Source code

Revision control

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
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim: set ts=8 sts=4 et sw=4 tw=99: */
/* 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 "ScriptPreloader-inl.h"
#include "mozilla/ScriptPreloader.h"
#include "mozilla/loader/ScriptCacheActors.h"

#include "mozilla/URLPreloader.h"

#include "mozilla/ArrayUtils.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/FileUtils.h"
#include "mozilla/Logging.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/Services.h"
#include "mozilla/Unused.h"
#include "mozilla/dom/ContentChild.h"
#include "mozilla/dom/ContentParent.h"

#include "MainThreadUtils.h"
#include "nsDebug.h"
#include "nsDirectoryServiceUtils.h"
#include "nsIFile.h"
#include "nsIObserverService.h"
#include "nsJSUtils.h"
#include "nsNetUtil.h"
#include "nsProxyRelease.h"
#include "nsThreadUtils.h"
#include "nsXULAppAPI.h"
#include "xpcpublic.h"

#define STARTUP_COMPLETE_TOPIC "browser-delayed-startup-finished"
#define DOC_ELEM_INSERTED_TOPIC "document-element-inserted"
#define CONTENT_DOCUMENT_LOADED_TOPIC "content-document-loaded"
#define CACHE_WRITE_TOPIC "browser-idle-startup-tasks-finished"
#define CLEANUP_TOPIC "xpcom-shutdown"
#define SHUTDOWN_TOPIC "quit-application-granted"
#define CACHE_INVALIDATE_TOPIC "startupcache-invalidate"

// The maximum time we'll wait for a child process to finish starting up before
// we send its script data back to the parent.
constexpr uint32_t CHILD_STARTUP_TIMEOUT_MS = 8000;

namespace mozilla {
namespace {
static LazyLogModule gLog("ScriptPreloader");

#define LOG(level, ...) MOZ_LOG(gLog, LogLevel::level, (__VA_ARGS__))
}

using mozilla::dom::AutoJSAPI;
using mozilla::dom::ContentChild;
using mozilla::dom::ContentParent;
using namespace mozilla::loader;

ProcessType ScriptPreloader::sProcessType;

// This type correspond to js::vm::XDRAlignment type, which is used as a size
// reference for alignment of XDR buffers.
using XDRAlign = uint16_t;
static const uint8_t sAlignPadding[sizeof(XDRAlign)] = { 0, 0 };

static inline size_t
ComputeByteAlignment(size_t bytes, size_t align)
{
    return (align - (bytes % align)) % align;
}

nsresult
ScriptPreloader::CollectReports(nsIHandleReportCallback* aHandleReport,
                                nsISupports* aData, bool aAnonymize)
{
    MOZ_COLLECT_REPORT(
        "explicit/script-preloader/heap/saved-scripts", KIND_HEAP, UNITS_BYTES,
        SizeOfHashEntries<ScriptStatus::Saved>(mScripts, MallocSizeOf),
        "Memory used to hold the scripts which have been executed in this "
        "session, and will be written to the startup script cache file.");

    MOZ_COLLECT_REPORT(
        "explicit/script-preloader/heap/restored-scripts", KIND_HEAP, UNITS_BYTES,
        SizeOfHashEntries<ScriptStatus::Restored>(mScripts, MallocSizeOf),
        "Memory used to hold the scripts which have been restored from the "
        "startup script cache file, but have not been executed in this session.");

    MOZ_COLLECT_REPORT(
        "explicit/script-preloader/heap/other", KIND_HEAP, UNITS_BYTES,
        ShallowHeapSizeOfIncludingThis(MallocSizeOf),
        "Memory used by the script cache service itself.");

    // Since the mem-mapped cache file is mapped into memory, we want to report
    // it as explicit memory somewhere. But since the child cache is shared
    // between all processes, we don't want to report it as explicit memory for
    // all of them. So we report it as explicit only in the parent process, and
    // non-explicit everywhere else.
    if (XRE_IsParentProcess()) {
        MOZ_COLLECT_REPORT(
            "explicit/script-preloader/non-heap/memmapped-cache", KIND_NONHEAP, UNITS_BYTES,
            mCacheData.nonHeapSizeOfExcludingThis(),
            "The memory-mapped startup script cache file.");
    } else {
        MOZ_COLLECT_REPORT(
            "script-preloader-memmapped-cache", KIND_NONHEAP, UNITS_BYTES,
            mCacheData.nonHeapSizeOfExcludingThis(),
            "The memory-mapped startup script cache file.");
    }

    return NS_OK;
}


ScriptPreloader&
ScriptPreloader::GetSingleton()
{
    static RefPtr<ScriptPreloader> singleton;

    if (!singleton) {
        if (XRE_IsParentProcess()) {
            singleton = new ScriptPreloader();
            singleton->mChildCache = &GetChildSingleton();
            Unused << singleton->InitCache();
        } else {
            singleton = &GetChildSingleton();
        }

