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   MOZ_COLLECT_REPORT(
  69       "explicit/startup-cache/mapping", KIND_NONHEAP, UNITS_BYTES,
  70       mCacheData.nonHeapSizeOfExcludingThis(),
  71       "Memory used to hold the mapping of the startup cache from file. "
  72       "This memory is likely to be swapped out shortly after start-up.");
  73
  74   MOZ_COLLECT_REPORT("explicit/startup-cache/data", KIND_HEAP, UNITS_BYTES,
  75                      HeapSizeOfIncludingThis(StartupCacheMallocSizeOf),
  76                      "Memory used by the startup cache for things other than "
  77                      "the file mapping.");
  78
  79   return NS_OK;
  80 }
  81
  82 static const uint8_t MAGIC[] = "startupcache0002";
  83 // This is a heuristic value for how much to reserve for mTable to avoid
  84 // rehashing. This is not a hard limit in release builds, but it is in
  85 // debug builds as it should be stable. If we exceed this number we should
  86 // just increase it.
  87 static const size_t STARTUP_CACHE_RESERVE_CAPACITY = 450;
  88 // This is a hard limit which we will assert on, to ensure that we don't
  89 // have some bug causing runaway cache growth.
  90 static const size_t STARTUP_CACHE_MAX_CAPACITY = 5000;
  91
  92 // Not const because we change it for gtests.
  93 static uint8_t STARTUP_CACHE_WRITE_TIMEOUT = 60;
  94
  95 #define STARTUP_CACHE_NAME "startupCache." SC_WORDSIZE "." SC_ENDIAN
  96
  97 static inline Result<Ok, nsresult> Write(PRFileDesc* fd, const void* data,
  98                                          int32_t len) {
  99   if (PR_Write(fd, data, len) != len) {
 100     return Err(NS_ERROR_FAILURE);
 101   }
 102   return Ok();
 103 }
 104
 105 static inline Result<Ok, nsresult> Seek(PRFileDesc* fd, int32_t offset) {
 106   if (PR_Seek(fd, offset, PR_SEEK_SET) == -1) {
 107     return Err(NS_ERROR_FAILURE);
 108   }
 109   return Ok();
 110 }
 111
 112 static nsresult MapLZ4ErrorToNsresult(size_t aError) {
 113   return NS_ERROR_FAILURE;
 114 }
 115
 116 StartupCache* StartupCache::GetSingletonNoInit() {
 117   return StartupCache::gStartupCache;
 118 }
 119
 120 StartupCache* StartupCache::GetSingleton() {
 121 #ifdef MOZ_BACKGROUNDTASKS
 122   if (BackgroundTasks::IsBackgroundTaskMode()) {
 123     return nullptr;
 124   }
 125 #endif
 126
 127   if (!gStartupCache) {
 128     if (!XRE_IsParentProcess()) {
 129       return nullptr;
 130     }
 131 #ifdef MOZ_DISABLE_STARTUPCACHE
 132     return nullptr;
 133 #else
 134     StartupCache::InitSingleton();
 135 #endif
 136   }
 137
 138   return StartupCache::gStartupCache;
 139 }
 140
 141 void StartupCache::DeleteSingleton() { StartupCache::gStartupCache = nullptr; }
 142
 143 nsresult StartupCache::InitSingleton() {
 144   nsresult rv;
 145   StartupCache::gStartupCache = new StartupCache();
 146
 147   rv = StartupCache::gStartupCache->Init();
 148   if (NS_FAILED(rv)) {
 149     StartupCache::gStartupCache = nullptr;
 150   }
 151   return rv;
 152 }
 153
 154 StaticRefPtr<StartupCache> StartupCache::gStartupCache;
 155 bool StartupCache::gShutdownInitiated;
 156 bool StartupCache::gIgnoreDiskCache;
 157 bool StartupCache::gFoundDiskCacheOnInit;
 158
 159 NS_IMPL_ISUPPORTS(StartupCache, nsIMemoryReporter)
 160
 161 StartupCache::StartupCache()
 162     : mTableLock("StartupCache::mTableLock"),
 163       mDirty(false),
 164       mWrittenOnce(false),
 165       mCurTableReferenced(false),
 166       mRequestedCount(0),
 167       mCacheEntriesBaseOffset(0),
 168       mPrefetchThread(nullptr) {}
 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   auto result = LoadArchive();
 233   rv = result.isErr() ? result.unwrapErr() : NS_OK;
 234
 235   gFoundDiskCacheOnInit = rv != NS_ERROR_FILE_NOT_FOUND;
 236
 237   // Sometimes we don't have a cache yet, that's ok.
