path: root/src/mongo/scripting/mozjs/implscope.cpp

/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kQuery

#include "mongo/platform/basic.h"

#include "mongo/scripting/mozjs/implscope.h"

#include <iostream>
#include <memory>

#include <js/CharacterEncoding.h>
#include <jscustomallocator.h>
#include <jsfriendapi.h>

#include "mongo/base/error_codes.h"
#include "mongo/config.h"
#include "mongo/db/operation_context.h"
#include "mongo/logv2/log.h"
#include "mongo/platform/decimal128.h"
#include "mongo/platform/mutex.h"
#include "mongo/platform/stack_locator.h"
#include "mongo/scripting/jsexception.h"
#include "mongo/scripting/mozjs/objectwrapper.h"
#include "mongo/scripting/mozjs/valuereader.h"
#include "mongo/scripting/mozjs/valuewriter.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/scopeguard.h"

#if !defined(__has_feature)
#define __has_feature(x) 0
#endif

namespace mongo {

// Generated symbols for JS files
namespace JSFiles {
extern const JSFile types;
extern const JSFile assert;
}  // namespace JSFiles

namespace mozjs {

const char* const MozJSImplScope::kExecResult = "__lastres__";
const char* const MozJSImplScope::kInvokeResult = "__returnValue";

namespace {

/**
 * The threshold (as a fraction of the max) after which garbage collection will be run during
 * interrupts.
 */
const double kInterruptGCThreshold = 0.8;

/**
 * The number of bytes to allocate after which garbage collection is run
 * The default is quite low and doesn't seem to directly correlate with
 * malloc'd bytes. We bound JS heap usage by JSHeapLimit independent of this GC limit.
 */
const int kMaxBytesBeforeGC = 0xffffffff;

/**
 * The size, in bytes, of each "stack chunk". 8192 is the recommended amount
 * from mozilla
 */
const int kStackChunkSize = 8192;

/**
 * Runtime's can race on first creation (on some function statics), so we just
 * serialize the initial Runtime creation.
 */
Mutex gRuntimeCreationMutex;
bool gFirstRuntimeCreated = false;

bool closeToMaxMemory() {
    return mongo::sm::get_total_bytes() > (kInterruptGCThreshold * mongo::sm::get_max_bytes());
}
}  // namespace

thread_local MozJSImplScope::ASANHandles* kCurrentASANHandles = nullptr;
thread_local MozJSImplScope* kCurrentScope = nullptr;

struct MozJSImplScope::MozJSEntry {
    MozJSEntry(MozJSImplScope* scope)
        : ar(scope->_context), ac(scope->_context, scope->_global), _scope(scope) {
        ++_scope->_inOp;
    }

    ~MozJSEntry() {
        --_scope->_inOp;
    }

    JSAutoRequest ar;
    JSAutoCompartment ac;
    MozJSImplScope* _scope;
};

std::string MozJSImplScope::getError() {
    return "";
}

void MozJSImplScope::registerOperation(OperationContext* opCtx) {
    invariant(_opCtx == nullptr);

    // getPooledScope may call registerOperation with a nullptr, so we have to
    // check for that here.
    if (!opCtx)
        return;

    _opCtx = opCtx;
    _opId = opCtx->getOpID();
    _opCtxThreadId = stdx::this_thread::get_id();

    _engine->registerOperation(opCtx, this);
}

void MozJSImplScope::unregisterOperation() {
    if (_opCtx) {
        _engine->unregisterOperation(_opId);
        _opCtx = nullptr;
    }
}

void MozJSImplScope::kill() {
    {
        stdx::lock_guard<Latch> lk(_mutex);

        // If we are on the right thread, in the middle of an operation, and we have a registered
        // opCtx, then we should check the opCtx for interrupts.
        if (_opCtxThreadId == stdx::this_thread::get_id() && _inOp > 0 && _opCtx) {
            _killStatus = _opCtx->checkForInterruptNoAssert();
        }

