gecko-dev/js/ipc/WrapperOwner.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=4 sw=2 et tw=80:
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "WrapperOwner.h"
#include "JavaScriptLogging.h"
#include "mozilla/Unused.h"
#include "mozilla/dom/BindingUtils.h"
#include "jsfriendapi.h"
#include "js/CharacterEncoding.h"
#include "js/RegExp.h"
#include "js/RegExpFlags.h"
#include "xpcprivate.h"
#include "WrapperFactory.h"

#include "nsIDocShellTreeItem.h"
#include "mozilla/dom/Document.h"

using namespace js;
using namespace JS;
using namespace mozilla;
using namespace mozilla::jsipc;

struct AuxCPOWData {
  ObjectId id;
  bool isCallable;
  bool isConstructor;
  bool isDOMObject;

  // The object tag is just some auxilliary information that clients can use
  // however they see fit.
  nsCString objectTag;

  // The class name for WrapperOwner::className, below.
  nsCString className;

  AuxCPOWData(ObjectId id, bool isCallable, bool isConstructor,
              bool isDOMObject, const nsACString& objectTag)
      : id(id),
        isCallable(isCallable),
        isConstructor(isConstructor),
        isDOMObject(isDOMObject),
        objectTag(objectTag) {}
};

WrapperOwner::WrapperOwner() : inactive_(false) {}

static inline AuxCPOWData* AuxCPOWDataOf(JSObject* obj) {
  MOZ_ASSERT(IsCPOW(obj));
  return static_cast<AuxCPOWData*>(GetProxyReservedSlot(obj, 1).toPrivate());
}

static inline WrapperOwner* OwnerOf(JSObject* obj) {
  MOZ_ASSERT(IsCPOW(obj));
  return reinterpret_cast<WrapperOwner*>(
      GetProxyReservedSlot(obj, 0).toPrivate());
}

ObjectId WrapperOwner::idOfUnchecked(JSObject* obj) {
  MOZ_ASSERT(IsCPOW(obj));

  AuxCPOWData* aux = AuxCPOWDataOf(obj);
  MOZ_ASSERT(!aux->id.isNull());
  return aux->id;
}

ObjectId WrapperOwner::idOf(JSObject* obj) {
  ObjectId objId = idOfUnchecked(obj);
  MOZ_ASSERT(hasCPOW(objId, obj));
  return objId;
}

class CPOWProxyHandler : public BaseProxyHandler {
 public:
  constexpr CPOWProxyHandler() : BaseProxyHandler(&family) {}

  virtual bool finalizeInBackground(const Value& priv) const override {
    return false;
  }

  virtual bool getOwnPropertyDescriptor(
      JSContext* cx, HandleObject proxy, HandleId id,
      MutableHandle<PropertyDescriptor> desc) const override;
  virtual bool defineProperty(JSContext* cx, HandleObject proxy, HandleId id,
                              Handle<PropertyDescriptor> desc,
                              ObjectOpResult& result) const override;
  virtual bool ownPropertyKeys(JSContext* cx, HandleObject proxy,
                               MutableHandleIdVector props) const override;
  virtual bool delete_(JSContext* cx, HandleObject proxy, HandleId id,
                       ObjectOpResult& result) const override;
  virtual bool enumerate(JSContext* cx, HandleObject proxy,
                         MutableHandleIdVector props) const override;
  virtual bool preventExtensions(JSContext* cx, HandleObject proxy,
                                 ObjectOpResult& result) const override;
  virtual bool isExtensible(JSContext* cx, HandleObject proxy,
                            bool* extensible) const override;
  virtual bool has(JSContext* cx, HandleObject proxy, HandleId id,
                   bool* bp) const override;
  virtual bool get(JSContext* cx, HandleObject proxy, HandleValue receiver,
                   HandleId id, MutableHandleValue vp) const override;
  virtual bool set(JSContext* cx, JS::HandleObject proxy, JS::HandleId id,
                   JS::HandleValue v, JS::HandleValue receiver,
                   JS::ObjectOpResult& result) const override;
  virtual bool call(JSContext* cx, HandleObject proxy,
                    const CallArgs& args) const override;
  virtual bool construct(JSContext* cx, HandleObject proxy,
                         const CallArgs& args) const override;