        ClearOnShutdown(&singleton);
    }

    return *singleton;
}

// The child singleton is available in all processes, including the parent, and
// is used for scripts which are expected to be loaded into child processes
// (such as process and frame scripts), or scripts that have already been loaded
// into a child. The child caches are managed as follows:
//
// - Every startup, we open the cache file from the last session, move it to a
//  new location, and begin pre-loading the scripts that are stored in it. There
//  is a separate cache file for parent and content processes, but the parent
//  process opens both the parent and content cache files.
//
// - Once startup is complete, we write a new cache file for the next session,
//   containing only the scripts that were used during early startup, so we don't
//   waste pre-loading scripts that may not be needed.
//
// - For content processes, opening and writing the cache file is handled in the
//  parent process. The first content process of each type sends back the data
//  for scripts that were loaded in early startup, and the parent merges them and
//  writes them to a cache file.
//
// - Currently, content processes only benefit from the cache data written
//  during the *previous* session. Ideally, new content processes should probably
//  use the cache data written during this session if there was no previous cache
//  file, but I'd rather do that as a follow-up.
ScriptPreloader&
ScriptPreloader::GetChildSingleton()
{
    static RefPtr<ScriptPreloader> singleton;

    if (!singleton) {
        singleton = new ScriptPreloader();
        if (XRE_IsParentProcess()) {
            Unused << singleton->InitCache(NS_LITERAL_STRING("scriptCache-child"));
        }
        ClearOnShutdown(&singleton);
    }

    return *singleton;
}

void
ScriptPreloader::InitContentChild(ContentParent& parent)
{
    auto& cache = GetChildSingleton();

    // We want startup script data from the first process of a given type.
    // That process sends back its script data before it executes any
    // untrusted code, and then we never accept further script data for that
    // type of process for the rest of the session.
    //
    // The script data from each process type is merged with the data from the
    // parent process's frame and process scripts, and shared between all
    // content process types in the next session.
    //
    // Note that if the first process of a given type crashes or shuts down
    // before sending us its script data, we silently ignore it, and data for
    // that process type is not included in the next session's cache. This
    // should be a sufficiently rare occurrence that it's not worth trying to
    // handle specially.
    auto processType = GetChildProcessType(parent.GetRemoteType());
    bool wantScriptData = !cache.mInitializedProcesses.contains(processType);
    cache.mInitializedProcesses += processType;

    auto fd = cache.mCacheData.cloneFileDescriptor();
    // Don't send original cache data to new processes if the cache has been
    // invalidated.
    if (fd.IsValid() && !cache.mCacheInvalidated) {
        Unused << parent.SendPScriptCacheConstructor(fd, wantScriptData);
    } else {
        Unused << parent.SendPScriptCacheConstructor(NS_ERROR_FILE_NOT_FOUND, wantScriptData);
    }
}

ProcessType
ScriptPreloader::GetChildProcessType(const nsAString& remoteType)
{
    if (remoteType.EqualsLiteral(EXTENSION_REMOTE_TYPE)) {
        return ProcessType::Extension;
    }
    if (remoteType.EqualsLiteral(PRIVILEGED_REMOTE_TYPE)) {
        return ProcessType::Privileged;
    }
    return ProcessType::Web;
}


namespace {

static void
TraceOp(JSTracer* trc, void* data)
{
    auto preloader = static_cast<ScriptPreloader*>(data);

    preloader->Trace(trc);
}

} // anonymous namespace

void
ScriptPreloader::Trace(JSTracer* trc)
{
    for (auto& script : IterHash(mScripts)) {
        JS::TraceEdge(trc, &script->mScript, "ScriptPreloader::CachedScript.mScript");
    }
}


ScriptPreloader::ScriptPreloader()
  : mMonitor("[ScriptPreloader.mMonitor]")
  , mSaveMonitor("[ScriptPreloader.mSaveMonitor]")
{
    // We do not set the process type for child processes here because the
    // remoteType in ContentChild is not ready yet.
    if (XRE_IsParentProcess()) {
        sProcessType = ProcessType::Parent;
    }

    nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
    MOZ_RELEASE_ASSERT(obs);

    if (XRE_IsParentProcess()) {
        // In the parent process, we want to freeze the script cache as soon
        // as idle tasks for the first browser window have completed.
        obs->AddObserver(this, STARTUP_COMPLETE_TOPIC, false);
        obs->AddObserver(this, CACHE_WRITE_TOPIC, false);
    }

    obs->AddObserver(this, SHUTDOWN_TOPIC, false);
    obs->AddObserver(this, CLEANUP_TOPIC, false);
    obs->AddObserver(this, CACHE_INVALIDATE_TOPIC, false);

    AutoSafeJSAPI jsapi;
    JS_AddExtraGCRootsTracer(jsapi.cx(), TraceOp, this);
}

void
ScriptPreloader::ForceWriteCacheFile()
{
    if (mSaveThread) {
        MonitorAutoLock mal(mSaveMonitor);

        // Make sure we've prepared scripts, so we don't risk deadlocking while
        // dispatching the prepare task during shutdown.
        PrepareCacheWrite();

        // Unblock the save thread, so it can start saving before we get to
        // XPCOM shutdown.
        mal.Notify();
    }
}

void
ScriptPreloader::Cleanup()
{
    if (mSaveThread) {
        MonitorAutoLock mal(mSaveMonitor);

