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)
 370     MOZ_NO_THREAD_SAFETY_ANALYSIS {
 371   AUTO_PROFILER_LABEL("StartupCache::GetBuffer", OTHER);
 372
 373   NS_ASSERTION(NS_IsMainThread(),
 374                "Startup cache only available on main thread");
 375
 376   Telemetry::LABELS_STARTUP_CACHE_REQUESTS label =
 377       Telemetry::LABELS_STARTUP_CACHE_REQUESTS::Miss;
 378   auto telemetry =
 379       MakeScopeExit([&label] { Telemetry::AccumulateCategorical(label); });
 380
 381   decltype(mTable)::Ptr p = mTable.lookup(nsDependentCString(id));
 382   if (!p) {
 383     return NS_ERROR_NOT_AVAILABLE;
 384   }
 385
 386   auto& value = p->value();
 387   if (value.mData) {
 388     label = Telemetry::LABELS_STARTUP_CACHE_REQUESTS::HitMemory;
 389   } else {
 390     if (!mCacheData.initialized()) {
 391       return NS_ERROR_NOT_AVAILABLE;
 392     }
 393 #ifdef DEBUG
 394     // It should be impossible for a write to be pending here. This is because
 395     // we just checked mCacheData.initialized(), and this is reset before
 396     // writing to the cache. It's not re-initialized unless we call
 397     // LoadArchive(), either from Init() (which must have already happened) or
 398     // InvalidateCache(). InvalidateCache() locks the mutex, so a write can't be
 399     // happening. Really, we want to MOZ_ASSERT(!mTableLock.IsLocked()) here,
 400     // but there is no such method. So we hack around by attempting to gain the
 401     // lock. This should always succeed; if it fails, someone's broken the
 402     // assumptions.
 403     if (!mTableLock.TryLock()) {
 404       MOZ_ASSERT(false, "Could not gain mTableLock - should never happen!");
 405       return NS_ERROR_NOT_AVAILABLE;
 406     }
 407     mTableLock.Unlock();
 408 #endif
 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         InvalidateCache();
 427         return NS_ERROR_FAILURE;
 428       }
 429       auto decompressionResult = result.unwrap();
 430       totalRead += decompressionResult.mSizeRead;
 431       totalWritten += decompressionResult.mSizeWritten;
 432       finished = decompressionResult.mFinished;
 433     }
 434
 435     MMAP_FAULT_HANDLER_CATCH(NS_ERROR_FAILURE)
 436
 437     label = Telemetry::LABELS_STARTUP_CACHE_REQUESTS::HitDisk;
 438   }
 439
 440   if (!value.mRequested) {
 441     value.mRequested = true;
 442     value.mRequestedOrder = ++mRequestedCount;
 443     MOZ_ASSERT(mRequestedCount <= mTable.count(),
 444                "Somehow we requested more StartupCache items than exist.");
 445     ResetStartupWriteTimerCheckingReadCount();
 446   }
 447
 448   // Track that something holds a reference into mTable, so we know to hold
 449   // onto it in case the cache is invalidated.
 450   mCurTableReferenced = true;
 451   *outbuf = value.mData.get();
 452   *length = value.mUncompressedSize;
 453   return NS_OK;
 454 }
 455
 456 // Makes a copy of the buffer, client retains ownership of inbuf.
 457 nsresult StartupCache::PutBuffer(const char* id, UniqueFreePtr<char[]>&& inbuf,
 458                                  uint32_t len) MOZ_NO_THREAD_SAFETY_ANALYSIS {
 459   NS_ASSERTION(NS_IsMainThread(),
 460                "Startup cache only available on main thread");
 461   if (StartupCache::gShutdownInitiated) {
 462     return NS_ERROR_NOT_AVAILABLE;
 463   }
 464
 465   bool exists = mTable.has(nsDependentCString(id));
 466
 467   if (exists) {
 468     NS_WARNING("Existing entry in StartupCache.");
 469     // Double-caching is undesirable but not an error.
 470     return NS_OK;
 471   }
 472   // Try to gain the table write lock. If the background task to write the
 473   // cache is running, this will fail.
 474   if (!mTableLock.TryLock()) {
 475     return NS_ERROR_NOT_AVAILABLE;
 476   }
 477   auto lockGuard = MakeScopeExit([&] {
 478     mTableLock.AssertCurrentThreadOwns();
 479     mTableLock.Unlock();
 480   });
 481
 482   // putNew returns false on alloc failure - in the very unlikely event we hit
 483   // that and aren't going to crash elsewhere, there's no reason we need to
 484   // crash here.
