replace LibGraalLoader.getJavaHome with a protocol shared between HostedLibGraalClassLoader and LibGraalFeature

Author: dougxc

compiler/src/jdk.graal.compiler.libgraal.loader/src/jdk/graal/compiler/libgraal/loader/HostedLibGraalClassLoader.java

@@ -61,7 +61,8 @@
 
 /**
  * A classloader that reads class files and resources from a jimage file and a module path at image
- * build time.
+ * build time. The {@code java.home} of the JDK containing the jimage can be obtained by converting
+ * the bytes of {@code getResourceAsStream("META-INF/libgraal.java.home")} to a string.
  */
 @Platforms(Platform.HOSTED_ONLY.class)
 public final class HostedLibGraalClassLoader extends ClassLoader implements LibGraalLoader {
@@ -72,6 +73,12 @@ public final class HostedLibGraalClassLoader extends ClassLoader implements LibG
      */
     private static final String LIBGRAAL_JAVA_HOME_PROPERTY_NAME = "libgraal.java.home";
 
+    /**
+     * The {@code java.home} of the JDK whose runtime image contains the Graal and JVMCI classes
+     * from which libgraal will be built.
+     */
+    private static final Path LIBGRAAL_JAVA_HOME = Path.of(System.getProperty(LIBGRAAL_JAVA_HOME_PROPERTY_NAME, System.getProperty("java.home")));
+
     /**
      * Name of the system property specifying a module path for the module(s) containing
      * {@code LibGraalFeature} and its dependencies that are not available in the runtime image.
@@ -177,13 +184,6 @@ byte[] readBytes() throws ClassNotFoundException {
         ClassLoader.registerAsParallelCapable();
     }
 
-    private final Path libgraalJavaHome = Path.of(System.getProperty(LIBGRAAL_JAVA_HOME_PROPERTY_NAME, System.getProperty("java.home")));
-
-    @Override
-    public Path getJavaHome() {
-        return libgraalJavaHome;
-    }
-
     /**
      * Converts the module path entry {@code s} to a {@link Path}.
      *
@@ -219,7 +219,7 @@ public HostedLibGraalClassLoader() {
 
             Map<String, String> modulesMap = new HashMap<>();
 
-            Path imagePath = libgraalJavaHome.resolve(Path.of("lib", "modules"));
+            Path imagePath = LIBGRAAL_JAVA_HOME.resolve(Path.of("lib", "modules"));
             this.imageReader = BasicImageReader.open(imagePath);
             for (var entry : imageReader.getEntryNames()) {
                 int secondSlash = entry.indexOf('/', 1);
@@ -316,6 +316,12 @@ protected Class<?> findClass(final String name) throws ClassNotFoundException {
      */
     private static final String SERVICE_PROTOCOL = "service-config";
 
+    /**
+     * Name of the protocol for accessing a file whose contents are the {@code java.home} of the JDK
+     * whose runtime image contains the Graal and JVMCI * classes from which libgraal will be built.
+     */
+    private static final String LIBGRAAL_JAVA_HOME_PROTOCOL = "libgraal-java-home";
+
     /**
      * Name of the protocol for accessing entries in {@link #resources}.
      */
@@ -329,7 +335,14 @@ protected URL findResource(String name) {
         if (handler == null) {
             this.serviceHandler = handler = new ImageURLStreamHandler();
         }
-        if (name.startsWith("META-INF/services/")) {
+        if (name.equals("META-INF/libgraal.java.home")) {
+            try {
+                var uri = new URI(LIBGRAAL_JAVA_HOME_PROTOCOL, "libgraal.java.home", null);
+                return URL.of(uri, handler);
+            } catch (URISyntaxException | MalformedURLException e) {
+                return null;
+            }
+        } else if (name.startsWith("META-INF/services/")) {
             String service = name.substring("META-INF/services/".length());
             if (services.containsKey(service)) {
                 try {
@@ -370,7 +383,12 @@ private class ImageURLStreamHandler extends URLStreamHandler {
         @Override
         public URLConnection openConnection(URL u) {
             String protocol = u.getProtocol();
-            if (protocol.equalsIgnoreCase(SERVICE_PROTOCOL)) {
+            if (protocol.equalsIgnoreCase(LIBGRAAL_JAVA_HOME_PROTOCOL)) {
+                if (!u.getPath().equals("libgraal.java.home")) {
+                    throw new IllegalArgumentException(u.toString());
+                }
+                return new ImageURLConnection(u, LIBGRAAL_JAVA_HOME.toString().getBytes());
+            } else if (protocol.equalsIgnoreCase(SERVICE_PROTOCOL)) {
                 List<String> providers = services.get(u.getPath());
                 if (providers != null) {
                     return new ImageURLConnection(u, String.join("\n", providers).getBytes());

compiler/src/jdk.graal.compiler.libgraal/src/jdk/graal/compiler/libgraal/GetJNIConfig.java

