DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Mercurial (c68fe15a81fc)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 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/. */

/* Per JSContext object */

#include "mozilla/MemoryReporting.h"
#include "mozilla/UniquePtr.h"

#include "xpcprivate.h"
#include "xpcpublic.h"
#include "XPCWrapper.h"
#include "XPCJSMemoryReporter.h"
#include "WrapperFactory.h"
#include "mozJSComponentLoader.h"
#include "nsNetUtil.h"
#include "nsThreadUtils.h"

#include "nsIObserverService.h"
#include "nsIDebug2.h"
#include "nsPIDOMWindow.h"
#include "nsPrintfCString.h"
#include "mozilla/Preferences.h"
#include "mozilla/Telemetry.h"
#include "mozilla/Services.h"
#ifdef FUZZING
#  include "mozilla/StaticPrefs_fuzzing.h"
#endif
#include "mozilla/StaticPrefs_browser.h"
#include "mozilla/StaticPrefs_javascript.h"
#include "mozilla/dom/ScriptSettings.h"

#include "nsContentUtils.h"
#include "nsCCUncollectableMarker.h"
#include "nsCycleCollectionNoteRootCallback.h"
#include "nsCycleCollector.h"
#include "jsapi.h"
#include "js/ContextOptions.h"
#include "js/MemoryMetrics.h"
#include "mozilla/dom/BindingUtils.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/ScriptLoader.h"
#include "mozilla/dom/WindowBinding.h"
#include "mozilla/extensions/WebExtensionPolicy.h"
#include "mozilla/Atomics.h"
#include "mozilla/Attributes.h"
#include "mozilla/ProcessHangMonitor.h"
#include "mozilla/Sprintf.h"
#include "mozilla/SystemPrincipal.h"
#include "mozilla/ThreadLocal.h"
#include "mozilla/UniquePtrExtensions.h"
#include "mozilla/Unused.h"
#include "AccessCheck.h"
#include "nsGlobalWindow.h"
#include "nsAboutProtocolUtils.h"

#include "GeckoProfiler.h"
#include "nsIXULRuntime.h"
#include "nsJSPrincipals.h"
#include "ExpandedPrincipal.h"
#ifdef MOZ_GECKO_PROFILER
#  include "ProfilerMarkerPayload.h"
#endif

#if defined(XP_LINUX) && !defined(ANDROID)
// For getrlimit and min/max.
#  include <algorithm>
#  include <sys/resource.h>
#endif

#ifdef XP_WIN
// For min.
#  include <algorithm>
#  include <windows.h>
#endif

using namespace mozilla;
using namespace xpc;
using namespace JS;
using mozilla::dom::AutoEntryScript;

// The watchdog thread loop is pretty trivial, and should not require much stack
// space to do its job. So only give it 32KiB or the platform minimum.
#if !defined(PTHREAD_STACK_MIN)
#  define PTHREAD_STACK_MIN 0
#endif
static constexpr size_t kWatchdogStackSize =
    PTHREAD_STACK_MIN < 32 * 1024 ? 32 * 1024 : PTHREAD_STACK_MIN;

static void WatchdogMain(void* arg);
class Watchdog;
class WatchdogManager;
class MOZ_RAII AutoLockWatchdog final {
  MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
  Watchdog* const mWatchdog;

 public:
  explicit AutoLockWatchdog(
      Watchdog* aWatchdog MOZ_GUARD_OBJECT_NOTIFIER_PARAM);
  ~AutoLockWatchdog();
};

class Watchdog {
 public:
  explicit Watchdog(WatchdogManager* aManager)
      : mManager(aManager),
        mLock(nullptr),
        mWakeup(nullptr),
        mThread(nullptr),
        mHibernating(false),
        mInitialized(false),
        mShuttingDown(false),
        mMinScriptRunTimeSeconds(1) {}
  ~Watchdog() { MOZ_ASSERT(!Initialized()); }

  WatchdogManager* Manager() { return mManager; }
  bool Initialized() { return mInitialized; }
  bool ShuttingDown() { return mShuttingDown; }
  PRLock* GetLock() { return mLock; }
  bool Hibernating() { return mHibernating; }
  void WakeUp() {
    MOZ_ASSERT(Initialized());
    MOZ_ASSERT(Hibernating());
    mHibernating = false;
    PR_NotifyCondVar(mWakeup);
  }

  //
  // Invoked by the main thread only.
  //

  void Init() {
    MOZ_ASSERT(NS_IsMainThread());
    mLock = PR_NewLock();
    if (!mLock) {
      MOZ_CRASH("PR_NewLock failed.");
    }

    mWakeup = PR_NewCondVar(mLock);
    if (!mWakeup) {
      MOZ_CRASH("PR_NewCondVar failed.");
    }

    {
      // Make sure the debug service is instantiated before we create the
      // watchdog thread, since we intentionally try to keep the thread's stack
      // segment as small as possible. It isn't always large enough to
      // instantiate a new service, and even when it is, we don't want fault in
      // extra pages if we can avoid it.
      nsCOMPtr<nsIDebug2> dbg = do_GetService("@mozilla.org/xpcom/debug;1");
      Unused << dbg;
    }

    {
      AutoLockWatchdog lock(this);

      // Gecko uses thread private for accounting and has to clean up at thread
      // exit. Therefore, even though we don't have a return value from the
      // watchdog, we need to join it on shutdown.
      mThread = PR_CreateThread(PR_USER_THREAD, WatchdogMain, this,
                                PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD,
                                PR_JOINABLE_THREAD, kWatchdogStackSize);
      if (!mThread) {
        MOZ_CRASH("PR_CreateThread failed!");
      }

      // WatchdogMain acquires the lock and then asserts mInitialized. So
      // make sure to set mInitialized before releasing the lock here so
      // that it's atomic with the creation of the thread.
      mInitialized = true;
    }
  }

  void Shutdown() {
    MOZ_ASSERT(NS_IsMainThread());
    MOZ_ASSERT(Initialized());
    {  // Scoped lock.
      AutoLockWatchdog lock(this);

      // Signal to the watchdog thread that it's time to shut down.
      mShuttingDown = true;

      // Wake up the watchdog, and wait for it to call us back.
      PR_NotifyCondVar(mWakeup);
    }

    PR_JoinThread(mThread);

    // The thread sets mShuttingDown to false as it exits.
    MOZ_ASSERT(!mShuttingDown);

    // Destroy state.
    mThread = nullptr;
    PR_DestroyCondVar(mWakeup);
    mWakeup = nullptr;
    PR_DestroyLock(mLock);
    mLock = nullptr;

    // All done.
    mInitialized = false;
  }

  void SetMinScriptRunTimeSeconds(int32_t seconds) {
    // This variable is atomic, and is set from the main thread without
    // locking.
    MOZ_ASSERT(seconds > 0);
    mMinScriptRunTimeSeconds = seconds;
  }

