startupcache/StartupCache.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "prio.h"
   8 #include "PLDHashTable.h"
   9 #include "mozilla/IOInterposer.h"
  10 #include "mozilla/AutoMemMap.h"
  11 #include "mozilla/IOBuffers.h"
  12 #include "mozilla/MemoryReporting.h"
  13 #include "mozilla/MemUtils.h"
  14 #include "mozilla/MmapFaultHandler.h"
  15 #include "mozilla/ResultExtensions.h"
  16 #include "mozilla/scache/StartupCache.h"
  17 #include "mozilla/ScopeExit.h"
  18
  19 #include "nsClassHashtable.h"
  20 #include "nsComponentManagerUtils.h"
  21 #include "nsCRT.h"
  22 #include "nsDirectoryServiceUtils.h"
  23 #include "nsIClassInfo.h"
  24 #include "nsIFile.h"
  25 #include "nsIObserver.h"
  26 #include "nsIOutputStream.h"
  27 #include "nsISupports.h"
  28 #include "nsITimer.h"
  29 #include "mozilla/Omnijar.h"
  30 #include "prenv.h"
  31 #include "mozilla/Telemetry.h"
  32 #include "nsThreadUtils.h"
  33 #include "nsXULAppAPI.h"
  34 #include "nsIProtocolHandler.h"
  35 #include "GeckoProfiler.h"
  36 #include "nsAppRunner.h"
  37 #include "xpcpublic.h"
  38 #ifdef MOZ_BACKGROUNDTASKS
  39 #  include "mozilla/BackgroundTasks.h"
  40 #endif
  41
  42 #if defined(XP_WIN)
  43 #  include <windows.h>
  44 #endif
  45
  46 #ifdef IS_BIG_ENDIAN
  47 #  define SC_ENDIAN "big"
  48 #else
  49 #  define SC_ENDIAN "little"
  50 #endif
  51
  52 #if PR_BYTES_PER_WORD == 4
  53 #  define SC_WORDSIZE "4"
  54 #else
  55 #  define SC_WORDSIZE "8"
  56 #endif
  57
  58 using namespace mozilla::Compression;
  59
  60 namespace mozilla {
  61 namespace scache {
  62
  63 MOZ_DEFINE_MALLOC_SIZE_OF(StartupCacheMallocSizeOf)
  64
  65 NS_IMETHODIMP
  66 StartupCache::CollectReports(nsIHandleReportCallback* aHandleReport,
  67                              nsISupports* aData, bool aAnonymize) {
  68   MutexAutoLock lock(mTableLock);
  69   MOZ_COLLECT_REPORT(
  70       "explicit/startup-cache/mapping", KIND_NONHEAP, UNITS_BYTES,
  71       mCacheData.nonHeapSizeOfExcludingThis(),
  72       "Memory used to hold the mapping of the startup cache from file. "
  73       "This memory is likely to be swapped out shortly after start-up.");
  74
  75   MOZ_COLLECT_REPORT("explicit/startup-cache/data", KIND_HEAP, UNITS_BYTES,
  76                      HeapSizeOfIncludingThis(StartupCacheMallocSizeOf),
  77                      "Memory used by the startup cache for things other than "
  78                      "the file mapping.");
  79
  80   return NS_OK;
  81 }
  82
  83 static const uint8_t MAGIC[] = "startupcache0002";
  84 // This is a heuristic value for how much to reserve for mTable to avoid
  85 // rehashing. This is not a hard limit in release builds, but it is in
  86 // debug builds as it should be stable. If we exceed this number we should
  87 // just increase it.
  88 static const size_t STARTUP_CACHE_RESERVE_CAPACITY = 450;
  89 // This is a hard limit which we will assert on, to ensure that we don't
  90 // have some bug causing runaway cache growth.
  91 static const size_t STARTUP_CACHE_MAX_CAPACITY = 5000;
  92
  93 // Not const because we change it for gtests.