        // If we didn't have a kill status, someone is killing us by hand here.
        if (_killStatus.isOK()) {
            _killStatus = Status(ErrorCodes::Interrupted, "JavaScript execution interrupted");
        }
    }
    _sleepCondition.notify_all();
    JS_RequestInterruptCallback(_context);
}

void MozJSImplScope::interrupt() {
    JS_RequestInterruptCallback(_context);
}

bool MozJSImplScope::isKillPending() const {
    stdx::lock_guard<Latch> lk(_mutex);
    return !_killStatus.isOK();
}

OperationContext* MozJSImplScope::getOpContext() const {
    return _opCtx;
}

bool MozJSImplScope::isJavaScriptProtectionEnabled() const {
    return _engine->isJavaScriptProtectionEnabled();
}

bool MozJSImplScope::_interruptCallback(JSContext* cx) {
    auto scope = getScope(cx);

    JS_DisableInterruptCallback(scope->_context);
    auto guard = makeGuard([&]() { JS_ResetInterruptCallback(scope->_context, false); });

    if (scope->_pendingGC.load() || closeToMaxMemory()) {
        scope->_pendingGC.store(false);
        JS_GC(scope->_context);
    } else {
        JS_MaybeGC(cx);
    }

    // Check our initial kill status (which might be fine).
    auto status = [&scope]() -> Status {
        stdx::lock_guard<Latch> lk(scope->_mutex);

        return scope->_killStatus;
    }();

    if (scope->_hasOutOfMemoryException) {
        status = Status(ErrorCodes::JSInterpreterFailure, "Out of memory");
    }

    if (!status.isOK())
        scope->setStatus(std::move(status));

    if (!scope->_status.isOK()) {
        scope->_engine->getDeadlineMonitor().stopDeadline(scope);
        scope->unregisterOperation();
    }

    return scope->_status.isOK();
}

void MozJSImplScope::_gcCallback(JSContext* rt, JSGCStatus status, void* data) {
    if (!shouldLog(logv2::LogSeverity::Debug(1))) {
        // don't collect stats unless verbose
        return;
    }

    LOGV2(22787,
          "MozJS GC {status_JSGC_BEGIN_prologue_epilogue} heap stats -  total: "
          "{mongo_sm_get_total_bytes} limit: {mongo_sm_get_max_bytes}",
          "status_JSGC_BEGIN_prologue_epilogue"_attr =
              (status == JSGC_BEGIN ? "prologue" : "epilogue"),
          "mongo_sm_get_total_bytes"_attr = mongo::sm::get_total_bytes(),
          "mongo_sm_get_max_bytes"_attr = mongo::sm::get_max_bytes());
}

#if __has_feature(address_sanitizer)

MozJSImplScope::ASANHandles::ASANHandles() {
    kCurrentASANHandles = this;
}

MozJSImplScope::ASANHandles::~ASANHandles() {
    invariant(kCurrentASANHandles == this);
    kCurrentASANHandles = nullptr;
}

void MozJSImplScope::ASANHandles::addPointer(void* ptr) {
    bool inserted;
    std::tie(std::ignore, inserted) = _handles.insert(ptr);
    invariant(inserted);
}

void MozJSImplScope::ASANHandles::removePointer(void* ptr) {
    invariant(_handles.erase(ptr));
}

#else

MozJSImplScope::ASANHandles::ASANHandles() {}

MozJSImplScope::ASANHandles::~ASANHandles() {}

void MozJSImplScope::ASANHandles::addPointer(void* ptr) {}

void MozJSImplScope::ASANHandles::removePointer(void* ptr) {}

#endif


MozJSImplScope::MozRuntime::MozRuntime(const MozJSScriptEngine* engine,
                                       boost::optional<int> jsHeapLimitMB) {
    /**
     * The maximum amount of memory to be given out per thread to mozilla. We
     * manage this by trapping all calls to malloc, free, etc. and keeping track of
     * counts in some thread locals. If 'jsHeapLimitMB' is specified then we use this instead of the
     * engine limit, given it does not exceed the engine limit.
     */
    const auto engineJsHeapLimit = engine->getJSHeapLimitMB();
    const auto jsHeapLimit =
        jsHeapLimitMB ? std::min(*jsHeapLimitMB, engineJsHeapLimit) : engineJsHeapLimit;

    if (jsHeapLimit != 0 && jsHeapLimit < 10) {
        LOGV2_WARNING(22788,
                      "JavaScript may not be able to initialize with a heap limit less than 10MB.");
    }
    size_t mallocMemoryLimit = 1024ul * 1024 * jsHeapLimit;
    mongo::sm::reset(mallocMemoryLimit);