  //
  // Invoked by the watchdog thread only.
  //

  void Hibernate() {
    MOZ_ASSERT(!NS_IsMainThread());
    mHibernating = true;
    Sleep(PR_INTERVAL_NO_TIMEOUT);
  }
  void Sleep(PRIntervalTime timeout) {
    MOZ_ASSERT(!NS_IsMainThread());
    MOZ_ALWAYS_TRUE(PR_WaitCondVar(mWakeup, timeout) == PR_SUCCESS);
  }
  void Finished() {
    MOZ_ASSERT(!NS_IsMainThread());
    mShuttingDown = false;
  }

  int32_t MinScriptRunTimeSeconds() { return mMinScriptRunTimeSeconds; }

 private:
  WatchdogManager* mManager;

  PRLock* mLock;
  PRCondVar* mWakeup;
  PRThread* mThread;
  bool mHibernating;
  bool mInitialized;
  bool mShuttingDown;
  mozilla::Atomic<int32_t> mMinScriptRunTimeSeconds;
};

#define PREF_MAX_SCRIPT_RUN_TIME_CONTENT "dom.max_script_run_time"
#define PREF_MAX_SCRIPT_RUN_TIME_CHROME "dom.max_chrome_script_run_time"
#define PREF_MAX_SCRIPT_RUN_TIME_EXT_CONTENT \
  "dom.max_ext_content_script_run_time"

static const char* gCallbackPrefs[] = {
    "dom.use_watchdog",
    PREF_MAX_SCRIPT_RUN_TIME_CONTENT,
    PREF_MAX_SCRIPT_RUN_TIME_CHROME,
    PREF_MAX_SCRIPT_RUN_TIME_EXT_CONTENT,
    nullptr,
};

class WatchdogManager {
 public:
  explicit WatchdogManager() {
    // All the timestamps start at zero.
    PodArrayZero(mTimestamps);

    // Register ourselves as an observer to get updates on the pref.
    Preferences::RegisterCallbacks(PrefsChanged, gCallbackPrefs, this);
  }

  virtual ~WatchdogManager() {
    // Shutting down the watchdog requires context-switching to the watchdog
    // thread, which isn't great to do in a destructor. So we require
    // consumers to shut it down manually before releasing it.
    MOZ_ASSERT(!mWatchdog);
  }

 private:
  static void PrefsChanged(const char* aPref, void* aSelf) {
    static_cast<WatchdogManager*>(aSelf)->RefreshWatchdog();
  }

 public:
  void Shutdown() {
    Preferences::UnregisterCallbacks(PrefsChanged, gCallbackPrefs, this);
  }

  void RegisterContext(XPCJSContext* aContext) {
    MOZ_ASSERT(NS_IsMainThread());
    AutoLockWatchdog lock(mWatchdog.get());

    if (aContext->mActive == XPCJSContext::CONTEXT_ACTIVE) {
      mActiveContexts.insertBack(aContext);
    } else {
      mInactiveContexts.insertBack(aContext);
    }

    // Enable the watchdog, if appropriate.
    RefreshWatchdog();
  }

  void UnregisterContext(XPCJSContext* aContext) {
    MOZ_ASSERT(NS_IsMainThread());
    AutoLockWatchdog lock(mWatchdog.get());

    // aContext must be in one of our two lists, simply remove it.
    aContext->LinkedListElement<XPCJSContext>::remove();

#ifdef DEBUG
    // If this was the last context, we should have already shut down
    // the watchdog.
    if (mActiveContexts.isEmpty() && mInactiveContexts.isEmpty()) {
      MOZ_ASSERT(!mWatchdog);
    }
#endif
  }

  // Context statistics. These live on the watchdog manager, are written
  // from the main thread, and are read from the watchdog thread (holding
  // the lock in each case).
  void RecordContextActivity(XPCJSContext* aContext, bool active) {
    // The watchdog reads this state, so acquire the lock before writing it.
    MOZ_ASSERT(NS_IsMainThread());
    AutoLockWatchdog lock(mWatchdog.get());

    // Write state.
    aContext->mLastStateChange = PR_Now();
    aContext->mActive =
        active ? XPCJSContext::CONTEXT_ACTIVE : XPCJSContext::CONTEXT_INACTIVE;
    UpdateContextLists(aContext);

    // The watchdog may be hibernating, waiting for the context to go
    // active. Wake it up if necessary.
    if (active && mWatchdog && mWatchdog->Hibernating()) {
      mWatchdog->WakeUp();
    }
  }

  bool IsAnyContextActive() { return !mActiveContexts.isEmpty(); }
  PRTime TimeSinceLastActiveContext() {
    // Must be called on the watchdog thread with the lock held.
    MOZ_ASSERT(!NS_IsMainThread());
    PR_ASSERT_CURRENT_THREAD_OWNS_LOCK(mWatchdog->GetLock());
    MOZ_ASSERT(mActiveContexts.isEmpty());
    MOZ_ASSERT(!mInactiveContexts.isEmpty());

    // We store inactive contexts with the most recently added inactive
    // context at the end of the list.
    return PR_Now() - mInactiveContexts.getLast()->mLastStateChange;
  }

  void RecordTimestamp(WatchdogTimestampCategory aCategory) {
    // Must be called on the watchdog thread with the lock held.
    MOZ_ASSERT(!NS_IsMainThread());
    PR_ASSERT_CURRENT_THREAD_OWNS_LOCK(mWatchdog->GetLock());
    MOZ_ASSERT(aCategory != TimestampContextStateChange,
               "Use RecordContextActivity to update this");

    mTimestamps[aCategory] = PR_Now();
  }

  PRTime GetContextTimestamp(XPCJSContext* aContext,
                             const AutoLockWatchdog& aProofOfLock) {
    return aContext->mLastStateChange;
  }

  PRTime GetTimestamp(WatchdogTimestampCategory aCategory,
                      const AutoLockWatchdog& aProofOfLock) {
    MOZ_ASSERT(aCategory != TimestampContextStateChange,
               "Use GetContextTimestamp to retrieve this");
    return mTimestamps[aCategory];
  }