  virtual bool hasOwn(JSContext* cx, HandleObject proxy, HandleId id,
                      bool* bp) const override;
  virtual bool getOwnEnumerablePropertyKeys(
      JSContext* cx, HandleObject proxy,
      MutableHandleIdVector props) const override;
  virtual bool hasInstance(JSContext* cx, HandleObject proxy,
                           MutableHandleValue v, bool* bp) const override;
  virtual bool getBuiltinClass(JSContext* cx, HandleObject obj,
                               js::ESClass* cls) const override;
  virtual bool isArray(JSContext* cx, HandleObject obj,
                       IsArrayAnswer* answer) const override;
  virtual const char* className(JSContext* cx,
                                HandleObject proxy) const override;
  virtual RegExpShared* regexp_toShared(JSContext* cx,
                                        HandleObject proxy) const override;
  virtual void finalize(JSFreeOp* fop, JSObject* proxy) const override;
  virtual size_t objectMoved(JSObject* proxy, JSObject* old) const override;
  virtual bool isCallable(JSObject* obj) const override;
  virtual bool isConstructor(JSObject* obj) const override;
  virtual bool getPrototype(JSContext* cx, HandleObject proxy,
                            MutableHandleObject protop) const override;
  virtual bool getPrototypeIfOrdinary(
      JSContext* cx, HandleObject proxy, bool* isOrdinary,
      MutableHandleObject protop) const override;

  static const char family;
  static const CPOWProxyHandler singleton;
};

const char CPOWProxyHandler::family = 0;
const CPOWProxyHandler CPOWProxyHandler::singleton;

#define FORWARD(call, args, failRetVal)                                 \
  AUTO_PROFILER_LABEL(__func__, JS);                                    \
  WrapperOwner* owner = OwnerOf(proxy);                                 \
  if (!owner->active()) {                                               \
    JS_ReportErrorASCII(cx, "cannot use a CPOW whose process is gone"); \
    return failRetVal;                                                  \
  }                                                                     \
  if (!owner->allowMessage(cx)) {                                       \
    return failRetVal;                                                  \
  }                                                                     \
  { return owner->call args; }

bool CPOWProxyHandler::getOwnPropertyDescriptor(
    JSContext* cx, HandleObject proxy, HandleId id,
    MutableHandle<PropertyDescriptor> desc) const {
  FORWARD(getOwnPropertyDescriptor, (cx, proxy, id, desc), false);
}

bool WrapperOwner::getOwnPropertyDescriptor(
    JSContext* cx, HandleObject proxy, HandleId id,
    MutableHandle<PropertyDescriptor> desc) {
  ObjectId objId = idOf(proxy);

  JSIDVariant idVar;
  if (!toJSIDVariant(cx, id, &idVar)) {
    return false;
  }

  ReturnStatus status;
  PPropertyDescriptor result;
  if (!SendGetOwnPropertyDescriptor(objId, idVar, &status, &result)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  if (!ok(cx, status)) {
    return false;
  }

  return toDescriptor(cx, result, desc);
}

bool CPOWProxyHandler::defineProperty(JSContext* cx, HandleObject proxy,
                                      HandleId id,
                                      Handle<PropertyDescriptor> desc,
                                      ObjectOpResult& result) const {
  FORWARD(defineProperty, (cx, proxy, id, desc, result), false);
}

bool WrapperOwner::defineProperty(JSContext* cx, HandleObject proxy,
                                  HandleId id, Handle<PropertyDescriptor> desc,
                                  ObjectOpResult& result) {
  ObjectId objId = idOf(proxy);

  JSIDVariant idVar;
  if (!toJSIDVariant(cx, id, &idVar)) {
    return false;
  }

  PPropertyDescriptor descriptor;
  if (!fromDescriptor(cx, desc, &descriptor)) {
    return false;
  }

  ReturnStatus status;
  if (!SendDefineProperty(objId, idVar, descriptor, &status)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  return ok(cx, status, result);
}

bool CPOWProxyHandler::ownPropertyKeys(JSContext* cx, HandleObject proxy,
                                       MutableHandleIdVector props) const {
  FORWARD(ownPropertyKeys, (cx, proxy, props), false);
}

bool WrapperOwner::ownPropertyKeys(JSContext* cx, HandleObject proxy,
                                   MutableHandleIdVector props) {
  return getPropertyKeys(
      cx, proxy, JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS, props);
}

bool CPOWProxyHandler::delete_(JSContext* cx, HandleObject proxy, HandleId id,
                               ObjectOpResult& result) const {
  FORWARD(delete_, (cx, proxy, id, result), false);
}

bool WrapperOwner::delete_(JSContext* cx, HandleObject proxy, HandleId id,
                           ObjectOpResult& result) {
  ObjectId objId = idOf(proxy);

  JSIDVariant idVar;
  if (!toJSIDVariant(cx, id, &idVar)) {
    return false;
  }

  ReturnStatus status;
  if (!SendDelete(objId, idVar, &status)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  return ok(cx, status, result);
}

bool CPOWProxyHandler::enumerate(JSContext* cx, HandleObject proxy,
                                 MutableHandleIdVector props) const {
  // Call the base hook. That will use our implementation of
  // getOwnEnumerablePropertyKeys and follow the proto chain.
  return BaseProxyHandler::enumerate(cx, proxy, props);
}

bool CPOWProxyHandler::has(JSContext* cx, HandleObject proxy, HandleId id,
                           bool* bp) const {
  FORWARD(has, (cx, proxy, id, bp), false);
}

bool WrapperOwner::has(JSContext* cx, HandleObject proxy, HandleId id,
                       bool* bp) {
  ObjectId objId = idOf(proxy);

