/*
 * Copyright (c) 2014, 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
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package jdk.vm.ci.hotspot;

import static java.lang.String.format;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.lang.reflect.Executable;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.security.AccessControlException;
import java.util.Arrays;
import java.util.Objects;

import jdk.vm.ci.common.JVMCIError;
import jdk.internal.org.objectweb.asm.ClassReader;
import jdk.internal.org.objectweb.asm.ClassVisitor;
import jdk.internal.org.objectweb.asm.Label;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.internal.org.objectweb.asm.Opcodes;
import jdk.internal.org.objectweb.asm.Type;
import sun.misc.Unsafe;

/**
 * A verifier that checks that {@link HotSpotVMConfig} does not access {@link Unsafe} from any of
 * its non-static, non-constructor methods. This ensures that a deserialized {@link HotSpotVMConfig}
 * object does not perform any unsafe reads on addresses that are only valid in the context in which
 * the object was serialized. Note that this does not catch cases where a client uses an address
 * stored in a {@link HotSpotVMConfig} field.
 */
final class HotSpotVMConfigVerifier {

    public static boolean check() {
        Class<?> cls = HotSpotVMConfig.class;
        String classFilePath = "/" + cls.getName().replace('.', '/') + ".class";
        try {
            InputStream classfile = cls.getResourceAsStream(classFilePath);
            ClassReader cr = new ClassReader(Objects.requireNonNull(classfile, "Could not find class file for " + cls.getName()));
            ClassVisitor cv = new Verifier();
            cr.accept(cv, 0);
            return true;
        } catch (AccessControlException e) {
            /*
             * When running with a security manager and +UseJVMCIClassLoader the ASM classes might
             * not be accessible.
             */
            return true;
        } catch (IOException e) {
            throw new JVMCIError(e);
        }
    }

    private static Class<?> resolve(String name) {
        try {
            return Class.forName(name.replace('/', '.'));
        } catch (ClassNotFoundException e) {
            throw new JVMCIError(e);
        }
    }

    private static class Verifier extends ClassVisitor {

        /**
         * Source file context for error reporting.
         */
        String sourceFile = null;

        /**
         * Line number for error reporting.
         */
        int lineNo = -1;

        Verifier() {
            super(Opcodes.ASM5);
        }

        @Override
        public void visitSource(String source, String debug) {
            this.sourceFile = source;
        }

        void verify(boolean condition, String message) {
            if (!condition) {
                error(message);
            }
        }

        void error(String message) {
            String errorMessage = format("%s:%d: %s is not allowed in the context of compilation replay. The unsafe access should be moved into the %s constructor and the result cached in a field",
                            sourceFile, lineNo, message, HotSpotVMConfig.class.getSimpleName());
            throw new JVMCIError(errorMessage);

        }

        @Override
        public MethodVisitor visitMethod(int access, String name, String d, String signature, String[] exceptions) {
            if (!Modifier.isStatic(access) && Modifier.isPublic(access) && !name.equals("<init>")) {
                return new MethodVisitor(Opcodes.ASM5) {

                    @Override
                    public void visitLineNumber(int line, Label start) {
                        lineNo = line;
                    }

                    private Executable resolveMethod(String owner, String methodName, String methodDesc) {
                        Class<?> declaringClass = resolve(owner);
                        while (declaringClass != null) {
                            if (methodName.equals("<init>")) {
                                for (Constructor<?> c : declaringClass.getDeclaredConstructors()) {
                                    if (methodDesc.equals(Type.getConstructorDescriptor(c))) {
                                        return c;
                                    }
                                }
                            } else {
                                Type[] argumentTypes = Type.getArgumentTypes(methodDesc);
                                for (Method m : declaringClass.getDeclaredMethods()) {
                                    if (m.getName().equals(methodName)) {
                                        if (Arrays.equals(argumentTypes, Type.getArgumentTypes(m))) {
                                            if (Type.getReturnType(methodDesc).equals(Type.getReturnType(m))) {
                                                return m;
                                            }
                                        }
                                    }
                                }
                            }
                            declaringClass = declaringClass.getSuperclass();
                        }
                        throw new NoSuchMethodError(owner + "." + methodName + methodDesc);
                    }

                    /**
                     * Checks whether a given method is allowed to be called.
                     */
                    private boolean checkInvokeTarget(Executable method) {
                        if (method.getDeclaringClass().equals(Unsafe.class)) {
                            return false;
                        }
                        return true;
                    }

                    @Override
                    public void visitMethodInsn(int opcode, String owner, String methodName, String methodDesc, boolean itf) {
                        Executable callee = resolveMethod(owner, methodName, methodDesc);
                        verify(checkInvokeTarget(callee), "invocation of " + callee);
                    }
                };
            } else {
                return null;
            }
        }
    }
}