  Watchdog* GetWatchdog() { return mWatchdog.get(); }

  void RefreshWatchdog() {
    bool wantWatchdog = Preferences::GetBool("dom.use_watchdog", true);
    if (wantWatchdog != !!mWatchdog) {
      if (wantWatchdog) {
        StartWatchdog();
      } else {
        StopWatchdog();
      }
    }

    if (mWatchdog) {
      int32_t contentTime =
          Preferences::GetInt(PREF_MAX_SCRIPT_RUN_TIME_CONTENT, 10);
      if (contentTime <= 0) {
        contentTime = INT32_MAX;
      }
      int32_t chromeTime =
          Preferences::GetInt(PREF_MAX_SCRIPT_RUN_TIME_CHROME, 20);
      if (chromeTime <= 0) {
        chromeTime = INT32_MAX;
      }
      int32_t extTime =
          Preferences::GetInt(PREF_MAX_SCRIPT_RUN_TIME_EXT_CONTENT, 5);
      if (extTime <= 0) {
        extTime = INT32_MAX;
      }
      mWatchdog->SetMinScriptRunTimeSeconds(
          std::min({contentTime, chromeTime, extTime}));
    }
  }

  void StartWatchdog() {
    MOZ_ASSERT(!mWatchdog);
    mWatchdog = mozilla::MakeUnique<Watchdog>(this);
    mWatchdog->Init();
  }

  void StopWatchdog() {
    MOZ_ASSERT(mWatchdog);
    mWatchdog->Shutdown();
    mWatchdog = nullptr;
  }

  template <class Callback>
  void ForAllActiveContexts(Callback&& aCallback) {
    // This function must be called on the watchdog thread with the lock held.
    MOZ_ASSERT(!NS_IsMainThread());
    PR_ASSERT_CURRENT_THREAD_OWNS_LOCK(mWatchdog->GetLock());

    for (auto* context = mActiveContexts.getFirst(); context;
         context = context->LinkedListElement<XPCJSContext>::getNext()) {
      if (!aCallback(context)) {
        return;
      }
    }
  }

 private:
  void UpdateContextLists(XPCJSContext* aContext) {
    // Given aContext whose activity state or timestamp has just changed,
    // put it back in the proper position in the proper list.
    aContext->LinkedListElement<XPCJSContext>::remove();
    auto& list = aContext->mActive == XPCJSContext::CONTEXT_ACTIVE
                     ? mActiveContexts
                     : mInactiveContexts;

    // Either the new list is empty or aContext must be more recent than
    // the existing last element.
    MOZ_ASSERT_IF(!list.isEmpty(), list.getLast()->mLastStateChange <
                                       aContext->mLastStateChange);
    list.insertBack(aContext);
  }

  LinkedList<XPCJSContext> mActiveContexts;
  LinkedList<XPCJSContext> mInactiveContexts;
  mozilla::UniquePtr<Watchdog> mWatchdog;

  // We store ContextStateChange on the contexts themselves.
  PRTime mTimestamps[kWatchdogTimestampCategoryCount - 1];
};

AutoLockWatchdog::AutoLockWatchdog(
    Watchdog* aWatchdog MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL)
    : mWatchdog(aWatchdog) {
  MOZ_GUARD_OBJECT_NOTIFIER_INIT;
  if (mWatchdog) {
    PR_Lock(mWatchdog->GetLock());
  }
}

AutoLockWatchdog::~AutoLockWatchdog() {
  if (mWatchdog) {
    PR_Unlock(mWatchdog->GetLock());
  }
}

static void WatchdogMain(void* arg) {
  AUTO_PROFILER_REGISTER_THREAD("JS Watchdog");
  // Create an nsThread wrapper for the thread and register it with the thread
  // manager.
  Unused << NS_GetCurrentThread();
  NS_SetCurrentThreadName("JS Watchdog");

  Watchdog* self = static_cast<Watchdog*>(arg);
  WatchdogManager* manager = self->Manager();

  // Lock lasts until we return
  AutoLockWatchdog lock(self);

  MOZ_ASSERT(self->Initialized());
  while (!self->ShuttingDown()) {
    // Sleep only 1 second if recently (or currently) active; otherwise,
    // hibernate
    if (manager->IsAnyContextActive() ||
        manager->TimeSinceLastActiveContext() <= PRTime(2 * PR_USEC_PER_SEC)) {
      self->Sleep(PR_TicksPerSecond());
    } else {
      manager->RecordTimestamp(TimestampWatchdogHibernateStart);
      self->Hibernate();
      manager->RecordTimestamp(TimestampWatchdogHibernateStop);
    }

    // Rise and shine.
    manager->RecordTimestamp(TimestampWatchdogWakeup);

    // Don't request an interrupt callback unless the current script has
    // been running long enough that we might show the slow script dialog.
    // Triggering the callback from off the main thread can be expensive.

    // We want to avoid showing the slow script dialog if the user's laptop
    // goes to sleep in the middle of running a script. To ensure this, we
    // invoke the interrupt callback after only half the timeout has
    // elapsed. The callback simply records the fact that it was called in
    // the mSlowScriptSecondHalf flag. Then we wait another (timeout/2)
    // seconds and invoke the callback again. This time around it sees
    // mSlowScriptSecondHalf is set and so it shows the slow script
    // dialog. If the computer is put to sleep during one of the (timeout/2)
    // periods, the script still has the other (timeout/2) seconds to
    // finish.
    if (!self->ShuttingDown() && manager->IsAnyContextActive()) {
      bool debuggerAttached = false;
      nsCOMPtr<nsIDebug2> dbg = do_GetService("@mozilla.org/xpcom/debug;1");
      if (dbg) {
        dbg->GetIsDebuggerAttached(&debuggerAttached);
      }
      if (debuggerAttached) {
        // We won't be interrupting these scripts anyway.
        continue;
      }

      PRTime usecs = self->MinScriptRunTimeSeconds() * PR_USEC_PER_SEC / 2;
      manager->ForAllActiveContexts([usecs, manager,
                                     &lock](XPCJSContext* aContext) -> bool {
        auto timediff = PR_Now() - manager->GetContextTimestamp(aContext, lock);
        if (timediff > usecs) {
          JS_RequestInterruptCallback(aContext->Context());
          return true;
        }
        return false;
      });
    }
  }

  // Tell the manager that we've shut down.
  self->Finished();
}

PRTime XPCJSContext::GetWatchdogTimestamp(WatchdogTimestampCategory aCategory) {
  AutoLockWatchdog lock(mWatchdogManager->GetWatchdog());
  return aCategory == TimestampContextStateChange
             ? mWatchdogManager->GetContextTimestamp(this, lock)
             : mWatchdogManager->GetTimestamp(aCategory, lock);
}

// static
bool XPCJSContext::RecordScriptActivity(bool aActive) {
  MOZ_ASSERT(NS_IsMainThread());

  XPCJSContext* xpccx = XPCJSContext::Get();
  if (!xpccx) {
    // mozilla::SpinEventLoopUntil may use AutoScriptActivity(false) after
    // we destroyed the XPCJSContext.
    MOZ_ASSERT(!aActive);
    return false;
  }

  bool oldValue = xpccx->SetHasScriptActivity(aActive);
  if (aActive == oldValue) {
    // Nothing to do.
    return oldValue;
  }

  if (!aActive) {
    ProcessHangMonitor::ClearHang();
  }
  xpccx->mWatchdogManager->RecordContextActivity(xpccx, aActive);

  return oldValue;
}

AutoScriptActivity::AutoScriptActivity(bool aActive)
    : mActive(aActive),
      mOldValue(XPCJSContext::RecordScriptActivity(aActive)) {}