        // Make sure the save thread is not blocked dispatching a sync task to
        // the main thread, or we will deadlock.
        MOZ_RELEASE_ASSERT(!mBlockedOnSyncDispatch);

        while (!mSaveComplete && mSaveThread) {
            mal.Wait();
        }
    }

    // Wait for any pending parses to finish before clearing the mScripts
    // hashtable, since the parse tasks depend on memory allocated by those
    // scripts.
    {
        MonitorAutoLock mal(mMonitor);
        FinishPendingParses(mal);

        mScripts.Clear();
    }

    AutoSafeJSAPI jsapi;
    JS_RemoveExtraGCRootsTracer(jsapi.cx(), TraceOp, this);

    UnregisterWeakMemoryReporter(this);
}

void
ScriptPreloader::InvalidateCache()
{
    mMonitor.AssertNotCurrentThreadOwns();
    MonitorAutoLock mal(mMonitor);

    mCacheInvalidated = true;

    // Wait for pending off-thread parses to finish, since they depend on the
    // memory allocated by our CachedScripts, and can't be canceled
    // asynchronously.
    FinishPendingParses(mal);

    // Pending scripts should have been cleared by the above, and new parses
    // should not have been queued.
    MOZ_ASSERT(mParsingScripts.empty());
    MOZ_ASSERT(mParsingSources.empty());
    MOZ_ASSERT(mPendingScripts.isEmpty());

    for (auto& script : IterHash(mScripts)) {
        script.Remove();
    }

    // If we've already finished saving the cache at this point, start a new
    // delayed save operation. This will write out an empty cache file in place
    // of any cache file we've already written out this session, which will
    // prevent us from falling back to the current session's cache file on the
    // next startup.
    if (mSaveComplete && mChildCache) {
        mSaveComplete = false;

        // Make sure scripts are prepared to avoid deadlock when invalidating
        // the cache during shutdown.
        PrepareCacheWriteInternal();

        Unused << NS_NewNamedThread("SaveScripts",
                                    getter_AddRefs(mSaveThread), this);
    }
}

nsresult
ScriptPreloader::Observe(nsISupports* subject, const char* topic, const char16_t* data)
{
    nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
    if (!strcmp(topic, STARTUP_COMPLETE_TOPIC)) {
        obs->RemoveObserver(this, STARTUP_COMPLETE_TOPIC);

        MOZ_ASSERT(XRE_IsParentProcess());

        mStartupFinished = true;
    } else if (!strcmp(topic, CACHE_WRITE_TOPIC)) {
        obs->RemoveObserver(this, CACHE_WRITE_TOPIC);

        MOZ_ASSERT(mStartupFinished);
        MOZ_ASSERT(XRE_IsParentProcess());

        if (mChildCache) {
            Unused << NS_NewNamedThread("SaveScripts",
                                        getter_AddRefs(mSaveThread), this);
        }
    } else if (mContentStartupFinishedTopic.Equals(topic)) {
        // If this is an uninitialized about:blank viewer or a chrome: document
        // (which should always be an XBL binding document), ignore it. We don't
        // have to worry about it loading malicious content.
        if (nsCOMPtr<nsIDocument> doc = do_QueryInterface(subject)) {
            nsCOMPtr<nsIURI> uri = doc->GetDocumentURI();

            bool schemeIs;
            if ((NS_IsAboutBlank(uri) &&
                 doc->GetReadyStateEnum() == doc->READYSTATE_UNINITIALIZED) ||
                (NS_SUCCEEDED(uri->SchemeIs("chrome", &schemeIs)) && schemeIs)) {
                return NS_OK;
            }
        }
        FinishContentStartup();
    } else if (!strcmp(topic, "timer-callback")) {
        FinishContentStartup();
    } else if (!strcmp(topic, SHUTDOWN_TOPIC)) {
        ForceWriteCacheFile();
    } else if (!strcmp(topic, CLEANUP_TOPIC)) {
        Cleanup();
    } else if (!strcmp(topic, CACHE_INVALIDATE_TOPIC)) {
        InvalidateCache();
    }

    return NS_OK;
}

void
ScriptPreloader::FinishContentStartup()
{
    MOZ_ASSERT(XRE_IsContentProcess());

#ifdef DEBUG
    if (mContentStartupFinishedTopic.Equals(CONTENT_DOCUMENT_LOADED_TOPIC)) {
        MOZ_ASSERT(sProcessType == ProcessType::Privileged);
    } else {
        MOZ_ASSERT(sProcessType != ProcessType::Privileged);
    }
#endif /* DEBUG */

    nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
    obs->RemoveObserver(this, mContentStartupFinishedTopic.get());

    mSaveTimer = nullptr;

    mStartupFinished = true;

    if (mChildActor) {
        mChildActor->SendScriptsAndFinalize(mScripts);
    }
}

bool
ScriptPreloader::WillWriteScripts()
{
    return Active() && (XRE_IsParentProcess() || mChildActor);
}

Result<nsCOMPtr<nsIFile>, nsresult>
ScriptPreloader::GetCacheFile(const nsAString& suffix)
{
    NS_ENSURE_TRUE(mProfD, Err(NS_ERROR_NOT_INITIALIZED));

    nsCOMPtr<nsIFile> cacheFile;
    MOZ_TRY(mProfD->Clone(getter_AddRefs(cacheFile)));

    MOZ_TRY(cacheFile->AppendNative(NS_LITERAL_CSTRING("startupCache")));
    Unused << cacheFile->Create(nsIFile::DIRECTORY_TYPE, 0777);

