Backed out changeset f2cf760a4668 (bug 1240984) for XPCShell failures
authorIris Hsiao <ihsiao@mozilla.com>
Thu, 21 Jul 2016 11:14:49 +0800
changeset 331055 56faf83bf0c3fa65d671c3334227923d9870eacd
parent 331054 c805161da79c471e266e8db70ca4e8b18b697e29
child 331056 439867de69353a878b0bf43b6d5d00e92d678304
push id9858
push userjlund@mozilla.com
push dateMon, 01 Aug 2016 14:37:10 +0000
treeherdermozilla-aurora@203106ef6cb6 [default view] [failures only]
perfherder[talos] [build metrics] [platform microbench] (compared to previous push)
bugs1240984
milestone50.0a1
backs outf2cf760a466829efa2b6182fa2243211f73429eb
Backed out changeset f2cf760a4668 (bug 1240984) for XPCShell failures
js/src/jit-test/tests/asm.js/testNeuter.js
js/src/jsfriendapi.h
js/src/vm/ArrayBufferObject.cpp
js/src/vm/ArrayBufferObject.h
js/src/vm/StructuredClone.cpp
--- a/js/src/jit-test/tests/asm.js/testNeuter.js
+++ b/js/src/jit-test/tests/asm.js/testNeuter.js
@@ -18,34 +18,32 @@ var m = asmCompile('stdlib', 'foreign', 
                        return i32[i>>2]|0
                    }
                    return {get:get, set:set}`);
 
 var buffer = new ArrayBuffer(BUF_MIN);
 var {get, set} = asmLink(m, this, null, buffer);
 set(4, 42);
 assertEq(get(4), 42);
-assertThrowsInstanceOf(() => detachArrayBuffer(buffer), Error);
+assertThrowsInstanceOf(() => detachArrayBuffer(buffer, "change-data"),
+                       InternalError);
+assertThrowsInstanceOf(() => detachArrayBuffer(buffer, "same-data"),
+                       InternalError);
 
 var m = asmCompile('stdlib', 'foreign', 'buffer',
                   `"use asm";
                    var i32 = new stdlib.Int32Array(buffer);
                    var ffi = foreign.ffi;
                    function inner(i) {
                        i=i|0;
                        ffi();
                        return i32[i>>2]|0
                    }
                    return inner`);
 
 var buffer = new ArrayBuffer(BUF_MIN);
 function ffi1()
 {
-    assertThrowsInstanceOf(() => detachArrayBuffer(buffer), Error);
+    assertThrowsInstanceOf(() => detachArrayBuffer(buffer, "change-data"),
+                           InternalError);
 }
 
 var inner = asmLink(m, this, {ffi: ffi1}, buffer);
-
-function ffi2()
-{
-    assertThrowsInstanceOf(() => serialize([], [buffer]), Error);
-}
-var inner2 = asmLink(m, this, {ffi: ffi2}, buffer);
--- a/js/src/jsfriendapi.h
+++ b/js/src/jsfriendapi.h
@@ -2102,17 +2102,22 @@ enum DetachDataDisposition {
     ChangeData,
     KeepData
 };
 
 /**
  * Detach an ArrayBuffer, causing all associated views to no longer refer to
  * the ArrayBuffer's original attached memory.
  *
- * The |changeData| argument is obsolete and ignored.
+ * The |changeData| argument is a hint to inform internal behavior with respect
+ * to the ArrayBuffer's internal pointer to associated data.  |ChangeData|
+ * attempts to set the internal pointer to fresh memory of the same size as the
+ * original memory; |KeepData| attempts to preserve the original pointer, even
+ * while the ArrayBuffer appears observably detached.  There is no guarantee
+ * this parameter is respected -- it's only a hint.
  */
 extern JS_FRIEND_API(bool)
 JS_DetachArrayBuffer(JSContext* cx, JS::HandleObject obj,
                      DetachDataDisposition changeData);
 
 /**
  * Check whether the obj is a detached ArrayBufferObject. Note that this may
  * return false if a security wrapper is encountered that denies the
--- a/js/src/vm/ArrayBufferObject.cpp
+++ b/js/src/vm/ArrayBufferObject.cpp
@@ -255,22 +255,24 @@ NoteViewBufferWasDetached(ArrayBufferVie
                           JSContext* cx)
 {
     view->notifyBufferDetached(newContents.data());
 
     // Notify compiled jit code that the base pointer has moved.
     MarkObjectStateChange(cx, view);
 }
 