AutoScriptActivity::~AutoScriptActivity() {
  MOZ_ALWAYS_TRUE(mActive == XPCJSContext::RecordScriptActivity(mOldValue));
}

// static
bool XPCJSContext::InterruptCallback(JSContext* cx) {
  XPCJSContext* self = XPCJSContext::Get();

  // Now is a good time to turn on profiling if it's pending.
  PROFILER_JS_INTERRUPT_CALLBACK();

#ifdef MOZ_GECKO_PROFILER
  nsDependentCString filename("unknown file");
  JS::AutoFilename scriptFilename;
  // Computing the line number can be very expensive (see bug 1330231 for
  // example), so don't request it here.
  if (JS::DescribeScriptedCaller(cx, &scriptFilename)) {
    if (const char* file = scriptFilename.get()) {
      filename.Assign(file, strlen(file));
    }
    PROFILER_ADD_MARKER_WITH_PAYLOAD("JS::InterruptCallback", JS,
                                     TextMarkerPayload,
                                     (filename, TimeStamp::Now()));
  }
#endif

  // Normally we record mSlowScriptCheckpoint when we start to process an
  // event. However, we can run JS outside of event handlers. This code takes
  // care of that case.
  if (self->mSlowScriptCheckpoint.IsNull()) {
    self->mSlowScriptCheckpoint = TimeStamp::NowLoRes();
    self->mSlowScriptSecondHalf = false;
    self->mSlowScriptActualWait = mozilla::TimeDuration();
    self->mTimeoutAccumulated = false;
    return true;
  }

  // Sometimes we get called back during XPConnect initialization, before Gecko
  // has finished bootstrapping. Avoid crashing in nsContentUtils below.
  if (!nsContentUtils::IsInitialized()) {
    return true;
  }

  // This is at least the second interrupt callback we've received since
  // returning to the event loop. See how long it's been, and what the limit
  // is.
  TimeDuration duration = TimeStamp::NowLoRes() - self->mSlowScriptCheckpoint;
  int32_t limit;

  nsString addonId;
  const char* prefName;

  auto principal = BasePrincipal::Cast(nsContentUtils::SubjectPrincipal(cx));
  bool chrome = principal->Is<SystemPrincipal>();
  if (chrome) {
    prefName = PREF_MAX_SCRIPT_RUN_TIME_CHROME;
    limit = Preferences::GetInt(prefName, 20);
  } else if (auto policy = principal->ContentScriptAddonPolicy()) {
    policy->GetId(addonId);
    prefName = PREF_MAX_SCRIPT_RUN_TIME_EXT_CONTENT;
    limit = Preferences::GetInt(prefName, 5);
  } else {
    prefName = PREF_MAX_SCRIPT_RUN_TIME_CONTENT;
    limit = Preferences::GetInt(prefName, 10);
  }

  // If there's no limit, or we're within the limit, let it go.
  if (limit == 0 || duration.ToSeconds() < limit / 2.0) {
    return true;
  }

  self->mSlowScriptActualWait += duration;

  // In order to guard against time changes or laptops going to sleep, we
  // don't trigger the slow script warning until (limit/2) seconds have
  // elapsed twice.
  if (!self->mSlowScriptSecondHalf) {
    self->mSlowScriptCheckpoint = TimeStamp::NowLoRes();
    self->mSlowScriptSecondHalf = true;
    return true;
  }

  //
  // This has gone on long enough! Time to take action. ;-)
  //

  // Get the DOM window associated with the running script. If the script is
  // running in a non-DOM scope, we have to just let it keep running.
  RootedObject global(cx, JS::CurrentGlobalOrNull(cx));
  RefPtr<nsGlobalWindowInner> win = WindowOrNull(global);
  if (!win && IsSandbox(global)) {
    // If this is a sandbox associated with a DOMWindow via a
    // sandboxPrototype, use that DOMWindow. This supports GreaseMonkey
    // and JetPack content scripts.
    JS::Rooted<JSObject*> proto(cx);
    if (!JS_GetPrototype(cx, global, &proto)) {
      return false;
    }
    if (proto && xpc::IsSandboxPrototypeProxy(proto) &&
        (proto = js::CheckedUnwrapDynamic(proto, cx,
                                          /* stopAtWindowProxy = */ false))) {
      win = WindowGlobalOrNull(proto);
    }
  }

  if (!win) {
    NS_WARNING("No active window");
    return true;
  }

  if (win->IsDying()) {
    // The window is being torn down. When that happens we try to prevent
    // the dispatch of new runnables, so it also makes sense to kill any
    // long-running script. The user is primarily interested in this page
    // going away.
    return false;
  }

  // Accumulate slow script invokation delay.
  if (!chrome && !self->mTimeoutAccumulated) {
    uint32_t delay = uint32_t(self->mSlowScriptActualWait.ToMilliseconds() -
                              (limit * 1000.0));
    Telemetry::Accumulate(Telemetry::SLOW_SCRIPT_NOTIFY_DELAY, delay);
    self->mTimeoutAccumulated = true;
  }

  // Show the prompt to the user, and kill if requested.
  nsGlobalWindowInner::SlowScriptResponse response =
      win->ShowSlowScriptDialog(cx, addonId);
  if (response == nsGlobalWindowInner::KillSlowScript) {
    if (Preferences::GetBool("dom.global_stop_script", true)) {
      xpc::Scriptability::Get(global).Block();
    }
    return false;
  }
  if (response == nsGlobalWindowInner::KillScriptGlobal) {
    nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();

    if (!IsSandbox(global) || !obs) {
      return false;
    }

    // Notify the extensions framework that the sandbox should be killed.
    nsIXPConnect* xpc = nsContentUtils::XPConnect();
    JS::RootedObject wrapper(cx, JS_NewPlainObject(cx));
    nsCOMPtr<nsISupports> supports;

    // Store the sandbox object on the wrappedJSObject property of the
    // subject so that JS recipients can access the JS value directly.
    if (!wrapper ||
        !JS_DefineProperty(cx, wrapper, "wrappedJSObject", global,
                           JSPROP_ENUMERATE) ||
        NS_FAILED(xpc->WrapJS(cx, wrapper, NS_GET_IID(nsISupports),
                              getter_AddRefs(supports)))) {
      return false;
    }

    obs->NotifyObservers(supports, "kill-content-script-sandbox", nullptr);
    return false;
  }

  // The user chose to continue the script. Reset the timer, and disable this
  // machinery with a pref of the user opted out of future slow-script dialogs.
  if (response != nsGlobalWindowInner::ContinueSlowScriptAndKeepNotifying) {
    self->mSlowScriptCheckpoint = TimeStamp::NowLoRes();
  }

  if (response == nsGlobalWindowInner::AlwaysContinueSlowScript) {
    Preferences::SetInt(prefName, 0);
  }

  return true;
}

#define JS_OPTIONS_DOT_STR "javascript.options."