 485   if (mTable.putNew(nsCString(id), StartupCacheEntry(std::move(inbuf), len,
 486                                                      ++mRequestedCount))) {
 487     return ResetStartupWriteTimer();
 488   }
 489   MOZ_DIAGNOSTIC_ASSERT(mTable.count() < STARTUP_CACHE_MAX_CAPACITY,
 490                         "Too many StartupCache entries.");
 491   return NS_OK;
 492 }
 493
 494 size_t StartupCache::HeapSizeOfIncludingThis(
 495     mozilla::MallocSizeOf aMallocSizeOf) const {
 496   // This function could measure more members, but they haven't been found by
 497   // DMD to be significant.  They can be added later if necessary.
 498
 499   size_t n = aMallocSizeOf(this);
 500
 501   n += mTable.shallowSizeOfExcludingThis(aMallocSizeOf);
 502   for (auto iter = mTable.iter(); !iter.done(); iter.next()) {
 503     if (iter.get().value().mData) {
 504       n += aMallocSizeOf(iter.get().value().mData.get());
 505     }
 506     n += iter.get().key().SizeOfExcludingThisIfUnshared(aMallocSizeOf);
 507   }
 508
 509   return n;
 510 }
 511
 512 /**
 513  * WriteToDisk writes the cache out to disk. Callers of WriteToDisk need to call
 514  * WaitOnWriteComplete to make sure there isn't a write
 515  * happening on another thread
 516  */
 517 Result<Ok, nsresult> StartupCache::WriteToDisk() {
 518   mTableLock.AssertCurrentThreadOwns();
 519
 520   if (!mDirty || mWrittenOnce) {
 521     return Ok();
 522   }
 523
 524   if (!mFile) {
 525     return Err(NS_ERROR_UNEXPECTED);
 526   }
 527
 528   AutoFDClose fd;
 529   MOZ_TRY(mFile->OpenNSPRFileDesc(PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE,
 530                                   0644, &fd.rwget()));
 531
 532   nsTArray<std::pair<const nsCString*, StartupCacheEntry*>> entries;
 533   for (auto iter = mTable.iter(); !iter.done(); iter.next()) {
 534     if (iter.get().value().mRequested) {
 535       entries.AppendElement(
 536           std::make_pair(&iter.get().key(), &iter.get().value()));
 537     }
 538   }
 539
 540   if (entries.IsEmpty()) {
 541     return Ok();
 542   }
 543
 544   entries.Sort(StartupCacheEntry::Comparator());
 545   loader::OutputBuffer buf;
 546   for (auto& e : entries) {
 547     auto key = e.first;
 548     auto value = e.second;
 549     auto uncompressedSize = value->mUncompressedSize;
 550     // Set the mHeaderOffsetInFile so we can go back and edit the offset.
 551     value->mHeaderOffsetInFile = buf.cursor();
 552     // Write a 0 offset/compressed size as a placeholder until we get the real
 553     // offset after compressing.
 554     buf.codeUint32(0);
 555     buf.codeUint32(0);
 556     buf.codeUint32(uncompressedSize);
 557     buf.codeString(*key);
 558   }
 559
 560   uint8_t headerSize[4];
 561   LittleEndian::writeUint32(headerSize, buf.cursor());
 562
 563   MOZ_TRY(Write(fd, MAGIC, sizeof(MAGIC)));
 564   MOZ_TRY(Write(fd, headerSize, sizeof(headerSize)));
 565   size_t headerStart = sizeof(MAGIC) + sizeof(headerSize);
 566   size_t dataStart = headerStart + buf.cursor();
 567   MOZ_TRY(Seek(fd, dataStart));
 568
 569   size_t offset = 0;
 570
 571   const size_t chunkSize = 1024 * 16;
 572   LZ4FrameCompressionContext ctx(6,         /* aCompressionLevel */
 573                                  chunkSize, /* aReadBufLen */
 574                                  true,      /* aChecksum */
 575                                  true);     /* aStableSrc */
 576   size_t writeBufLen = ctx.GetRequiredWriteBufferLength();
 577   auto writeBuffer = MakeUnique<char[]>(writeBufLen);
 578   auto writeSpan = Span(writeBuffer.get(), writeBufLen);
 579
 580   for (auto& e : entries) {
 581     auto value = e.second;
 582     value->mOffset = offset;
 583     Span<const char> result;
 584     MOZ_TRY_VAR(result,
 585                 ctx.BeginCompressing(writeSpan).mapErr(MapLZ4ErrorToNsresult));
 586     MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 587     offset += result.Length();
 588