  JSIDVariant idVar;
  if (!toJSIDVariant(cx, id, &idVar)) {
    return false;
  }

  ReturnStatus status;
  if (!SendHas(objId, idVar, &status, bp)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  return ok(cx, status);
}

bool CPOWProxyHandler::hasOwn(JSContext* cx, HandleObject proxy, HandleId id,
                              bool* bp) const {
  FORWARD(hasOwn, (cx, proxy, id, bp), false);
}

bool WrapperOwner::hasOwn(JSContext* cx, HandleObject proxy, HandleId id,
                          bool* bp) {
  ObjectId objId = idOf(proxy);

  JSIDVariant idVar;
  if (!toJSIDVariant(cx, id, &idVar)) {
    return false;
  }

  ReturnStatus status;
  if (!SendHasOwn(objId, idVar, &status, bp)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  return !!ok(cx, status);
}

bool CPOWProxyHandler::get(JSContext* cx, HandleObject proxy,
                           HandleValue receiver, HandleId id,
                           MutableHandleValue vp) const {
  FORWARD(get, (cx, proxy, receiver, id, vp), false);
}

static bool CPOWDOMQI(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  if (!args.thisv().isObject() || !IsCPOW(&args.thisv().toObject())) {
    JS_ReportErrorASCII(cx, "bad this object passed to special QI");
    return false;
  }

  RootedObject proxy(cx, &args.thisv().toObject());
  FORWARD(DOMQI, (cx, proxy, args), false);
}

static bool CPOWToString(JSContext* cx, unsigned argc, Value* vp) {
  CallArgs args = CallArgsFromVp(argc, vp);
  RootedObject callee(cx, &args.callee());
  RootedValue cpowValue(cx);
  if (!JS_GetProperty(cx, callee, "__cpow__", &cpowValue)) {
    return false;
  }

  if (!cpowValue.isObject() || !IsCPOW(&cpowValue.toObject())) {
    JS_ReportErrorASCII(cx, "CPOWToString called on an incompatible object");
    return false;
  }

  RootedObject proxy(cx, &cpowValue.toObject());
  FORWARD(toString, (cx, proxy, args), false);
}

bool WrapperOwner::toString(JSContext* cx, HandleObject cpow,
                            JS::CallArgs& args) {
  // Ask the other side to call its toString method. Update the callee so that
  // it points to the CPOW and not to the synthesized CPOWToString function.
  args.setCallee(ObjectValue(*cpow));
  if (!callOrConstruct(cx, cpow, args, false)) {
    return false;
  }

  if (!args.rval().isString()) {
    return true;
  }

  RootedString cpowResult(cx, args.rval().toString());
  nsAutoJSString toStringResult;
  if (!toStringResult.init(cx, cpowResult)) {
    return false;
  }

  // We don't want to wrap toString() results for things like the location
  // object, where toString() is supposed to return a URL and nothing else.
  nsAutoString result;
  if (toStringResult[0] == '[') {
    result.AppendLiteral("[object CPOW ");
    result += toStringResult;
    result.AppendLiteral("]");
  } else {
    result += toStringResult;
  }

  JSString* str = JS_NewUCStringCopyN(cx, result.get(), result.Length());
  if (!str) {
    return false;
  }

  args.rval().setString(str);
  return true;
}

bool WrapperOwner::DOMQI(JSContext* cx, JS::HandleObject proxy,
                         JS::CallArgs& args) {
  // Someone's calling us, handle nsISupports specially to avoid unnecessary
  // CPOW traffic.
  if (Maybe<nsID> id = xpc::JSValue2ID(cx, args[0])) {
    if (id->Equals(NS_GET_IID(nsISupports))) {
      args.rval().set(args.thisv());
      return true;
    }

    // Webidl-implemented DOM objects never have nsIClassInfo.
    if (id->Equals(NS_GET_IID(nsIClassInfo))) {
      return Throw(cx, NS_ERROR_NO_INTERFACE);
    }
  }