static mozilla::Atomic<bool> sDiscardSystemSource(false);

bool xpc::ShouldDiscardSystemSource() { return sDiscardSystemSource; }

static mozilla::Atomic<bool> sSharedMemoryEnabled(false);
static mozilla::Atomic<bool> sStreamsEnabled(false);

static mozilla::Atomic<bool> sPropertyErrorMessageFixEnabled(false);
static mozilla::Atomic<bool> sWeakRefsEnabled(false);
static mozilla::Atomic<bool> sWeakRefsExposeCleanupSome(false);
static mozilla::Atomic<bool> sIteratorHelpersEnabled(false);

static JS::WeakRefSpecifier GetWeakRefsEnabled() {
  if (!sWeakRefsEnabled) {
    return JS::WeakRefSpecifier::Disabled;
  }

  if (sWeakRefsExposeCleanupSome) {
    return JS::WeakRefSpecifier::EnabledWithCleanupSome;
  }

  return JS::WeakRefSpecifier::EnabledWithoutCleanupSome;
}

void xpc::SetPrefableRealmOptions(JS::RealmOptions& options) {
  options.creationOptions()
      .setSharedMemoryAndAtomicsEnabled(sSharedMemoryEnabled)
      .setCoopAndCoepEnabled(
          StaticPrefs::browser_tabs_remote_useCrossOriginOpenerPolicy() &&
          StaticPrefs::browser_tabs_remote_useCrossOriginEmbedderPolicy())
      .setStreamsEnabled(sStreamsEnabled)
      .setWritableStreamsEnabled(
          StaticPrefs::javascript_options_writable_streams())
      .setPropertyErrorMessageFixEnabled(sPropertyErrorMessageFixEnabled)
      .setWeakRefsEnabled(GetWeakRefsEnabled())
      .setIteratorHelpersEnabled(sIteratorHelpersEnabled);
}

static void LoadStartupJSPrefs(XPCJSContext* xpccx) {
  // Prefs that require a restart are handled here. This includes the
  // process-wide JIT options because toggling these at runtime can easily cause
  // races or get us into an inconsistent state.
  //
  // 'Live' prefs are handled by ReloadPrefsCallback below.

  JSContext* cx = xpccx->Context();

  bool useBaselineInterp = Preferences::GetBool(JS_OPTIONS_DOT_STR "blinterp");
  bool useBaselineJit = Preferences::GetBool(JS_OPTIONS_DOT_STR "baselinejit");
  bool useIon = Preferences::GetBool(JS_OPTIONS_DOT_STR "ion");
  bool useJitForTrustedPrincipals =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "jit_trustedprincipals");
  bool useNativeRegExp =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "native_regexp");

  bool offthreadIonCompilation =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "ion.offthread_compilation");
  bool useBaselineEager = Preferences::GetBool(
      JS_OPTIONS_DOT_STR "baselinejit.unsafe_eager_compilation");
  bool useIonEager =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "ion.unsafe_eager_compilation");
#ifdef DEBUG
  bool fullJitDebugChecks =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "jit.full_debug_checks");
#endif

  int32_t baselineInterpThreshold =
      Preferences::GetInt(JS_OPTIONS_DOT_STR "blinterp.threshold", -1);
  int32_t baselineThreshold =
      Preferences::GetInt(JS_OPTIONS_DOT_STR "baselinejit.threshold", -1);
  int32_t normalIonThreshold =
      Preferences::GetInt(JS_OPTIONS_DOT_STR "ion.threshold", -1);
  int32_t fullIonThreshold =
      Preferences::GetInt(JS_OPTIONS_DOT_STR "ion.full.threshold", -1);
  int32_t ionFrequentBailoutThreshold = Preferences::GetInt(
      JS_OPTIONS_DOT_STR "ion.frequent_bailout_threshold", -1);

  bool spectreIndexMasking =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "spectre.index_masking");
  bool spectreObjectMitigationsBarriers = Preferences::GetBool(
      JS_OPTIONS_DOT_STR "spectre.object_mitigations.barriers");
  bool spectreObjectMitigationsMisc = Preferences::GetBool(
      JS_OPTIONS_DOT_STR "spectre.object_mitigations.misc");
  bool spectreStringMitigations =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "spectre.string_mitigations");
  bool spectreValueMasking =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "spectre.value_masking");
  bool spectreJitToCxxCalls =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "spectre.jit_to_C++_calls");

  bool disableWasmHugeMemory =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm_disable_huge_memory");

  nsCOMPtr<nsIXULRuntime> xr = do_GetService("@mozilla.org/xre/runtime;1");
  if (xr) {
    bool safeMode = false;
    xr->GetInSafeMode(&safeMode);
    if (safeMode) {
      useBaselineInterp = false;
      useBaselineJit = false;
      useIon = false;
      useJitForTrustedPrincipals = false;
      useNativeRegExp = false;
    }
  }

  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_BASELINE_INTERPRETER_ENABLE,
                                useBaselineInterp);
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_BASELINE_ENABLE,
                                useBaselineJit);
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_ION_ENABLE, useIon);
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_JIT_TRUSTEDPRINCIPALS_ENABLE,
                                useJitForTrustedPrincipals);
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_NATIVE_REGEXP_ENABLE,
                                useNativeRegExp);

  JS_SetOffthreadIonCompilationEnabled(cx, offthreadIonCompilation);

  JS_SetGlobalJitCompilerOption(
      cx, JSJITCOMPILER_BASELINE_INTERPRETER_WARMUP_TRIGGER,
      baselineInterpThreshold);
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_BASELINE_WARMUP_TRIGGER,
                                useBaselineEager ? 0 : baselineThreshold);
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_ION_NORMAL_WARMUP_TRIGGER,
                                useIonEager ? 0 : normalIonThreshold);
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_ION_FULL_WARMUP_TRIGGER,
                                useIonEager ? 0 : fullIonThreshold);
  JS_SetGlobalJitCompilerOption(cx,
                                JSJITCOMPILER_ION_FREQUENT_BAILOUT_THRESHOLD,
                                ionFrequentBailoutThreshold);

#ifdef DEBUG
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_FULL_DEBUG_CHECKS,
                                fullJitDebugChecks);
#endif

  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_SPECTRE_INDEX_MASKING,
                                spectreIndexMasking);
  JS_SetGlobalJitCompilerOption(
      cx, JSJITCOMPILER_SPECTRE_OBJECT_MITIGATIONS_BARRIERS,
      spectreObjectMitigationsBarriers);
  JS_SetGlobalJitCompilerOption(cx,
                                JSJITCOMPILER_SPECTRE_OBJECT_MITIGATIONS_MISC,
                                spectreObjectMitigationsMisc);
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_SPECTRE_STRING_MITIGATIONS,
                                spectreStringMitigations);
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_SPECTRE_VALUE_MASKING,
                                spectreValueMasking);
  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_SPECTRE_JIT_TO_CXX_CALLS,
                                spectreJitToCxxCalls);
  if (disableWasmHugeMemory) {
    bool disabledHugeMemory = JS::DisableWasmHugeMemory();
    MOZ_RELEASE_ASSERT(disabledHugeMemory);
  }
}

static void ReloadPrefsCallback(const char* pref, void* aXpccx) {
  // Note: Prefs that require a restart are handled in LoadStartupJSPrefs above.