-/* static */ void
+/* static */ bool
 ArrayBufferObject::detach(JSContext* cx, Handle<ArrayBufferObject*> buffer,
                           BufferContents newContents)
 {
-    MOZ_ASSERT(!buffer->isWasm(), "WASM/asm.js ArrayBuffers cannot be detached");
-    MOZ_ASSERT(buffer->hasDetachableContents(), "detaching the non-detachable");
+    if (buffer->isWasm()) {
+        JS_ReportErrorNumber(cx, GetErrorMessage, nullptr, JSMSG_OUT_OF_MEMORY);
+        return false;
+    }
 
     // When detaching buffers where we don't know all views, the new data must
     // match the old data. All missing views are typed objects, which do not
     // expect their data to ever change.
     MOZ_ASSERT_IF(buffer->forInlineTypedObject(),
                   newContents.data() == buffer->dataPointer());
 
     // When detaching a buffer with typed object views, any jitcode accessing
@@ -307,16 +309,17 @@ ArrayBufferObject::detach(JSContext* cx,
         }
     }
 
     if (newContents.data() != buffer->dataPointer())
         buffer->setNewOwnedData(cx->runtime()->defaultFreeOp(), newContents);
 
     buffer->setByteLength(0);
     buffer->setIsDetached();
+    return true;
 }
 
 void
 ArrayBufferObject::setNewOwnedData(FreeOp* fop, BufferContents newContents)
 {
     if (ownsData()) {
         MOZ_ASSERT(newContents.data() != dataPointer());
         releaseData(fop);
@@ -721,49 +724,45 @@ bool
 ArrayBufferObject::createDataViewForThis(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
     return CallNonGenericMethod<IsArrayBuffer, createDataViewForThisImpl>(cx, args);
 }
 
 /* static */ ArrayBufferObject::BufferContents
 ArrayBufferObject::stealContents(JSContext* cx, Handle<ArrayBufferObject*> buffer,
-                                 bool forceCopy)
+                                 bool hasStealableContents)
 {
-    if (buffer->isDetached()) {
-        JS_ReportErrorNumber(cx, GetErrorMessage, nullptr, JSMSG_TYPED_ARRAY_DETACHED);
-        return BufferContents::createPlain(nullptr);
-    }
-    if (!buffer->hasDetachableContents()) {
-        JS_ReportErrorNumber(cx, GetErrorMessage, nullptr, JSMSG_TYPED_ARRAY_BAD_ARGS);
-        return BufferContents::createPlain(nullptr);
-    }
+    MOZ_ASSERT_IF(hasStealableContents, buffer->hasStealableContents());
 
     BufferContents oldContents(buffer->dataPointer(), buffer->bufferKind());
+    BufferContents newContents = AllocateArrayBufferContents(cx, buffer->byteLength());
+    if (!newContents)
+        return BufferContents::createPlain(nullptr);
 
-    if (!forceCopy && buffer->ownsData()) {
-        // Return the old contents and reset the detached buffer's data
-        // pointer. This pointer should never be accessed.
-        auto newContents = BufferContents::createPlain(nullptr);
-        buffer->setOwnsData(DoesntOwnData); // Do not free the stolen data.
-        ArrayBufferObject::detach(cx, buffer, newContents);
-        buffer->setOwnsData(DoesntOwnData); // Do not free the nullptr.
+    if (hasStealableContents) {
+        // Return the old contents and give the detached buffer a pointer to
+        // freshly allocated memory that we will never write to and should
+        // never get committed.
+        buffer->setOwnsData(DoesntOwnData);
+        if (!ArrayBufferObject::detach(cx, buffer, newContents)) {
+            js_free(newContents.data());
+            return BufferContents::createPlain(nullptr);
+        }
         return oldContents;
     }
 
-    // Create a new chunk of memory to return since we cannot remove the
-    // existing contents pointer from the buffer.
-    BufferContents contentsCopy = AllocateArrayBufferContents(cx, buffer->byteLength());
-    if (!contentsCopy)
+    // Create a new chunk of memory to return since we cannot steal the
+    // existing contents away from the buffer.
+    memcpy(newContents.data(), oldContents.data(), buffer->byteLength());
+    if (!ArrayBufferObject::detach(cx, buffer, oldContents)) {
+        js_free(newContents.data());
         return BufferContents::createPlain(nullptr);
-
-    if (buffer->byteLength() > 0)
-        memcpy(contentsCopy.data(), oldContents.data(), buffer->byteLength());
-    ArrayBufferObject::detach(cx, buffer, oldContents);
-    return contentsCopy;
+    }
+    return newContents;
 }
 