  94 static uint8_t STARTUP_CACHE_WRITE_TIMEOUT = 60;
  95
  96 #define STARTUP_CACHE_NAME "startupCache." SC_WORDSIZE "." SC_ENDIAN
  97
  98 static inline Result<Ok, nsresult> Write(PRFileDesc* fd, const void* data,
  99                                          int32_t len) {
 100   if (PR_Write(fd, data, len) != len) {
 101     return Err(NS_ERROR_FAILURE);
 102   }
 103   return Ok();
 104 }
 105
 106 static inline Result<Ok, nsresult> Seek(PRFileDesc* fd, int32_t offset) {
 107   if (PR_Seek(fd, offset, PR_SEEK_SET) == -1) {
 108     return Err(NS_ERROR_FAILURE);
 109   }
 110   return Ok();
 111 }
 112
 113 static nsresult MapLZ4ErrorToNsresult(size_t aError) {
 114   return NS_ERROR_FAILURE;
 115 }
 116
 117 StartupCache* StartupCache::GetSingletonNoInit() {
 118   return StartupCache::gStartupCache;
 119 }
 120
 121 StartupCache* StartupCache::GetSingleton() {
 122 #ifdef MOZ_BACKGROUNDTASKS
 123   if (BackgroundTasks::IsBackgroundTaskMode()) {
 124     return nullptr;
 125   }
 126 #endif
 127
 128   if (!gStartupCache) {
 129     if (!XRE_IsParentProcess()) {
 130       return nullptr;
 131     }
 132 #ifdef MOZ_DISABLE_STARTUPCACHE
 133     return nullptr;
 134 #else
 135     StartupCache::InitSingleton();
 136 #endif
 137   }
 138
 139   return StartupCache::gStartupCache;
 140 }
 141
 142 void StartupCache::DeleteSingleton() { StartupCache::gStartupCache = nullptr; }
 143
 144 nsresult StartupCache::InitSingleton() {
 145   nsresult rv;
 146   StartupCache::gStartupCache = new StartupCache();
 147
 148   rv = StartupCache::gStartupCache->Init();
 149   if (NS_FAILED(rv)) {
 150     StartupCache::gStartupCache = nullptr;
 151   }
 152   return rv;
 153 }
 154
 155 StaticRefPtr<StartupCache> StartupCache::gStartupCache;
 156 bool StartupCache::gShutdownInitiated;
 157 bool StartupCache::gIgnoreDiskCache;
 158 bool StartupCache::gFoundDiskCacheOnInit;
 159
 160 NS_IMPL_ISUPPORTS(StartupCache, nsIMemoryReporter)
 161
 162 StartupCache::StartupCache()
 163     : mTableLock("StartupCache::mTableLock"),
 164       mDirty(false),
 165       mWrittenOnce(false),
 166       mCurTableReferenced(false),
 167       mRequestedCount(0),
 168       mCacheEntriesBaseOffset(0) {}
 169
 170 StartupCache::~StartupCache() { UnregisterWeakMemoryReporter(this); }
 171
 172 nsresult StartupCache::Init() {
 173   // workaround for bug 653936
 174   nsCOMPtr<nsIProtocolHandler> jarInitializer(
 175       do_GetService(NS_NETWORK_PROTOCOL_CONTRACTID_PREFIX "jar"));
 176
 177   nsresult rv;
 178
 179   if (mozilla::RunningGTest()) {
 180     STARTUP_CACHE_WRITE_TIMEOUT = 3;
 181   }
 182
 183   // This allows to override the startup cache filename
 184   // which is useful from xpcshell, when there is no ProfLDS directory to keep
 185   // cache in.
 186   char* env = PR_GetEnv("MOZ_STARTUP_CACHE");
 187   if (env && *env) {
 188     rv = NS_NewLocalFile(NS_ConvertUTF8toUTF16(env), false,
 189                          getter_AddRefs(mFile));
 190   } else {
 191     nsCOMPtr<nsIFile> file;
 192     rv = NS_GetSpecialDirectory("ProfLDS", getter_AddRefs(file));
 193     if (NS_FAILED(rv)) {
 194       // return silently, this will fail in mochitests's xpcshell process.
 195       return rv;
 196     }
 197
 198     rv = file->AppendNative("startupCache"_ns);
 199     NS_ENSURE_SUCCESS(rv, rv);
 200
 201     // Try to create the directory if it's not there yet
 202     rv = file->Create(nsIFile::DIRECTORY_TYPE, 0777);
 203     if (NS_FAILED(rv) && rv != NS_ERROR_FILE_ALREADY_EXISTS) return rv;
 204
 205     rv = file->AppendNative(nsLiteralCString(STARTUP_CACHE_NAME));
 206
 207     NS_ENSURE_SUCCESS(rv, rv);
 208
 209     mFile = file;
 210   }
 211
 212   NS_ENSURE_TRUE(mFile, NS_ERROR_UNEXPECTED);
 213
 214   mObserverService = do_GetService("@mozilla.org/observer-service;1");
 215
 216   if (!mObserverService) {
 217     NS_WARNING("Could not get observerService.");
 218     return NS_ERROR_UNEXPECTED;
 219   }
 220
 221   mListener = new StartupCacheListener();
 222   rv = mObserverService->AddObserver(mListener, NS_XPCOM_SHUTDOWN_OBSERVER_ID,
 223                                      false);
 224   NS_ENSURE_SUCCESS(rv, rv);
 225   rv = mObserverService->AddObserver(mListener, "startupcache-invalidate",
 226                                      false);
 227   NS_ENSURE_SUCCESS(rv, rv);
 228   rv = mObserverService->AddObserver(mListener, "intl:app-locales-changed",
 229                                      false);
 230   NS_ENSURE_SUCCESS(rv, rv);
 231
 232   {
 233     MutexAutoLock lock(mTableLock);
 234     auto result = LoadArchive();
 235     rv = result.isErr() ? result.unwrapErr() : NS_OK;
 236   }
 237
 238   gFoundDiskCacheOnInit = rv != NS_ERROR_FILE_NOT_FOUND;
 239
 240   // Sometimes we don't have a cache yet, that's ok.
 241   // If it's corrupted, just remove it and start over.