    MOZ_TRY(cacheFile->Append(mBaseName + suffix));

    return std::move(cacheFile);
}

static const uint8_t MAGIC[] = "mozXDRcachev002";

Result<Ok, nsresult>
ScriptPreloader::OpenCache()
{
    MOZ_TRY(NS_GetSpecialDirectory("ProfLDS", getter_AddRefs(mProfD)));

    nsCOMPtr<nsIFile> cacheFile;
    MOZ_TRY_VAR(cacheFile, GetCacheFile(NS_LITERAL_STRING(".bin")));

    bool exists;
    MOZ_TRY(cacheFile->Exists(&exists));
    if (exists) {
        MOZ_TRY(cacheFile->MoveTo(nullptr, mBaseName + NS_LITERAL_STRING("-current.bin")));
    } else {
        MOZ_TRY(cacheFile->SetLeafName(mBaseName + NS_LITERAL_STRING("-current.bin")));
        MOZ_TRY(cacheFile->Exists(&exists));
        if (!exists) {
            return Err(NS_ERROR_FILE_NOT_FOUND);
        }
    }

    MOZ_TRY(mCacheData.init(cacheFile));

    return Ok();
}

// Opens the script cache file for this session, and initializes the script
// cache based on its contents. See WriteCache for details of the cache file.
Result<Ok, nsresult>
ScriptPreloader::InitCache(const nsAString& basePath)
{
    mCacheInitialized = true;
    mBaseName = basePath;

    RegisterWeakMemoryReporter(this);

    if (!XRE_IsParentProcess()) {
        return Ok();
    }

    // Grab the compilation scope before initializing the URLPreloader, since
    // it's not safe to run component loader code during its critical section.
    AutoSafeJSAPI jsapi;
    JS::RootedObject scope(jsapi.cx(), xpc::CompilationScope());

    // Note: Code on the main thread *must not access Omnijar in any way* until
    // this AutoBeginReading guard is destroyed.
    URLPreloader::AutoBeginReading abr;

    MOZ_TRY(OpenCache());

    return InitCacheInternal(scope);
}

Result<Ok, nsresult>
ScriptPreloader::InitCache(const Maybe<ipc::FileDescriptor>& cacheFile, ScriptCacheChild* cacheChild)
{
    MOZ_ASSERT(XRE_IsContentProcess());

    mCacheInitialized = true;
    mChildActor = cacheChild;
    sProcessType = GetChildProcessType(dom::ContentChild::GetSingleton()->GetRemoteType());

    nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
    MOZ_RELEASE_ASSERT(obs);

    if (sProcessType == ProcessType::Privileged) {
        // Since we control all of the documents loaded in the privileged
        // content process, we can increase the window of active time for the
        // ScriptPreloader to include the scripts that are loaded until the
        // first document finishes loading.
        mContentStartupFinishedTopic.AssignLiteral(CONTENT_DOCUMENT_LOADED_TOPIC);
    } else {
        // In the child process, we need to freeze the script cache before any
        // untrusted code has been executed. The insertion of the first DOM
        // document element may sometimes be earlier than is ideal, but at
        // least it should always be safe.
        mContentStartupFinishedTopic.AssignLiteral(DOC_ELEM_INSERTED_TOPIC);
    }
    obs->AddObserver(this, mContentStartupFinishedTopic.get(), false);

    RegisterWeakMemoryReporter(this);

    auto cleanup = MakeScopeExit([&] {
        // If the parent is expecting cache data from us, make sure we send it
        // before it writes out its cache file. For normal proceses, this isn't
        // a concern, since they begin loading documents quite early. For the
        // preloaded process, we may end up waiting a long time (or, indeed,
        // never loading a document), so we need an additional timeout.
        if (cacheChild) {
            NS_NewTimerWithObserver(getter_AddRefs(mSaveTimer),
                                    this, CHILD_STARTUP_TIMEOUT_MS,
                                    nsITimer::TYPE_ONE_SHOT);
        }
    });

    if (cacheFile.isNothing()){
        return Ok();
    }

    MOZ_TRY(mCacheData.init(cacheFile.ref()));

    return InitCacheInternal();
}

Result<Ok, nsresult>
ScriptPreloader::InitCacheInternal(JS::HandleObject scope)
{
    auto size = mCacheData.size();

    uint32_t headerSize;
    if (size < sizeof(MAGIC) + sizeof(headerSize)) {
        return Err(NS_ERROR_UNEXPECTED);
    }

    auto data = mCacheData.get<uint8_t>();
    uint8_t* start = data.get();
    MOZ_ASSERT(reinterpret_cast<uintptr_t>(start) % sizeof(XDRAlign) == 0);
    auto end = data + size;

    if (memcmp(MAGIC, data.get(), sizeof(MAGIC))) {
        return Err(NS_ERROR_UNEXPECTED);
    }
    data += sizeof(MAGIC);

    headerSize = LittleEndian::readUint32(data.get());
    data += sizeof(headerSize);

    if (data + headerSize > end) {
        return Err(NS_ERROR_UNEXPECTED);
    }

    {
        auto cleanup = MakeScopeExit([&] () {
            mScripts.Clear();
        });

        LinkedList<CachedScript> scripts;