  auto xpccx = static_cast<XPCJSContext*>(aXpccx);
  JSContext* cx = xpccx->Context();

  bool useAsmJS = Preferences::GetBool(JS_OPTIONS_DOT_STR "asmjs");
  bool useWasm = Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm");
  bool useWasmTrustedPrincipals =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm_trustedprincipals");
  bool useWasmIon = Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm_ionjit");
  bool useWasmBaseline =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm_baselinejit");
#ifdef ENABLE_WASM_CRANELIFT
  bool useWasmCranelift =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm_cranelift");
#endif
  bool useWasmReftypes =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm_reftypes");
#ifdef ENABLE_WASM_GC
  bool useWasmGc = Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm_gc");
#endif
#ifdef ENABLE_WASM_MULTI_VALUE
  bool useWasmMultiValue =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm_multi_value");
#endif
#ifdef ENABLE_WASM_SIMD
  bool useWasmSimd = Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm_simd");
#endif
  bool useWasmVerbose = Preferences::GetBool(JS_OPTIONS_DOT_STR "wasm_verbose");
  bool throwOnAsmJSValidationFailure = Preferences::GetBool(
      JS_OPTIONS_DOT_STR "throw_on_asmjs_validation_failure");

  bool parallelParsing =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "parallel_parsing");

  sDiscardSystemSource =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "discardSystemSource");

  bool useSourcePragmas =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "source_pragmas");
  bool useAsyncStack = Preferences::GetBool(JS_OPTIONS_DOT_STR "asyncstack");
  bool useAsyncStackCaptureDebuggeeOnly = Preferences::GetBool(
      JS_OPTIONS_DOT_STR "asyncstack_capture_debuggee_only");

  bool throwOnDebuggeeWouldRun =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "throw_on_debuggee_would_run");

  bool dumpStackOnDebuggeeWouldRun = Preferences::GetBool(
      JS_OPTIONS_DOT_STR "dump_stack_on_debuggee_would_run");

  sSharedMemoryEnabled =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "shared_memory");
  sStreamsEnabled = Preferences::GetBool(JS_OPTIONS_DOT_STR "streams");
  sPropertyErrorMessageFixEnabled =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "property_error_message_fix");
  sWeakRefsEnabled = Preferences::GetBool(JS_OPTIONS_DOT_STR "weakrefs");
  sWeakRefsExposeCleanupSome = Preferences::GetBool(
      JS_OPTIONS_DOT_STR "experimental.weakrefs.expose_cleanupSome");
#ifdef NIGHTLY_BUILD
  sIteratorHelpersEnabled =
      Preferences::GetBool(JS_OPTIONS_DOT_STR "experimental.iterator_helpers");
#endif

#ifdef JS_GC_ZEAL
  int32_t zeal = Preferences::GetInt(JS_OPTIONS_DOT_STR "gczeal", -1);
  int32_t zeal_frequency = Preferences::GetInt(
      JS_OPTIONS_DOT_STR "gczeal.frequency", JS_DEFAULT_ZEAL_FREQ);
  if (zeal >= 0) {
    JS_SetGCZeal(cx, (uint8_t)zeal, zeal_frequency);
  }
#endif  // JS_GC_ZEAL

#ifdef FUZZING
  bool fuzzingEnabled = StaticPrefs::fuzzing_enabled();
#endif

  JS::ContextOptionsRef(cx)
      .setAsmJS(useAsmJS)
#ifdef FUZZING
      .setFuzzing(fuzzingEnabled)
#endif
      .setWasm(useWasm)
      .setWasmForTrustedPrinciples(useWasmTrustedPrincipals)
      .setWasmIon(useWasmIon)
      .setWasmBaseline(useWasmBaseline)
      .setWasmReftypes(useWasmReftypes)
#ifdef ENABLE_WASM_CRANELIFT
      .setWasmCranelift(useWasmCranelift)
#endif
#ifdef ENABLE_WASM_GC
      .setWasmGc(useWasmGc)
#endif
#ifdef ENABLE_WASM_MULTI_VALUE
      .setWasmMultiValue(useWasmMultiValue)
#endif
#ifdef ENABLE_WASM_SIMD
      .setWasmSimd(useWasmSimd)
#endif
      .setWasmVerbose(useWasmVerbose)
      .setThrowOnAsmJSValidationFailure(throwOnAsmJSValidationFailure)
      .setSourcePragmas(useSourcePragmas)
      .setAsyncStack(useAsyncStack)
      .setAsyncStackCaptureDebuggeeOnly(useAsyncStackCaptureDebuggeeOnly)
      .setThrowOnDebuggeeWouldRun(throwOnDebuggeeWouldRun)
      .setDumpStackOnDebuggeeWouldRun(dumpStackOnDebuggeeWouldRun);

  nsCOMPtr<nsIXULRuntime> xr = do_GetService("@mozilla.org/xre/runtime;1");
  if (xr) {
    bool safeMode = false;
    xr->GetInSafeMode(&safeMode);
    if (safeMode) {
      JS::ContextOptionsRef(cx).disableOptionsForSafeMode();
    }
  }

  JS_SetParallelParsingEnabled(cx, parallelParsing);
}

XPCJSContext::~XPCJSContext() {
  MOZ_COUNT_DTOR_INHERITED(XPCJSContext, CycleCollectedJSContext);
  // Elsewhere we abort immediately if XPCJSContext initialization fails.
  // Therefore the context must be non-null.
  MOZ_ASSERT(MaybeContext());

  Preferences::UnregisterPrefixCallback(ReloadPrefsCallback, JS_OPTIONS_DOT_STR,
                                        this);

#ifdef FUZZING
  Preferences::UnregisterCallback(ReloadPrefsCallback, "fuzzing.enabled", this);
#endif

  // Clear any pending exception.  It might be an XPCWrappedJS, and if we try
  // to destroy it later we will crash.
  SetPendingException(nullptr);