 242   if (gIgnoreDiskCache || (NS_FAILED(rv) && rv != NS_ERROR_FILE_NOT_FOUND)) {
 243     NS_WARNING("Failed to load startupcache file correctly, removing!");
 244     InvalidateCache();
 245   }
 246
 247   RegisterWeakMemoryReporter(this);
 248   mDecompressionContext = MakeUnique<LZ4FrameDecompressionContext>(true);
 249
 250   return NS_OK;
 251 }
 252
 253 void StartupCache::StartPrefetchMemory() {
 254   {
 255     MonitorAutoLock lock(mPrefetchComplete);
 256     mPrefetchInProgress = true;
 257   }
 258   NS_DispatchBackgroundTask(NewRunnableMethod(
 259       "StartupCache::ThreadedPrefetch", this, &StartupCache::ThreadedPrefetch));
 260 }
 261
 262 /**
 263  * LoadArchive can only be called from the main thread.
 264  */
 265 Result<Ok, nsresult> StartupCache::LoadArchive() {
 266   MOZ_ASSERT(NS_IsMainThread(), "Can only load startup cache on main thread");
 267   if (gIgnoreDiskCache) return Err(NS_ERROR_FAILURE);
 268
 269   mTableLock.AssertCurrentThreadOwns();
 270
 271   MOZ_TRY(mCacheData.init(mFile));
 272   auto size = mCacheData.size();
 273   if (CanPrefetchMemory()) {
 274     StartPrefetchMemory();
 275   }
 276
 277   uint32_t headerSize;
 278   if (size < sizeof(MAGIC) + sizeof(headerSize)) {
 279     return Err(NS_ERROR_UNEXPECTED);
 280   }
 281
 282   auto data = mCacheData.get<uint8_t>();
 283   auto end = data + size;
 284
 285   MMAP_FAULT_HANDLER_BEGIN_BUFFER(data.get(), size)
 286
 287   if (memcmp(MAGIC, data.get(), sizeof(MAGIC))) {
 288     return Err(NS_ERROR_UNEXPECTED);
 289   }
 290   data += sizeof(MAGIC);
 291
 292   headerSize = LittleEndian::readUint32(data.get());
 293   data += sizeof(headerSize);
 294
 295   if (headerSize > end - data) {
 296     MOZ_ASSERT(false, "StartupCache file is corrupt.");
 297     return Err(NS_ERROR_UNEXPECTED);
 298   }
 299
 300   Range<uint8_t> header(data, data + headerSize);
 301   data += headerSize;
 302
 303   mCacheEntriesBaseOffset = sizeof(MAGIC) + sizeof(headerSize) + headerSize;
 304   {
 305     if (!mTable.reserve(STARTUP_CACHE_RESERVE_CAPACITY)) {
 306       return Err(NS_ERROR_UNEXPECTED);
 307     }
 308     auto cleanup = MakeScopeExit([&]() {
 309       mTableLock.AssertCurrentThreadOwns();
 310       WaitOnPrefetch();
 311       mTable.clear();
 312       mCacheData.reset();
 313     });
 314     loader::InputBuffer buf(header);
 315
 316     uint32_t currentOffset = 0;
 317     while (!buf.finished()) {
 318       uint32_t offset = 0;
 319       uint32_t compressedSize = 0;
 320       uint32_t uncompressedSize = 0;
 321       nsCString key;
 322       buf.codeUint32(offset);
 323       buf.codeUint32(compressedSize);
 324       buf.codeUint32(uncompressedSize);
 325       buf.codeString(key);
 326
 327       if (offset + compressedSize > end - data) {
 328         MOZ_ASSERT(false, "StartupCache file is corrupt.");
 329         return Err(NS_ERROR_UNEXPECTED);
 330       }
 331
 332       // Make sure offsets match what we'd expect based on script ordering and
 333       // size, as a basic sanity check.
 334       if (offset != currentOffset) {
 335         return Err(NS_ERROR_UNEXPECTED);
 336       }
 337       currentOffset += compressedSize;
 338
 339       // We could use mTable.putNew if we knew the file we're loading weren't
 340       // corrupt. However, we don't know that, so check if the key already
 341       // exists. If it does, we know the file must be corrupt.