        Range<uint8_t> header(data, data + headerSize);
        data += headerSize;

        InputBuffer buf(header);

        size_t len = data.get() - start;
        size_t alignLen = ComputeByteAlignment(len, sizeof(XDRAlign));
        data += alignLen;

        size_t offset = 0;
        while (!buf.finished()) {
            auto script = MakeUnique<CachedScript>(*this, buf);
            MOZ_RELEASE_ASSERT(script);

            auto scriptData = data + script->mOffset;
            if (scriptData + script->mSize > end) {
                return Err(NS_ERROR_UNEXPECTED);
            }

            // Make sure offsets match what we'd expect based on script ordering and
            // size, as a basic sanity check.
            if (script->mOffset != offset) {
                return Err(NS_ERROR_UNEXPECTED);
            }
            offset += script->mSize;

            MOZ_ASSERT(reinterpret_cast<uintptr_t>(scriptData.get()) % sizeof(XDRAlign) == 0);
            script->mXDRRange.emplace(scriptData, scriptData + script->mSize);

            // Don't pre-decode the script unless it was used in this process type during the
            // previous session.
            if (script->mOriginalProcessTypes.contains(CurrentProcessType())) {
                scripts.insertBack(script.get());
            } else {
                script->mReadyToExecute = true;
            }

            mScripts.Put(script->mCachePath, script.get());
            Unused << script.release();
        }

        if (buf.error()) {
            return Err(NS_ERROR_UNEXPECTED);
        }

        mPendingScripts = std::move(scripts);
        cleanup.release();
    }

    DecodeNextBatch(OFF_THREAD_FIRST_CHUNK_SIZE, scope);
    return Ok();
}

void
ScriptPreloader::PrepareCacheWriteInternal()
{
    MOZ_ASSERT(NS_IsMainThread());

    mMonitor.AssertCurrentThreadOwns();

    auto cleanup = MakeScopeExit([&] () {
        if (mChildCache) {
            mChildCache->PrepareCacheWrite();
        }
    });

    if (mDataPrepared) {
        return;
    }

    AutoSafeJSAPI jsapi;
    bool found = false;
    for (auto& script : IterHash(mScripts, Match<ScriptStatus::Saved>())) {
        // Don't write any scripts that are also in the child cache. They'll be
        // loaded from the child cache in that case, so there's no need to write
        // them twice.
        CachedScript* childScript = mChildCache ? mChildCache->mScripts.Get(script->mCachePath) : nullptr;
        if (childScript && !childScript->mProcessTypes.isEmpty()) {
            childScript->UpdateLoadTime(script->mLoadTime);
            childScript->mProcessTypes += script->mProcessTypes;
            script.Remove();
            continue;
        }

        if (!(script->mProcessTypes == script->mOriginalProcessTypes)) {
            // Note: EnumSet doesn't support operator!=, hence the weird form above.
            found = true;
        }

        if (!script->mSize && !script->XDREncode(jsapi.cx())) {
            script.Remove();
        }
    }

    if (!found) {
        mSaveComplete = true;
        return;
    }

    mDataPrepared = true;
}

void
ScriptPreloader::PrepareCacheWrite()
{
    MonitorAutoLock mal(mMonitor);

    PrepareCacheWriteInternal();
}

// Writes out a script cache file for the scripts accessed during early
// startup in this session. The cache file is a little-endian binary file with
// the following format:
//
// - A uint32 containing the size of the header block.
//
// - A header entry for each file stored in the cache containing:
//   - The URL that the script was originally read from.
//   - Its cache key.
//   - The offset of its XDR data within the XDR data block.
//   - The size of its XDR data in the XDR data block.
//   - A bit field describing which process types the script is used in.
//
// - A block of XDR data for the encoded scripts, with each script's data at
//   an offset from the start of the block, as specified above.
Result<Ok, nsresult>
ScriptPreloader::WriteCache()
{
    MOZ_ASSERT(!NS_IsMainThread());

    if (!mDataPrepared && !mSaveComplete) {
        MOZ_ASSERT(!mBlockedOnSyncDispatch);
        mBlockedOnSyncDispatch = true;

        MonitorAutoUnlock mau(mSaveMonitor);

        NS_DispatchToMainThread(
          NewRunnableMethod("ScriptPreloader::PrepareCacheWrite",
                            this,
                            &ScriptPreloader::PrepareCacheWrite),
          NS_DISPATCH_SYNC);
    }

    mBlockedOnSyncDispatch = false;

    if (mSaveComplete) {
        // If we don't have anything we need to save, we're done.
        return Ok();
    }

    nsCOMPtr<nsIFile> cacheFile;
    MOZ_TRY_VAR(cacheFile, GetCacheFile(NS_LITERAL_STRING("-new.bin")));

    bool exists;
    MOZ_TRY(cacheFile->Exists(&exists));
    if (exists) {
        MOZ_TRY(cacheFile->Remove(false));
    }

    {
        AutoFDClose fd;
        MOZ_TRY(cacheFile->OpenNSPRFileDesc(PR_WRONLY | PR_CREATE_FILE, 0644, &fd.rwget()));