  // It wasn't nsISupports, call into the other process to do the QI for us
  // (since we don't know what other interfaces our object supports). Note
  // that we have to use JS_GetPropertyDescriptor here to avoid infinite
  // recursion back into CPOWDOMQI via WrapperOwner::get().
  // We could stash the actual QI function on our own function object to avoid
  // if we're called multiple times, but since we're transient, there's no
  // point right now.
  JS::Rooted<PropertyDescriptor> propDesc(cx);
  if (!JS_GetPropertyDescriptor(cx, proxy, "QueryInterface", &propDesc)) {
    return false;
  }

  if (!propDesc.value().isObject()) {
    MOZ_ASSERT_UNREACHABLE("We didn't get QueryInterface off a node");
    return Throw(cx, NS_ERROR_UNEXPECTED);
  }
  return JS_CallFunctionValue(cx, proxy, propDesc.value(), args, args.rval());
}

bool WrapperOwner::get(JSContext* cx, HandleObject proxy, HandleValue receiver,
                       HandleId id, MutableHandleValue vp) {
  ObjectId objId = idOf(proxy);

  JSVariant receiverVar;
  if (!toVariant(cx, receiver, &receiverVar)) {
    return false;
  }

  JSIDVariant idVar;
  if (!toJSIDVariant(cx, id, &idVar)) {
    return false;
  }

  AuxCPOWData* data = AuxCPOWDataOf(proxy);
  if (data->isDOMObject && idVar.type() == JSIDVariant::TnsString &&
      idVar.get_nsString().EqualsLiteral("QueryInterface")) {
    // Handle QueryInterface on DOM Objects specially since we can assume
    // certain things about their implementation.
    RootedFunction qi(cx,
                      JS_NewFunction(cx, CPOWDOMQI, 1, 0, "QueryInterface"));
    if (!qi) {
      return false;
    }

    vp.set(ObjectValue(*JS_GetFunctionObject(qi)));
    return true;
  }

  JSVariant val;
  ReturnStatus status;
  if (!SendGet(objId, receiverVar, idVar, &status, &val)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  if (!ok(cx, status)) {
    return false;
  }

  if (!fromVariant(cx, val, vp)) {
    return false;
  }

  if (idVar.type() == JSIDVariant::TnsString &&
      idVar.get_nsString().EqualsLiteral("toString")) {
    RootedFunction toString(cx,
                            JS_NewFunction(cx, CPOWToString, 0, 0, "toString"));
    if (!toString) {
      return false;
    }

    RootedObject toStringObj(cx, JS_GetFunctionObject(toString));

    if (!JS_DefineProperty(cx, toStringObj, "__cpow__", vp,
                           JSPROP_PERMANENT | JSPROP_READONLY)) {
      return false;
    }

    vp.set(ObjectValue(*toStringObj));
  }

  return true;
}

bool CPOWProxyHandler::set(JSContext* cx, JS::HandleObject proxy,
                           JS::HandleId id, JS::HandleValue v,
                           JS::HandleValue receiver,
                           JS::ObjectOpResult& result) const {
  FORWARD(set, (cx, proxy, id, v, receiver, result), false);
}

bool WrapperOwner::set(JSContext* cx, JS::HandleObject proxy, JS::HandleId id,
                       JS::HandleValue v, JS::HandleValue receiver,
                       JS::ObjectOpResult& result) {
  ObjectId objId = idOf(proxy);

  JSIDVariant idVar;
  if (!toJSIDVariant(cx, id, &idVar)) {
    return false;
  }

  JSVariant val;
  if (!toVariant(cx, v, &val)) {
    return false;
  }

  JSVariant receiverVar;
  if (!toVariant(cx, receiver, &receiverVar)) {
    return false;
  }

  ReturnStatus status;
  if (!SendSet(objId, idVar, val, receiverVar, &status)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  return ok(cx, status, result);
}

bool CPOWProxyHandler::getOwnEnumerablePropertyKeys(
    JSContext* cx, HandleObject proxy, MutableHandleIdVector props) const {
  FORWARD(getOwnEnumerablePropertyKeys, (cx, proxy, props), false);
}

bool WrapperOwner::getOwnEnumerablePropertyKeys(JSContext* cx,
                                                HandleObject proxy,
                                                MutableHandleIdVector props) {
  return getPropertyKeys(cx, proxy, JSITER_OWNONLY, props);
}

bool CPOWProxyHandler::preventExtensions(JSContext* cx, HandleObject proxy,
                                         ObjectOpResult& result) const {
  FORWARD(preventExtensions, (cx, proxy, result), false);
}

bool WrapperOwner::preventExtensions(JSContext* cx, HandleObject proxy,
                                     ObjectOpResult& result) {
  ObjectId objId = idOf(proxy);

  ReturnStatus status;
  if (!SendPreventExtensions(objId, &status)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  return ok(cx, status, result);
}

bool CPOWProxyHandler::isExtensible(JSContext* cx, HandleObject proxy,
                                    bool* extensible) const {
  FORWARD(isExtensible, (cx, proxy, extensible), false);
}

bool WrapperOwner::isExtensible(JSContext* cx, HandleObject proxy,
                                bool* extensible) {
  ObjectId objId = idOf(proxy);

