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8310053: VarHandle and slice handle derived from layout are lacking alignment check #14475

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8310053: VarHandle and slice handle derived from layout are lacking alignment check #14475

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f984574
Add root layout alignment check to varHandle and sliceHandle
JornVernee Jun 14, 2023
1abe758
add note to sliceHandle too
JornVernee Jun 14, 2023
668e9c3
formatting
JornVernee Jun 14, 2023
9907626
Drop alignment checks from accessed elements
JornVernee Jun 14, 2023
b486d46
only check alignment of root for the first deref in a chain
JornVernee Jun 15, 2023
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19 changes: 16 additions & 3 deletions src/java.base/share/classes/jdk/internal/foreign/LayoutPath.java
View file
Original file line number Diff line number Diff line change
@@ -58,6 +58,7 @@ public class LayoutPath {

private static final MethodHandle MH_ADD_SCALED_OFFSET;
private static final MethodHandle MH_SLICE;
private static final MethodHandle MH_SLICE_LAYOUT;
private static final MethodHandle MH_CHECK_ALIGN;
private static final MethodHandle MH_SEGMENT_RESIZE;

@@ -67,6 +68,8 @@ public class LayoutPath {
MH_ADD_SCALED_OFFSET = lookup.findStatic(LayoutPath.class, "addScaledOffset",
MethodType.methodType(long.class, long.class, long.class, long.class, long.class));
MH_SLICE = lookup.findVirtual(MemorySegment.class, "asSlice",
MethodType.methodType(MemorySegment.class, long.class, long.class));
MH_SLICE_LAYOUT = lookup.findVirtual(MemorySegment.class, "asSlice",
MethodType.methodType(MemorySegment.class, long.class, MemoryLayout.class));
MH_CHECK_ALIGN = lookup.findStatic(LayoutPath.class, "checkAlign",
MethodType.methodType(MemorySegment.class, MemorySegment.class, MemoryLayout.class));
@@ -196,7 +199,10 @@ public VarHandle dereferenceHandle(boolean adapt) {
throw new IllegalArgumentException("Path does not select a value layout");
}

VarHandle handle = Utils.makeSegmentViewVarHandle(valueLayout);
// If we have an enclosing layout, drop the alignment check for the accessed element,
// we check the root layout instead
ValueLayout accessedLayout = enclosing != null ? valueLayout.withByteAlignment(1) : valueLayout;
VarHandle handle = Utils.makeSegmentViewVarHandle(accessedLayout);
handle = MethodHandles.collectCoordinates(handle, 1, offsetHandle());
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nice simplification!

if (enclosing != null) {
MethodHandle checkHandle = MethodHandles.insertArguments(MH_CHECK_ALIGN, 1, rootLayout());
@@ -234,8 +240,15 @@ private MemoryLayout rootLayout() {
}

public MethodHandle sliceHandle() {
MethodHandle sliceHandle = MH_SLICE; // (MS, long, MemoryLayout) -> MS
sliceHandle = MethodHandles.insertArguments(sliceHandle, 2, layout); // (MS, long) -> MS
MethodHandle sliceHandle;
if (enclosing != null) {
// drop the alignment check for the accessed element, we check the root layout instead
sliceHandle = MH_SLICE; // (MS, long, long) -> MS
sliceHandle = MethodHandles.insertArguments(sliceHandle, 2, layout.byteSize()); // (MS, long) -> MS
} else {
sliceHandle = MH_SLICE_LAYOUT; // (MS, long, MemoryLayout) -> MS
sliceHandle = MethodHandles.insertArguments(sliceHandle, 2, layout); // (MS, long) -> MS
}
sliceHandle = MethodHandles.collectArguments(sliceHandle, 1, offsetHandle()); // (MS, ...) -> MS

if (enclosing != null) {
26 changes: 11 additions & 15 deletions test/jdk/java/foreign/TestLayoutPaths.java
View file
Original file line number Diff line number Diff line change
@@ -149,21 +149,17 @@ public void testBadAlignmentOfRoot() throws Throwable {

String expectedMessage = "Target offset incompatible with alignment constraints: " + struct.byteAlignment();

try {
VarHandle vhX = struct.varHandle(groupElement("x"));
vhX.set(seg, (short) 42); // should throw
fail("var handle didn't throw");
} catch (IllegalArgumentException e) {
assertEquals(e.getMessage(), expectedMessage);
}

try {
MethodHandle sliceX = struct.sliceHandle(groupElement("x"));
MemorySegment slice = (MemorySegment) sliceX.invokeExact(seg); // should throw
fail("slice handle didn't throw");
} catch (IllegalArgumentException e) {
assertEquals(e.getMessage(), expectedMessage);
}
VarHandle vhX = struct.varHandle(groupElement("x"));
IllegalArgumentException iae = expectThrows(IllegalArgumentException.class, () -> {
vhX.set(seg, (short) 42);
});
assertEquals(iae.getMessage(), expectedMessage);

MethodHandle sliceX = struct.sliceHandle(groupElement("x"));
iae = expectThrows(IllegalArgumentException.class, () -> {
MemorySegment slice = (MemorySegment) sliceX.invokeExact(seg);
});
assertEquals(iae.getMessage(), expectedMessage);
}
}