Verify that DynamicHubs are addressable.

Author: christianhaeubl

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ChunkedImageHeapLayouter.java

@@ -158,7 +158,7 @@ private ImageHeapLayoutInfo doLayout(ImageHeap imageHeap, int pageSize) {
         for (ChunkedImageHeapPartition partition : getPartitions()) {
             partition.layout(allocator);
         }
-        return populateInfoObjects(imageHeap.countDynamicHubs(), pageSize);
+        return populateInfoObjects(imageHeap.countAndVerifyDynamicHubs(), pageSize);
     }
 
     private ImageHeapLayoutInfo populateInfoObjects(int dynamicHubCount, int pageSize) {

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ObjectHeaderImpl.java

@@ -303,7 +303,6 @@ public static boolean isConsumedHeapChunkZapped(UnsignedWord header) {
     @Override
     public long encodeAsImageHeapObjectHeader(ImageHeapObject obj, long hubOffsetFromHeapBase) {
         long header = hubOffsetFromHeapBase << numReservedExtraBits;
-        VMError.guarantee((header >>> numReservedExtraBits) == hubOffsetFromHeapBase, "Hub is too far from heap base for encoding in object header");
         assert (header & reservedBitsMask) == 0 : "Object header bits must be zero initially";
         if (obj.getPartition() instanceof ChunkedImageHeapPartition partition) {
             if (partition.isWritable() && HeapImpl.usesImageHeapCardMarking()) {
@@ -321,6 +320,16 @@ public long encodeAsImageHeapObjectHeader(ImageHeapObject obj, long hubOffsetFro
         return header;
     }
 
+    @Override
+    public void verifyDynamicHubOffsetInImageHeap(long offsetFromHeapBase) {
+        long referenceSizeMask = getReferenceSize() == Integer.BYTES ? 0xFFFF_FFFFL : -1L;
+        long encoded = (offsetFromHeapBase << numReservedExtraBits) & referenceSizeMask;
+        boolean shiftLosesInformation = (encoded >>> numReservedExtraBits != offsetFromHeapBase);
+        if (shiftLosesInformation) {
+            throw VMError.shouldNotReachHere("Hub is too far from heap base for encoding in object header: " + offsetFromHeapBase);
+        }
+    }
+
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     public static boolean isAlignedObject(Object o) {
         return !isUnalignedObject(o);

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/ObjectHeader.java

@@ -69,6 +69,8 @@ protected ObjectHeader() {
 
     public abstract Word encodeAsUnmanagedObjectHeader(DynamicHub hub);
 
+    public abstract void verifyDynamicHubOffsetInImageHeap(long offsetFromHeapBase);
+
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     public DynamicHub dynamicHubFromObjectHeader(Word header) {
         return (DynamicHub) extractPotentialDynamicHubFromHeader(header).toObject();

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/image/ImageHeap.java

@@ -33,5 +33,5 @@ public interface ImageHeap {
 
     ImageHeapObject addFillerObject(int size);
 
-    int countDynamicHubs();
+    int countAndVerifyDynamicHubs();
 }

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/NativeImageHeap.java

@@ -61,6 +61,8 @@
 import com.oracle.svm.core.config.ConfigurationValues;
 import com.oracle.svm.core.config.ObjectLayout;
 import com.oracle.svm.core.heap.FillerObject;
+import com.oracle.svm.core.heap.Heap;
+import com.oracle.svm.core.heap.ObjectHeader;
 import com.oracle.svm.core.hub.DynamicHub;
 import com.oracle.svm.core.hub.DynamicHubCompanion;
 import com.oracle.svm.core.hub.LayoutEncoding;
@@ -415,10 +417,12 @@ private int computeIdentityHashCode(JavaConstant constant) {
     }
 
     @Override
-    public int countDynamicHubs() {
+    public int countAndVerifyDynamicHubs() {
+        ObjectHeader objHeader = Heap.getHeap().getObjectHeader();
         int count = 0;
         for (ObjectInfo o : getObjects()) {
             if (!o.constant.isWrittenInPreviousLayer() && hMetaAccess.isInstanceOf(o.getConstant(), DynamicHub.class)) {
+                objHeader.verifyDynamicHubOffsetInImageHeap(o.getOffset());
                 count++;
             }
         }

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/NativeImageHeapWriter.java

@@ -278,7 +278,7 @@ private void writeObjectHeader(RelocatableBuffer buffer, int index, ObjectInfo o
         DynamicHub hub = obj.getClazz().getHub();
         assert hub != null : "Null DynamicHub found during native image generation.";
         ObjectInfo hubInfo = heap.getObjectInfo(hub);
-        assert hubInfo != null : "Unknown object " + hub.toString() + " found. Static field or an object referenced from a static field changed during native image generation?";
+        assert hubInfo != null : "Unknown object " + hub + " found. Static field or an object referenced from a static field changed during native image generation?";
 
         ObjectHeader objectHeader = Heap.getHeap().getObjectHeader();
         if (NativeImageHeap.useHeapBase()) {
@@ -356,7 +356,7 @@ private void writeReferenceValue(RelocatableBuffer buffer, int index, long value
         if (referenceSize() == Long.BYTES) {
             buffer.getByteBuffer().putLong(index, value);
         } else if (referenceSize() == Integer.BYTES) {
-            buffer.getByteBuffer().putInt(index, NumUtil.safeToInt(value));
+            buffer.getByteBuffer().putInt(index, NumUtil.safeToUInt(value));
         } else {
             throw shouldNotReachHere("Unsupported reference size: " + referenceSize());
         }