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SubstrateVM image builder components
/*
* Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.oracle.svm.jni;
import org.graalvm.compiler.api.replacements.Fold;
import org.graalvm.compiler.word.Word;
import org.graalvm.nativeimage.CurrentIsolate;
import org.graalvm.nativeimage.Isolate;
import org.graalvm.nativeimage.ObjectHandle;
import org.graalvm.word.Pointer;
import org.graalvm.word.SignedWord;
import org.graalvm.word.UnsignedWord;
import org.graalvm.word.WordFactory;
import com.oracle.svm.core.Isolates;
import com.oracle.svm.core.RuntimeAssertionsSupport;
import com.oracle.svm.core.SubstrateOptions;
import com.oracle.svm.core.annotate.NeverInline;
import com.oracle.svm.core.handles.ObjectHandlesImpl;
import com.oracle.svm.core.handles.ThreadLocalHandles;
import com.oracle.svm.core.heap.Heap;
import com.oracle.svm.core.threadlocal.FastThreadLocalFactory;
import com.oracle.svm.core.threadlocal.FastThreadLocalObject;
import com.oracle.svm.jni.nativeapi.JNIObjectHandle;
import com.oracle.svm.jni.nativeapi.JNIObjectRefType;
/**
* Centralized management of {@linkplain JNIObjectHandle JNI handles for Java objects}. There are
* different kinds of JNI handles and the main purpose of this class is to abstract their
* differences when working with handles. In order to do that efficiently, we partition the value
* range of the word-sized handles into subranges for the different kinds:
*
* - Local handles as defined in the JNI specification can be created and released implicitly or
* explicitly and are valid only in the current thread.
* - Global handles as defined in the JNI specification must be created explicitly and are valid
* in the entire isolate until they are explicitly released. Individual global handles can be weak,
* in which case they don't prevent garbage collection of their target object. See:
* {@link JNIGlobalHandles}.
* - Image heap handles refer to objects in the image heap. This handle type is specific to our
* implementation. Handles can be either local, global or weak-global according to the JNI
* specification, so they need some special treatment. See: {@link JNIImageHeapHandles}.
*
*/
public final class JNIObjectHandles {
@Fold
static boolean haveAssertions() {
return RuntimeAssertionsSupport.singleton().desiredAssertionStatus(JNIObjectHandles.class);
}
public static T nullHandle() {
return ThreadLocalHandles.nullHandle();
}
/**
* Minimum available local handles according to specification: "Before it enters a native
* method, the VM automatically ensures that at least 16 local references can be created".
*/
static final int NATIVE_CALL_MIN_LOCAL_HANDLE_CAPACITY = 16;
@SuppressWarnings("rawtypes") private static final FastThreadLocalObject handles //
= FastThreadLocalFactory.createObject(ThreadLocalHandles.class);
@Fold
static boolean useImageHeapHandles() {
/*
* Image heap handles are intended for JNI code that is unaware of isolates. Without isolate
* support, this type of handle is not needed. Also, when isolate support is turned off, the
* heap is written into the data/rodata sections instead of having a contiguous section,
* which would require a different approach.