    {
        stdx::unique_lock<Latch> lk(gRuntimeCreationMutex);

        if (gFirstRuntimeCreated) {
            // If we've already made a runtime, just proceed
            lk.unlock();
        } else {
            // If this is the first one, hold the lock until after the first
            // one's done
            gFirstRuntimeCreated = true;
        }

        _context = std::unique_ptr<JSContext, std::function<void(JSContext*)>>(
            JS_NewContext(kMaxBytesBeforeGC, JS::DefaultNurseryBytes),
            [](JSContext* ptr) { JS_DestroyContext(ptr); });
        uassert(ErrorCodes::JSInterpreterFailure, "Failed to initialize JSContext", _context);

        // We turn on a variety of optimizations if the jit is enabled
        if (engine->isJITEnabled()) {
            JS::ContextOptionsRef(_context.get())
                .setAsmJS(true)
                .setThrowOnAsmJSValidationFailure(true)
                .setBaseline(true)
                .setIon(true)
                .setAsyncStack(false)
                .setNativeRegExp(true);
        } else {
            JS::ContextOptionsRef(_context.get())
                .setAsmJS(false)
                .setThrowOnAsmJSValidationFailure(false)
                .setBaseline(false)
                .setIon(false)
                .setAsyncStack(false)
                .setNativeRegExp(false);
        }

        uassert(ErrorCodes::JSInterpreterFailure,
                "UseInternalJobQueues",
                js::UseInternalJobQueues(_context.get(), true));

        uassert(ErrorCodes::JSInterpreterFailure,
                "InitSelfHostedCode",
                JS::InitSelfHostedCode(_context.get()));

        uassert(ErrorCodes::ExceededMemoryLimit,
                "Out of memory while trying to initialize javascript scope",
                mallocMemoryLimit == 0 || mongo::sm::get_total_bytes() < mallocMemoryLimit);

        const StackLocator locator;
        const auto available = locator.available();
        if (available) {
            // We fudge by 64k for a two reasons. First, it appears
            // that the internal recursion checks that SM performs can
            // have stack usage between checks of more than 32k in
            // some builds. Second, some platforms report the guard
            // page (in the linux sense) as "part of the stack", even
            // though accessing that page will fault the process. We
            // don't have a good way of getting information about the
            // guard page on those platforms.
            //
            // TODO: What if we are running on a platform with very
            // large pages, like 4MB?
            const auto available_stack_space = available.get();

#if defined(__powerpc64__) && defined(MONGO_CONFIG_DEBUG_BUILD)
            // From experimentation, we need a larger reservation of 96k since debug ppc64le code
            // needs more stack space to process stack overflow. In debug builds, more variables are
            // stored on the stack which increases the stack pressure. It does not affects non-debug
            // builds.
            const decltype(available_stack_space) reserve_stack_space = 96 * 1024;
#elif defined(_WIN32)
            // Windows is greedy for stack space while processing exceptions.
            const decltype(available_stack_space) reserve_stack_space = 96 * 1024;
#else
            const decltype(available_stack_space) reserve_stack_space = 64 * 1024;
#endif

            JS_SetNativeStackQuota(_context.get(), available_stack_space - reserve_stack_space);
        }

        // The memory limit is in megabytes
        JS_SetGCParametersBasedOnAvailableMemory(_context.get(), engine->getJSHeapLimitMB());
    }
}

