterRedefine();
byte[] buf = RedefineClassHelper.replaceClassName(cvar, "TestClassOld", "TestClassXXX");
Class<?> old = cvar.defineClass(null, buf, 0, buf.length);
Method foo = old.getMethod("foo");
Object result = foo.invoke(null);
assertTrue("java-lang-String".equals(result));
System.out.println(old.getSimpleName() + ".foo() = " + result);
buf = getBytecodes("TestClassNew");
// Rename class "TestClassNew" to "TestClassXXX" so we can use it for
// redefining the original version of "TestClassXXX" (i.e. "TestClassOld").
replaceAllStrings(buf, "TestClassNew", "TestClassXXX");
// Now redine the original version of "TestClassXXX" (i.e. "TestClassOld").
buf = RedefineClassHelper.replaceClassName(cvar, "TestClassNew", "TestClassXXX");
// Now redefine the original version of "TestClassXXX" (i.e. "TestClassOld").
RedefineClassHelper.redefineClass(old, buf);
result = foo.invoke(null);
assertTrue("java.lang.String".equals(result));

46
test/lib/RedefineClassHelper.java
View File

@@ -1,5 +1,5 @@
/*
* Copyright (c) 2014, 2022, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2014, 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -21,8 +21,14 @@
* questions.
*/
import java.lang.instrument.Instrumentation;
import java.io.InputStream;
import java.lang.classfile.ClassElement;
import java.lang.classfile.ClassFile;
import java.lang.classfile.ClassModel;
import java.lang.constant.ClassDesc;
import java.lang.instrument.ClassDefinition;
import java.lang.instrument.Instrumentation;
import jdk.test.lib.compiler.InMemoryJavaCompiler;
import jdk.test.lib.helpers.ClassFileInstaller;
@@ -33,6 +39,7 @@ import jdk.test.lib.helpers.ClassFileInstaller;
*
* See sample test in test/testlibrary_tests/RedefineClassTest.java
*/
public class RedefineClassHelper {
public static Instrumentation instrumentation;
@@ -61,6 +68,41 @@ public class RedefineClassHelper {
instrumentation.redefineClasses(new ClassDefinition(clazz, bytecode));
}
private static byte[] getBytecodes(ClassLoader loader, String name) throws Exception {
try (InputStream is = loader.getResourceAsStream(name + ".class")) {
byte[] buf = is.readAllBytes();
System.out.println("sizeof(" + name + ".class) == " + buf.length);
return buf;
}
}
/*
* Copy the class defined by `bytes`, replacing the name of the class with `newClassName`,
* so that both old and new classes can be compiled by jtreg for the test.
*
* @param bytes read from the original class file.
* @param newClassName new class name for the returned class representation
* @return a copy of the class represented by `bytes` but with the name `newClassName`
*/
public static byte[] replaceClassName(byte[] bytes, String newClassName) throws Exception {
ClassModel classModel = ClassFile.of().parse(bytes);
return ClassFile.of().build(ClassDesc.of(newClassName), classModel::forEach);
}
/*
* Replace class name in bytecodes to the class we're trying to redefine, so that both
* old and new classes can be compiled with jtreg for the test.
*
* @param loader ClassLoader to find the bytes for the old class.
* @param oldClassName old class name.
* @param newClassName new class name to replace with old class name.
* @return a copy of the class represented by `bytes` but with the name `newClassName`
*/
public static byte[] replaceClassName(ClassLoader loader, String oldClassName, String newClassName) throws Exception {
byte[] buf = getBytecodes(loader, oldClassName);
return replaceClassName(buf, newClassName);
}
/**
* Main method to be invoked before test to create the redefineagent.jar
*/