 /* static */ void
 ArrayBufferObject::addSizeOfExcludingThis(JSObject* obj, mozilla::MallocSizeOf mallocSizeOf,
                                           JS::ClassInfo* info)
 {
     ArrayBufferObject& buffer = AsArrayBuffer(obj);
 
@@ -1028,21 +1027,20 @@ ArrayBufferViewObject::trace(JSTracer* t
     HeapSlot& bufSlot = obj->getFixedSlotRef(TypedArrayObject::BUFFER_SLOT);
     TraceEdge(trc, &bufSlot, "typedarray.buffer");
 
     // Update obj's data pointer if it moved.
     if (bufSlot.isObject()) {
         if (IsArrayBuffer(&bufSlot.toObject())) {
             ArrayBufferObject& buf = AsArrayBuffer(MaybeForwarded(&bufSlot.toObject()));
             uint32_t offset = uint32_t(obj->getFixedSlot(TypedArrayObject::BYTEOFFSET_SLOT).toInt32());
+            MOZ_ASSERT(buf.dataPointer() != nullptr);
             MOZ_ASSERT(offset <= INT32_MAX);
 
             if (buf.forInlineTypedObject()) {
-                MOZ_ASSERT(buf.dataPointer() != nullptr);
-
                 // The data is inline with an InlineTypedObject associated with the
                 // buffer. Get a new address for the typed object if it moved.
                 JSObject* view = buf.firstView();
 
                 // Mark the object to move it into the tenured space.
                 TraceManuallyBarrieredEdge(trc, &view, "typed array nursery owner");
                 MOZ_ASSERT(view->is<InlineTypedObject>());
                 MOZ_ASSERT(view != obj);
@@ -1052,18 +1050,16 @@ ArrayBufferViewObject::trace(JSTracer* t
                 obj->setPrivateUnbarriered(dstData);
 
                 // We can't use a direct forwarding pointer here, as there might
                 // not be enough bytes available, and other views might have data
                 // pointers whose forwarding pointers would overlap this one.
                 trc->runtime()->gc.nursery.maybeSetForwardingPointer(trc, srcData, dstData,
                                                                      /* direct = */ false);
             } else {
-                MOZ_ASSERT_IF(buf.dataPointer() == nullptr, offset == 0);
-
                 // The data may or may not be inline with the buffer. The buffer
                 // can only move during a compacting GC, in which case its
                 // objectMoved hook has already updated the buffer's data pointer.
                 obj->initPrivate(buf.dataPointer() + offset);
             }
         }
     }
 }
@@ -1080,16 +1076,17 @@ bool
 JSObject::is<js::ArrayBufferObjectMaybeShared>() const
 {
     return is<ArrayBufferObject>() || is<SharedArrayBufferObject>();
 }
 
 void
 ArrayBufferViewObject::notifyBufferDetached(void* newData)
 {
+    MOZ_ASSERT(newData != nullptr);
     if (is<DataViewObject>()) {
         as<DataViewObject>().notifyBufferDetached(newData);
     } else if (is<TypedArrayObject>()) {
         if (as<TypedArrayObject>().isSharedMemory())
             return;
         as<TypedArrayObject>().notifyBufferDetached(newData);
     } else {
         as<OutlineTypedObject>().notifyBufferDetached(newData);
@@ -1188,31 +1185,30 @@ JS_DetachArrayBuffer(JSContext* cx, Hand
 {
     if (!obj->is<ArrayBufferObject>()) {
         JS_ReportError(cx, "ArrayBuffer object required");
         return false;
     }
 
     Rooted<ArrayBufferObject*> buffer(cx, &obj->as<ArrayBufferObject>());
 
-    if (buffer->isDetached())
-        return true;
-
-    if (buffer->isWasm()) {
-        JS_ReportError(cx, "Cannot detach WASM ArrayBuffer");
-        return false;
+    if (changeData == ChangeData && buffer->hasStealableContents()) {
+        ArrayBufferObject::BufferContents newContents =
+            AllocateArrayBufferContents(cx, buffer->byteLength());
+        if (!newContents)
+            return false;
+        if (!ArrayBufferObject::detach(cx, buffer, newContents)) {
+            js_free(newContents.data());
+            return false;
+        }
+    } else {
+        if (!ArrayBufferObject::detach(cx, buffer, buffer->contents()))
+            return false;
     }
 
-    if (!buffer->hasDetachableContents()) {
-        JS_ReportError(cx, "Cannot detach ArrayBuffer");
-        return false;
-    }
-
-    ArrayBufferObject::detach(cx, buffer, buffer->contents());
-
     return true;
 }
 