MozJSImplScope::MozJSImplScope(MozJSScriptEngine* engine, boost::optional<int> jsHeapLimitMB)
    : _engine(engine),
      _mr(engine, jsHeapLimitMB),
      _context(_mr._context.get()),
      _globalProto(_context),
      _global(_globalProto.getProto()),
      _funcs(),
      _internedStrings(_context),
      _killStatus(Status::OK()),
      _opId(0),
      _opCtx(nullptr),
      _inOp(0),
      _pendingGC(false),
      _connectState(ConnectState::Not),
      _status(Status::OK()),
      _generation(0),
      _requireOwnedObjects(false),
      _hasOutOfMemoryException(false),
      _inReportError(false),
      _binDataProto(_context),
      _bsonProto(_context),
      _codeProto(_context),
      _countDownLatchProto(_context),
      _cursorHandleProto(_context),
      _cursorProto(_context),
      _dbCollectionProto(_context),
      _dbProto(_context),
      _dbPointerProto(_context),
      _dbQueryProto(_context),
      _dbRefProto(_context),
      _errorProto(_context),
      _jsThreadProto(_context),
      _maxKeyProto(_context),
      _minKeyProto(_context),
      _mongoExternalProto(_context),
      _mongoHelpersProto(_context),
      _nativeFunctionProto(_context),
      _numberDecimalProto(_context),
      _numberIntProto(_context),
      _numberLongProto(_context),
      _objectProto(_context),
      _oidProto(_context),
      _regExpProto(_context),
      _sessionProto(_context),
      _statusProto(_context),
      _timestampProto(_context),
      _uriProto(_context) {
    kCurrentScope = this;

    JS_AddInterruptCallback(_context, _interruptCallback);
    JS_SetGCCallback(_context, _gcCallback, this);
    JS_SetContextPrivate(_context, this);
    JSAutoRequest ar(_context);

    JSAutoCompartment ac(_context, _global);

    _checkErrorState(JS_InitStandardClasses(_context, _global));

    installBSONTypes();

    JS_FireOnNewGlobalObject(_context, _global);

    execSetup(JSFiles::assert);
    execSetup(JSFiles::types);

    // install global utility functions
    installGlobalUtils(*this);
    _mongoHelpersProto.install(_global);

    // install process-specific utilities in the global scope (dependancy: types.js, assert.js)
    if (_engine->getScopeInitCallback())
        _engine->getScopeInitCallback()(*this);
}

MozJSImplScope::~MozJSImplScope() {
    for (auto&& x : _funcs) {
        x.reset();
    }

    unregisterOperation();

    kCurrentScope = nullptr;
}

bool MozJSImplScope::hasOutOfMemoryException() {
    return _hasOutOfMemoryException;
}

void MozJSImplScope::init(const BSONObj* data) {
    if (!data)
        return;

    BSONObjIterator i(*data);
    while (i.more()) {
        BSONElement e = i.next();
        setElement(e.fieldName(), e, *data);
    }
}

template <typename ImplScopeFunction>
auto MozJSImplScope::_runSafely(ImplScopeFunction&& functionToRun) -> decltype(functionToRun()) {
    try {
        MozJSEntry entry(this);
        return functionToRun();
    } catch (...) {
        // There may have already been an error reported by SpiderMonkey. If not, then we use the
        // active C++ exception as the cause of the error.
        if (_status.isOK()) {
            _status = exceptionToStatus();
        }

        if (auto extraInfo = _status.extraInfo<JSExceptionInfo>()) {
            // We intentionally don't transmit an JSInterpreterFailureWithStack error over the wire
            // because of the complexity it'd entail on the recipient to reach inside to the
            // underlying error for how it should be handled. Instead, the error is unwrapped and
            // the JavaScript stacktrace is included as part of the error message.
            str::stream reasonWithStack;
            reasonWithStack << extraInfo->originalError.reason() << " :\n" << extraInfo->stack;
            _status = extraInfo->originalError.withReason(reasonWithStack);
        }

        _error = _status.reason();