        // We also need to hold mMonitor while we're touching scripts in
        // mScripts, or they may be freed before we're done with them.
        mMonitor.AssertNotCurrentThreadOwns();
        MonitorAutoLock mal(mMonitor);

        nsTArray<CachedScript*> scripts;
        for (auto& script : IterHash(mScripts, Match<ScriptStatus::Saved>())) {
            scripts.AppendElement(script);
        }

        // Sort scripts by load time, with async loaded scripts before sync scripts.
        // Since async scripts are always loaded immediately at startup, it helps to
        // have them stored contiguously.
        scripts.Sort(CachedScript::Comparator());

        OutputBuffer buf;
        size_t offset = 0;
        for (auto script : scripts) {
            MOZ_ASSERT(offset % sizeof(XDRAlign) == 0);
            script->mOffset = offset;
            script->Code(buf);

            offset += script->mSize;
        }

        uint8_t headerSize[4];
        LittleEndian::writeUint32(headerSize, buf.cursor());

        size_t len = 0;
        MOZ_TRY(Write(fd, MAGIC, sizeof(MAGIC)));
        len += sizeof(MAGIC);
        MOZ_TRY(Write(fd, headerSize, sizeof(headerSize)));
        len += sizeof(headerSize);
        MOZ_TRY(Write(fd, buf.Get(), buf.cursor()));
        len += buf.cursor();
        size_t alignLen = ComputeByteAlignment(len, sizeof(XDRAlign));
        if (alignLen) {
            MOZ_TRY(Write(fd, sAlignPadding, alignLen));
            len += alignLen;
        }
        for (auto script : scripts) {
            MOZ_ASSERT(script->mSize % sizeof(XDRAlign) == 0);
            MOZ_TRY(Write(fd, script->Range().begin().get(), script->mSize));
            len += script->mSize;

            if (script->mScript) {
                script->FreeData();
            }
        }
    }

    MOZ_TRY(cacheFile->MoveTo(nullptr, mBaseName + NS_LITERAL_STRING(".bin")));

    return Ok();
}

// Runs in the mSaveThread thread, and writes out the cache file for the next
// session after a reasonable delay.
nsresult
ScriptPreloader::Run()
{
    MonitorAutoLock mal(mSaveMonitor);

    // Ideally wait about 10 seconds before saving, to avoid unnecessary IO
    // during early startup. But only if the cache hasn't been invalidated,
    // since that can trigger a new write during shutdown, and we don't want to
    // cause shutdown hangs.
    if (!mCacheInvalidated) {
        mal.Wait(TimeDuration::FromSeconds(10));
    }

    auto result = URLPreloader::GetSingleton().WriteCache();
    Unused << NS_WARN_IF(result.isErr());

    result = WriteCache();
    Unused << NS_WARN_IF(result.isErr());

    result = mChildCache->WriteCache();
    Unused << NS_WARN_IF(result.isErr());

    mSaveComplete = true;
    NS_ReleaseOnMainThreadSystemGroup("ScriptPreloader::mSaveThread",
                                      mSaveThread.forget());

    mal.NotifyAll();
    return NS_OK;
}

void
ScriptPreloader::NoteScript(const nsCString& url, const nsCString& cachePath,
                            JS::HandleScript jsscript, bool isRunOnce)
{
    if (!Active()) {
        if (isRunOnce) {
            if (auto script = mScripts.Get(cachePath)) {
                script->mIsRunOnce = true;
                script->MaybeDropScript();
            }
        }
        return;
    }

    // Don't bother trying to cache any URLs with cache-busting query
    // parameters.
    if (cachePath.FindChar('?') >= 0) {
        return;
    }

    // Don't bother caching files that belong to the mochitest harness.
    NS_NAMED_LITERAL_CSTRING(mochikitPrefix, "chrome://mochikit/");
    if (StringHead(url, mochikitPrefix.Length()) == mochikitPrefix) {
        return;
    }

    auto script = mScripts.LookupOrAdd(cachePath, *this, url, cachePath, jsscript);
    if (isRunOnce) {
        script->mIsRunOnce = true;
    }

    if (!script->MaybeDropScript() && !script->mScript) {
        MOZ_ASSERT(jsscript);
        script->mScript = jsscript;
        script->mReadyToExecute = true;
    }

    script->UpdateLoadTime(TimeStamp::Now());
    script->mProcessTypes += CurrentProcessType();
}

void
ScriptPreloader::NoteScript(const nsCString& url, const nsCString& cachePath,
                            ProcessType processType, nsTArray<uint8_t>&& xdrData,
                            TimeStamp loadTime)
{
    // After data has been prepared, there's no point in noting further scripts,
    // since the cache either has already been written, or is about to be
    // written. Any time prior to the data being prepared, we can safely mutate
    // mScripts without locking. After that point, the save thread is free to
    // access it, and we can't alter it without locking.
    if (mDataPrepared) {
        return;
    }

    auto script = mScripts.LookupOrAdd(cachePath, *this, url, cachePath, nullptr);

    if (!script->HasRange()) {
        MOZ_ASSERT(!script->HasArray());

        script->mSize = xdrData.Length();
        script->mXDRData.construct<nsTArray<uint8_t>>(std::forward<nsTArray<uint8_t>>(xdrData));

        auto& data = script->Array();
        script->mXDRRange.emplace(data.Elements(), data.Length());
    }

