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 #include "mozilla/Try.h"
  19
  20 #include "nsClassHashtable.h"
  21 #include "nsComponentManagerUtils.h"
  22 #include "nsCRT.h"
  23 #include "nsDirectoryServiceUtils.h"
  24 #include "nsIClassInfo.h"
  25 #include "nsIFile.h"
  26 #include "nsIObserver.h"
  27 #include "nsIOutputStream.h"
  28 #include "nsISupports.h"
  29 #include "nsITimer.h"
  30 #include "mozilla/Omnijar.h"
  31 #include "prenv.h"
  32 #include "mozilla/Telemetry.h"
  33 #include "nsThreadUtils.h"
  34 #include "nsXULAppAPI.h"
  35 #include "nsIProtocolHandler.h"
  36 #include "GeckoProfiler.h"
  37 #include "nsAppRunner.h"
  38 #include "xpcpublic.h"
  39 #ifdef MOZ_BACKGROUNDTASKS
  40 #  include "mozilla/BackgroundTasks.h"
  41 #endif
  42
  43 #if defined(XP_WIN)
  44 #  include <windows.h>
  45 #endif
  46
  47 #ifdef IS_BIG_ENDIAN
  48 #  define SC_ENDIAN "big"
  49 #else
  50 #  define SC_ENDIAN "little"
  51 #endif
  52
  53 #if PR_BYTES_PER_WORD == 4
  54 #  define SC_WORDSIZE "4"
  55 #else
  56 #  define SC_WORDSIZE "8"
  57 #endif
  58
  59 using namespace mozilla::Compression;
  60
  61 namespace mozilla {
  62 namespace scache {
  63
  64 MOZ_DEFINE_MALLOC_SIZE_OF(StartupCacheMallocSizeOf)
  65
  66 NS_IMETHODIMP
  67 StartupCache::CollectReports(nsIHandleReportCallback* aHandleReport,
  68                              nsISupports* aData, bool aAnonymize) {
  69   MutexAutoLock lock(mTableLock);
  70   MOZ_COLLECT_REPORT(
  71       "explicit/startup-cache/mapping", KIND_NONHEAP, UNITS_BYTES,
  72       mCacheData.nonHeapSizeOfExcludingThis(),
  73       "Memory used to hold the mapping of the startup cache from file. "
  74       "This memory is likely to be swapped out shortly after start-up.");
  75
  76   MOZ_COLLECT_REPORT("explicit/startup-cache/data", KIND_HEAP, UNITS_BYTES,
  77                      HeapSizeOfIncludingThis(StartupCacheMallocSizeOf),
  78                      "Memory used by the startup cache for things other than "
  79                      "the file mapping.");
  80
  81   return NS_OK;
  82 }
  83
  84 static const uint8_t MAGIC[] = "startupcache0002";
  85 // This is a heuristic value for how much to reserve for mTable to avoid
  86 // rehashing. This is not a hard limit in release builds, but it is in
  87 // debug builds as it should be stable. If we exceed this number we should
  88 // just increase it.
  89 static const size_t STARTUP_CACHE_RESERVE_CAPACITY = 450;
  90 // This is a hard limit which we will assert on, to ensure that we don't
  91 // have some bug causing runaway cache growth.
  92 static const size_t STARTUP_CACHE_MAX_CAPACITY = 5000;
  93
  94 // Not const because we change it for gtests.