  // If we're the last XPCJSContext around, clean up the watchdog manager.
  if (--sInstanceCount == 0) {
    if (mWatchdogManager->GetWatchdog()) {
      mWatchdogManager->StopWatchdog();
    }

    mWatchdogManager->UnregisterContext(this);
    mWatchdogManager->Shutdown();
    sWatchdogInstance = nullptr;
  } else {
    // Otherwise, simply remove ourselves from the list.
    mWatchdogManager->UnregisterContext(this);
  }

  if (mCallContext) {
    mCallContext->SystemIsBeingShutDown();
  }

  PROFILER_CLEAR_JS_CONTEXT();
}

XPCJSContext::XPCJSContext()
    : mCallContext(nullptr),
      mAutoRoots(nullptr),
      mResolveName(JSID_VOID),
      mResolvingWrapper(nullptr),
      mWatchdogManager(GetWatchdogManager()),
      mSlowScriptSecondHalf(false),
      mTimeoutAccumulated(false),
      mHasScriptActivity(false),
      mPendingResult(NS_OK),
      mActive(CONTEXT_INACTIVE),
      mLastStateChange(PR_Now()) {
  MOZ_COUNT_CTOR_INHERITED(XPCJSContext, CycleCollectedJSContext);
  MOZ_ASSERT(mWatchdogManager);
  ++sInstanceCount;
  mWatchdogManager->RegisterContext(this);
}

/* static */
XPCJSContext* XPCJSContext::Get() {
  // Do an explicit null check, because this can get called from a process that
  // does not run JS.
  nsXPConnect* xpc = static_cast<nsXPConnect*>(nsXPConnect::XPConnect());
  return xpc ? xpc->GetContext() : nullptr;
}

#ifdef XP_WIN
static size_t GetWindowsStackSize() {
  // First, get the stack base. Because the stack grows down, this is the top
  // of the stack.
  const uint8_t* stackTop;
#  ifdef _WIN64
  PNT_TIB64 pTib = reinterpret_cast<PNT_TIB64>(NtCurrentTeb());
  stackTop = reinterpret_cast<const uint8_t*>(pTib->StackBase);
#  else
  PNT_TIB pTib = reinterpret_cast<PNT_TIB>(NtCurrentTeb());
  stackTop = reinterpret_cast<const uint8_t*>(pTib->StackBase);
#  endif

  // Now determine the stack bottom. Note that we can't use tib->StackLimit,
  // because that's the size of the committed area and we're also interested
  // in the reserved pages below that.
  MEMORY_BASIC_INFORMATION mbi;
  if (!VirtualQuery(&mbi, &mbi, sizeof(mbi))) {
    MOZ_CRASH("VirtualQuery failed");
  }

  const uint8_t* stackBottom =
      reinterpret_cast<const uint8_t*>(mbi.AllocationBase);

  // Do some sanity checks.
  size_t stackSize = size_t(stackTop - stackBottom);
  MOZ_RELEASE_ASSERT(stackSize >= 1 * 1024 * 1024);
  MOZ_RELEASE_ASSERT(stackSize <= 32 * 1024 * 1024);

  // Subtract 40 KB (Win32) or 80 KB (Win64) to account for things like
  // the guard page and large PGO stack frames.
  return stackSize - 10 * sizeof(uintptr_t) * 1024;
}
#endif

XPCJSRuntime* XPCJSContext::Runtime() const {
  return static_cast<XPCJSRuntime*>(CycleCollectedJSContext::Runtime());
}

CycleCollectedJSRuntime* XPCJSContext::CreateRuntime(JSContext* aCx) {
  return new XPCJSRuntime(aCx);
}

nsresult XPCJSContext::Initialize() {
  nsresult rv =
      CycleCollectedJSContext::Initialize(nullptr, JS::DefaultHeapMaxBytes);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  MOZ_ASSERT(Context());
  JSContext* cx = Context();

  // The JS engine permits us to set different stack limits for system code,
  // trusted script, and untrusted script. We have tests that ensure that
  // we can always execute 10 "heavy" (eval+with) stack frames deeper in
  // privileged code. Our stack sizes vary greatly in different configurations,
  // so satisfying those tests requires some care. Manual measurements of the
  // number of heavy stack frames achievable gives us the following rough data,
  // ordered by the effective categories in which they are grouped in the
  // JS_SetNativeStackQuota call (which predates this analysis).
  //
  // The following "Stack Frames" numbers come from `chromeLimit` in
  // js/xpconnect/tests/chrome/test_bug732665.xul
  //
  //  Platform   | Build | Stack Quota | Stack Frames | Stack Frame Size
  // ------------+-------+-------------+--------------+------------------
  //  OSX 64     | Opt   | 7MB         | 1331         | ~5.4k
  //  OSX 64     | Debug | 7MB         | 1202         | ~6.0k
  // ------------+-------+-------------+--------------+------------------
  //  Linux 32   | Opt   | 7.875MB     | 2513         | ~3.2k
  //  Linux 32   | Debug | 7.875MB     | 2146         | ~3.8k
  // ------------+-------+-------------+--------------+------------------
  //  Linux 64   | Opt   | 7.875MB     | 1360         | ~5.9k
  //  Linux 64   | Debug | 7.875MB     | 1180         | ~6.8k
  //  Linux 64   | ASan  | 7.875MB     | 473          | ~17.0k
  // ------------+-------+-------------+--------------+------------------
  //  Windows 32 | Opt   | 984k        | 188          | ~5.2k
  //  Windows 32 | Debug | 984k        | 208          | ~4.7k
  // ------------+-------+-------------+--------------+------------------
  //  Windows 64 | Opt   | 1.922MB     | 189          | ~10.4k
  //  Windows 64 | Debug | 1.922MB     | 175          | ~11.2k
  //
  // We tune the trusted/untrusted quotas for each configuration to achieve our
  // invariants while attempting to minimize overhead. In contrast, our buffer
  // between system code and trusted script is a very unscientific 10k.
  const size_t kSystemCodeBuffer = 10 * 1024;

  // Our "default" stack is what we use in configurations where we don't have
  // a compelling reason to do things differently. This is effectively 512KB
  // on 32-bit platforms and 1MB on 64-bit platforms.
  const size_t kDefaultStackQuota = 128 * sizeof(size_t) * 1024;

  // Set maximum stack size for different configurations. This value is then
  // capped below because huge stacks are not web-compatible.

#if defined(XP_MACOSX) || defined(DARWIN)
  // MacOS has a gargantuan default stack size of 8MB. Go wild with 7MB,
  // and give trusted script 180k extra. The stack is huge on mac anyway.
  const size_t kUncappedStackQuota = 7 * 1024 * 1024;
  const size_t kTrustedScriptBuffer = 180 * 1024;
#elif defined(XP_LINUX) && !defined(ANDROID)
  // Most Linux distributions set default stack size to 8MB.  Use it as the
  // maximum value.
  const size_t kStackQuotaMax = 8 * 1024 * 1024;
#  if defined(MOZ_ASAN) || defined(DEBUG)
  // Bug 803182: account for the 4x difference in the size of js::Interpret
  // between optimized and debug builds.  We use 2x since the JIT part
  // doesn't increase much.
  // See the standalone MOZ_ASAN branch below for the ASan case.
  const size_t kStackQuotaMin = 2 * kDefaultStackQuota;
#  else
  const size_t kStackQuotaMin = kDefaultStackQuota;
#  endif
  // Allocate 128kB margin for the safe space.
  const size_t kStackSafeMargin = 128 * 1024;