 342       decltype(mTable)::AddPtr p = mTable.lookupForAdd(key);
 343       if (p) {
 344         return Err(NS_ERROR_UNEXPECTED);
 345       }
 346
 347       if (!mTable.add(
 348               p, key,
 349               StartupCacheEntry(offset, compressedSize, uncompressedSize))) {
 350         return Err(NS_ERROR_UNEXPECTED);
 351       }
 352     }
 353
 354     if (buf.error()) {
 355       return Err(NS_ERROR_UNEXPECTED);
 356     }
 357
 358     cleanup.release();
 359   }
 360
 361   MMAP_FAULT_HANDLER_CATCH(Err(NS_ERROR_UNEXPECTED))
 362
 363   return Ok();
 364 }
 365
 366 bool StartupCache::HasEntry(const char* id) {
 367   AUTO_PROFILER_LABEL("StartupCache::HasEntry", OTHER);
 368
 369   MOZ_ASSERT(NS_IsMainThread(), "Startup cache only available on main thread");
 370
 371   MutexAutoLock lock(mTableLock);
 372   return mTable.has(nsDependentCString(id));
 373 }
 374
 375 nsresult StartupCache::GetBuffer(const char* id, const char** outbuf,
 376                                  uint32_t* length)
 377     MOZ_NO_THREAD_SAFETY_ANALYSIS {
 378   AUTO_PROFILER_LABEL("StartupCache::GetBuffer", OTHER);
 379
 380   NS_ASSERTION(NS_IsMainThread(),
 381                "Startup cache only available on main thread");
 382
 383   Telemetry::LABELS_STARTUP_CACHE_REQUESTS label =
 384       Telemetry::LABELS_STARTUP_CACHE_REQUESTS::Miss;
 385   auto telemetry =
 386       MakeScopeExit([&label] { Telemetry::AccumulateCategorical(label); });
 387
 388   MutexAutoLock lock(mTableLock);
 389   decltype(mTable)::Ptr p = mTable.lookup(nsDependentCString(id));
 390   if (!p) {
 391     return NS_ERROR_NOT_AVAILABLE;
 392   }
 393
 394   auto& value = p->value();
 395   if (value.mData) {
 396     label = Telemetry::LABELS_STARTUP_CACHE_REQUESTS::HitMemory;
 397   } else {
 398     if (!mCacheData.initialized()) {
 399       return NS_ERROR_NOT_AVAILABLE;
 400     }
 401
 402     size_t totalRead = 0;
 403     size_t totalWritten = 0;
 404     Span<const char> compressed = Span(
 405         mCacheData.get<char>().get() + mCacheEntriesBaseOffset + value.mOffset,
 406         value.mCompressedSize);
 407     value.mData = UniqueFreePtr<char[]>(reinterpret_cast<char*>(
 408         malloc(sizeof(char) * value.mUncompressedSize)));
 409     Span<char> uncompressed = Span(value.mData.get(), value.mUncompressedSize);
 410     MMAP_FAULT_HANDLER_BEGIN_BUFFER(uncompressed.Elements(),
 411                                     uncompressed.Length())
 412     bool finished = false;
 413     while (!finished) {
 414       auto result = mDecompressionContext->Decompress(
 415           uncompressed.From(totalWritten), compressed.From(totalRead));
 416       if (NS_WARN_IF(result.isErr())) {
 417         value.mData = nullptr;
 418         MutexAutoUnlock unlock(mTableLock);
 419         InvalidateCache();
 420         return NS_ERROR_FAILURE;
 421       }
 422       auto decompressionResult = result.unwrap();
 423       totalRead += decompressionResult.mSizeRead;
 424       totalWritten += decompressionResult.mSizeWritten;
 425       finished = decompressionResult.mFinished;
 426     }
 427
 428     MMAP_FAULT_HANDLER_CATCH(NS_ERROR_FAILURE)
 429
 430     label = Telemetry::LABELS_STARTUP_CACHE_REQUESTS::HitDisk;
 431   }
 432
 433   if (!value.mRequested) {
 434     value.mRequested = true;
 435     value.mRequestedOrder = ++mRequestedCount;
 436     MOZ_ASSERT(mRequestedCount <= mTable.count(),
 437                "Somehow we requested more StartupCache items than exist.");
 438     ResetStartupWriteTimerCheckingReadCount();
 439   }
 440
 441   // Track that something holds a reference into mTable, so we know to hold
 442   // onto it in case the cache is invalidated.
 443   mCurTableReferenced = true;
 444   *outbuf = value.mData.get();
 445   *length = value.mUncompressedSize;
 446   return NS_OK;
 447 }
 448
 449 // Makes a copy of the buffer, client retains ownership of inbuf.
 450 nsresult StartupCache::PutBuffer(const char* id, UniqueFreePtr<char[]>&& inbuf,
 451                                  uint32_t len) MOZ_NO_THREAD_SAFETY_ANALYSIS {
 452   NS_ASSERTION(NS_IsMainThread(),
 453                "Startup cache only available on main thread");
 454   if (StartupCache::gShutdownInitiated) {
 455     return NS_ERROR_NOT_AVAILABLE;
 456   }
 457
 458   // Try to gain the table write lock. If the background task to write the
 459   // cache is running, this will fail.
 460   MutexAutoTryLock lock(mTableLock);
 461   if (!lock) {
 462     return NS_ERROR_NOT_AVAILABLE;
 463   }
 464   mTableLock.AssertCurrentThreadOwns();
 465   bool exists = mTable.has(nsDependentCString(id));
 466   if (exists) {
 467     NS_WARNING("Existing entry in StartupCache.");
 468     // Double-caching is undesirable but not an error.
 469     return NS_OK;
 470   }
 471
 472   // putNew returns false on alloc failure - in the very unlikely event we hit
 473   // that and aren't going to crash elsewhere, there's no reason we need to
 474   // crash here.