  95 static uint8_t STARTUP_CACHE_WRITE_TIMEOUT = 60;
  96
  97 #define STARTUP_CACHE_NAME "startupCache." SC_WORDSIZE "." SC_ENDIAN
  98
  99 static inline Result<Ok, nsresult> Write(PRFileDesc* fd, const void* data,
 100                                          int32_t len) {
 101   if (PR_Write(fd, data, len) != len) {
 102     return Err(NS_ERROR_FAILURE);
 103   }
 104   return Ok();
 105 }
 106
 107 static inline Result<Ok, nsresult> Seek(PRFileDesc* fd, int32_t offset) {
 108   if (PR_Seek(fd, offset, PR_SEEK_SET) == -1) {
 109     return Err(NS_ERROR_FAILURE);
 110   }
 111   return Ok();
 112 }
 113
 114 static nsresult MapLZ4ErrorToNsresult(size_t aError) {
 115   return NS_ERROR_FAILURE;
 116 }
 117
 118 StartupCache* StartupCache::GetSingletonNoInit() {
 119   return StartupCache::gStartupCache;
 120 }
 121
 122 StartupCache* StartupCache::GetSingleton() {
 123 #ifdef MOZ_BACKGROUNDTASKS
 124   if (BackgroundTasks::IsBackgroundTaskMode()) {
 125     return nullptr;
 126   }
 127 #endif
 128
 129   if (!gStartupCache) {
 130     if (!XRE_IsParentProcess()) {
 131       return nullptr;
 132     }
 133 #ifdef MOZ_DISABLE_STARTUPCACHE
 134     return nullptr;
 135 #else
 136     StartupCache::InitSingleton();
 137 #endif
 138   }
 139
 140   return StartupCache::gStartupCache;
 141 }
 142
 143 void StartupCache::DeleteSingleton() { StartupCache::gStartupCache = nullptr; }
 144
 145 nsresult StartupCache::InitSingleton() {
 146   nsresult rv;
 147   StartupCache::gStartupCache = new StartupCache();
 148
 149   rv = StartupCache::gStartupCache->Init();
 150   if (NS_FAILED(rv)) {
 151     StartupCache::gStartupCache = nullptr;
 152   }
 153   return rv;
 154 }
 155
 156 StaticRefPtr<StartupCache> StartupCache::gStartupCache;
 157 bool StartupCache::gShutdownInitiated;
 158 bool StartupCache::gIgnoreDiskCache;
 159 bool StartupCache::gFoundDiskCacheOnInit;
 160
 161 NS_IMPL_ISUPPORTS(StartupCache, nsIMemoryReporter)
 162
 163 StartupCache::StartupCache()
 164     : mTableLock("StartupCache::mTableLock"),
 165       mDirty(false),
 166       mWrittenOnce(false),
 167       mCurTableReferenced(false),
 168       mRequestedCount(0),
 169       mCacheEntriesBaseOffset(0) {}
 170
 171 StartupCache::~StartupCache() { UnregisterWeakMemoryReporter(this); }
 172
 173 nsresult StartupCache::Init() {
 174   // workaround for bug 653936
 175   nsCOMPtr<nsIProtocolHandler> jarInitializer(
 176       do_GetService(NS_NETWORK_PROTOCOL_CONTRACTID_PREFIX "jar"));
 177
 178   nsresult rv;
 179
 180   if (mozilla::RunningGTest()) {
 181     STARTUP_CACHE_WRITE_TIMEOUT = 3;
 182   }
 183
 184   // This allows to override the startup cache filename
 185   // which is useful from xpcshell, when there is no ProfLDS directory to keep
 186   // cache in.
 187   char* env = PR_GetEnv("MOZ_STARTUP_CACHE");
 188   if (env && *env) {
 189     rv = NS_NewLocalFile(NS_ConvertUTF8toUTF16(env), false,
 190                          getter_AddRefs(mFile));
 191   } else {
 192     nsCOMPtr<nsIFile> file;
 193     rv = NS_GetSpecialDirectory("ProfLDS", getter_AddRefs(file));
 194     if (NS_FAILED(rv)) {
 195       // return silently, this will fail in mochitests's xpcshell process.
 196       return rv;
 197     }
 198
 199     rv = file->AppendNative("startupCache"_ns);
 200     NS_ENSURE_SUCCESS(rv, rv);
 201
 202     // Try to create the directory if it's not there yet
 203     rv = file->Create(nsIFile::DIRECTORY_TYPE, 0777);
 204     if (NS_FAILED(rv) && rv != NS_ERROR_FILE_ALREADY_EXISTS) return rv;
 205
 206     rv = file->AppendNative(nsLiteralCString(STARTUP_CACHE_NAME));
 207
 208     NS_ENSURE_SUCCESS(rv, rv);
 209
 210     mFile = file;
 211   }
 212
 213   NS_ENSURE_TRUE(mFile, NS_ERROR_UNEXPECTED);
 214
 215   mObserverService = do_GetService("@mozilla.org/observer-service;1");
 216
 217   if (!mObserverService) {
 218     NS_WARNING("Could not get observerService.");
 219     return NS_ERROR_UNEXPECTED;
 220   }
 221
 222   mListener = new StartupCacheListener();
 223   rv = mObserverService->AddObserver(mListener, NS_XPCOM_SHUTDOWN_OBSERVER_ID,
 224                                      false);
 225   NS_ENSURE_SUCCESS(rv, rv);
 226   rv = mObserverService->AddObserver(mListener, "startupcache-invalidate",
 227                                      false);
 228   NS_ENSURE_SUCCESS(rv, rv);
 229   rv = mObserverService->AddObserver(mListener, "intl:app-locales-changed",
 230                                      false);
 231   NS_ENSURE_SUCCESS(rv, rv);
 232
 233   {
 234     MutexAutoLock lock(mTableLock);
 235     auto result = LoadArchive();
 236     rv = result.isErr() ? result.unwrapErr() : NS_OK;
 237   }
 238
 239   gFoundDiskCacheOnInit = rv != NS_ERROR_FILE_NOT_FOUND;
 240
 241   // Sometimes we don't have a cache yet, that's ok.