 589     for (size_t i = 0; i < value->mUncompressedSize; i += chunkSize) {
 590       size_t size = std::min(chunkSize, value->mUncompressedSize - i);
 591       char* uncompressed = value->mData.get() + i;
 592       MOZ_TRY_VAR(result, ctx.ContinueCompressing(Span(uncompressed, size))
 593                               .mapErr(MapLZ4ErrorToNsresult));
 594       MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 595       offset += result.Length();
 596     }
 597
 598     MOZ_TRY_VAR(result, ctx.EndCompressing().mapErr(MapLZ4ErrorToNsresult));
 599     MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 600     offset += result.Length();
 601     value->mCompressedSize = offset - value->mOffset;
 602     MOZ_TRY(Seek(fd, dataStart + offset));
 603   }
 604
 605   for (auto& e : entries) {
 606     auto value = e.second;
 607     uint8_t* headerEntry = buf.Get() + value->mHeaderOffsetInFile;
 608     LittleEndian::writeUint32(headerEntry, value->mOffset);
 609     LittleEndian::writeUint32(headerEntry + sizeof(value->mOffset),
 610                               value->mCompressedSize);
 611   }
 612   MOZ_TRY(Seek(fd, headerStart));
 613   MOZ_TRY(Write(fd, buf.Get(), buf.cursor()));
 614
 615   mDirty = false;
 616   mWrittenOnce = true;
 617
 618   return Ok();
 619 }
 620
 621 void StartupCache::InvalidateCache(bool memoryOnly) {
 622   WaitOnPrefetchThread();
 623   // Ensure we're not writing using mTable...
 624   MutexAutoLock unlock(mTableLock);
 625
 626   mWrittenOnce = false;
 627   if (memoryOnly) {
 628     // This should only be called in tests.
 629     auto writeResult = WriteToDisk();
 630     if (NS_WARN_IF(writeResult.isErr())) {
 631       gIgnoreDiskCache = true;
 632       return;
 633     }
 634   }
 635   if (mCurTableReferenced) {
 636     // There should be no way for this assert to fail other than a user manually
 637     // sending startupcache-invalidate messages through the Browser Toolbox. If
 638     // something knowingly invalidates the cache, the event can be counted with
 639     // mAllowedInvalidationsCount.
 640     MOZ_DIAGNOSTIC_ASSERT(
 641         xpc::IsInAutomation() ||
 642             // The allowed invalidations can grow faster than the old tables, so
 643             // guard against incorrect unsigned subtraction.
 644             mAllowedInvalidationsCount > mOldTables.Length() ||
 645             // Now perform the real check.
 646             mOldTables.Length() - mAllowedInvalidationsCount < 10,
 647         "Startup cache invalidated too many times.");
 648     mOldTables.AppendElement(std::move(mTable));
 649     mCurTableReferenced = false;
 650   } else {
 651     mTable.clear();
 652   }
 653   mRequestedCount = 0;
 654   if (!memoryOnly) {
 655     mCacheData.reset();
 656     nsresult rv = mFile->Remove(false);
 657     if (NS_FAILED(rv) && rv != NS_ERROR_FILE_NOT_FOUND) {
 658       gIgnoreDiskCache = true;
 659       return;
 660     }
 661   }
 662   gIgnoreDiskCache = false;
 663   auto result = LoadArchive();
 664   if (NS_WARN_IF(result.isErr())) {
 665     gIgnoreDiskCache = true;
 666   }
 667 }
 668
 669 void StartupCache::CountAllowedInvalidation() { mAllowedInvalidationsCount++; }
 670
 671 void StartupCache::MaybeInitShutdownWrite() {
 672   if (mTimer) {
 673     mTimer->Cancel();
 674   }
 675   gShutdownInitiated = true;
 676
 677   MaybeWriteOffMainThread();
 678 }
 679
 680 void StartupCache::EnsureShutdownWriteComplete() {
 681   // If we've already written or there's nothing to write,
 682   // we don't need to do anything. This is the common case.
 683   if (mWrittenOnce || (mCacheData.initialized() && !ShouldCompactCache())) {
 684     return;
 685   }
 686   // Otherwise, ensure the write happens. The timer should have been cancelled
 687   // already in MaybeInitShutdownWrite.
 688   if (!mTableLock.TryLock()) {
 689     // Uh oh, we're writing away from the main thread. Wait to gain the lock,
 690     // to ensure the write completes.