  ReturnStatus status;
  if (!SendIsExtensible(objId, &status, extensible)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  return ok(cx, status);
}

bool CPOWProxyHandler::call(JSContext* cx, HandleObject proxy,
                            const CallArgs& args) const {
  FORWARD(callOrConstruct, (cx, proxy, args, false), false);
}

bool CPOWProxyHandler::construct(JSContext* cx, HandleObject proxy,
                                 const CallArgs& args) const {
  FORWARD(callOrConstruct, (cx, proxy, args, true), false);
}

bool WrapperOwner::callOrConstruct(JSContext* cx, HandleObject proxy,
                                   const CallArgs& args, bool construct) {
  ObjectId objId = idOf(proxy);

  InfallibleTArray<JSParam> vals;
  RootedValueVector outobjects(cx);

  RootedValue v(cx);
  for (size_t i = 0; i < args.length() + 2; i++) {
    // The |this| value for constructors is a magic value that we won't be
    // able to convert, so skip it.
    if (i == 1 && construct) {
      v = UndefinedValue();
    } else {
      v = args.base()[i];
    }
    if (v.isObject()) {
      RootedObject obj(cx, &v.toObject());
      if (xpc::IsOutObject(cx, obj)) {
        // Make sure it is not an in-out object.
        bool found;
        if (!JS_HasProperty(cx, obj, "value", &found)) {
          return false;
        }
        if (found) {
          JS_ReportErrorASCII(cx,
                              "in-out objects cannot be sent via CPOWs yet");
          return false;
        }

        vals.AppendElement(JSParam(void_t()));
        if (!outobjects.append(ObjectValue(*obj))) {
          return false;
        }
        continue;
      }
    }
    JSVariant val;
    if (!toVariant(cx, v, &val)) {
      return false;
    }
    vals.AppendElement(JSParam(val));
  }

  JSVariant result;
  ReturnStatus status;
  InfallibleTArray<JSParam> outparams;
  if (!SendCallOrConstruct(objId, vals, construct, &status, &result,
                           &outparams)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  if (!ok(cx, status)) {
    return false;
  }

  if (outparams.Length() != outobjects.length()) {
    return ipcfail(cx);
  }

  RootedObject obj(cx);
  for (size_t i = 0; i < outparams.Length(); i++) {
    // Don't bother doing anything for outparams that weren't set.
    if (outparams[i].type() == JSParam::Tvoid_t) {
      continue;
    }

    // Take the value the child process returned, and set it on the XPC
    // object.
    if (!fromVariant(cx, outparams[i], &v)) {
      return false;
    }

    obj = &outobjects[i].toObject();
    if (!JS_SetProperty(cx, obj, "value", v)) {
      return false;
    }
  }

  if (!fromVariant(cx, result, args.rval())) {
    return false;
  }

  return true;
}

bool CPOWProxyHandler::hasInstance(JSContext* cx, HandleObject proxy,
                                   MutableHandleValue v, bool* bp) const {
  FORWARD(hasInstance, (cx, proxy, v, bp), false);
}

bool WrapperOwner::hasInstance(JSContext* cx, HandleObject proxy,
                               MutableHandleValue v, bool* bp) {
  ObjectId objId = idOf(proxy);

  JSVariant vVar;
  if (!toVariant(cx, v, &vVar)) {
    return false;
  }

  ReturnStatus status;
  if (!SendHasInstance(objId, vVar, &status, bp)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  return ok(cx, status);
}

bool CPOWProxyHandler::getBuiltinClass(JSContext* cx, HandleObject proxy,
                                       ESClass* cls) const {
  FORWARD(getBuiltinClass, (cx, proxy, cls), false);
}

bool WrapperOwner::getBuiltinClass(JSContext* cx, HandleObject proxy,
                                   ESClass* cls) {
  ObjectId objId = idOf(proxy);

  uint32_t classValue = uint32_t(ESClass::Other);
  ReturnStatus status;
  if (!SendGetBuiltinClass(objId, &status, &classValue)) {
    return ipcfail(cx);
  }
  *cls = ESClass(classValue);

  LOG_STACK();

  return ok(cx, status);
}

bool CPOWProxyHandler::isArray(JSContext* cx, HandleObject proxy,
                               IsArrayAnswer* answer) const {
  FORWARD(isArray, (cx, proxy, answer), false);
}

bool WrapperOwner::isArray(JSContext* cx, HandleObject proxy,
                           IsArrayAnswer* answer) {
  ObjectId objId = idOf(proxy);

  uint32_t ans;
  ReturnStatus status;
  if (!SendIsArray(objId, &status, &ans)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  *answer = IsArrayAnswer(ans);
  MOZ_ASSERT(*answer == IsArrayAnswer::Array ||
             *answer == IsArrayAnswer::NotArray ||
             *answer == IsArrayAnswer::RevokedProxy);