 238   // If it's corrupted, just remove it and start over.
 239   if (gIgnoreDiskCache || (NS_FAILED(rv) && rv != NS_ERROR_FILE_NOT_FOUND)) {
 240     NS_WARNING("Failed to load startupcache file correctly, removing!");
 241     InvalidateCache();
 242   }
 243
 244   RegisterWeakMemoryReporter(this);
 245   mDecompressionContext = MakeUnique<LZ4FrameDecompressionContext>(true);
 246
 247   return NS_OK;
 248 }
 249
 250 void StartupCache::StartPrefetchMemoryThread() {
 251   // XXX: It would be great for this to not create its own thread, unfortunately
 252   // there doesn't seem to be an existing thread that makes sense for this, so
 253   // barring a coordinated global scheduling system this is the best we get.
 254   mPrefetchThread = PR_CreateThread(
 255       PR_USER_THREAD, StartupCache::ThreadedPrefetch, this, PR_PRIORITY_NORMAL,
 256       PR_GLOBAL_THREAD, PR_JOINABLE_THREAD, 256 * 1024);
 257 }
 258
 259 /**
 260  * LoadArchive can only be called from the main thread.
 261  */
 262 Result<Ok, nsresult> StartupCache::LoadArchive() {
 263   MOZ_ASSERT(NS_IsMainThread(), "Can only load startup cache on main thread");
 264   if (gIgnoreDiskCache) return Err(NS_ERROR_FAILURE);
 265
 266   MOZ_TRY(mCacheData.init(mFile));
 267   auto size = mCacheData.size();
 268   if (CanPrefetchMemory()) {
 269     StartPrefetchMemoryThread();
 270   }
 271
 272   uint32_t headerSize;
 273   if (size < sizeof(MAGIC) + sizeof(headerSize)) {
 274     return Err(NS_ERROR_UNEXPECTED);
 275   }
 276
 277   auto data = mCacheData.get<uint8_t>();
 278   auto end = data + size;
 279
 280   MMAP_FAULT_HANDLER_BEGIN_BUFFER(data.get(), size)
 281
 282   if (memcmp(MAGIC, data.get(), sizeof(MAGIC))) {
 283     return Err(NS_ERROR_UNEXPECTED);
 284   }
 285   data += sizeof(MAGIC);
 286
 287   headerSize = LittleEndian::readUint32(data.get());
 288   data += sizeof(headerSize);
 289
 290   if (headerSize > end - data) {
 291     MOZ_ASSERT(false, "StartupCache file is corrupt.");
 292     return Err(NS_ERROR_UNEXPECTED);
 293   }
 294
 295   Range<uint8_t> header(data, data + headerSize);
 296   data += headerSize;
 297
 298   mCacheEntriesBaseOffset = sizeof(MAGIC) + sizeof(headerSize) + headerSize;
 299   {
 300     if (!mTable.reserve(STARTUP_CACHE_RESERVE_CAPACITY)) {
 301       return Err(NS_ERROR_UNEXPECTED);
 302     }
 303     auto cleanup = MakeScopeExit([&]() {
 304       WaitOnPrefetchThread();
 305       mTable.clear();
 306       mCacheData.reset();
 307     });
 308     loader::InputBuffer buf(header);
 309
 310     uint32_t currentOffset = 0;
 311     while (!buf.finished()) {
 312       uint32_t offset = 0;
 313       uint32_t compressedSize = 0;
 314       uint32_t uncompressedSize = 0;
 315       nsCString key;
 316       buf.codeUint32(offset);
 317       buf.codeUint32(compressedSize);
 318       buf.codeUint32(uncompressedSize);
 319       buf.codeString(key);
 320
 321       if (offset + compressedSize > end - data) {
 322         MOZ_ASSERT(false, "StartupCache file is corrupt.");
 323         return Err(NS_ERROR_UNEXPECTED);
 324       }
 325
 326       // Make sure offsets match what we'd expect based on script ordering and
 327       // size, as a basic sanity check.
