Implement static field base and offset substitutions for Unsafe

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/SunMiscSubstitutions.java

@@ -32,6 +32,7 @@
 import java.security.ProtectionDomain;
 import java.util.function.Function;
 
+import com.oracle.svm.core.StaticFieldsSupport;
 import org.graalvm.compiler.nodes.extended.MembarNode;
 import org.graalvm.compiler.serviceprovider.JavaVersionUtil;
 import org.graalvm.nativeimage.Platform;
@@ -206,14 +207,13 @@ public void ensureClassInitialized(Class<?> c) {
         DynamicHub.fromClass(c).ensureInitialized();
     }
 
-    @Substitute
-    private long staticFieldOffset(Field f) {
-        throw VMError.unsupportedFeature("Unsupported method of Unsafe");
-    }
-
     @Substitute
     private Object staticFieldBase(Field f) {
-        throw VMError.unsupportedFeature("Unsupported method of Unsafe");
+        if (f.getType().isPrimitive()) {
+            return StaticFieldsSupport.getStaticPrimitiveFields();
+        } else {
+            return StaticFieldsSupport.getStaticObjectFields();
+        }
     }
 
     @Substitute

substratevm/src/com.oracle.svm.reflect/src/com/oracle/svm/reflect/target/Target_jdk_internal_misc_Unsafe_Reflection.java

@@ -47,6 +47,7 @@ public long objectFieldOffset(Target_java_lang_reflect_Field field) {
         if (offset > 0) {
             return offset;
         }
+
         throw VMError.unsupportedFeature("The offset of " + field + " is accessed without the field being first registered as unsafe accessed. " +
                         "Please register the field as unsafe accessed. You can do so with a reflection configuration that " +
                         "contains an entry for the field with the attribute \"allowUnsafeAccess\": true. Such a configuration " +
@@ -67,4 +68,9 @@ public long objectFieldOffset(Class<?> c, String name) {
             throw new InternalError();
         }
     }
+
+    @Substitute
+    private long staticFieldOffset(Target_java_lang_reflect_Field f) {
+        return f.offset;
+    }
 }