@@ -42,6 +42,7 @@
 
 import jdk.graal.compiler.serviceprovider.GraalServices;
 import jdk.graal.compiler.util.SignatureUtil;
+import jdk.graal.nativeimage.LibGraalLoader;
 import org.graalvm.nativeimage.Platform;
 import org.graalvm.nativeimage.Platforms;
 import org.graalvm.nativeimage.hosted.RuntimeJNIAccess;
@@ -78,9 +79,9 @@ final class GetJNIConfig implements AutoCloseable {
 
     int lineNo;
 
-    private GetJNIConfig(ClassLoader loader) {
+    private GetJNIConfig(ClassLoader loader, Path libgraalJavaHome) {
         this.loader = loader;
-        Path javaExe = getJavaExe(Path.of(GraalServices.getSavedProperty("java.home")));
+        Path javaExe = getJavaExe(libgraalJavaHome);
         configFilePath = Path.of("libgraal_jniconfig.txt");
 
         String[] command = {javaExe.toFile().getAbsolutePath(), "-XX:+UnlockExperimentalVMOptions", "-XX:+EnableJVMCI", "-XX:JVMCILibDumpJNIConfig=" + configFilePath};
@@ -196,8 +197,8 @@ private GraalError error(String format, Object... args) {
      * @param loader used to resolve type names in the config
      */
     @SuppressWarnings("try")
-    public static void register(ClassLoader loader) {
-        try (GetJNIConfig source = new GetJNIConfig(loader)) {
+    public static void register(ClassLoader loader, Path libgraalJavaHome) {
+        try (GetJNIConfig source = new GetJNIConfig(loader, libgraalJavaHome)) {
             Map<String, Class<?>> classes = new HashMap<>();
             for (String line : source.lines) {
                 source.lineNo++;

compiler/src/jdk.graal.compiler.libgraal/src/jdk/graal/compiler/libgraal/LibGraalFeature.java

@@ -24,6 +24,8 @@
  */
 package jdk.graal.compiler.libgraal;
 
+import java.io.IOException;
+import java.io.InputStream;
 import java.lang.module.ModuleDescriptor;
 import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
@@ -114,7 +116,23 @@ public boolean getAsBoolean() {
         }
     }
 
+    /**
+     * See javadoc for {@code jdk.graal.compiler.libgraal.loader.HostedLibGraalClassLoader}.
+     */
+    private static Path readLibgraalJavaHome(ClassLoader cl) {
+        try (InputStream in = cl.getResourceAsStream("META-INF/libgraal.java.home")) {
+            if (in == null) {
+                throw new GraalError(cl.getClass().getName() + " does not support META-INF/libgraal.java.home protocol (see javadoc of HostedLibGraalClassLoader)");
+            }
+            return Path.of(new String(in.readAllBytes()));
+        } catch (IOException e) {
+            throw new GraalError(e);
+        }
+    }
+
     private final LibGraalLoader libgraalLoader = (LibGraalLoader) getClass().getClassLoader();
+    private final Path libgraalJavaHome = readLibgraalJavaHome(getClass().getClassLoader());
+
     private BeforeAnalysisAccess beforeAnalysisAccess;
     private BeforeCompilationAccess beforeCompilationAccess;
     private OptionCollector optionCollector;
@@ -158,7 +176,7 @@ public void duringSetup(DuringSetupAccess access) {
                 beforeAnalysisAccess.registerAsUnsafeAllocated(clazz);
             }
         }, NodeClass.class);
-        GetJNIConfig.register((ClassLoader) libgraalLoader);
+        GetJNIConfig.register((ClassLoader) libgraalLoader, libgraalJavaHome);
     }
 
     /**
@@ -275,8 +293,7 @@ public void beforeAnalysis(BeforeAnalysisAccess access) {
 
         doLegacyJVMCIInitialization();
 
-        Path libGraalJavaHome = libgraalLoader.getJavaHome();
-        GetCompilerConfig.Result configResult = GetCompilerConfig.from(libGraalJavaHome);
+        GetCompilerConfig.Result configResult = GetCompilerConfig.from(libgraalJavaHome);
         for (var e : configResult.opens().entrySet()) {
             Module module = ModuleLayer.boot().findModule(e.getKey()).orElseThrow();
             for (String source : e.getValue()) {

sdk/src/jdk.graal.nativeimage/src/jdk/graal/nativeimage/LibGraalLoader.java

@@ -40,7 +40,6 @@
  */
 package jdk.graal.nativeimage;
 
-import java.nio.file.Path;
 import java.util.Map;
 
 /**
@@ -51,12 +50,6 @@
  */
 public interface LibGraalLoader {
 
-    /**
-     * Gets the {@code java.home} of the JDK whose runtime image contains the Graal and JVMCI
-     * classes from which libgraal will be built.
-     */
-    Path getJavaHome();
-
     /**
      * Gets a map from the {@linkplain Class#forName(String) name} of a class to the name of its
      * enclosing module. There is one entry in the map for each class available for loading by this