Prevent that an invalid direct memory size is cached in java.nio.Bits#MAX_MEMORY.

Author: christianhaeubl

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

@@ -27,9 +27,11 @@
 import java.util.concurrent.atomic.AtomicLong;
 
 import com.oracle.svm.core.annotate.Alias;
+import com.oracle.svm.core.annotate.InjectAccessors;
 import com.oracle.svm.core.annotate.RecomputeFieldValue;
 import com.oracle.svm.core.annotate.RecomputeFieldValue.Kind;
 import com.oracle.svm.core.annotate.TargetClass;
+import com.oracle.svm.core.heap.PhysicalMemory;
 
 @TargetClass(className = "java.nio.Bits")
 final class Target_java_nio_Bits {
@@ -40,9 +42,9 @@ final class Target_java_nio_Bits {
     private static int PAGE_SIZE = -1;
 
     @Alias @RecomputeFieldValue(kind = Kind.FromAlias) //
-    private static boolean MEMORY_LIMIT_SET = false;
-    @Alias @RecomputeFieldValue(kind = Kind.FromAlias) //
-    private static long MAX_MEMORY = -1;
+    private static boolean MEMORY_LIMIT_SET = true;
+    @Alias @InjectAccessors(MaxMemoryAccessor.class) //
+    private static long MAX_MEMORY;
 
     @Alias @RecomputeFieldValue(kind = Kind.FromAlias) //
     private static AtomicLong RESERVED_MEMORY = new AtomicLong();
@@ -53,3 +55,23 @@ final class Target_java_nio_Bits {
 
     // Checkstyle: resume
 }
+
+/**
+ * {@code java.nio.Bits} caches the max. direct memory size in the field {@code MAX_MEMORY}. We
+ * disable this cache and always call {@link DirectMemoryAccessors#getDirectMemory()} instead, which
+ * uses our own cache. Otherwise, it could happen that {@code MAX_MEMORY} caches a temporary value
+ * that is used during early VM startup, before {@link PhysicalMemory} is fully initialized.
+ */
+final class MaxMemoryAccessor {
+    // Checkstyle: stop
+
+    static long getMAX_MEMORY() {
+        return DirectMemoryAccessors.getDirectMemory();
+    }
+
+    static void setMAX_MEMORY(long value) {
+        /* Nothing to do. */
+    }
+
+    // Checkstyle: resume
+}