 328       if (offset != currentOffset) {
 329         return Err(NS_ERROR_UNEXPECTED);
 330       }
 331       currentOffset += compressedSize;
 332
 333       // We could use mTable.putNew if we knew the file we're loading weren't
 334       // corrupt. However, we don't know that, so check if the key already
 335       // exists. If it does, we know the file must be corrupt.
 336       decltype(mTable)::AddPtr p = mTable.lookupForAdd(key);
 337       if (p) {
 338         return Err(NS_ERROR_UNEXPECTED);
 339       }
 340
 341       if (!mTable.add(
 342               p, key,
 343               StartupCacheEntry(offset, compressedSize, uncompressedSize))) {
 344         return Err(NS_ERROR_UNEXPECTED);
 345       }
 346     }
 347
 348     if (buf.error()) {
 349       return Err(NS_ERROR_UNEXPECTED);
 350     }
 351
 352     cleanup.release();
 353   }
 354
 355   MMAP_FAULT_HANDLER_CATCH(Err(NS_ERROR_UNEXPECTED))
 356
 357   return Ok();
 358 }
 359
 360 bool StartupCache::HasEntry(const char* id) {
 361   AUTO_PROFILER_LABEL("StartupCache::HasEntry", OTHER);
 362
 363   MOZ_ASSERT(NS_IsMainThread(), "Startup cache only available on main thread");
 364
 365   return mTable.has(nsDependentCString(id));
 366 }
 367
 368 nsresult StartupCache::GetBuffer(const char* id, const char** outbuf,
 369                                  uint32_t* length) NO_THREAD_SAFETY_ANALYSIS {
 370   AUTO_PROFILER_LABEL("StartupCache::GetBuffer", OTHER);
 371
 372   NS_ASSERTION(NS_IsMainThread(),
 373                "Startup cache only available on main thread");
 374
 375   Telemetry::LABELS_STARTUP_CACHE_REQUESTS label =
 376       Telemetry::LABELS_STARTUP_CACHE_REQUESTS::Miss;
 377   auto telemetry =
 378       MakeScopeExit([&label] { Telemetry::AccumulateCategorical(label); });
 379
 380   decltype(mTable)::Ptr p = mTable.lookup(nsDependentCString(id));
 381   if (!p) {
 382     return NS_ERROR_NOT_AVAILABLE;
 383   }
 384
 385   auto& value = p->value();
 386   if (value.mData) {
 387     label = Telemetry::LABELS_STARTUP_CACHE_REQUESTS::HitMemory;
 388   } else {
 389     if (!mCacheData.initialized()) {
 390       return NS_ERROR_NOT_AVAILABLE;
 391     }
 392 #ifdef DEBUG
 393     // It should be impossible for a write to be pending here. This is because
 394     // we just checked mCacheData.initialized(), and this is reset before
 395     // writing to the cache. It's not re-initialized unless we call
 396     // LoadArchive(), either from Init() (which must have already happened) or
 397     // InvalidateCache(). InvalidateCache() locks the mutex, so a write can't be
 398     // happening. Really, we want to MOZ_ASSERT(!mTableLock.IsLocked()) here,
 399     // but there is no such method. So we hack around by attempting to gain the
 400     // lock. This should always succeed; if it fails, someone's broken the
 401     // assumptions.