*/
return SubstrateOptions.SpawnIsolates.getValue();
}
@SuppressWarnings("unchecked")
private static ThreadLocalHandles getOrCreateLocals() {
ThreadLocalHandles result = handles.get();
if (result == null) {
result = createLocals();
}
return result;
}
@NeverInline("slow path that is executed once per thread; do not bloat machine code by inlining the allocations")
private static ThreadLocalHandles createLocals() {
ThreadLocalHandles result = new ThreadLocalHandles<>(NATIVE_CALL_MIN_LOCAL_HANDLE_CAPACITY);
handles.set(result);
return result;
}
@SuppressWarnings("unchecked")
private static ThreadLocalHandles getExistingLocals() {
return handles.get();
}
private static boolean isInLocalRange(JNIObjectHandle handle) {
return ThreadLocalHandles.isInRange((ObjectHandle) handle);
}
private static ObjectHandle decodeLocal(JNIObjectHandle handle) {
return (ObjectHandle) handle;
}
private static JNIObjectHandle encodeLocal(ObjectHandle handle) {
return (JNIObjectHandle) handle;
}
public static T getObject(JNIObjectHandle handle) {
if (handle.equal(nullHandle())) {
return null;
}
if (isInLocalRange(handle)) {
return getExistingLocals().getObject(decodeLocal(handle));
}
if (useImageHeapHandles() && JNIImageHeapHandles.isInRange(handle)) {
return JNIImageHeapHandles.getObject(handle);
}
if (JNIGlobalHandles.isInRange(handle)) {
return JNIGlobalHandles.getObject(handle);
}
throw throwIllegalArgumentException();
}
@NeverInline("Exception slow path")
private static IllegalArgumentException throwIllegalArgumentException() {
throw new IllegalArgumentException("Invalid object handle");
}
public static JNIObjectRefType getHandleType(JNIObjectHandle handle) {
if (isInLocalRange(handle)) {
return JNIObjectRefType.Local;
}
if (useImageHeapHandles() && JNIImageHeapHandles.isInRange(handle)) {
return JNIImageHeapHandles.getHandleType(handle);
}
if (JNIGlobalHandles.isInRange(handle)) {
return JNIGlobalHandles.getHandleType(handle);
}
return JNIObjectRefType.Invalid; // intentionally includes the null handle
}
public static JNIObjectHandle createLocal(Object obj) {
if (useImageHeapHandles() && JNIImageHeapHandles.isInImageHeap(obj)) {
return JNIImageHeapHandles.asLocal(obj);
}
return encodeLocal(getOrCreateLocals().create(obj));
}
public static JNIObjectHandle newLocalRef(JNIObjectHandle ref) {
if (useImageHeapHandles() && JNIImageHeapHandles.isInRange(ref)) {
return JNIImageHeapHandles.toLocal(ref);
}
return encodeLocal(getOrCreateLocals().create(getObject(ref)));
}
public static void deleteLocalRef(JNIObjectHandle localRef) {
if (!useImageHeapHandles() || !JNIImageHeapHandles.isInRange(localRef)) {
getOrCreateLocals().delete(decodeLocal(localRef));
}
}
public static int pushLocalFrame(int capacity) {
return getOrCreateLocals().pushFrame(capacity);
}
public static void popLocalFrame() {
getExistingLocals().popFrame();
}
public static void popLocalFramesIncluding(int frame) {
getExistingLocals().popFramesIncluding(frame);
}
public static void ensureLocalCapacity(int capacity) {
getOrCreateLocals().ensureCapacity(capacity);
}
public static JNIObjectHandle newGlobalRef(JNIObjectHandle handle) {
JNIObjectHandle result = nullHandle();
if (useImageHeapHandles() && JNIImageHeapHandles.isInRange(handle)) {
result = JNIImageHeapHandles.toGlobal(handle);
} else {
Object obj = getObject(handle);
if (obj != null) {
result = JNIGlobalHandles.create(obj);
}
}
return result;
}
public static void deleteGlobalRef(JNIObjectHandle globalRef) {
if (!useImageHeapHandles() || !JNIImageHeapHandles.isInRange(globalRef)) {
JNIGlobalHandles.destroy(globalRef);
}
}
public static JNIObjectHandle newWeakGlobalRef(JNIObjectHandle handle) {
JNIObjectHandle result = nullHandle();
if (useImageHeapHandles() && JNIImageHeapHandles.isInRange(handle)) {
result = JNIImageHeapHandles.toWeakGlobal(handle);
} else {
Object obj = getObject(handle);
if (obj != null) {
result = JNIGlobalHandles.createWeak(obj);
}
}
return result;
}
public static void deleteWeakGlobalRef(JNIObjectHandle weakRef) {
if (!useImageHeapHandles() || !JNIImageHeapHandles.isInRange(weakRef)) {
JNIGlobalHandles.destroyWeak(weakRef);
}
}
static int getLocalHandleCount() {
ThreadLocalHandles locals = getExistingLocals();
return locals == null ? 0 : locals.getHandleCount();
}
static long computeCurrentGlobalHandleCount() {
return JNIGlobalHandles.computeCurrentCount();
}
}
/**
* Manages JNI global handles, which must be explicitly created and can be accessed in all threads
* of an isolate until they are explicitly deleted. These handles have a most significant bit of 1,
* i.e. they are negative as signed integers. When assertions are enabled, we encode a hash of the
* current {@link Isolate} to detect when global handles are incorrectly passed between isolates,
* for example by native code that is unaware of isolates.