 242   // If it's corrupted, just remove it and start over.
 243   if (gIgnoreDiskCache || (NS_FAILED(rv) && rv != NS_ERROR_FILE_NOT_FOUND)) {
 244     NS_WARNING("Failed to load startupcache file correctly, removing!");
 245     InvalidateCache();
 246   }
 247
 248   RegisterWeakMemoryReporter(this);
 249   mDecompressionContext = MakeUnique<LZ4FrameDecompressionContext>(true);
 250
 251   return NS_OK;
 252 }
 253
 254 void StartupCache::StartPrefetchMemory() {
 255   {
 256     MonitorAutoLock lock(mPrefetchComplete);
 257     mPrefetchInProgress = true;
 258   }
 259   NS_DispatchBackgroundTask(NewRunnableMethod<uint8_t*, size_t>(
 260       "StartupCache::ThreadedPrefetch", this, &StartupCache::ThreadedPrefetch,
 261       mCacheData.get<uint8_t>().get(), mCacheData.size()));
 262 }
 263
 264 /**
 265  * LoadArchive can only be called from the main thread.
 266  */
 267 Result<Ok, nsresult> StartupCache::LoadArchive() {
 268   MOZ_ASSERT(NS_IsMainThread(), "Can only load startup cache on main thread");
 269   if (gIgnoreDiskCache) return Err(NS_ERROR_FAILURE);
 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     // It is impossible for a write to be pending here. This is because
 402     // we just checked mCacheData.initialized(), and this is reset before
 403     // writing to the cache. It's not re-initialized unless we call
 404     // LoadArchive(), either from Init() (which must have already happened) or
 405     // InvalidateCache(). InvalidateCache() locks the mutex, so a write can't be
 406     // happening.
 407     // Also, WriteToDisk() requires mTableLock, so while it's writing we can't
 408     // be here.
 409
 410     size_t totalRead = 0;
 411     size_t totalWritten = 0;
 412     Span<const char> compressed = Span(
 413         mCacheData.get<char>().get() + mCacheEntriesBaseOffset + value.mOffset,
 414         value.mCompressedSize);
 415     value.mData = UniqueFreePtr<char[]>(reinterpret_cast<char*>(
 416         malloc(sizeof(char) * value.mUncompressedSize)));
 417     Span<char> uncompressed = Span(value.mData.get(), value.mUncompressedSize);
 418     MMAP_FAULT_HANDLER_BEGIN_BUFFER(uncompressed.Elements(),
 419                                     uncompressed.Length())
 420     bool finished = false;
 421     while (!finished) {
 422       auto result = mDecompressionContext->Decompress(
 423           uncompressed.From(totalWritten), compressed.From(totalRead));
 424       if (NS_WARN_IF(result.isErr())) {
 425         value.mData = nullptr;
 426         MutexAutoUnlock unlock(mTableLock);
 427         InvalidateCache();
 428         return NS_ERROR_FAILURE;
 429       }
 430       auto decompressionResult = result.unwrap();
 431       totalRead += decompressionResult.mSizeRead;
 432       totalWritten += decompressionResult.mSizeWritten;
 433       finished = decompressionResult.mFinished;
 434     }
 435
 436     MMAP_FAULT_HANDLER_CATCH(NS_ERROR_FAILURE)
 437
 438     label = Telemetry::LABELS_STARTUP_CACHE_REQUESTS::HitDisk;
 439   }
 440
 441   if (!value.mRequested) {
 442     value.mRequested = true;
 443     value.mRequestedOrder = ++mRequestedCount;
 444     MOZ_ASSERT(mRequestedCount <= mTable.count(),
 445                "Somehow we requested more StartupCache items than exist.");
 446     ResetStartupWriteTimerCheckingReadCount();
 447   }
 448
 449   // Track that something holds a reference into mTable, so we know to hold
 450   // onto it in case the cache is invalidated.