        // Clear the status state
        auto status = std::move(_status);
        uassertStatusOK(status);
        MONGO_UNREACHABLE;
    }
}

void MozJSImplScope::setNumber(const char* field, double val) {
    _runSafely([&] { ObjectWrapper(_context, _global).setNumber(field, val); });
}

void MozJSImplScope::setString(const char* field, StringData val) {
    _runSafely([&] { ObjectWrapper(_context, _global).setString(field, val); });
}

void MozJSImplScope::setBoolean(const char* field, bool val) {
    _runSafely([&] { ObjectWrapper(_context, _global).setBoolean(field, val); });
}

void MozJSImplScope::setElement(const char* field, const BSONElement& e, const BSONObj& parent) {
    _runSafely([&] { ObjectWrapper(_context, _global).setBSONElement(field, e, parent, false); });
}

void MozJSImplScope::setObject(const char* field, const BSONObj& obj, bool readOnly) {
    _runSafely([&] { ObjectWrapper(_context, _global).setBSON(field, obj, readOnly); });
}

int MozJSImplScope::type(const char* field) {
    return _runSafely([&] { return ObjectWrapper(_context, _global).type(field); });
}

double MozJSImplScope::getNumber(const char* field) {
    return _runSafely([&] { return ObjectWrapper(_context, _global).getNumber(field); });
}

int MozJSImplScope::getNumberInt(const char* field) {
    return _runSafely(
        [this, &field] { return ObjectWrapper(_context, _global).getNumberInt(field); });
}

long long MozJSImplScope::getNumberLongLong(const char* field) {
    return _runSafely(
        [this, &field] { return ObjectWrapper(_context, _global).getNumberLongLong(field); });
}

Decimal128 MozJSImplScope::getNumberDecimal(const char* field) {
    return _runSafely(
        [this, &field] { return ObjectWrapper(_context, _global).getNumberDecimal(field); });
}

std::string MozJSImplScope::getString(const char* field) {
    return _runSafely([&] { return ObjectWrapper(_context, _global).getString(field); });
}

bool MozJSImplScope::getBoolean(const char* field) {
    return _runSafely(
        [this, &field] { return ObjectWrapper(_context, _global).getBoolean(field); });
}

BSONObj MozJSImplScope::getObject(const char* field) {
    return _runSafely([&] { return ObjectWrapper(_context, _global).getObject(field); });
}

void MozJSImplScope::newFunction(StringData raw, JS::MutableHandleValue out) {
    _runSafely([&] { _MozJSCreateFunction(raw, std::move(out)); });
}

void MozJSImplScope::_MozJSCreateFunction(StringData raw, JS::MutableHandleValue fun) {
    std::string code = str::stream()
        << "(" << parseJSFunctionOrExpression(_context, StringData(raw)) << ")";

    JS::CompileOptions co(_context);
    setCompileOptions(&co);

    _checkErrorState(JS::Evaluate(_context, co, code.c_str(), code.length(), fun));
    uassert(10232,
            "not a function",
            fun.isObject() && JS_ObjectIsFunction(_context, fun.toObjectOrNull()));
}

BSONObj MozJSImplScope::callThreadArgs(const BSONObj& args) {
    // The _runSafely() function is called for all codepaths of executing JavaScript other than
    // callThreadArgs(). We intentionally don't unwrap the JSInterpreterFailureWithStack error to
    // make it possible for the parent thread to chain its JavaScript stacktrace with the child
    // thread's JavaScript stacktrace.
    MozJSEntry entry(this);

    JS::RootedValue function(_context);
    auto firstElem = args.firstElement();

    // The first argument must be the thread start function
    if (firstElem.type() != mongo::Code)
        uasserted(ErrorCodes::BadValue, "first thread argument must be a function");

    getScope(_context)->newFunction(firstElem.valueStringData(), &function);

    int argc = args.nFields() - 1;

    JS::AutoValueVector argv(_context);
    BSONObjIterator it(args);
    it.next();
    JS::RootedValue value(_context);

    for (int i = 0; i < argc; ++i) {
        ValueReader(_context, &value).fromBSONElement(*it, args, true);
        if (!argv.append(value))
            uasserted(ErrorCodes::JSInterpreterFailure, "Failed to append property");
        it.next();
    }