 475   if (mTable.putNew(nsCString(id), StartupCacheEntry(std::move(inbuf), len,
 476                                                      ++mRequestedCount))) {
 477     return ResetStartupWriteTimer();
 478   }
 479   MOZ_DIAGNOSTIC_ASSERT(mTable.count() < STARTUP_CACHE_MAX_CAPACITY,
 480                         "Too many StartupCache entries.");
 481   return NS_OK;
 482 }
 483
 484 size_t StartupCache::HeapSizeOfIncludingThis(
 485     mozilla::MallocSizeOf aMallocSizeOf) const {
 486   // This function could measure more members, but they haven't been found by
 487   // DMD to be significant.  They can be added later if necessary.
 488
 489   size_t n = aMallocSizeOf(this);
 490
 491   n += mTable.shallowSizeOfExcludingThis(aMallocSizeOf);
 492   for (auto iter = mTable.iter(); !iter.done(); iter.next()) {
 493     if (iter.get().value().mData) {
 494       n += aMallocSizeOf(iter.get().value().mData.get());
 495     }
 496     n += iter.get().key().SizeOfExcludingThisIfUnshared(aMallocSizeOf);
 497   }
 498
 499   return n;
 500 }
 501
 502 /**
 503  * WriteToDisk writes the cache out to disk. Callers of WriteToDisk need to call
 504  * WaitOnWriteComplete to make sure there isn't a write
 505  * happening on another thread.
 506  * We own the mTableLock here.
 507  */
 508 Result<Ok, nsresult> StartupCache::WriteToDisk() {
 509   if (!mDirty || mWrittenOnce) {
 510     return Ok();
 511   }
 512
 513   if (!mFile) {
 514     return Err(NS_ERROR_UNEXPECTED);
 515   }
 516
 517   AutoFDClose fd;
 518   MOZ_TRY(mFile->OpenNSPRFileDesc(PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE,
 519                                   0644, &fd.rwget()));
 520
 521   nsTArray<std::pair<const nsCString*, StartupCacheEntry*>> entries;
 522   for (auto iter = mTable.iter(); !iter.done(); iter.next()) {
 523     if (iter.get().value().mRequested) {
 524       entries.AppendElement(
 525           std::make_pair(&iter.get().key(), &iter.get().value()));
 526     }
 527   }
 528
 529   if (entries.IsEmpty()) {
 530     return Ok();
 531   }
 532
 533   entries.Sort(StartupCacheEntry::Comparator());
 534   loader::OutputBuffer buf;
 535   for (auto& e : entries) {
 536     auto key = e.first;
 537     auto value = e.second;
 538     auto uncompressedSize = value->mUncompressedSize;
 539     // Set the mHeaderOffsetInFile so we can go back and edit the offset.
 540     value->mHeaderOffsetInFile = buf.cursor();
 541     // Write a 0 offset/compressed size as a placeholder until we get the real
 542     // offset after compressing.
 543     buf.codeUint32(0);
 544     buf.codeUint32(0);
 545     buf.codeUint32(uncompressedSize);
 546     buf.codeString(*key);
 547   }
 548
 549   uint8_t headerSize[4];
 550   LittleEndian::writeUint32(headerSize, buf.cursor());
 551
 552   MOZ_TRY(Write(fd, MAGIC, sizeof(MAGIC)));
 553   MOZ_TRY(Write(fd, headerSize, sizeof(headerSize)));
 554   size_t headerStart = sizeof(MAGIC) + sizeof(headerSize);
 555   size_t dataStart = headerStart + buf.cursor();
 556   MOZ_TRY(Seek(fd, dataStart));
 557
 558   size_t offset = 0;
 559
 560   const size_t chunkSize = 1024 * 16;
 561   LZ4FrameCompressionContext ctx(6,         /* aCompressionLevel */
 562                                  chunkSize, /* aReadBufLen */
 563                                  true,      /* aChecksum */
 564                                  true);     /* aStableSrc */
 565   size_t writeBufLen = ctx.GetRequiredWriteBufferLength();
 566   auto writeBuffer = MakeUnique<char[]>(writeBufLen);
 567   auto writeSpan = Span(writeBuffer.get(), writeBufLen);
 568
 569   for (auto& e : entries) {
 570     auto value = e.second;
 571     value->mOffset = offset;
 572     Span<const char> result;
 573     MOZ_TRY_VAR(result,
 574                 ctx.BeginCompressing(writeSpan).mapErr(MapLZ4ErrorToNsresult));
 575     MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 576     offset += result.Length();
 577
 578     for (size_t i = 0; i < value->mUncompressedSize; i += chunkSize) {
 579       size_t size = std::min(chunkSize, value->mUncompressedSize - i);
 580       char* uncompressed = value->mData.get() + i;
 581       MOZ_TRY_VAR(result, ctx.ContinueCompressing(Span(uncompressed, size))
 582                               .mapErr(MapLZ4ErrorToNsresult));
 583       MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 584       offset += result.Length();
 585     }
 586
 587     MOZ_TRY_VAR(result, ctx.EndCompressing().mapErr(MapLZ4ErrorToNsresult));
 588     MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 589     offset += result.Length();
 590     value->mCompressedSize = offset - value->mOffset;
 591     MOZ_TRY(Seek(fd, dataStart + offset));
 592   }
 593
 594   for (auto& e : entries) {
 595     auto value = e.second;
 596     uint8_t* headerEntry = buf.Get() + value->mHeaderOffsetInFile;
 597     LittleEndian::writeUint32(headerEntry, value->mOffset);
 598     LittleEndian::writeUint32(headerEntry + sizeof(value->mOffset),
 599                               value->mCompressedSize);
 600   }
 601   MOZ_TRY(Seek(fd, headerStart));
 602   MOZ_TRY(Write(fd, buf.Get(), buf.cursor()));
 603
 604   mDirty = false;
 605   mWrittenOnce = true;
 606
 607   return Ok();
 608 }
 609
 610 void StartupCache::InvalidateCache(bool memoryOnly) {
 611   WaitOnPrefetch();
 612   // Ensure we're not writing using mTable...