  return ok(cx, status);
}

const char* CPOWProxyHandler::className(JSContext* cx,
                                        HandleObject proxy) const {
  WrapperOwner* parent = OwnerOf(proxy);
  if (!parent->active()) {
    return "<dead CPOW>";
  }
  return parent->className(cx, proxy);
}

const char* WrapperOwner::className(JSContext* cx, HandleObject proxy) {
  AuxCPOWData* data = AuxCPOWDataOf(proxy);
  if (data->className.IsEmpty()) {
    ObjectId objId = idOf(proxy);

    if (!SendClassName(objId, &data->className)) {
      return "<error>";
    }

    LOG_STACK();
  }

  return data->className.get();
}

bool CPOWProxyHandler::getPrototype(JSContext* cx, HandleObject proxy,
                                    MutableHandleObject objp) const {
  FORWARD(getPrototype, (cx, proxy, objp), false);
}

bool WrapperOwner::getPrototype(JSContext* cx, HandleObject proxy,
                                MutableHandleObject objp) {
  ObjectId objId = idOf(proxy);

  ObjectOrNullVariant val;
  ReturnStatus status;
  if (!SendGetPrototype(objId, &status, &val)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  if (!ok(cx, status)) {
    return false;
  }

  objp.set(fromObjectOrNullVariant(cx, val));

  return true;
}

bool CPOWProxyHandler::getPrototypeIfOrdinary(JSContext* cx, HandleObject proxy,
                                              bool* isOrdinary,
                                              MutableHandleObject objp) const {
  FORWARD(getPrototypeIfOrdinary, (cx, proxy, isOrdinary, objp), false);
}

bool WrapperOwner::getPrototypeIfOrdinary(JSContext* cx, HandleObject proxy,
                                          bool* isOrdinary,
                                          MutableHandleObject objp) {
  ObjectId objId = idOf(proxy);

  ObjectOrNullVariant val;
  ReturnStatus status;
  if (!SendGetPrototypeIfOrdinary(objId, &status, isOrdinary, &val)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  if (!ok(cx, status)) {
    return false;
  }

  objp.set(fromObjectOrNullVariant(cx, val));

  return true;
}

RegExpShared* CPOWProxyHandler::regexp_toShared(JSContext* cx,
                                                HandleObject proxy) const {
  FORWARD(regexp_toShared, (cx, proxy), nullptr);
}

RegExpShared* WrapperOwner::regexp_toShared(JSContext* cx, HandleObject proxy) {
  ObjectId objId = idOf(proxy);

  ReturnStatus status;
  nsString source;
  unsigned flags = 0;
  if (!SendRegExpToShared(objId, &status, &source, &flags)) {
    MOZ_ALWAYS_FALSE(ipcfail(cx));
    return nullptr;
  }
  LOG_STACK();

  if (!ok(cx, status)) {
    return nullptr;
  }

  RootedObject regexp(cx);
  regexp = JS::NewUCRegExpObject(cx, source.get(), source.Length(),
                                 RegExpFlags(flags));
  if (!regexp) {
    return nullptr;
  }

  return js::RegExpToSharedNonInline(cx, regexp);
}

void CPOWProxyHandler::finalize(JSFreeOp* fop, JSObject* proxy) const {
  AuxCPOWData* aux = AuxCPOWDataOf(proxy);

  OwnerOf(proxy)->drop(proxy);

  if (aux) {
    delete aux;
  }
}

size_t CPOWProxyHandler::objectMoved(JSObject* proxy, JSObject* old) const {
  OwnerOf(proxy)->updatePointer(proxy, old);
  return 0;
}

bool CPOWProxyHandler::isCallable(JSObject* proxy) const {
  AuxCPOWData* aux = AuxCPOWDataOf(proxy);
  return aux->isCallable;
}

bool CPOWProxyHandler::isConstructor(JSObject* proxy) const {
  AuxCPOWData* aux = AuxCPOWDataOf(proxy);
  return aux->isConstructor;
}

void WrapperOwner::drop(JSObject* obj) {
  // The association may have already been swept from the table but if it's
  // there then remove it.
  ObjectId objId = idOfUnchecked(obj);
  if (cpows_.findPreserveColor(objId) == obj) {
    cpows_.remove(objId);
  }

  if (active()) {
    Unused << SendDropObject(objId);
  }
  decref();
}

void WrapperOwner::updatePointer(JSObject* obj, const JSObject* old) {
  ObjectId objId = idOfUnchecked(obj);
  MOZ_ASSERT(hasCPOW(objId, old));
  cpows_.add(objId, obj);
}

bool WrapperOwner::getPropertyKeys(JSContext* cx, HandleObject proxy,
                                   uint32_t flags,
                                   MutableHandleIdVector props) {
  ObjectId objId = idOf(proxy);

