[GR-62046] Support -H:+MetadataTracing with an empty configuration file.

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/metadata/MetadataTracer.java

@@ -0,0 +1,168 @@
+/*
+ * Copyright (c) 2025, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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 com.oracle.svm.core.metadata;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+
+import org.graalvm.nativeimage.ImageSingletons;
+import org.graalvm.nativeimage.hosted.Feature;
+
+import com.oracle.svm.configure.config.ConfigurationSet;
+import com.oracle.svm.core.feature.AutomaticallyRegisteredFeature;
+import com.oracle.svm.core.feature.InternalFeature;
+import com.oracle.svm.core.jdk.RuntimeSupport;
+import com.oracle.svm.core.jdk.RuntimeSupportFeature;
+import com.oracle.svm.core.log.Log;
+import com.oracle.svm.core.option.HostedOptionKey;
+import com.oracle.svm.core.option.RuntimeOptionKey;
+import com.oracle.svm.core.option.SubstrateOptionsParser;
+import com.oracle.svm.core.util.VMError;
+
+import jdk.graal.compiler.api.replacements.Fold;
+import jdk.graal.compiler.options.Option;
+
+/**
+ * Implements reachability metadata tracing during native image execution. Enabling
+ * {@link Options#MetadataTracingSupport} at build time will generate code to trace all accesses of
+ * reachability metadata. When {@link Options#RecordMetadata} is specified at run time, the image
+ * will trace and emit metadata to the specified path.
+ */
+public final class MetadataTracer {
+
+    public static class Options {
+        @Option(help = "Enables the run-time code to trace reachability metadata accesses in the produced native image by using -XX:RecordMetadata=<path>.")//
+        public static final HostedOptionKey<Boolean> MetadataTracingSupport = new HostedOptionKey<>(false);
+
+        @Option(help = "The path of the directory to write traced metadata to. Metadata tracing is enabled only when this option is provided.")//
+        public static final RuntimeOptionKey<String> RecordMetadata = new RuntimeOptionKey<>("");
+    }
+
+    private ConfigurationSet config;
+
+    private Path recordMetadataPath;
+
+    @Fold
+    public static MetadataTracer singleton() {
+        return ImageSingletons.lookup(MetadataTracer.class);
+    }
+
+    private static void initialize() {
+        assert Options.MetadataTracingSupport.getValue();
+        MetadataTracer singleton = MetadataTracer.singleton();
+        String recordMetadataValue = Options.RecordMetadata.getValue();
+        if (recordMetadataValue.isEmpty()) {
+            throw new IllegalArgumentException("Empty path provided for " + Options.RecordMetadata.getName() + ".");
+        }
+        Path recordMetadataPath = Paths.get(recordMetadataValue);
+        try {
+            Files.createDirectories(recordMetadataPath);
+        } catch (IOException ex) {
+            throw new IllegalArgumentException("Exception occurred creating the output directory for tracing (" + recordMetadataPath + ")", ex);
+        }
+        singleton.recordMetadataPath = recordMetadataPath;
+        singleton.config = new ConfigurationSet();
+    }
+
+    private static void shutdown() {
+        assert Options.MetadataTracingSupport.getValue();
+        MetadataTracer singleton = MetadataTracer.singleton();
+        ConfigurationSet config = singleton.config;
+        if (config != null) {
+            try {
+                config.writeConfiguration(configFile -> singleton.recordMetadataPath.resolve(configFile.getFileName()));
+            } catch (IOException ex) {
+                Log log = Log.log();
+                log.string("Failed to write out reachability metadata to directory ").string(singleton.recordMetadataPath.toString());
+                log.string(":").string(ex.getMessage());
+                log.newline();
+            }
+        }
+    }
+
+    static RuntimeSupport.Hook initializeMetadataTracingHook() {
+        return isFirstIsolate -> {
+            if (!isFirstIsolate) {
+                return;
+            }
+            VMError.guarantee(Options.MetadataTracingSupport.getValue());
+            if (Options.RecordMetadata.hasBeenSet()) {
+                initialize();
+            }
+        };
+    }
+
+    static RuntimeSupport.Hook shutDownMetadataTracingHook() {
+        return isFirstIsolate -> {
+            if (!isFirstIsolate) {
+                return;
+            }
+            VMError.guarantee(Options.MetadataTracingSupport.getValue());
+            if (Options.RecordMetadata.hasBeenSet()) {
+                shutdown();
+            }
+        };
+    }
+
+    static RuntimeSupport.Hook checkImproperOptionUsageHook() {
+        // Compute argument at build time (hosted option should not be reached in image code)
+        String hostedOptionCommandArgument = SubstrateOptionsParser.commandArgument(Options.MetadataTracingSupport, "+");
+
+        return isFirstIsolate -> {
+            if (!isFirstIsolate) {
+                return;
+            }
+            VMError.guarantee(!Options.MetadataTracingSupport.getValue());
+            if (Options.RecordMetadata.hasBeenSet()) {
+                throw new IllegalArgumentException(
+                                "The option " + Options.RecordMetadata.getName() + " can only be used if metadata tracing is enabled at build time (using " +
+                                                hostedOptionCommandArgument + ").");
+
+            }
+        };
+    }
+}
+
+@AutomaticallyRegisteredFeature
+class MetadataTracerFeature implements InternalFeature {
+    @Override
+    public List<Class<? extends Feature>> getRequiredFeatures() {
+        return List.of(RuntimeSupportFeature.class);
+    }
+
+    @Override
+    public void beforeAnalysis(BeforeAnalysisAccess access) {
+        if (MetadataTracer.Options.MetadataTracingSupport.getValue()) {
+            ImageSingletons.add(MetadataTracer.class, new MetadataTracer());
+            RuntimeSupport.getRuntimeSupport().addInitializationHook(MetadataTracer.initializeMetadataTracingHook());
+            RuntimeSupport.getRuntimeSupport().addTearDownHook(MetadataTracer.shutDownMetadataTracingHook());
+        } else {
+            RuntimeSupport.getRuntimeSupport().addInitializationHook(MetadataTracer.checkImproperOptionUsageHook());
+        }
+    }
+}