 402     if (!mTableLock.TryLock()) {
 403       MOZ_ASSERT(false, "Could not gain mTableLock - should never happen!");
 404       return NS_ERROR_NOT_AVAILABLE;
 405     }
 406     mTableLock.Unlock();
 407 #endif
 408
 409     size_t totalRead = 0;
 410     size_t totalWritten = 0;
 411     Span<const char> compressed = Span(
 412         mCacheData.get<char>().get() + mCacheEntriesBaseOffset + value.mOffset,
 413         value.mCompressedSize);
 414     value.mData = MakeUnique<char[]>(value.mUncompressedSize);
 415     Span<char> uncompressed = Span(value.mData.get(), value.mUncompressedSize);
 416     MMAP_FAULT_HANDLER_BEGIN_BUFFER(uncompressed.Elements(),
 417                                     uncompressed.Length())
 418     bool finished = false;
 419     while (!finished) {
 420       auto result = mDecompressionContext->Decompress(
 421           uncompressed.From(totalWritten), compressed.From(totalRead));
 422       if (NS_WARN_IF(result.isErr())) {
 423         value.mData = nullptr;
 424         InvalidateCache();
 425         return NS_ERROR_FAILURE;
 426       }
 427       auto decompressionResult = result.unwrap();
 428       totalRead += decompressionResult.mSizeRead;
 429       totalWritten += decompressionResult.mSizeWritten;
 430       finished = decompressionResult.mFinished;
 431     }
 432
 433     MMAP_FAULT_HANDLER_CATCH(NS_ERROR_FAILURE)
 434
 435     label = Telemetry::LABELS_STARTUP_CACHE_REQUESTS::HitDisk;
 436   }
 437
 438   if (!value.mRequested) {
 439     value.mRequested = true;
 440     value.mRequestedOrder = ++mRequestedCount;
 441     MOZ_ASSERT(mRequestedCount <= mTable.count(),
 442                "Somehow we requested more StartupCache items than exist.");
 443     ResetStartupWriteTimerCheckingReadCount();
 444   }
 445
 446   // Track that something holds a reference into mTable, so we know to hold
 447   // onto it in case the cache is invalidated.
 448   mCurTableReferenced = true;
 449   *outbuf = value.mData.get();
 450   *length = value.mUncompressedSize;
 451   return NS_OK;
 452 }
 453
 454 // Makes a copy of the buffer, client retains ownership of inbuf.
 455 nsresult StartupCache::PutBuffer(const char* id, UniquePtr<char[]>&& inbuf,
 456                                  uint32_t len) NO_THREAD_SAFETY_ANALYSIS {
 457   NS_ASSERTION(NS_IsMainThread(),
 458                "Startup cache only available on main thread");
 459   if (StartupCache::gShutdownInitiated) {
 460     return NS_ERROR_NOT_AVAILABLE;
 461   }
 462
 463   bool exists = mTable.has(nsDependentCString(id));
 464
 465   if (exists) {
 466     NS_WARNING("Existing entry in StartupCache.");
 467     // Double-caching is undesirable but not an error.
 468     return NS_OK;
 469   }
 470   // Try to gain the table write lock. If the background task to write the
 471   // cache is running, this will fail.
 472   if (!mTableLock.TryLock()) {
 473     return NS_ERROR_NOT_AVAILABLE;
 474   }
 475   auto lockGuard = MakeScopeExit([&] {
 476     mTableLock.AssertCurrentThreadOwns();
 477     mTableLock.Unlock();
 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  */
 515 Result<Ok, nsresult> StartupCache::WriteToDisk() {
 516   mTableLock.AssertCurrentThreadOwns();
 517
 518   if (!mDirty || mWrittenOnce) {
 519     return Ok();
 520   }
 521
 522   if (!mFile) {
 523     return Err(NS_ERROR_UNEXPECTED);
 524   }
 525
 526   AutoFDClose fd;
 527   MOZ_TRY(mFile->OpenNSPRFileDesc(PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE,
 528                                   0644, &fd.rwget()));
 529
 530   nsTArray<std::pair<const nsCString*, StartupCacheEntry*>> entries;
 531   for (auto iter = mTable.iter(); !iter.done(); iter.next()) {
 532     if (iter.get().value().mRequested) {
 533       entries.AppendElement(
 534           std::make_pair(&iter.get().key(), &iter.get().value()));
 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   WaitOnPrefetchThread();
 621   // Ensure we're not writing using mTable...