 691     mTableLock.Lock();
 692   } else {
 693     // We got the lock. Keep the following in sync with
 694     // MaybeWriteOffMainThread:
 695     WaitOnPrefetchThread();
 696     mDirty = true;
 697     mCacheData.reset();
 698     // Most of this should be redundant given MaybeWriteOffMainThread should
 699     // have run before now.
 700
 701     auto writeResult = WriteToDisk();
 702     Unused << NS_WARN_IF(writeResult.isErr());
 703     // We've had the lock, and `WriteToDisk()` sets mWrittenOnce and mDirty
 704     // when done, and checks for them when starting, so we don't need to do
 705     // anything else.
 706   }
 707   mTableLock.Unlock();
 708 }
 709
 710 void StartupCache::IgnoreDiskCache() {
 711   gIgnoreDiskCache = true;
 712   if (gStartupCache) gStartupCache->InvalidateCache();
 713 }
 714
 715 void StartupCache::WaitOnPrefetchThread() {
 716   if (!mPrefetchThread || mPrefetchThread == PR_GetCurrentThread()) return;
 717
 718   PR_JoinThread(mPrefetchThread);
 719   mPrefetchThread = nullptr;
 720 }
 721
 722 void StartupCache::ThreadedPrefetch(void* aClosure) {
 723   AUTO_PROFILER_REGISTER_THREAD("StartupCache");
 724   NS_SetCurrentThreadName("StartupCache");
 725   mozilla::IOInterposer::RegisterCurrentThread();
 726   StartupCache* startupCacheObj = static_cast<StartupCache*>(aClosure);
 727   uint8_t* buf = startupCacheObj->mCacheData.get<uint8_t>().get();
 728   size_t size = startupCacheObj->mCacheData.size();
 729   MMAP_FAULT_HANDLER_BEGIN_BUFFER(buf, size)
 730   PrefetchMemory(buf, size);
 731   MMAP_FAULT_HANDLER_CATCH()
 732   mozilla::IOInterposer::UnregisterCurrentThread();
 733 }
 734
 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   if (mWrittenOnce) {
 765     return;
 766   }
 767
 768   if (mCacheData.initialized() && !ShouldCompactCache()) {
 769     return;
 770   }
 771
 772   // Keep this code in sync with EnsureShutdownWriteComplete.
 773   WaitOnPrefetchThread();
 774   mDirty = true;
 775   mCacheData.reset();
 776
 777   RefPtr<StartupCache> self = this;
 778   nsCOMPtr<nsIRunnable> runnable =
 779       NS_NewRunnableFunction("StartupCache::Write", [self]() mutable {
 780         MutexAutoLock unlock(self->mTableLock);
 781         auto result = self->WriteToDisk();
 782         Unused << NS_WARN_IF(result.isErr());
 783       });
 784   NS_DispatchBackgroundTask(runnable.forget(), NS_DISPATCH_EVENT_MAY_BLOCK);
 785 }
 786
 787 // We don't want to refcount StartupCache, so we'll just
 788 // hold a ref to this and pass it to observerService instead.
 789 NS_IMPL_ISUPPORTS(StartupCacheListener, nsIObserver)
 790
 791 nsresult StartupCacheListener::Observe(nsISupports* subject, const char* topic,
 792                                        const char16_t* data) {
 793   StartupCache* sc = StartupCache::GetSingleton();
 794   if (!sc) return NS_OK;
 795
 796   if (strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
 797     // Do not leave the thread running past xpcom shutdown
 798     sc->WaitOnPrefetchThread();
 799     StartupCache::gShutdownInitiated = true;
 800     // Note that we don't do anything special for the background write
 801     // task; we expect the threadpool to finish running any tasks already
 802     // posted to it prior to shutdown. FastShutdown will call
 803     // EnsureShutdownWriteComplete() to ensure any pending writes happen
 804     // in that case.
 805   } else if (strcmp(topic, "startupcache-invalidate") == 0) {
 806     sc->InvalidateCache(data && nsCRT::strcmp(data, u"memoryOnly") == 0);
 807   } else if (strcmp(topic, "intl:app-locales-changed") == 0) {
 808     // Live language switching invalidates the startup cache due to the history
 809     // sidebar retaining localized strings in its internal SQL query. This
 810     // should be a relatively rare event, but a user could do it an arbitrary
 811     // number of times.