 451   mCurTableReferenced = true;
 452   *outbuf = value.mData.get();
 453   *length = value.mUncompressedSize;
 454   return NS_OK;
 455 }
 456
 457 // Makes a copy of the buffer, client retains ownership of inbuf.
 458 nsresult StartupCache::PutBuffer(const char* id, UniqueFreePtr<char[]>&& inbuf,
 459                                  uint32_t len) MOZ_NO_THREAD_SAFETY_ANALYSIS {
 460   NS_ASSERTION(NS_IsMainThread(),
 461                "Startup cache only available on main thread");
 462   if (StartupCache::gShutdownInitiated) {
 463     return NS_ERROR_NOT_AVAILABLE;
 464   }
 465
 466   // Try to gain the table write lock. If the background task to write the
 467   // cache is running, this will fail.
 468   MutexAutoTryLock lock(mTableLock);
 469   if (!lock) {
 470     return NS_ERROR_NOT_AVAILABLE;
 471   }
 472   mTableLock.AssertCurrentThreadOwns();
 473   bool exists = mTable.has(nsDependentCString(id));
 474   if (exists) {
 475     NS_WARNING("Existing entry in StartupCache.");
 476     // Double-caching is undesirable but not an error.
 477     return NS_OK;
 478   }
 479
 480   // putNew returns false on alloc failure - in the very unlikely event we hit
 481   // that and aren't going to crash elsewhere, there's no reason we need to
 482   // crash here.
 483   if (mTable.putNew(nsCString(id), StartupCacheEntry(std::move(inbuf), len,
 484                                                      ++mRequestedCount))) {
 485     return ResetStartupWriteTimer();
 486   }
 487   MOZ_DIAGNOSTIC_ASSERT(mTable.count() < STARTUP_CACHE_MAX_CAPACITY,
 488                         "Too many StartupCache entries.");
 489   return NS_OK;
 490 }
 491
 492 size_t StartupCache::HeapSizeOfIncludingThis(
 493     mozilla::MallocSizeOf aMallocSizeOf) const {
 494   // This function could measure more members, but they haven't been found by
 495   // DMD to be significant.  They can be added later if necessary.
 496
 497   size_t n = aMallocSizeOf(this);
 498
 499   n += mTable.shallowSizeOfExcludingThis(aMallocSizeOf);
 500   for (auto iter = mTable.iter(); !iter.done(); iter.next()) {
 501     if (iter.get().value().mData) {
 502       n += aMallocSizeOf(iter.get().value().mData.get());
 503     }
 504     n += iter.get().key().SizeOfExcludingThisIfUnshared(aMallocSizeOf);
 505   }
 506
 507   return n;
 508 }
 509
 510 /**
 511  * WriteToDisk writes the cache out to disk. Callers of WriteToDisk need to call
 512  * WaitOnWriteComplete to make sure there isn't a write
 513  * happening on another thread.
 514  * We own the mTableLock here.
 515  */
 516 Result<Ok, nsresult> StartupCache::WriteToDisk() {
 517   if (!mDirty || mWrittenOnce) {
 518     return Ok();
 519   }
 520
 521   if (!mFile) {
 522     return Err(NS_ERROR_UNEXPECTED);
 523   }
 524
 525   AutoFDClose fd;
 526   MOZ_TRY(mFile->OpenNSPRFileDesc(PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE,
 527                                   0644, &fd.rwget()));
 528
 529   nsTArray<StartupCacheEntry::KeyValuePair> entries(mTable.count());
 530   for (auto iter = mTable.iter(); !iter.done(); iter.next()) {
 531     if (iter.get().value().mRequested) {
 532       StartupCacheEntry::KeyValuePair kv(&iter.get().key(),
 533                                          &iter.get().value());
 534       entries.AppendElement(kv);
 535     }
 536   }
 537
 538   if (entries.IsEmpty()) {
 539     return Ok();
 540   }
 541
 542   entries.Sort(StartupCacheEntry::Comparator());
 543   loader::OutputBuffer buf;
 544   for (auto& e : entries) {
 545     auto* key = e.first;
 546     auto* value = e.second;
 547     auto uncompressedSize = value->mUncompressedSize;
 548     // Set the mHeaderOffsetInFile so we can go back and edit the offset.
 549     value->mHeaderOffsetInFile = buf.cursor();
 550     // Write a 0 offset/compressed size as a placeholder until we get the real
 551     // offset after compressing.