 JS_FRIEND_API(bool)
 JS_IsDetachedArrayBufferObject(JSObject* obj)
 {
     obj = CheckedUnwrap(obj);
     if (!obj)
@@ -1285,24 +1281,28 @@ JS_StealArrayBufferContents(JSContext* c
         return nullptr;
 
     if (!obj->is<ArrayBufferObject>()) {
         JS_ReportErrorNumber(cx, GetErrorMessage, nullptr, JSMSG_TYPED_ARRAY_BAD_ARGS);
         return nullptr;
     }
 
     Rooted<ArrayBufferObject*> buffer(cx, &obj->as<ArrayBufferObject>());
+    if (buffer->isDetached()) {
+        JS_ReportErrorNumber(cx, GetErrorMessage, nullptr, JSMSG_TYPED_ARRAY_DETACHED);
+        return nullptr;
+    }
 
-    // The caller assumes that a plain malloc'd buffer is returned. ownsData is
-    // true for (owned) mapped buffers, so we must additionally require that
-    // the buffer is plain. In the future, we could consider returning
-    // something that handles releasing the memory.
-    bool forceCopy = !buffer->ownsData() || !buffer->hasMallocedContents();
+    // The caller assumes that a plain malloc'd buffer is returned.
+    // hasStealableContents is true for mapped buffers, so we must additionally
+    // require that the buffer is plain. In the future, we could consider
+    // returning something that handles releasing the memory.
+    bool hasStealableContents = buffer->hasStealableContents() && buffer->hasMallocedContents();
 
-    return ArrayBufferObject::stealContents(cx, buffer, forceCopy).data();
+    return ArrayBufferObject::stealContents(cx, buffer, hasStealableContents).data();
 }
 
 JS_PUBLIC_API(JSObject*)
 JS_NewMappedArrayBufferWithContents(JSContext* cx, size_t nbytes, void* data)
 {
     MOZ_ASSERT(data);
     ArrayBufferObject::BufferContents contents =
         ArrayBufferObject::BufferContents::create<ArrayBufferObject::MAPPED>(data);
--- a/js/src/vm/ArrayBufferObject.h
+++ b/js/src/vm/ArrayBufferObject.h
@@ -208,16 +208,19 @@ class ArrayBufferObject : public ArrayBu
     static const JSFunctionSpec jsstaticfuncs[];
     static const JSPropertySpec jsstaticprops[];
 
     static bool byteLengthGetter(JSContext* cx, unsigned argc, Value* vp);
 
     static bool fun_slice(JSContext* cx, unsigned argc, Value* vp);
 
     static bool fun_isView(JSContext* cx, unsigned argc, Value* vp);
+#ifdef NIGHTLY_BUILD
+    static bool fun_transfer(JSContext* cx, unsigned argc, Value* vp);
+#endif
 
     static bool fun_species(JSContext* cx, unsigned argc, Value* vp);
 
     static bool class_constructor(JSContext* cx, unsigned argc, Value* vp);
 
     static ArrayBufferObject* create(JSContext* cx, uint32_t nbytes,
                                      BufferContents contents,
                                      OwnsState ownsState = OwnsData,
@@ -238,29 +241,31 @@ class ArrayBufferObject : public ArrayBu
 
     static void copyData(Handle<ArrayBufferObject*> toBuffer,
                          Handle<ArrayBufferObject*> fromBuffer,
                          uint32_t fromIndex, uint32_t count);
 
     static void trace(JSTracer* trc, JSObject* obj);
     static void objectMoved(JSObject* obj, const JSObject* old);
 
-    // Detach the ArrayBuffer and return its contents (if possible), or
-    // possibly a copy of its contents (if forceCopy is passed or the buffer
-    // does not own the data).
     static BufferContents stealContents(JSContext* cx,
                                         Handle<ArrayBufferObject*> buffer,
-                                        bool forceCopy);
+                                        bool hasStealableContents);
+
+    bool hasStealableContents() const {
+        // Inline elements strictly adhere to the corresponding buffer.
+        if (!ownsData())
+            return false;
 
-    // Some types of buffer are simply not willing to be detached, eg Wasm
-    // buffers.
-    bool hasDetachableContents() const {
-        if (isDetached())
-            return false;
-        return isPlain() || isMapped();
+        // Detached contents aren't transferrable because we want a detached
+        // buffer's contents to be backed by zeroed memory equal in length to
+        // the original buffer contents.  Transferring these contents would
+        // allocate new ones based on the current byteLength, which is 0 for a
+        // detached buffer -- not the original byteLength.
+        return !isDetached();
     }
 
     // Return whether the buffer is allocated by js_malloc and should be freed
     // with js_free.
     bool hasMallocedContents() const {
         return (ownsData() && isPlain()) || isWasmMalloced();
     }
 