    if (!script->mSize && !script->mScript) {
        // If the content process is sending us a script entry for a script
        // which was in the cache at startup, it expects us to already have this
        // script data, so it doesn't send it.
        //
        // However, the cache may have been invalidated at this point (usually
        // due to the add-on manager installing or uninstalling a legacy
        // extension during very early startup), which means we may no longer
        // have an entry for this script. Since that means we have no data to
        // write to the new cache, and no JSScript to generate it from, we need
        // to discard this entry.
        mScripts.Remove(cachePath);
        return;
    }

    script->UpdateLoadTime(loadTime);
    script->mProcessTypes += processType;
}

JSScript*
ScriptPreloader::GetCachedScript(JSContext* cx, const nsCString& path)
{
    // If a script is used by both the parent and the child, it's stored only
    // in the child cache.
    if (mChildCache) {
        auto script = mChildCache->GetCachedScript(cx, path);
        if (script) {
            return script;
        }
    }

    auto script = mScripts.Get(path);
    if (script) {
        return WaitForCachedScript(cx, script);
    }

    return nullptr;
}

JSScript*
ScriptPreloader::WaitForCachedScript(JSContext* cx, CachedScript* script)
{
    // Check for finished operations before locking so that we can move onto
    // decoding the next batch as soon as possible after the pending batch is
    // ready. If we wait until we hit an unfinished script, we wind up having at
    // most one batch of buffered scripts, and occasionally under-running that
    // buffer.
    MaybeFinishOffThreadDecode();

    if (!script->mReadyToExecute) {
        LOG(Info, "Must wait for async script load: %s\n", script->mURL.get());
        auto start = TimeStamp::Now();

        mMonitor.AssertNotCurrentThreadOwns();
        MonitorAutoLock mal(mMonitor);

        // Check for finished operations again *after* locking, or we may race
        // against mToken being set between our last check and the time we
        // entered the mutex.
        MaybeFinishOffThreadDecode();

        if (!script->mReadyToExecute && script->mSize < MAX_MAINTHREAD_DECODE_SIZE) {
            LOG(Info, "Script is small enough to recompile on main thread\n");

            script->mReadyToExecute = true;
        } else {
            while (!script->mReadyToExecute) {
                mal.Wait();

                MonitorAutoUnlock mau(mMonitor);
                MaybeFinishOffThreadDecode();
            }
        }

        LOG(Debug, "Waited %fms\n", (TimeStamp::Now() - start).ToMilliseconds());
    }

    return script->GetJSScript(cx);
}



/* static */ void
ScriptPreloader::OffThreadDecodeCallback(JS::OffThreadToken* token, void* context)
{
    auto cache = static_cast<ScriptPreloader*>(context);

    cache->mMonitor.AssertNotCurrentThreadOwns();
    MonitorAutoLock mal(cache->mMonitor);

    // First notify any tasks that are already waiting on scripts, since they'll
    // be blocking the main thread, and prevent any runnables from executing.
    cache->mToken = token;
    mal.NotifyAll();

    // If nothing processed the token, and we don't already have a pending
    // runnable, then dispatch a new one to finish the processing on the main
    // thread as soon as possible.
    if (cache->mToken && !cache->mFinishDecodeRunnablePending) {
        cache->mFinishDecodeRunnablePending = true;
        NS_DispatchToMainThread(
          NewRunnableMethod("ScriptPreloader::DoFinishOffThreadDecode",
                            cache,
                            &ScriptPreloader::DoFinishOffThreadDecode));
    }
}

void
ScriptPreloader::FinishPendingParses(MonitorAutoLock& aMal)
{
    mMonitor.AssertCurrentThreadOwns();

    mPendingScripts.clear();

    MaybeFinishOffThreadDecode();

    // Loop until all pending decode operations finish.
    while (!mParsingScripts.empty()) {
        aMal.Wait();
        MaybeFinishOffThreadDecode();
    }
}

void
ScriptPreloader::DoFinishOffThreadDecode()
{
    mFinishDecodeRunnablePending = false;
    MaybeFinishOffThreadDecode();
}

void
ScriptPreloader::MaybeFinishOffThreadDecode()
{
    if (!mToken) {
        return;
    }

    auto cleanup = MakeScopeExit([&] () {
        mToken = nullptr;
        mParsingSources.clear();
        mParsingScripts.clear();

        DecodeNextBatch(OFF_THREAD_CHUNK_SIZE);
    });

    AutoSafeJSAPI jsapi;
    JSContext* cx = jsapi.cx();

    JSAutoRealm ar(cx, xpc::CompilationScope());
    JS::Rooted<JS::ScriptVector> jsScripts(cx, JS::ScriptVector(cx));