 552     buf.codeUint32(0);
 553     buf.codeUint32(0);
 554     buf.codeUint32(uncompressedSize);
 555     buf.codeString(*key);
 556   }
 557
 558   uint8_t headerSize[4];
 559   LittleEndian::writeUint32(headerSize, buf.cursor());
 560
 561   MOZ_TRY(Write(fd, MAGIC, sizeof(MAGIC)));
 562   MOZ_TRY(Write(fd, headerSize, sizeof(headerSize)));
 563   size_t headerStart = sizeof(MAGIC) + sizeof(headerSize);
 564   size_t dataStart = headerStart + buf.cursor();
 565   MOZ_TRY(Seek(fd, dataStart));
 566
 567   size_t offset = 0;
 568
 569   const size_t chunkSize = 1024 * 16;
 570   LZ4FrameCompressionContext ctx(6,         /* aCompressionLevel */
 571                                  chunkSize, /* aReadBufLen */
 572                                  true,      /* aChecksum */
 573                                  true);     /* aStableSrc */
 574   size_t writeBufLen = ctx.GetRequiredWriteBufferLength();
 575   auto writeBuffer = MakeUnique<char[]>(writeBufLen);
 576   auto writeSpan = Span(writeBuffer.get(), writeBufLen);
 577
 578   for (auto& e : entries) {
 579     auto value = e.second;
 580     value->mOffset = offset;
 581     Span<const char> result;
 582     MOZ_TRY_VAR(result,
 583                 ctx.BeginCompressing(writeSpan).mapErr(MapLZ4ErrorToNsresult));
 584     MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 585     offset += result.Length();
 586
 587     for (size_t i = 0; i < value->mUncompressedSize; i += chunkSize) {
 588       size_t size = std::min(chunkSize, value->mUncompressedSize - i);
 589       char* uncompressed = value->mData.get() + i;
 590       MOZ_TRY_VAR(result, ctx.ContinueCompressing(Span(uncompressed, size))
 591                               .mapErr(MapLZ4ErrorToNsresult));
 592       MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 593       offset += result.Length();
 594     }
 595
 596     MOZ_TRY_VAR(result, ctx.EndCompressing().mapErr(MapLZ4ErrorToNsresult));
 597     MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 598     offset += result.Length();
 599     value->mCompressedSize = offset - value->mOffset;
 600     MOZ_TRY(Seek(fd, dataStart + offset));
 601   }
 602
 603   for (auto& e : entries) {
 604     auto value = e.second;
 605     uint8_t* headerEntry = buf.Get() + value->mHeaderOffsetInFile;
 606     LittleEndian::writeUint32(headerEntry, value->mOffset);
 607     LittleEndian::writeUint32(headerEntry + sizeof(value->mOffset),
 608                               value->mCompressedSize);
 609   }
 610   MOZ_TRY(Seek(fd, headerStart));
 611   MOZ_TRY(Write(fd, buf.Get(), buf.cursor()));
 612
 613   mDirty = false;
 614   mWrittenOnce = true;
 615
 616   return Ok();
 617 }
 618
 619 void StartupCache::InvalidateCache(bool memoryOnly) {
 620   WaitOnPrefetch();
 621   // Ensure we're not writing using mTable...
 622   MutexAutoLock lock(mTableLock);
 623
 624   mWrittenOnce = false;
 625   if (memoryOnly) {
 626     // This should only be called in tests.
 627     auto writeResult = WriteToDisk();
 628     if (NS_WARN_IF(writeResult.isErr())) {
 629       gIgnoreDiskCache = true;
 630       return;
 631     }
 632   }
 633   if (mCurTableReferenced) {
 634     // There should be no way for this assert to fail other than a user manually
 635     // sending startupcache-invalidate messages through the Browser Toolbox. If
 636     // something knowingly invalidates the cache, the event can be counted with
 637     // mAllowedInvalidationsCount.
 638     MOZ_DIAGNOSTIC_ASSERT(
 639         xpc::IsInAutomation() ||
 640             // The allowed invalidations can grow faster than the old tables, so
 641             // guard against incorrect unsigned subtraction.
 642             mAllowedInvalidationsCount > mOldTables.Length() ||
 643             // Now perform the real check.