@@ -276,18 +281,18 @@ class ArrayBufferObject : public ArrayBu
 
     bool addView(JSContext* cx, JSObject* view);
 
     void setNewOwnedData(FreeOp* fop, BufferContents newContents);
     void changeContents(JSContext* cx, BufferContents newContents);
 
     // Detach this buffer from its original memory.  (This necessarily makes
     // views of this buffer unusable for modifying that original memory.)
-    static void detach(JSContext* cx, Handle<ArrayBufferObject*> buffer,
-                       BufferContents newContents);
+    static MOZ_MUST_USE bool
+    detach(JSContext* cx, Handle<ArrayBufferObject*> buffer, BufferContents newContents);
 
   private:
     void changeViewContents(JSContext* cx, ArrayBufferViewObject* view,
                             uint8_t* oldDataPointer, BufferContents newContents);
     void setFirstView(ArrayBufferViewObject* view);
 
     uint8_t* inlineDataPointer() const;
 
@@ -315,18 +320,16 @@ class ArrayBufferObject : public ArrayBu
     BufferKind bufferKind() const { return BufferKind(flags() & BUFFER_KIND_MASK); }
     bool isPlain() const { return bufferKind() == PLAIN; }
     bool isWasmMapped() const { return bufferKind() == WASM_MAPPED; }
     bool isWasmMalloced() const { return bufferKind() == WASM_MALLOCED; }
     bool isWasm() const { return isWasmMapped() || isWasmMalloced(); }
     bool isMapped() const { return bufferKind() == MAPPED; }
     bool isDetached() const { return flags() & DETACHED; }
 
-    bool ownsData() const { return flags() & OWNS_DATA; }
-
     static ArrayBufferObject* createForWasm(JSContext* cx, uint32_t numBytes, bool signalsForOOB);
     static bool prepareForAsmJS(JSContext* cx, Handle<ArrayBufferObject*> buffer, bool signalsForOOB);
 
     static void finalize(FreeOp* fop, JSObject* obj);
 
     static BufferContents createMappedContents(int fd, size_t offset, size_t length);
 
     static size_t offsetOfFlagsSlot() {
@@ -347,16 +350,17 @@ class ArrayBufferObject : public ArrayBu
 
   protected:
     void setDataPointer(BufferContents contents, OwnsState ownsState);
     void setByteLength(uint32_t length);
 
     uint32_t flags() const;
     void setFlags(uint32_t flags);
 
+    bool ownsData() const { return flags() & OWNS_DATA; }
     void setOwnsData(OwnsState owns) {
         setFlags(owns ? (flags() | OWNS_DATA) : (flags() & ~OWNS_DATA));
     }
 
     bool hasTypedObjectViews() const { return flags() & TYPED_OBJECT_VIEWS; }
 
     void setIsWasmMalloced() { setFlags((flags() & ~KIND_MASK) | WASM_MALLOCED); }
     void setIsDetached() { setFlags(flags() | DETACHED); }
--- a/js/src/vm/StructuredClone.cpp
+++ b/js/src/vm/StructuredClone.cpp
@@ -1334,20 +1334,23 @@ JSStructuredCloneWriter::transferOwnersh
         if (cls == ESClass::ArrayBuffer) {
             // The current setup of the array buffer inheritance hierarchy doesn't
             // lend itself well to generic manipulation via proxies.
             Rooted<ArrayBufferObject*> arrayBuffer(context(), &CheckedUnwrap(obj)->as<ArrayBufferObject>());
             size_t nbytes = arrayBuffer->byteLength();
 
             // Structured cloning currently only has optimizations for mapped
             // and malloc'd buffers, not asm.js-ified buffers.
+            bool hasStealableContents = arrayBuffer->hasStealableContents() &&
+                                        (arrayBuffer->isMapped() || arrayBuffer->hasMallocedContents());
+
             ArrayBufferObject::BufferContents bufContents =
-                ArrayBufferObject::stealContents(context(), arrayBuffer, false);
+                ArrayBufferObject::stealContents(context(), arrayBuffer, hasStealableContents);
             if (!bufContents)
-                return false; // already transferred data or non-transferable buffer type
+                return false; // Destructor will clean up the already-transferred data.
 
             content = bufContents.data();
             tag = SCTAG_TRANSFER_MAP_ARRAY_BUFFER;
             if (bufContents.kind() == ArrayBufferObject::MAPPED)
                 ownership = JS::SCTAG_TMO_MAPPED_DATA;
             else
                 ownership = JS::SCTAG_TMO_ALLOC_DATA;
             extraData = nbytes;