 613   MutexAutoLock lock(mTableLock);
 614
 615   mWrittenOnce = false;
 616   if (memoryOnly) {
 617     // This should only be called in tests.
 618     auto writeResult = WriteToDisk();
 619     if (NS_WARN_IF(writeResult.isErr())) {
 620       gIgnoreDiskCache = true;
 621       return;
 622     }
 623   }
 624   if (mCurTableReferenced) {
 625     // There should be no way for this assert to fail other than a user manually
 626     // sending startupcache-invalidate messages through the Browser Toolbox. If
 627     // something knowingly invalidates the cache, the event can be counted with
 628     // mAllowedInvalidationsCount.
 629     MOZ_DIAGNOSTIC_ASSERT(
 630         xpc::IsInAutomation() ||
 631             // The allowed invalidations can grow faster than the old tables, so
 632             // guard against incorrect unsigned subtraction.
 633             mAllowedInvalidationsCount > mOldTables.Length() ||
 634             // Now perform the real check.
 635             mOldTables.Length() - mAllowedInvalidationsCount < 10,
 636         "Startup cache invalidated too many times.");
 637     mOldTables.AppendElement(std::move(mTable));
 638     mCurTableReferenced = false;
 639   } else {
 640     mTable.clear();
 641   }
 642   mRequestedCount = 0;
 643   if (!memoryOnly) {
 644     mCacheData.reset();
 645     nsresult rv = mFile->Remove(false);
 646     if (NS_FAILED(rv) && rv != NS_ERROR_FILE_NOT_FOUND) {
 647       gIgnoreDiskCache = true;
 648       return;
 649     }
 650   }
 651   gIgnoreDiskCache = false;
 652   auto result = LoadArchive();
 653   if (NS_WARN_IF(result.isErr())) {
 654     gIgnoreDiskCache = true;
 655   }
 656 }
 657
 658 void StartupCache::CountAllowedInvalidation() { mAllowedInvalidationsCount++; }
 659
 660 void StartupCache::MaybeInitShutdownWrite() {
 661   if (mTimer) {
 662     mTimer->Cancel();
 663   }
 664   gShutdownInitiated = true;
 665
 666   MaybeWriteOffMainThread();
 667 }
 668
 669 void StartupCache::EnsureShutdownWriteComplete() {
 670   MutexAutoLock lock(mTableLock);
 671   // If we've already written or there's nothing to write,
 672   // we don't need to do anything. This is the common case.
 673   if (mWrittenOnce || (mCacheData.initialized() && !ShouldCompactCache())) {
 674     return;
 675   }
 676   // Otherwise, ensure the write happens. The timer should have been cancelled
 677   // already in MaybeInitShutdownWrite.
 678
 679   // We got the lock. Keep the following in sync with
 680   // MaybeWriteOffMainThread:
 681   WaitOnPrefetch();
 682   mDirty = true;
 683   mCacheData.reset();
 684   // Most of this should be redundant given MaybeWriteOffMainThread should
 685   // have run before now.
 686
 687   auto writeResult = WriteToDisk();
 688   Unused << NS_WARN_IF(writeResult.isErr());
 689   // We've had the lock, and `WriteToDisk()` sets mWrittenOnce and mDirty
 690   // when done, and checks for them when starting, so we don't need to do
 691   // anything else.
 692 }
 693
 694 void StartupCache::IgnoreDiskCache() {
 695   gIgnoreDiskCache = true;
 696   if (gStartupCache) gStartupCache->InvalidateCache();
 697 }
 698
 699 bool StartupCache::GetIgnoreDiskCache() { return gIgnoreDiskCache; }
 700
 701 void StartupCache::WaitOnPrefetch() {
 702   // This can't be called from within ThreadedPrefetch()
 703   MonitorAutoLock lock(mPrefetchComplete);
 704   while (mPrefetchInProgress) {
 705     mPrefetchComplete.Wait();
 706   }
 707 }
 708
 709 void StartupCache::ThreadedPrefetch() {
 710   uint8_t* buf;
 711   size_t size;
 712   {
 713     MutexAutoLock lock(mTableLock);
 714     buf = mCacheData.get<uint8_t>().get();
 715     size = mCacheData.size();
 716   }
 717   // PrefetchMemory does madvise/equivalent, but doesn't access the memory
 718   // pointed to by buf
 719   MMAP_FAULT_HANDLER_BEGIN_BUFFER(buf, size)
 720   PrefetchMemory(buf, size);
 721   MMAP_FAULT_HANDLER_CATCH()
 722   MonitorAutoLock lock(mPrefetchComplete);
 723   mPrefetchInProgress = false;
 724   mPrefetchComplete.NotifyAll();
 725 }
 726
 727 // mTableLock must be held
 728 bool StartupCache::ShouldCompactCache() {
 729   // If we've requested less than 4/5 of the startup cache, then we should
 730   // probably compact it down. This can happen quite easily after the first run,
 731   // which seems to request quite a few more things than subsequent runs.