*/
final class JNIGlobalHandles {
static final SignedWord MIN_VALUE = WordFactory.signed(Long.MIN_VALUE);
static final SignedWord MAX_VALUE = JNIObjectHandles.nullHandle().subtract(1);
static {
assert JNIObjectHandles.nullHandle().equal(WordFactory.zero());
}
private static final int HANDLE_BITS_COUNT = 31;
private static final SignedWord HANDLE_BITS_MASK = WordFactory.signed((1L << HANDLE_BITS_COUNT) - 1);
private static final int VALIDATION_BITS_SHIFT = HANDLE_BITS_COUNT;
private static final int VALIDATION_BITS_COUNT = 32;
private static final SignedWord VALIDATION_BITS_MASK = WordFactory.signed((1L << VALIDATION_BITS_COUNT) - 1).shiftLeft(VALIDATION_BITS_SHIFT);
private static final SignedWord MSB = WordFactory.signed(1L << 63);
private static final ObjectHandlesImpl globalHandles = new ObjectHandlesImpl(JNIObjectHandles.nullHandle().add(1), HANDLE_BITS_MASK, JNIObjectHandles.nullHandle());
static boolean isInRange(JNIObjectHandle handle) {
return MIN_VALUE.lessOrEqual((SignedWord) handle) && MAX_VALUE.greaterThan((SignedWord) handle);
}
private static Word isolateHash() {
int isolateHash = Long.hashCode(CurrentIsolate.getIsolate().rawValue());
return WordFactory.unsigned(isolateHash);
}
private static JNIObjectHandle encode(ObjectHandle handle) {
SignedWord h = (Word) handle;
if (JNIObjectHandles.haveAssertions()) {
assert h.and(HANDLE_BITS_MASK).equal(h) : "unencoded handle must fit in range";
Word v = isolateHash().shiftLeft(VALIDATION_BITS_SHIFT);
assert v.and(VALIDATION_BITS_MASK).equal(v) : "validation value must fit in its range";
h = h.or(v);
}
h = h.or(MSB);
assert isInRange((JNIObjectHandle) h);
return (JNIObjectHandle) h;
}
private static ObjectHandle decode(JNIObjectHandle handle) {
assert isInRange(handle);
assert ((Word) handle).and(VALIDATION_BITS_MASK).unsignedShiftRight(VALIDATION_BITS_SHIFT)
.equal(isolateHash()) : "mismatching validation value -- passed a handle from a different isolate?";
return (ObjectHandle) HANDLE_BITS_MASK.and((Word) handle);
}
static T getObject(JNIObjectHandle handle) {
return globalHandles.get(decode(handle));
}
static JNIObjectRefType getHandleType(JNIObjectHandle handle) {
assert isInRange(handle);
if (globalHandles.isWeak(decode(handle))) {
return JNIObjectRefType.WeakGlobal;
}
return JNIObjectRefType.Global;
}
static JNIObjectHandle create(Object obj) {
return encode(globalHandles.create(obj));
}
static void destroy(JNIObjectHandle handle) {
globalHandles.destroy(decode(handle));
}
static JNIObjectHandle createWeak(Object obj) {
return encode(globalHandles.createWeak(obj));
}
static void destroyWeak(JNIObjectHandle weakRef) {
globalHandles.destroyWeak(decode(weakRef));
}
public static long computeCurrentCount() {
return globalHandles.computeCurrentCount();
}
}
/**
* Support for isolate-independent JNI handles for objects in the image heap. These objects never
* move and are not garbage-collected, so the handle just contains an object's offset in the image
* heap. This approach has the major benefit that handles are valid across isolates that are created
* from the same image, which helps with native code that is unaware of multiple isolates.
*
* Although this type of handle doesn't need explicit management, we still distinguish between
* local, global and weak-global references by means of a bit pattern in order to comply with the
* JNI specification (in particular, for function {@code GetObjectRefType}).