    JS::RootedValue out(_context);
    JS::RootedObject thisv(_context);

    if (!_checkErrorState(JS::Call(_context, thisv, function, argv, &out), false, true)) {
        // Run all of the async JS functions
        js::RunJobs(_context);
    }

    JS::RootedObject rout(_context, JS_NewPlainObject(_context));
    ObjectWrapper wout(_context, rout);
    wout.setValue("ret", out);

    return wout.toBSON();
}

bool hasFunctionIdentifier(StringData code) {
    if (code.size() < 9 || code.find("function") != 0)
        return false;

    return code[8] == ' ' || code[8] == '(';
}

ScriptingFunction MozJSImplScope::_createFunction(const char* raw) {
    return _runSafely([&] {
        JS::RootedValue fun(_context);
        auto it = _funcCodeToHandleMap.find(StringData(raw));
        if (it != _funcCodeToHandleMap.end()) {
            return it->second;
        }
        _MozJSCreateFunction(raw, &fun);
        _funcs.emplace_back(_context, fun.get());
        _funcCodeToHandleMap.emplace(raw, _funcs.size());
        return ScriptingFunction(_funcs.size());
    });
}

void MozJSImplScope::setFunction(const char* field, const char* code) {
    _runSafely([&] {
        JS::RootedValue fun(_context);
        _MozJSCreateFunction(code, &fun);
        ObjectWrapper(_context, _global).setValue(field, fun);
    });
}

void MozJSImplScope::rename(const char* from, const char* to) {
    _runSafely([&] { ObjectWrapper(_context, _global).rename(from, to); });
}

int MozJSImplScope::invoke(ScriptingFunction func,
                           const BSONObj* argsObject,
                           const BSONObj* recv,
                           int timeoutMs,
                           bool ignoreReturn,
                           bool readOnlyArgs,
                           bool readOnlyRecv) {
    return _runSafely([&] {
        auto funcValue = _funcs[func - 1];
        JS::RootedValue result(_context);

        const int nargs = argsObject ? argsObject->nFields() : 0;

        JS::AutoValueVector args(_context);

        if (nargs) {
            BSONObjIterator it(*argsObject);
            for (int i = 0; i < nargs; i++) {
                BSONElement next = it.next();

                JS::RootedValue value(_context);
                ValueReader(_context, &value).fromBSONElement(next, *argsObject, readOnlyArgs);

                if (!args.append(value))
                    uasserted(ErrorCodes::JSInterpreterFailure, "Failed to append property");
            }
        }

        JS::RootedValue smrecv(_context);
        if (recv)
            ValueReader(_context, &smrecv).fromBSON(*recv, nullptr, readOnlyRecv);
        else
            smrecv.setObjectOrNull(_global);

        if (timeoutMs)
            _engine->getDeadlineMonitor().startDeadline(this, timeoutMs);
        else {
            _engine->getDeadlineMonitor().startDeadline(this, -1);
        }

        JS::RootedValue out(_context);
        {
            auto guard = makeGuard([&] { _engine->getDeadlineMonitor().stopDeadline(this); });

            JS::RootedObject obj(_context, smrecv.toObjectOrNull());

            bool success = JS::Call(_context, obj, funcValue, args, &out);

            if (!_checkErrorState(success)) {
                // Run all of the async JS functions
                js::RunJobs(_context);
            }
        }

        if (!ignoreReturn) {
            // must validate the handle because TerminateExecution may have
            // been thrown after the above checks
            if (out.isObject() && _nativeFunctionProto.instanceOf(out)) {
                LOGV2_WARNING(22789, "storing native function as return value");
                _lastRetIsNativeCode = true;
            } else {
                _lastRetIsNativeCode = false;
            }