 732   CheckedInt<uint32_t> threshold = CheckedInt<uint32_t>(mTable.count()) * 4 / 5;
 733   MOZ_RELEASE_ASSERT(threshold.isValid(), "Runaway StartupCache size");
 734   return mRequestedCount < threshold.value();
 735 }
 736
 737 /*
 738  * The write-thread is spawned on a timeout(which is reset with every write).
 739  * This can avoid a slow shutdown.
 740  */
 741 void StartupCache::WriteTimeout(nsITimer* aTimer, void* aClosure) {
 742   /*
 743    * It is safe to use the pointer passed in aClosure to reference the
 744    * StartupCache object because the timer's lifetime is tightly coupled to
 745    * the lifetime of the StartupCache object; this timer is canceled in the
 746    * StartupCache destructor, guaranteeing that this function runs if and only
 747    * if the StartupCache object is valid.
 748    */
 749   StartupCache* startupCacheObj = static_cast<StartupCache*>(aClosure);
 750   startupCacheObj->MaybeWriteOffMainThread();
 751 }
 752
 753 /*
 754  * See StartupCache::WriteTimeout above - this is just the non-static body.
 755  */
 756 void StartupCache::MaybeWriteOffMainThread() {
 757   {
 758     MutexAutoLock lock(mTableLock);
 759     if (mWrittenOnce || (mCacheData.initialized() && !ShouldCompactCache())) {
 760       return;
 761     }
 762   }
 763   // Keep this code in sync with EnsureShutdownWriteComplete.
 764   WaitOnPrefetch();
 765   {
 766     MutexAutoLock lock(mTableLock);
 767     mDirty = true;
 768     mCacheData.reset();
 769   }
 770
 771   RefPtr<StartupCache> self = this;
 772   nsCOMPtr<nsIRunnable> runnable =
 773       NS_NewRunnableFunction("StartupCache::Write", [self]() mutable {
 774         MutexAutoLock lock(self->mTableLock);
 775         auto result = self->WriteToDisk();
 776         Unused << NS_WARN_IF(result.isErr());
 777       });
 778   NS_DispatchBackgroundTask(runnable.forget(), NS_DISPATCH_EVENT_MAY_BLOCK);
 779 }
 780
 781 // We don't want to refcount StartupCache, so we'll just
 782 // hold a ref to this and pass it to observerService instead.
 783 NS_IMPL_ISUPPORTS(StartupCacheListener, nsIObserver)
 784
 785 nsresult StartupCacheListener::Observe(nsISupports* subject, const char* topic,
 786                                        const char16_t* data) {
 787   StartupCache* sc = StartupCache::GetSingleton();
 788   if (!sc) return NS_OK;
 789
 790   if (strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
 791     // Do not leave the thread running past xpcom shutdown
 792     sc->WaitOnPrefetch();
 793     StartupCache::gShutdownInitiated = true;
 794     // Note that we don't do anything special for the background write
 795     // task; we expect the threadpool to finish running any tasks already
 796     // posted to it prior to shutdown. FastShutdown will call
 797     // EnsureShutdownWriteComplete() to ensure any pending writes happen
 798     // in that case.
 799   } else if (strcmp(topic, "startupcache-invalidate") == 0) {
 800     sc->InvalidateCache(data && nsCRT::strcmp(data, u"memoryOnly") == 0);
 801   } else if (strcmp(topic, "intl:app-locales-changed") == 0) {
 802     // Live language switching invalidates the startup cache due to the history
 803     // sidebar retaining localized strings in its internal SQL query. This
 804     // should be a relatively rare event, but a user could do it an arbitrary
 805     // number of times.
 806     sc->CountAllowedInvalidation();
 807   }
 808   return NS_OK;
 809 }
 810
 811 nsresult StartupCache::GetDebugObjectOutputStream(
 812     nsIObjectOutputStream* aStream, nsIObjectOutputStream** aOutStream) {
 813   NS_ENSURE_ARG_POINTER(aStream);
 814 #ifdef DEBUG
 815   auto* stream = new StartupCacheDebugOutputStream(aStream, &mWriteObjectMap);
 816   NS_ADDREF(*aOutStream = stream);
 817 #else
 818   NS_ADDREF(*aOutStream = aStream);
 819 #endif
 820
 821   return NS_OK;
 822 }
 823
 824 nsresult StartupCache::ResetStartupWriteTimerCheckingReadCount() {
 825   nsresult rv = NS_OK;
 826   if (!mTimer)
 827     mTimer = NS_NewTimer();
 828   else
 829     rv = mTimer->Cancel();
 830   NS_ENSURE_SUCCESS(rv, rv);
 831   // Wait for the specified timeout, then write out the cache.