*/
final class JNIImageHeapHandles {
private static final int OBJ_OFFSET_BITS_COUNT = 32;
private static final Word OBJ_OFFSET_BITS_MASK = WordFactory.unsigned((1L << OBJ_OFFSET_BITS_COUNT) - 1);
private static final SignedWord LOCAL_RANGE_MIN = WordFactory.signed(0b01).shiftLeft(OBJ_OFFSET_BITS_COUNT);
private static final SignedWord GLOBAL_RANGE_MIN = WordFactory.signed(0b10).shiftLeft(OBJ_OFFSET_BITS_COUNT);
private static final SignedWord WEAK_GLOBAL_RANGE_MIN = WordFactory.signed(0b11).shiftLeft(OBJ_OFFSET_BITS_COUNT);
private static final SignedWord ENTIRE_RANGE_MIN = LOCAL_RANGE_MIN;
private static final SignedWord ENTIRE_RANGE_MAX = WEAK_GLOBAL_RANGE_MIN.add(OBJ_OFFSET_BITS_MASK);
static { // no overlaps with the regular JNI handle ranges
assert ENTIRE_RANGE_MAX.lessThan(ThreadLocalHandles.MIN_VALUE) || ENTIRE_RANGE_MIN.greaterThan(ThreadLocalHandles.MAX_VALUE);
assert ENTIRE_RANGE_MAX.lessThan(JNIGlobalHandles.MIN_VALUE) || ENTIRE_RANGE_MIN.greaterThan(JNIGlobalHandles.MAX_VALUE);
}
static boolean isInImageHeap(Object target) {
return target != null && Heap.getHeap().isInImageHeap(target);
}
static boolean isInRange(JNIObjectHandle handle) {
SignedWord handleValue = (SignedWord) handle;
return handleValue.greaterOrEqual(ENTIRE_RANGE_MIN) && handleValue.lessOrEqual(ENTIRE_RANGE_MAX);
}
static JNIObjectHandle asLocal(Object target) {
assert isInImageHeap(target);
SignedWord base = (SignedWord) Isolates.getHeapBase(CurrentIsolate.getIsolate());
SignedWord offset = Word.objectToUntrackedPointer(target).subtract(base);
// NOTE: we could support further bits due to the object alignment in the image heap
assert offset.and(OBJ_OFFSET_BITS_MASK).equal(offset) : "does not fit in range";
return (JNIObjectHandle) LOCAL_RANGE_MIN.add(offset);
}
static JNIObjectHandle toLocal(JNIObjectHandle handle) {
return toRange(handle, LOCAL_RANGE_MIN);
}
static JNIObjectHandle toGlobal(JNIObjectHandle handle) {
return toRange(handle, GLOBAL_RANGE_MIN);
}
static JNIObjectHandle toWeakGlobal(JNIObjectHandle handle) {
return toRange(handle, WEAK_GLOBAL_RANGE_MIN);
}
private static JNIObjectHandle toRange(JNIObjectHandle handle, SignedWord rangeMin) {
assert isInRange(handle) : "assert isInRange(handle) failed";
return (JNIObjectHandle) ((SignedWord) handle).and(OBJ_OFFSET_BITS_MASK).add(rangeMin);
}
static T getObject(JNIObjectHandle handle) {
assert isInRange(handle);
UnsignedWord base = (UnsignedWord) Isolates.getHeapBase(CurrentIsolate.getIsolate());
Pointer offset = ((Pointer) handle).and(OBJ_OFFSET_BITS_MASK).add(base);
@SuppressWarnings("unchecked")
T obj = (T) offset.toObjectNonNull();
assert isInImageHeap(obj);
return obj;
}
static JNIObjectRefType getHandleType(JNIObjectHandle handle) {
assert isInRange(handle);
SignedWord handleValue = (SignedWord) handle;
if (handleValue.greaterOrEqual(WEAK_GLOBAL_RANGE_MIN)) {
return JNIObjectRefType.WeakGlobal;
} else if (handleValue.greaterOrEqual(GLOBAL_RANGE_MIN)) {
return JNIObjectRefType.Global;
} else if (handleValue.greaterOrEqual(LOCAL_RANGE_MIN)) {
return JNIObjectRefType.Local;
}
return JNIObjectRefType.Invalid;
}
}