    // If this fails, we still need to mark the scripts as finished. Any that
    // weren't successfully compiled in this operation (which should never
    // happen under ordinary circumstances) will be re-decoded on the main
    // thread, and raise the appropriate errors when they're executed.
    //
    // The exception from the off-thread decode operation will be reported when
    // we pop the AutoJSAPI off the stack.
    Unused << JS::FinishMultiOffThreadScriptsDecoder(cx, mToken, &jsScripts);

    unsigned i = 0;
    for (auto script : mParsingScripts) {
        LOG(Debug, "Finished off-thread decode of %s\n", script->mURL.get());
        if (i < jsScripts.length()) {
            script->mScript = jsScripts[i++];
        }
        script->mReadyToExecute = true;
    }
}

void
ScriptPreloader::DecodeNextBatch(size_t chunkSize, JS::HandleObject scope)
{
    MOZ_ASSERT(mParsingSources.length() == 0);
    MOZ_ASSERT(mParsingScripts.length() == 0);

    auto cleanup = MakeScopeExit([&] () {
        mParsingScripts.clearAndFree();
        mParsingSources.clearAndFree();
    });

    auto start = TimeStamp::Now();
    LOG(Debug, "Off-thread decoding scripts...\n");

    size_t size = 0;
    for (CachedScript* next = mPendingScripts.getFirst(); next;) {
        auto script = next;
        next = script->getNext();

        // Skip any scripts that we decoded on the main thread rather than
        // waiting for an off-thread operation to complete.
        if (script->mReadyToExecute) {
            script->remove();
            continue;
        }
        // If we have enough data for one chunk and this script would put us
        // over our chunk size limit, we're done.
        if (size > SMALL_SCRIPT_CHUNK_THRESHOLD &&
            size + script->mSize > chunkSize) {
            break;
        }
        if (!mParsingScripts.append(script) ||
            !mParsingSources.emplaceBack(script->Range(), script->mURL.get(), 0)) {
            break;
        }

        LOG(Debug, "Beginning off-thread decode of script %s (%u bytes)\n",
            script->mURL.get(), script->mSize);

        script->remove();
        size += script->mSize;
    }

    if (size == 0 && mPendingScripts.isEmpty()) {
        return;
    }

    AutoSafeJSAPI jsapi;
    JSContext* cx = jsapi.cx();
    JSAutoRealm ar(cx, scope ? scope : xpc::CompilationScope());

    JS::CompileOptions options(cx);
    options.setNoScriptRval(true)
           .setSourceIsLazy(true);

    if (!JS::CanCompileOffThread(cx, options, size) ||
        !JS::DecodeMultiOffThreadScripts(cx, options, mParsingSources,
                                         OffThreadDecodeCallback,
                                         static_cast<void*>(this))) {
        // If we fail here, we don't move on to process the next batch, so make
        // sure we don't have any other scripts left to process.
        MOZ_ASSERT(mPendingScripts.isEmpty());
        for (auto script : mPendingScripts) {
            script->mReadyToExecute = true;
        }

        LOG(Info, "Can't decode %lu bytes of scripts off-thread", (unsigned long)size);
        for (auto script : mParsingScripts) {
            script->mReadyToExecute = true;
        }
        return;
    }

    cleanup.release();

    LOG(Debug, "Initialized decoding of %u scripts (%u bytes) in %fms\n",
        (unsigned)mParsingSources.length(), (unsigned)size, (TimeStamp::Now() - start).ToMilliseconds());
}


ScriptPreloader::CachedScript::CachedScript(ScriptPreloader& cache, InputBuffer& buf)
    : mCache(cache)
{
    Code(buf);

    // Swap the mProcessTypes and mOriginalProcessTypes values, since we want to
    // start with an empty set of processes loaded into for this session, and
    // compare against last session's values later.
    mOriginalProcessTypes = mProcessTypes;
    mProcessTypes = {};
}

bool
ScriptPreloader::CachedScript::XDREncode(JSContext* cx)
{
    auto cleanup = MakeScopeExit([&] () {
        MaybeDropScript();
    });

    JSAutoRealm ar(cx, mScript);
    JS::RootedScript jsscript(cx, mScript);

    mXDRData.construct<JS::TranscodeBuffer>();

    JS::TranscodeResult code = JS::EncodeScript(cx, Buffer(), jsscript);
    if (code == JS::TranscodeResult_Ok) {
        mXDRRange.emplace(Buffer().begin(), Buffer().length());
        mSize = Range().length();
        return true;
    }
    mXDRData.destroy();
    JS_ClearPendingException(cx);
    return false;
}

JSScript*
ScriptPreloader::CachedScript::GetJSScript(JSContext* cx)
{
    MOZ_ASSERT(mReadyToExecute);
    if (mScript) {
        return mScript;
    }

    if (!HasRange()) {
        // We've already executed the script, and thrown it away. But it wasn't
        // in the cache at startup, so we don't have any data to decode. Give
        // up.
        return nullptr;
    }

    // If we have no script at this point, the script was too small to decode
    // off-thread, or it was needed before the off-thread compilation was
    // finished, and is small enough to decode on the main thread rather than
    // wait for the off-thread decoding to finish. In either case, we decode
    // it synchronously the first time it's needed.

    auto start = TimeStamp::Now();
    LOG(Info, "Decoding script %s on main thread...\n", mURL.get());

    JS::RootedScript script(cx);
    if (JS::DecodeScript(cx, Range(), &script)) {
        mScript = script;

        if (mCache.mSaveComplete) {
            FreeData();
        }
    }

    LOG(Debug, "Finished decoding in %fms", (TimeStamp::Now() - start).ToMilliseconds());

    return mScript;
}

NS_IMPL_ISUPPORTS(ScriptPreloader, nsIObserver, nsIRunnable, nsIMemoryReporter)

#undef LOG

} // namespace mozilla