  struct rlimit rlim;
  const size_t kUncappedStackQuota =
      getrlimit(RLIMIT_STACK, &rlim) == 0
          ? std::max(std::min(size_t(rlim.rlim_cur - kStackSafeMargin),
                              kStackQuotaMax - kStackSafeMargin),
                     kStackQuotaMin)
          : kStackQuotaMin;
#  if defined(MOZ_ASAN)
  // See the standalone MOZ_ASAN branch below for the ASan case.
  const size_t kTrustedScriptBuffer = 450 * 1024;
#  else
  const size_t kTrustedScriptBuffer = 180 * 1024;
#  endif
#elif defined(XP_WIN)
  // 1MB is the default stack size on Windows. We use the -STACK linker flag
  // (see WIN32_EXE_LDFLAGS in config/config.mk) to request a larger stack, so
  // we determine the stack size at runtime.
  const size_t kUncappedStackQuota = GetWindowsStackSize();
#  if defined(MOZ_ASAN)
  // See the standalone MOZ_ASAN branch below for the ASan case.
  const size_t kTrustedScriptBuffer = 450 * 1024;
#  else
  const size_t kTrustedScriptBuffer = (sizeof(size_t) == 8)
                                          ? 180 * 1024   // win64
                                          : 120 * 1024;  // win32
#  endif
#elif defined(MOZ_ASAN)
  // ASan requires more stack space due to red-zones, so give it double the
  // default (1MB on 32-bit, 2MB on 64-bit). ASAN stack frame measurements
  // were not taken at the time of this writing, so we hazard a guess that
  // ASAN builds have roughly thrice the stack overhead as normal builds.
  // On normal builds, the largest stack frame size we might encounter is
  // 9.0k (see above), so let's use a buffer of 9.0 * 5 * 10 = 450k.
  //
  // FIXME: Does this branch make sense for Windows and Android?
  // (See bug 1415195)
  const size_t kUncappedStackQuota = 2 * kDefaultStackQuota;
  const size_t kTrustedScriptBuffer = 450 * 1024;
#elif defined(ANDROID)
  // Android appears to have 1MB stacks. Allow the use of 3/4 of that size
  // (768KB on 32-bit), since otherwise we can crash with a stack overflow
  // when nearing the 1MB limit.
  const size_t kUncappedStackQuota =
      kDefaultStackQuota + kDefaultStackQuota / 2;
  const size_t kTrustedScriptBuffer = sizeof(size_t) * 12800;
#else
  // Catch-all configuration for other environments.
#  if defined(DEBUG)
  const size_t kUncappedStackQuota = 2 * kDefaultStackQuota;
#  else
  const size_t kUncappedStackQuota = kDefaultStackQuota;
#  endif
  // Given the numbers above, we use 50k and 100k trusted buffers on 32-bit
  // and 64-bit respectively.
  const size_t kTrustedScriptBuffer = sizeof(size_t) * 12800;
#endif

  // Avoid an unused variable warning on platforms where we don't use the
  // default.
  (void)kDefaultStackQuota;

  // Large stacks are not web-compatible so cap to a smaller value.
  // See bug 1537609 and bug 1562700.
  const size_t kStackQuotaCap =
      StaticPrefs::javascript_options_main_thread_stack_quota_cap();
  const size_t kStackQuota = std::min(kUncappedStackQuota, kStackQuotaCap);

  JS_SetNativeStackQuota(
      cx, kStackQuota, kStackQuota - kSystemCodeBuffer,
      kStackQuota - kSystemCodeBuffer - kTrustedScriptBuffer);

  PROFILER_SET_JS_CONTEXT(cx);

  JS_AddInterruptCallback(cx, InterruptCallback);

  Runtime()->Initialize(cx);

  LoadStartupJSPrefs(this);

  // Watch for the JS boolean options.
  ReloadPrefsCallback(nullptr, this);
  Preferences::RegisterPrefixCallback(ReloadPrefsCallback, JS_OPTIONS_DOT_STR,
                                      this);

#ifdef FUZZING
  Preferences::RegisterCallback(ReloadPrefsCallback, "fuzzing.enabled", this);
#endif

  if (!JS::InitSelfHostedCode(cx)) {
    // Note: If no exception is pending, failure is due to OOM.
    if (!JS_IsExceptionPending(cx) || JS_IsThrowingOutOfMemory(cx)) {
      NS_ABORT_OOM(0);  // Size is unknown.
    }

    // Failed to execute self-hosted JavaScript! Uh oh.
    MOZ_CRASH("InitSelfHostedCode failed");
  }

  MOZ_RELEASE_ASSERT(Runtime()->InitializeStrings(cx),
                     "InitializeStrings failed");

  return NS_OK;
}

// static
uint32_t XPCJSContext::sInstanceCount;

// static
StaticAutoPtr<WatchdogManager> XPCJSContext::sWatchdogInstance;

// static
WatchdogManager* XPCJSContext::GetWatchdogManager() {
  if (sWatchdogInstance) {
    return sWatchdogInstance;
  }

  MOZ_ASSERT(sInstanceCount == 0);
  sWatchdogInstance = new WatchdogManager();
  return sWatchdogInstance;
}

// static
XPCJSContext* XPCJSContext::NewXPCJSContext() {
  XPCJSContext* self = new XPCJSContext();
  nsresult rv = self->Initialize();
  if (NS_FAILED(rv)) {
    MOZ_CRASH("new XPCJSContext failed to initialize.");
  }

  if (self->Context()) {
    return self;
  }

  MOZ_CRASH("new XPCJSContext failed to initialize.");
}

void XPCJSContext::BeforeProcessTask(bool aMightBlock) {
  MOZ_ASSERT(NS_IsMainThread());

  // Start the slow script timer.
  mSlowScriptCheckpoint = mozilla::TimeStamp::NowLoRes();
  mSlowScriptSecondHalf = false;
  mSlowScriptActualWait = mozilla::TimeDuration();
  mTimeoutAccumulated = false;
  CycleCollectedJSContext::BeforeProcessTask(aMightBlock);
}

void XPCJSContext::AfterProcessTask(uint32_t aNewRecursionDepth) {
  // Now that we're back to the event loop, reset the slow script checkpoint.
  mSlowScriptCheckpoint = mozilla::TimeStamp();
  mSlowScriptSecondHalf = false;

  // Call cycle collector occasionally.
  MOZ_ASSERT(NS_IsMainThread());
  nsJSContext::MaybePokeCC();
  CycleCollectedJSContext::AfterProcessTask(aNewRecursionDepth);

  // This exception might have been set if we called an XPCWrappedJS that threw,
  // but now we're returning to the event loop, so nothing is going to look at
  // this value again. Clear it to prevent leaks.
  SetPendingException(nullptr);
}

bool XPCJSContext::IsSystemCaller() const {
  return nsContentUtils::IsSystemCaller(Context());
}