 644             mOldTables.Length() - mAllowedInvalidationsCount < 10,
 645         "Startup cache invalidated too many times.");
 646     mOldTables.AppendElement(std::move(mTable));
 647     mCurTableReferenced = false;
 648   } else {
 649     mTable.clear();
 650   }
 651   mRequestedCount = 0;
 652   if (!memoryOnly) {
 653     mCacheData.reset();
 654     nsresult rv = mFile->Remove(false);
 655     if (NS_FAILED(rv) && rv != NS_ERROR_FILE_NOT_FOUND) {
 656       gIgnoreDiskCache = true;
 657       return;
 658     }
 659   }
 660   gIgnoreDiskCache = false;
 661   auto result = LoadArchive();
 662   if (NS_WARN_IF(result.isErr())) {
 663     gIgnoreDiskCache = true;
 664   }
 665 }
 666
 667 void StartupCache::CountAllowedInvalidation() { mAllowedInvalidationsCount++; }
 668
 669 void StartupCache::MaybeInitShutdownWrite() {
 670   if (mTimer) {
 671     mTimer->Cancel();
 672   }
 673   gShutdownInitiated = true;
 674
 675   MaybeWriteOffMainThread();
 676 }
 677
 678 void StartupCache::EnsureShutdownWriteComplete() {
 679   MutexAutoLock lock(mTableLock);
 680   // If we've already written or there's nothing to write,
 681   // we don't need to do anything. This is the common case.
 682   if (mWrittenOnce || (mCacheData.initialized() && !ShouldCompactCache())) {
 683     return;
 684   }
 685   // Otherwise, ensure the write happens. The timer should have been cancelled
 686   // already in MaybeInitShutdownWrite.
 687
 688   // We got the lock. Keep the following in sync with
 689   // MaybeWriteOffMainThread:
 690   WaitOnPrefetch();
 691   mDirty = true;
 692   mCacheData.reset();
 693   // Most of this should be redundant given MaybeWriteOffMainThread should
 694   // have run before now.
 695
 696   auto writeResult = WriteToDisk();
 697   Unused << NS_WARN_IF(writeResult.isErr());
 698   // We've had the lock, and `WriteToDisk()` sets mWrittenOnce and mDirty
 699   // when done, and checks for them when starting, so we don't need to do
 700   // anything else.
 701 }
 702
 703 void StartupCache::IgnoreDiskCache() {
 704   gIgnoreDiskCache = true;
 705   if (gStartupCache) gStartupCache->InvalidateCache();
 706 }
 707
 708 bool StartupCache::GetIgnoreDiskCache() { return gIgnoreDiskCache; }
 709
 710 void StartupCache::WaitOnPrefetch() {
 711   // This can't be called from within ThreadedPrefetch()
 712   MonitorAutoLock lock(mPrefetchComplete);
 713   while (mPrefetchInProgress) {
 714     mPrefetchComplete.Wait();
 715   }
 716 }
 717
 718 void StartupCache::ThreadedPrefetch(uint8_t* aStart, size_t aSize) {
 719   // Always notify of completion, even if MMAP_FAULT_HANDLER_CATCH()
 720   // early-returns.
 721   auto notifyPrefetchComplete = MakeScopeExit([&] {
 722     MonitorAutoLock lock(mPrefetchComplete);
 723     mPrefetchInProgress = false;
 724     mPrefetchComplete.NotifyAll();
 725   });
 726
 727   // PrefetchMemory does madvise/equivalent, but doesn't access the memory
 728   // pointed to by aStart
 729   MMAP_FAULT_HANDLER_BEGIN_BUFFER(aStart, aSize)
 730   PrefetchMemory(aStart, aSize);
 731   MMAP_FAULT_HANDLER_CATCH()
 732 }
 733
 734 // mTableLock must be held
 735 bool StartupCache::ShouldCompactCache() {
 736   // If we've requested less than 4/5 of the startup cache, then we should
 737   // probably compact it down. This can happen quite easily after the first run,
 738   // which seems to request quite a few more things than subsequent runs.
 739   CheckedInt<uint32_t> threshold = CheckedInt<uint32_t>(mTable.count()) * 4 / 5;
 740   MOZ_RELEASE_ASSERT(threshold.isValid(), "Runaway StartupCache size");
 741   return mRequestedCount < threshold.value();
 742 }
 743
 744 /*
 745  * The write-thread is spawned on a timeout(which is reset with every write).
 746  * This can avoid a slow shutdown.
 747  */
 748 void StartupCache::WriteTimeout(nsITimer* aTimer, void* aClosure) {
 749   /*
 750    * It is safe to use the pointer passed in aClosure to reference the
 751    * StartupCache object because the timer's lifetime is tightly coupled to
 752    * the lifetime of the StartupCache object; this timer is canceled in the
 753    * StartupCache destructor, guaranteeing that this function runs if and only
 754    * if the StartupCache object is valid.