 832   mTimer->InitWithNamedFuncCallback(
 833       StartupCache::WriteTimeout, this, STARTUP_CACHE_WRITE_TIMEOUT * 1000,
 834       nsITimer::TYPE_ONE_SHOT, "StartupCache::WriteTimeout");
 835   return NS_OK;
 836 }
 837
 838 // For test code only
 839 nsresult StartupCache::ResetStartupWriteTimerAndLock() {
 840   MutexAutoLock lock(mTableLock);
 841   return ResetStartupWriteTimer();
 842 }
 843
 844 nsresult StartupCache::ResetStartupWriteTimer() {
 845   mDirty = true;
 846   nsresult rv = NS_OK;
 847   if (!mTimer)
 848     mTimer = NS_NewTimer();
 849   else
 850     rv = mTimer->Cancel();
 851   NS_ENSURE_SUCCESS(rv, rv);
 852   // Wait for the specified timeout, then write out the cache.
 853   mTimer->InitWithNamedFuncCallback(
 854       StartupCache::WriteTimeout, this, STARTUP_CACHE_WRITE_TIMEOUT * 1000,
 855       nsITimer::TYPE_ONE_SHOT, "StartupCache::WriteTimeout");
 856   return NS_OK;
 857 }
 858
 859 // Used only in tests:
 860 bool StartupCache::StartupWriteComplete() {
 861   // Need to have written to disk and not added new things since;
 862   MutexAutoLock lock(mTableLock);
 863   return !mDirty && mWrittenOnce;
 864 }
 865
 866 // StartupCacheDebugOutputStream implementation
 867 #ifdef DEBUG
 868 NS_IMPL_ISUPPORTS(StartupCacheDebugOutputStream, nsIObjectOutputStream,
 869                   nsIBinaryOutputStream, nsIOutputStream)
 870
 871 bool StartupCacheDebugOutputStream::CheckReferences(nsISupports* aObject) {
 872   nsresult rv;
 873
 874   nsCOMPtr<nsIClassInfo> classInfo = do_QueryInterface(aObject);
 875   if (!classInfo) {
 876     NS_ERROR("aObject must implement nsIClassInfo");
 877     return false;
 878   }
 879
 880   uint32_t flags;
 881   rv = classInfo->GetFlags(&flags);
 882   NS_ENSURE_SUCCESS(rv, false);
 883   if (flags & nsIClassInfo::SINGLETON) return true;
 884
 885   bool inserted = mObjectMap->EnsureInserted(aObject);
 886   if (!inserted) {
 887     NS_ERROR(
 888         "non-singleton aObject is referenced multiple times in this"
 889         "serialization, we don't support that.");
 890   }
 891
 892   return inserted;
 893 }
 894
 895 // nsIObjectOutputStream implementation
 896 nsresult StartupCacheDebugOutputStream::WriteObject(nsISupports* aObject,
 897                                                     bool aIsStrongRef) {
 898   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 899
 900   NS_ASSERTION(rootObject.get() == aObject,
 901                "bad call to WriteObject -- call WriteCompoundObject!");
 902   bool check = CheckReferences(aObject);
 903   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 904   return mBinaryStream->WriteObject(aObject, aIsStrongRef);
 905 }
 906
 907 nsresult StartupCacheDebugOutputStream::WriteSingleRefObject(
 908     nsISupports* aObject) {
 909   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 910
 911   NS_ASSERTION(rootObject.get() == aObject,
 912                "bad call to WriteSingleRefObject -- call WriteCompoundObject!");
 913   bool check = CheckReferences(aObject);
 914   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 915   return mBinaryStream->WriteSingleRefObject(aObject);
 916 }
 917
 918 nsresult StartupCacheDebugOutputStream::WriteCompoundObject(
 919     nsISupports* aObject, const nsIID& aIID, bool aIsStrongRef) {
 920   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 921
 922   nsCOMPtr<nsISupports> roundtrip;
 923   rootObject->QueryInterface(aIID, getter_AddRefs(roundtrip));
 924   NS_ASSERTION(roundtrip.get() == aObject,
 925                "bad aggregation or multiple inheritance detected by call to "
 926                "WriteCompoundObject!");
 927
 928   bool check = CheckReferences(aObject);
 929   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 930   return mBinaryStream->WriteCompoundObject(aObject, aIID, aIsStrongRef);
 931 }
 932
 933 nsresult StartupCacheDebugOutputStream::WriteID(nsID const& aID) {
 934   return mBinaryStream->WriteID(aID);
 935 }
 936
 937 char* StartupCacheDebugOutputStream::GetBuffer(uint32_t aLength,
 938                                                uint32_t aAlignMask) {
 939   return mBinaryStream->GetBuffer(aLength, aAlignMask);
 940 }
 941
 942 void StartupCacheDebugOutputStream::PutBuffer(char* aBuffer, uint32_t aLength) {
 943   mBinaryStream->PutBuffer(aBuffer, aLength);
 944 }
 945 #endif  // DEBUG
 946
 947 }  // namespace scache
 948 }  // namespace mozilla