            ObjectWrapper(_context, _global).setValue(kInvokeResult, out);
        }

        return 0;
    });
}

bool MozJSImplScope::exec(StringData code,
                          const std::string& name,
                          bool printResult,
                          bool reportError,
                          bool assertOnError,
                          int timeoutMs) {
    return _runSafely([&] {
        JS::CompileOptions co(_context);
        setCompileOptions(&co);
        co.setFileAndLine(name.c_str(), 1);
        JS::RootedScript script(_context);

        bool success = JS::Compile(_context, co, code.rawData(), code.size(), &script);

        if (_checkErrorState(success, reportError, assertOnError))
            return false;

        if (timeoutMs) {
            _engine->getDeadlineMonitor().startDeadline(this, timeoutMs);
        } else {
            _engine->getDeadlineMonitor().startDeadline(this, -1);
        }

        JS::RootedValue out(_context);
        {
            auto guard = makeGuard([&] { _engine->getDeadlineMonitor().stopDeadline(this); });

            success = JS_ExecuteScript(_context, script, &out);

            if (_checkErrorState(success, reportError, assertOnError))
                return false;
            // Run all of the async JS functions
            js::RunJobs(_context);
        }

        ObjectWrapper(_context, _global).setValue(kExecResult, out);

        if (printResult && !out.isUndefined()) {
            // appears to only be used by shell
            std::cout << ValueWriter(_context, out).toString() << std::endl;
        }

        return true;
    });
}

void MozJSImplScope::injectNative(const char* field, NativeFunction func, void* data) {
    _runSafely([&] {
        JS::RootedObject obj(_context);

        NativeFunctionInfo::make(_context, &obj, func, data);

        JS::RootedValue value(_context);
        value.setObjectOrNull(obj);
        ObjectWrapper(_context, _global).setValue(field, value);
    });
}

void MozJSImplScope::gc() {
    _pendingGC.store(true);
    JS_RequestInterruptCallback(_context);
}

void MozJSImplScope::sleep(Milliseconds ms) {
    stdx::unique_lock<Latch> lk(_mutex);

    uassert(ErrorCodes::JSUncatchableError,
            "sleep was interrupted by kill",
            !_sleepCondition.wait_for(
                lk, ms.toSystemDuration(), [this] { return !_killStatus.isOK(); }));
}

void MozJSImplScope::externalSetup() {
    _runSafely([&] {
        if (_connectState == ConnectState::External)
            return;

        // install db access functions in the global object
        installDBAccess();

        // install thread-related functions (e.g. _threadInject)
        installFork();

        // install the Mongo function object
        _mongoExternalProto.install(_global);
        execCoreFiles();
        _connectState = ConnectState::External;
    });
}

void MozJSImplScope::reset() {
    unregisterOperation();
    _killStatus = Status::OK();
    _pendingGC.store(false);
    _requireOwnedObjects = false;
    advanceGeneration();
}

void MozJSImplScope::installBSONTypes() {
    _objectProto.install(_global);
    _errorProto.install(_global);
    _binDataProto.install(_global);
    _bsonProto.install(_global);
    _codeProto.install(_global);
    _dbPointerProto.install(_global);
    _dbRefProto.install(_global);
    _maxKeyProto.install(_global);
    _minKeyProto.install(_global);
    _nativeFunctionProto.install(_global);
    _numberIntProto.install(_global);
    _numberLongProto.install(_global);
    _numberDecimalProto.install(_global);
    _oidProto.install(_global);
    _regExpProto.install(_global);
    _timestampProto.install(_global);
    _uriProto.install(_global);
    _statusProto.install(_global);

    // This builtin map is a javascript 6 thing.  We want our version.  so
    // take theirs out
    ObjectWrapper(_context, _global).deleteProperty("Map");
}

void MozJSImplScope::installDBAccess() {
    _cursorProto.install(_global);
    _cursorHandleProto.install(_global);
    _dbProto.install(_global);
    _dbQueryProto.install(_global);
    _dbCollectionProto.install(_global);
    _sessionProto.install(_global);
}

void MozJSImplScope::installFork() {
    _countDownLatchProto.install(_global);
    _jsThreadProto.install(_global);
}

void MozJSImplScope::setStatus(Status status) {
    _status = std::move(status);
}

bool MozJSImplScope::_checkErrorState(bool success, bool reportError, bool assertOnError) {
    {
        stdx::lock_guard<Latch> lk(_mutex);
        if (!_killStatus.isOK()) {
            success = false;
            setStatus(_killStatus);
        }
    }