 755    */
 756   StartupCache* startupCacheObj = static_cast<StartupCache*>(aClosure);
 757   startupCacheObj->MaybeWriteOffMainThread();
 758 }
 759
 760 /*
 761  * See StartupCache::WriteTimeout above - this is just the non-static body.
 762  */
 763 void StartupCache::MaybeWriteOffMainThread() {
 764   {
 765     MutexAutoLock lock(mTableLock);
 766     if (mWrittenOnce || (mCacheData.initialized() && !ShouldCompactCache())) {
 767       return;
 768     }
 769   }
 770   // Keep this code in sync with EnsureShutdownWriteComplete.
 771   WaitOnPrefetch();
 772   {
 773     MutexAutoLock lock(mTableLock);
 774     mDirty = true;
 775     mCacheData.reset();
 776   }
 777
 778   RefPtr<StartupCache> self = this;
 779   nsCOMPtr<nsIRunnable> runnable =
 780       NS_NewRunnableFunction("StartupCache::Write", [self]() mutable {
 781         MutexAutoLock lock(self->mTableLock);
 782         auto result = self->WriteToDisk();
 783         Unused << NS_WARN_IF(result.isErr());
 784       });
 785   NS_DispatchBackgroundTask(runnable.forget(), NS_DISPATCH_EVENT_MAY_BLOCK);
 786 }
 787
 788 // We don't want to refcount StartupCache, so we'll just
 789 // hold a ref to this and pass it to observerService instead.
 790 NS_IMPL_ISUPPORTS(StartupCacheListener, nsIObserver)
 791
 792 nsresult StartupCacheListener::Observe(nsISupports* subject, const char* topic,
 793                                        const char16_t* data) {
 794   StartupCache* sc = StartupCache::GetSingleton();
 795   if (!sc) return NS_OK;
 796
 797   if (strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
 798     // Do not leave the thread running past xpcom shutdown
 799     sc->WaitOnPrefetch();
 800     StartupCache::gShutdownInitiated = true;
 801     // Note that we don't do anything special for the background write
 802     // task; we expect the threadpool to finish running any tasks already
 803     // posted to it prior to shutdown. FastShutdown will call
 804     // EnsureShutdownWriteComplete() to ensure any pending writes happen
 805     // in that case.
 806   } else if (strcmp(topic, "startupcache-invalidate") == 0) {
 807     sc->InvalidateCache(data && nsCRT::strcmp(data, u"memoryOnly") == 0);
 808   } else if (strcmp(topic, "intl:app-locales-changed") == 0) {
 809     // Live language switching invalidates the startup cache due to the history
 810     // sidebar retaining localized strings in its internal SQL query. This
 811     // should be a relatively rare event, but a user could do it an arbitrary
 812     // number of times.
 813     sc->CountAllowedInvalidation();
 814   }
 815   return NS_OK;
 816 }
 817
 818 nsresult StartupCache::GetDebugObjectOutputStream(
 819     nsIObjectOutputStream* aStream, nsIObjectOutputStream** aOutStream) {
 820   NS_ENSURE_ARG_POINTER(aStream);
 821 #ifdef DEBUG
 822   auto* stream = new StartupCacheDebugOutputStream(aStream, &mWriteObjectMap);
 823   NS_ADDREF(*aOutStream = stream);
 824 #else
 825   NS_ADDREF(*aOutStream = aStream);
 826 #endif
 827
 828   return NS_OK;
 829 }
 830
 831 nsresult StartupCache::ResetStartupWriteTimerCheckingReadCount() {
 832   nsresult rv = NS_OK;
 833   if (!mTimer)
 834     mTimer = NS_NewTimer();
 835   else
 836     rv = mTimer->Cancel();
 837   NS_ENSURE_SUCCESS(rv, rv);
 838   // Wait for the specified timeout, then write out the cache.
 839   mTimer->InitWithNamedFuncCallback(
 840       StartupCache::WriteTimeout, this, STARTUP_CACHE_WRITE_TIMEOUT * 1000,
 841       nsITimer::TYPE_ONE_SHOT, "StartupCache::WriteTimeout");
 842   return NS_OK;
 843 }
 844
 845 // For test code only
 846 nsresult StartupCache::ResetStartupWriteTimerAndLock() {
 847   MutexAutoLock lock(mTableLock);
 848   return ResetStartupWriteTimer();
 849 }
 850
 851 nsresult StartupCache::ResetStartupWriteTimer() {
 852   mDirty = true;
 853   nsresult rv = NS_OK;
 854   if (!mTimer)
 855     mTimer = NS_NewTimer();
 856   else
 857     rv = mTimer->Cancel();
 858   NS_ENSURE_SUCCESS(rv, rv);
 859   // Wait for the specified timeout, then write out the cache.