 622   MutexAutoLock unlock(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_TARGET_DOES_NOT_EXIST &&
 656         rv != NS_ERROR_FILE_NOT_FOUND) {
 657       gIgnoreDiskCache = true;
 658       return;
 659     }
 660   }
 661   gIgnoreDiskCache = false;
 662   auto result = LoadArchive();
 663   if (NS_WARN_IF(result.isErr())) {
 664     gIgnoreDiskCache = true;
 665   }
 666 }
 667
 668 void StartupCache::CountAllowedInvalidation() { mAllowedInvalidationsCount++; }
 669
 670 void StartupCache::MaybeInitShutdownWrite() {
 671   if (mTimer) {
 672     mTimer->Cancel();
 673   }
 674   gShutdownInitiated = true;
 675
 676   MaybeWriteOffMainThread();
 677 }
 678
 679 void StartupCache::EnsureShutdownWriteComplete() {
 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   if (!mTableLock.TryLock()) {
 688     // Uh oh, we're writing away from the main thread. Wait to gain the lock,
 689     // to ensure the write completes.
 690     mTableLock.Lock();
 691   } else {
 692     // We got the lock. Keep the following in sync with
 693     // MaybeWriteOffMainThread:
 694     WaitOnPrefetchThread();
 695     mDirty = true;
 696     mCacheData.reset();
 697     // Most of this should be redundant given MaybeWriteOffMainThread should
 698     // have run before now.
 699
 700     auto writeResult = WriteToDisk();
 701     Unused << NS_WARN_IF(writeResult.isErr());
 702     // We've had the lock, and `WriteToDisk()` sets mWrittenOnce and mDirty
 703     // when done, and checks for them when starting, so we don't need to do
 704     // anything else.
 705   }
 706   mTableLock.Unlock();
 707 }
 708
 709 void StartupCache::IgnoreDiskCache() {
 710   gIgnoreDiskCache = true;
 711   if (gStartupCache) gStartupCache->InvalidateCache();
 712 }
 713
 714 void StartupCache::WaitOnPrefetchThread() {
 715   if (!mPrefetchThread || mPrefetchThread == PR_GetCurrentThread()) return;
 716
 717   PR_JoinThread(mPrefetchThread);
 718   mPrefetchThread = nullptr;
 719 }
 720
 721 void StartupCache::ThreadedPrefetch(void* aClosure) {
 722   AUTO_PROFILER_REGISTER_THREAD("StartupCache");
 723   NS_SetCurrentThreadName("StartupCache");
 724   mozilla::IOInterposer::RegisterCurrentThread();
 725   StartupCache* startupCacheObj = static_cast<StartupCache*>(aClosure);
 726   uint8_t* buf = startupCacheObj->mCacheData.get<uint8_t>().get();
 727   size_t size = startupCacheObj->mCacheData.size();
 728   MMAP_FAULT_HANDLER_BEGIN_BUFFER(buf, size)
 729   PrefetchMemory(buf, size);
 730   MMAP_FAULT_HANDLER_CATCH()
 731   mozilla::IOInterposer::UnregisterCurrentThread();
 732 }
 733
 734 bool StartupCache::ShouldCompactCache() {
 735   // If we've requested less than 4/5 of the startup cache, then we should
 736   // probably compact it down. This can happen quite easily after the first run,
 737   // which seems to request quite a few more things than subsequent runs.
 738   CheckedInt<uint32_t> threshold = CheckedInt<uint32_t>(mTable.count()) * 4 / 5;
 739   MOZ_RELEASE_ASSERT(threshold.isValid(), "Runaway StartupCache size");
 740   return mRequestedCount < threshold.value();
 741 }
 742
 743 /*
 744  * The write-thread is spawned on a timeout(which is reset with every write).
 745  * This can avoid a slow shutdown.
 746  */
 747 void StartupCache::WriteTimeout(nsITimer* aTimer, void* aClosure) {
 748   /*
 749    * It is safe to use the pointer passed in aClosure to reference the
 750    * StartupCache object because the timer's lifetime is tightly coupled to
 751    * the lifetime of the StartupCache object; this timer is canceled in the
 752    * StartupCache destructor, guaranteeing that this function runs if and only
 753    * if the StartupCache object is valid.
 754    */
 755   StartupCache* startupCacheObj = static_cast<StartupCache*>(aClosure);
 756   startupCacheObj->MaybeWriteOffMainThread();
 757 }
 758
 759 /*
 760  * See StartupCache::WriteTimeout above - this is just the non-static body.