  ReturnStatus status;
  InfallibleTArray<JSIDVariant> ids;
  if (!SendGetPropertyKeys(objId, flags, &status, &ids)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  if (!ok(cx, status)) {
    return false;
  }

  for (size_t i = 0; i < ids.Length(); i++) {
    RootedId id(cx);
    if (!fromJSIDVariant(cx, ids[i], &id)) {
      return false;
    }
    if (!props.append(id)) {
      return false;
    }
  }

  return true;
}

namespace mozilla {
namespace jsipc {

bool IsCPOW(JSObject* obj) {
  return IsProxy(obj) && GetProxyHandler(obj) == &CPOWProxyHandler::singleton;
}

bool IsWrappedCPOW(JSObject* obj) {
  JSObject* unwrapped = js::UncheckedUnwrap(obj, true);
  if (!unwrapped) {
    return false;
  }
  return IsCPOW(unwrapped);
}

void GetWrappedCPOWTag(JSObject* obj, nsACString& out) {
  JSObject* unwrapped = js::UncheckedUnwrap(obj, true);
  MOZ_ASSERT(IsCPOW(unwrapped));

  AuxCPOWData* aux = AuxCPOWDataOf(unwrapped);
  if (aux) {
    out = aux->objectTag;
  }
}

nsresult InstanceOf(JSObject* proxy, const nsID* id, bool* bp) {
  WrapperOwner* parent = OwnerOf(proxy);
  if (!parent->active()) {
    return NS_ERROR_UNEXPECTED;
  }
  return parent->instanceOf(proxy, id, bp);
}

bool DOMInstanceOf(JSContext* cx, JSObject* proxyArg, int prototypeID,
                   int depth, bool* bp) {
  RootedObject proxy(cx, proxyArg);
  FORWARD(domInstanceOf, (cx, proxy, prototypeID, depth, bp), false);
}

} /* namespace jsipc */
} /* namespace mozilla */

nsresult WrapperOwner::instanceOf(JSObject* obj, const nsID* id, bool* bp) {
  ObjectId objId = idOf(obj);

  JSIID iid;
  ConvertID(*id, &iid);

  ReturnStatus status;
  if (!SendInstanceOf(objId, iid, &status, bp)) {
    return NS_ERROR_UNEXPECTED;
  }

  if (status.type() != ReturnStatus::TReturnSuccess) {
    return NS_ERROR_UNEXPECTED;
  }

  return NS_OK;
}

bool WrapperOwner::domInstanceOf(JSContext* cx, JSObject* obj, int prototypeID,
                                 int depth, bool* bp) {
  ObjectId objId = idOf(obj);

  ReturnStatus status;
  if (!SendDOMInstanceOf(objId, prototypeID, depth, &status, bp)) {
    return ipcfail(cx);
  }

  LOG_STACK();

  return ok(cx, status);
}

void WrapperOwner::ActorDestroy(ActorDestroyReason why) {
  inactive_ = true;

  objects_.clear();
  unwaivedObjectIds_.clear();
  waivedObjectIds_.clear();
}

bool WrapperOwner::ipcfail(JSContext* cx) {
  JS_ReportErrorASCII(cx, "cross-process JS call failed");
  return false;
}

bool WrapperOwner::ok(JSContext* cx, const ReturnStatus& status) {
  if (status.type() == ReturnStatus::TReturnSuccess) {
    return true;
  }

  if (status.type() == ReturnStatus::TReturnDeadCPOW) {
    JS_ReportErrorASCII(cx, "operation not possible on dead CPOW");
    return false;
  }

  RootedValue exn(cx);
  if (!fromVariant(cx, status.get_ReturnException().exn(), &exn)) {
    return false;
  }

  JS_SetPendingException(cx, exn);
  return false;
}

bool WrapperOwner::ok(JSContext* cx, const ReturnStatus& status,
                      ObjectOpResult& result) {
  if (status.type() == ReturnStatus::TReturnObjectOpResult) {
    return result.fail(status.get_ReturnObjectOpResult().code());
  }
  if (!ok(cx, status)) {
    return false;
  }
  return result.succeed();
}