 860   mTimer->InitWithNamedFuncCallback(
 861       StartupCache::WriteTimeout, this, STARTUP_CACHE_WRITE_TIMEOUT * 1000,
 862       nsITimer::TYPE_ONE_SHOT, "StartupCache::WriteTimeout");
 863   return NS_OK;
 864 }
 865
 866 // Used only in tests:
 867 bool StartupCache::StartupWriteComplete() {
 868   // Need to have written to disk and not added new things since;
 869   MutexAutoLock lock(mTableLock);
 870   return !mDirty && mWrittenOnce;
 871 }
 872
 873 // StartupCacheDebugOutputStream implementation
 874 #ifdef DEBUG
 875 NS_IMPL_ISUPPORTS(StartupCacheDebugOutputStream, nsIObjectOutputStream,
 876                   nsIBinaryOutputStream, nsIOutputStream)
 877
 878 bool StartupCacheDebugOutputStream::CheckReferences(nsISupports* aObject) {
 879   nsresult rv;
 880
 881   nsCOMPtr<nsIClassInfo> classInfo = do_QueryInterface(aObject);
 882   if (!classInfo) {
 883     NS_ERROR("aObject must implement nsIClassInfo");
 884     return false;
 885   }
 886
 887   uint32_t flags;
 888   rv = classInfo->GetFlags(&flags);
 889   NS_ENSURE_SUCCESS(rv, false);
 890   if (flags & nsIClassInfo::SINGLETON) return true;
 891
 892   bool inserted = mObjectMap->EnsureInserted(aObject);
 893   if (!inserted) {
 894     NS_ERROR(
 895         "non-singleton aObject is referenced multiple times in this"
 896         "serialization, we don't support that.");
 897   }
 898
 899   return inserted;
 900 }
 901
 902 // nsIObjectOutputStream implementation
 903 nsresult StartupCacheDebugOutputStream::WriteObject(nsISupports* aObject,
 904                                                     bool aIsStrongRef) {
 905   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 906
 907   NS_ASSERTION(rootObject.get() == aObject,
 908                "bad call to WriteObject -- call WriteCompoundObject!");
 909   bool check = CheckReferences(aObject);
 910   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 911   return mBinaryStream->WriteObject(aObject, aIsStrongRef);
 912 }
 913
 914 nsresult StartupCacheDebugOutputStream::WriteSingleRefObject(
 915     nsISupports* aObject) {
 916   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 917
 918   NS_ASSERTION(rootObject.get() == aObject,
 919                "bad call to WriteSingleRefObject -- call WriteCompoundObject!");
 920   bool check = CheckReferences(aObject);
 921   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 922   return mBinaryStream->WriteSingleRefObject(aObject);
 923 }
 924
 925 nsresult StartupCacheDebugOutputStream::WriteCompoundObject(
 926     nsISupports* aObject, const nsIID& aIID, bool aIsStrongRef) {
 927   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 928
 929   nsCOMPtr<nsISupports> roundtrip;
 930   rootObject->QueryInterface(aIID, getter_AddRefs(roundtrip));
 931   NS_ASSERTION(roundtrip.get() == aObject,
 932                "bad aggregation or multiple inheritance detected by call to "
 933                "WriteCompoundObject!");
 934
 935   bool check = CheckReferences(aObject);
 936   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 937   return mBinaryStream->WriteCompoundObject(aObject, aIID, aIsStrongRef);
 938 }
 939
 940 nsresult StartupCacheDebugOutputStream::WriteID(nsID const& aID) {
 941   return mBinaryStream->WriteID(aID);
 942 }
 943
 944 char* StartupCacheDebugOutputStream::GetBuffer(uint32_t aLength,
 945                                                uint32_t aAlignMask) {
 946   return mBinaryStream->GetBuffer(aLength, aAlignMask);
 947 }
 948
 949 void StartupCacheDebugOutputStream::PutBuffer(char* aBuffer, uint32_t aLength) {
 950   mBinaryStream->PutBuffer(aBuffer, aLength);
 951 }
 952 #endif  // DEBUG
 953
 954 }  // namespace scache
 955 }  // namespace mozilla