    if (success) {
        return false;
    }

    if (_status.isOK()) {
        JS::RootedValue excn(_context);
        if (JS_GetPendingException(_context, &excn)) {
            if (excn.isObject()) {
                str::stream ss;
                // exceptions originating from c++ don't get the "uncaught exception: " prefix
                if (!JS_GetPrivate(excn.toObjectOrNull())) {
                    ss << "uncaught exception: ";
                }
                ss << ValueWriter(_context, excn).toString();
                auto stackStr = ObjectWrapper(_context, excn).getString(InternedString::stack);
                auto status =
                    jsExceptionToStatus(_context, excn, ErrorCodes::JSInterpreterFailure, ss);
                auto fnameStr = ObjectWrapper(_context, excn).getString(InternedString::fileName);
                auto lineNum =
                    ObjectWrapper(_context, excn).getNumberInt(InternedString::lineNumber);
                auto colNum =
                    ObjectWrapper(_context, excn).getNumberInt(InternedString::columnNumber);

                if (stackStr.empty()) {
                    // The JavaScript Error objects resulting from C++ exceptions may not always
                    // have a
                    // non-empty "stack" property. We instead use the line and column numbers of
                    // where
                    // in the JavaScript code the C++ function was called from.
                    str::stream ss;
                    ss << "@" << fnameStr << ":" << lineNum << ":" << colNum << "\n";
                    stackStr = ss;
                }
                _status = Status(JSExceptionInfo(std::move(stackStr), status), ss);

            } else {
                str::stream ss;
                ss << "uncaught exception: " << ValueWriter(_context, excn).toString();
                _status = Status(ErrorCodes::UnknownError, ss);
            }
        } else {
            _status = Status(ErrorCodes::UnknownError, "Unknown Failure from JSInterpreter");
        }
    }
    JS_ClearPendingException(_context);

    if (auto extraInfo = _status.extraInfo<JSExceptionInfo>()) {
        str::stream reasonWithStack;
        reasonWithStack << _status.reason() << " :\n" << extraInfo->stack;
        _error = reasonWithStack;
    } else {
        _error = _status.reason();
    }

    if (reportError)
        LOGV2_OPTIONS(4635900,
                      logv2::LogOptions(logv2::LogTag::kPlainShell, logv2::LogTruncation::Disabled),
                      "{message}",
                      "message"_attr = redact(_error));

    // Clear the status state
    auto status = std::move(_status);

    if (assertOnError) {
        // Throw if necessary
        uassertStatusOK(status);
    }

    return true;
}


void MozJSImplScope::setCompileOptions(JS::CompileOptions* co) {
    co->setUTF8(true);
}

MozJSImplScope* MozJSImplScope::getThreadScope() {
    return kCurrentScope;
}

auto MozJSImplScope::ASANHandles::getThreadASANHandles() -> ASANHandles* {
    return kCurrentASANHandles;
}

void MozJSImplScope::setOOM() {
    _hasOutOfMemoryException = true;
    JS_RequestInterruptCallback(_context);
}

void MozJSImplScope::setParentStack(std::string parentStack) {
    _parentStack = std::move(parentStack);
}

std::size_t MozJSImplScope::getGeneration() const {
    return _generation;
}

void MozJSImplScope::advanceGeneration() {
    _generation++;
}

void MozJSImplScope::requireOwnedObjects() {
    _requireOwnedObjects = true;
}

bool MozJSImplScope::requiresOwnedObjects() const {
    return _requireOwnedObjects;
}

const std::string& MozJSImplScope::getParentStack() const {
    return _parentStack;
}

std::string MozJSImplScope::buildStackString() {
    JS::RootedObject stack(_context);

    if (!JS::CaptureCurrentStack(_context, &stack)) {
        return {};
    }

    JS::RootedString out(_context);
    if (JS::BuildStackString(_context, stack, &out)) {
        return JSStringWrapper(_context, out.get()).toString();
    } else {
        return {};
    }
}

}  // namespace mozjs
}  // namespace mongo