 761  */
 762 void StartupCache::MaybeWriteOffMainThread() {
 763   if (mWrittenOnce) {
 764     return;
 765   }
 766
 767   if (mCacheData.initialized() && !ShouldCompactCache()) {
 768     return;
 769   }
 770
 771   // Keep this code in sync with EnsureShutdownWriteComplete.
 772   WaitOnPrefetchThread();
 773   mDirty = true;
 774   mCacheData.reset();
 775
 776   RefPtr<StartupCache> self = this;
 777   nsCOMPtr<nsIRunnable> runnable =
 778       NS_NewRunnableFunction("StartupCache::Write", [self]() mutable {
 779         MutexAutoLock unlock(self->mTableLock);
 780         auto result = self->WriteToDisk();
 781         Unused << NS_WARN_IF(result.isErr());
 782       });
 783   NS_DispatchBackgroundTask(runnable.forget(), NS_DISPATCH_EVENT_MAY_BLOCK);
 784 }
 785
 786 // We don't want to refcount StartupCache, so we'll just
 787 // hold a ref to this and pass it to observerService instead.
 788 NS_IMPL_ISUPPORTS(StartupCacheListener, nsIObserver)
 789
 790 nsresult StartupCacheListener::Observe(nsISupports* subject, const char* topic,
 791                                        const char16_t* data) {
 792   StartupCache* sc = StartupCache::GetSingleton();
 793   if (!sc) return NS_OK;
 794
 795   if (strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
 796     // Do not leave the thread running past xpcom shutdown
 797     sc->WaitOnPrefetchThread();
 798     StartupCache::gShutdownInitiated = true;
 799     // Note that we don't do anything special for the background write
 800     // task; we expect the threadpool to finish running any tasks already
 801     // posted to it prior to shutdown. FastShutdown will call
 802     // EnsureShutdownWriteComplete() to ensure any pending writes happen
 803     // in that case.
 804   } else if (strcmp(topic, "startupcache-invalidate") == 0) {
 805     sc->InvalidateCache(data && nsCRT::strcmp(data, u"memoryOnly") == 0);
 806   } else if (strcmp(topic, "intl:app-locales-changed") == 0) {
 807     // Live language switching invalidates the startup cache due to the history
 808     // sidebar retaining localized strings in its internal SQL query. This
 809     // should be a relatively rare event, but a user could do it an arbitrary
 810     // number of times.
 811     sc->CountAllowedInvalidation();
 812   }
 813   return NS_OK;
 814 }
 815
 816 nsresult StartupCache::GetDebugObjectOutputStream(
 817     nsIObjectOutputStream* aStream, nsIObjectOutputStream** aOutStream) {
 818   NS_ENSURE_ARG_POINTER(aStream);
 819 #ifdef DEBUG
 820   auto* stream = new StartupCacheDebugOutputStream(aStream, &mWriteObjectMap);
 821   NS_ADDREF(*aOutStream = stream);
 822 #else
 823   NS_ADDREF(*aOutStream = aStream);
 824 #endif
 825
 826   return NS_OK;
 827 }
 828
 829 nsresult StartupCache::ResetStartupWriteTimerCheckingReadCount() {
 830   nsresult rv = NS_OK;
 831   if (!mTimer)
 832     mTimer = NS_NewTimer();
 833   else
 834     rv = mTimer->Cancel();
 835   NS_ENSURE_SUCCESS(rv, rv);
 836   // Wait for the specified timeout, then write out the cache.
 837   mTimer->InitWithNamedFuncCallback(
 838       StartupCache::WriteTimeout, this, STARTUP_CACHE_WRITE_TIMEOUT * 1000,
 839       nsITimer::TYPE_ONE_SHOT, "StartupCache::WriteTimeout");
 840   return NS_OK;
 841 }
 842
 843 nsresult StartupCache::ResetStartupWriteTimer() {
 844   mDirty = true;
 845   nsresult rv = NS_OK;
 846   if (!mTimer)
 847     mTimer = NS_NewTimer();
 848   else
 849     rv = mTimer->Cancel();
 850   NS_ENSURE_SUCCESS(rv, rv);
 851   // Wait for the specified timeout, then write out the cache.