// CPOWs can have a tag string attached to them, originating in the local
// process from this function.  It's sent with the CPOW to the remote process,
// where it can be fetched with Components.utils.getCrossProcessWrapperTag.
static nsCString GetRemoteObjectTag(JS::Handle<JSObject*> obj) {
  // OK to use ReflectorToISupportsStatic, because we only care about docshells
  // and documents here.
  if (nsCOMPtr<nsISupports> supports = xpc::ReflectorToISupportsStatic(obj)) {
    nsCOMPtr<nsIDocShellTreeItem> treeItem(do_QueryInterface(supports));
    if (treeItem) {
      return NS_LITERAL_CSTRING("ContentDocShellTreeItem");
    }

    nsCOMPtr<dom::Document> doc(do_QueryInterface(supports));
    if (doc) {
      return NS_LITERAL_CSTRING("ContentDocument");
    }
  }

  return NS_LITERAL_CSTRING("generic");
}

static RemoteObject MakeRemoteObject(JSContext* cx, ObjectId id,
                                     HandleObject obj) {
  return RemoteObject(id.serialize(), JS::IsCallable(obj),
                      JS::IsConstructor(obj), dom::IsDOMObject(obj),
                      GetRemoteObjectTag(obj));
}

bool WrapperOwner::toObjectVariant(JSContext* cx, JSObject* objArg,
                                   ObjectVariant* objVarp) {
  RootedObject obj(cx, objArg);
  MOZ_ASSERT(obj);

  // We always save objects unwrapped in the CPOW table. If we stored
  // wrappers, then the wrapper might be GCed while the target remained alive.
  // Whenever operating on an object that comes from the table, we wrap it
  // in findObjectById.
  unsigned wrapperFlags = 0;
  obj = js::UncheckedUnwrap(obj, true, &wrapperFlags);
  if (obj && IsCPOW(obj) && OwnerOf(obj) == this) {
    *objVarp = LocalObject(idOf(obj).serialize());
    return true;
  }
  bool waiveXray = wrapperFlags & xpc::WrapperFactory::WAIVE_XRAY_WRAPPER_FLAG;

  ObjectId id = objectIdMap(waiveXray).find(obj);
  if (!id.isNull()) {
    MOZ_ASSERT(id.hasXrayWaiver() == waiveXray);
    *objVarp = MakeRemoteObject(cx, id, obj);
    return true;
  }

  // Need to call PreserveWrapper on |obj| in case it's a reflector.
  // FIXME: What if it's an XPCWrappedNative?
  if (mozilla::dom::IsDOMObject(obj)) {
    mozilla::dom::TryPreserveWrapper(obj);
  }

  id = ObjectId(nextSerialNumber_++, waiveXray);
  if (!objects_.add(id, obj)) {
    return false;
  }
  if (!objectIdMap(waiveXray).add(cx, obj, id)) {
    return false;
  }

  *objVarp = MakeRemoteObject(cx, id, obj);
  return true;
}

JSObject* WrapperOwner::fromObjectVariant(JSContext* cx,
                                          const ObjectVariant& objVar) {
  if (objVar.type() == ObjectVariant::TRemoteObject) {
    return fromRemoteObjectVariant(cx, objVar.get_RemoteObject());
  } else {
    return fromLocalObjectVariant(cx, objVar.get_LocalObject());
  }
}

JSObject* WrapperOwner::fromRemoteObjectVariant(JSContext* cx,
                                                const RemoteObject& objVar) {
  Maybe<ObjectId> maybeObjId(ObjectId::deserialize(objVar.serializedId()));
  if (maybeObjId.isNothing()) {
    return nullptr;
  }

  ObjectId objId = maybeObjId.value();
  RootedObject obj(cx, findCPOWById(objId));
  if (!obj) {
    // All CPOWs live in the privileged junk scope.
    RootedObject junkScope(cx, xpc::PrivilegedJunkScope());
    JSAutoRealm ar(cx, junkScope);
    RootedValue v(cx, UndefinedValue());
    // We need to setLazyProto for the getPrototype/getPrototypeIfOrdinary
    // hooks.
    ProxyOptions options;
    options.setLazyProto(true);
    obj = NewProxyObject(cx, &CPOWProxyHandler::singleton, v, nullptr, options);
    if (!obj) {
      return nullptr;
    }

    if (!cpows_.add(objId, obj)) {
      return nullptr;
    }

    nextCPOWNumber_ = objId.serialNumber() + 1;

    // Incref once we know the decref will be called.
    incref();

    AuxCPOWData* aux =
        new AuxCPOWData(objId, objVar.isCallable(), objVar.isConstructor(),
                        objVar.isDOMObject(), objVar.objectTag());

    SetProxyReservedSlot(obj, 0, PrivateValue(this));
    SetProxyReservedSlot(obj, 1, PrivateValue(aux));
  }

  if (!JS_WrapObject(cx, &obj)) {
    return nullptr;
  }
  return obj;
}

JSObject* WrapperOwner::fromLocalObjectVariant(JSContext* cx,
                                               const LocalObject& objVar) {
  Maybe<ObjectId> id(ObjectId::deserialize(objVar.serializedId()));
  if (id.isNothing()) {
    return nullptr;
  }
  Rooted<JSObject*> obj(cx, findObjectById(cx, id.value()));
  if (!obj) {
    return nullptr;
  }
  if (!JS_WrapObject(cx, &obj)) {
    return nullptr;
  }
  return obj;
}