 852   mTimer->InitWithNamedFuncCallback(
 853       StartupCache::WriteTimeout, this, STARTUP_CACHE_WRITE_TIMEOUT * 1000,
 854       nsITimer::TYPE_ONE_SHOT, "StartupCache::WriteTimeout");
 855   return NS_OK;
 856 }
 857
 858 // Used only in tests:
 859 bool StartupCache::StartupWriteComplete() {
 860   // Need to have written to disk and not added new things since;
 861   return !mDirty && mWrittenOnce;
 862 }
 863
 864 // StartupCacheDebugOutputStream implementation
 865 #ifdef DEBUG
 866 NS_IMPL_ISUPPORTS(StartupCacheDebugOutputStream, nsIObjectOutputStream,
 867                   nsIBinaryOutputStream, nsIOutputStream)
 868
 869 bool StartupCacheDebugOutputStream::CheckReferences(nsISupports* aObject) {
 870   nsresult rv;
 871
 872   nsCOMPtr<nsIClassInfo> classInfo = do_QueryInterface(aObject);
 873   if (!classInfo) {
 874     NS_ERROR("aObject must implement nsIClassInfo");
 875     return false;
 876   }
 877
 878   uint32_t flags;
 879   rv = classInfo->GetFlags(&flags);
 880   NS_ENSURE_SUCCESS(rv, false);
 881   if (flags & nsIClassInfo::SINGLETON) return true;
 882
 883   bool inserted = mObjectMap->EnsureInserted(aObject);
 884   if (!inserted) {
 885     NS_ERROR(
 886         "non-singleton aObject is referenced multiple times in this"
 887         "serialization, we don't support that.");
 888   }
 889
 890   return inserted;
 891 }
 892
 893 // nsIObjectOutputStream implementation
 894 nsresult StartupCacheDebugOutputStream::WriteObject(nsISupports* aObject,
 895                                                     bool aIsStrongRef) {
 896   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 897
 898   NS_ASSERTION(rootObject.get() == aObject,
 899                "bad call to WriteObject -- call WriteCompoundObject!");
 900   bool check = CheckReferences(aObject);
 901   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 902   return mBinaryStream->WriteObject(aObject, aIsStrongRef);
 903 }
 904
 905 nsresult StartupCacheDebugOutputStream::WriteSingleRefObject(
 906     nsISupports* aObject) {
 907   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 908
 909   NS_ASSERTION(rootObject.get() == aObject,
 910                "bad call to WriteSingleRefObject -- call WriteCompoundObject!");
 911   bool check = CheckReferences(aObject);
 912   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 913   return mBinaryStream->WriteSingleRefObject(aObject);
 914 }
 915
 916 nsresult StartupCacheDebugOutputStream::WriteCompoundObject(
 917     nsISupports* aObject, const nsIID& aIID, bool aIsStrongRef) {
 918   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 919
 920   nsCOMPtr<nsISupports> roundtrip;
 921   rootObject->QueryInterface(aIID, getter_AddRefs(roundtrip));
 922   NS_ASSERTION(roundtrip.get() == aObject,
 923                "bad aggregation or multiple inheritance detected by call to "
 924                "WriteCompoundObject!");
 925
 926   bool check = CheckReferences(aObject);
 927   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 928   return mBinaryStream->WriteCompoundObject(aObject, aIID, aIsStrongRef);
 929 }
 930
 931 nsresult StartupCacheDebugOutputStream::WriteID(nsID const& aID) {
 932   return mBinaryStream->WriteID(aID);
 933 }
 934
 935 char* StartupCacheDebugOutputStream::GetBuffer(uint32_t aLength,
 936                                                uint32_t aAlignMask) {
 937   return mBinaryStream->GetBuffer(aLength, aAlignMask);
 938 }
 939
 940 void StartupCacheDebugOutputStream::PutBuffer(char* aBuffer, uint32_t aLength) {
 941   mBinaryStream->PutBuffer(aBuffer, aLength);
 942 }
 943 #endif  // DEBUG
 944
 945 }  // namespace scache
 946 }  // namespace mozilla