 812     sc->CountAllowedInvalidation();
 813   }
 814   return NS_OK;
 815 }
 816
 817 nsresult StartupCache::GetDebugObjectOutputStream(
 818     nsIObjectOutputStream* aStream, nsIObjectOutputStream** aOutStream) {
 819   NS_ENSURE_ARG_POINTER(aStream);
 820 #ifdef DEBUG
 821   auto* stream = new StartupCacheDebugOutputStream(aStream, &mWriteObjectMap);
 822   NS_ADDREF(*aOutStream = stream);
 823 #else
 824   NS_ADDREF(*aOutStream = aStream);
 825 #endif
 826
 827   return NS_OK;
 828 }
 829
 830 nsresult StartupCache::ResetStartupWriteTimerCheckingReadCount() {
 831   nsresult rv = NS_OK;
 832   if (!mTimer)
 833     mTimer = NS_NewTimer();
 834   else
 835     rv = mTimer->Cancel();
 836   NS_ENSURE_SUCCESS(rv, rv);
 837   // Wait for the specified timeout, then write out the cache.
 838   mTimer->InitWithNamedFuncCallback(
 839       StartupCache::WriteTimeout, this, STARTUP_CACHE_WRITE_TIMEOUT * 1000,
 840       nsITimer::TYPE_ONE_SHOT, "StartupCache::WriteTimeout");
 841   return NS_OK;
 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   return !mDirty && mWrittenOnce;
 863 }
 864
 865 // StartupCacheDebugOutputStream implementation
 866 #ifdef DEBUG
 867 NS_IMPL_ISUPPORTS(StartupCacheDebugOutputStream, nsIObjectOutputStream,
 868                   nsIBinaryOutputStream, nsIOutputStream)
 869
 870 bool StartupCacheDebugOutputStream::CheckReferences(nsISupports* aObject) {
 871   nsresult rv;
 872
 873   nsCOMPtr<nsIClassInfo> classInfo = do_QueryInterface(aObject);
 874   if (!classInfo) {
 875     NS_ERROR("aObject must implement nsIClassInfo");
 876     return false;
 877   }
 878
 879   uint32_t flags;
 880   rv = classInfo->GetFlags(&flags);
 881   NS_ENSURE_SUCCESS(rv, false);
 882   if (flags & nsIClassInfo::SINGLETON) return true;
 883
 884   bool inserted = mObjectMap->EnsureInserted(aObject);
 885   if (!inserted) {
 886     NS_ERROR(
 887         "non-singleton aObject is referenced multiple times in this"
 888         "serialization, we don't support that.");
 889   }
 890
 891   return inserted;
 892 }
 893
 894 // nsIObjectOutputStream implementation
 895 nsresult StartupCacheDebugOutputStream::WriteObject(nsISupports* aObject,
 896                                                     bool aIsStrongRef) {
 897   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 898
 899   NS_ASSERTION(rootObject.get() == aObject,
 900                "bad call to WriteObject -- call WriteCompoundObject!");
 901   bool check = CheckReferences(aObject);
 902   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 903   return mBinaryStream->WriteObject(aObject, aIsStrongRef);
 904 }
 905
 906 nsresult StartupCacheDebugOutputStream::WriteSingleRefObject(
 907     nsISupports* aObject) {
 908   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 909
 910   NS_ASSERTION(rootObject.get() == aObject,
 911                "bad call to WriteSingleRefObject -- call WriteCompoundObject!");
 912   bool check = CheckReferences(aObject);
 913   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 914   return mBinaryStream->WriteSingleRefObject(aObject);
 915 }
 916
 917 nsresult StartupCacheDebugOutputStream::WriteCompoundObject(
 918     nsISupports* aObject, const nsIID& aIID, bool aIsStrongRef) {
 919   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 920
 921   nsCOMPtr<nsISupports> roundtrip;
 922   rootObject->QueryInterface(aIID, getter_AddRefs(roundtrip));
 923   NS_ASSERTION(roundtrip.get() == aObject,
 924                "bad aggregation or multiple inheritance detected by call to "
 925                "WriteCompoundObject!");
 926
 927   bool check = CheckReferences(aObject);
 928   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 929   return mBinaryStream->WriteCompoundObject(aObject, aIID, aIsStrongRef);
 930 }
 931
 932 nsresult StartupCacheDebugOutputStream::WriteID(nsID const& aID) {
 933   return mBinaryStream->WriteID(aID);
 934 }
 935
 936 char* StartupCacheDebugOutputStream::GetBuffer(uint32_t aLength,
 937                                                uint32_t aAlignMask) {
 938   return mBinaryStream->GetBuffer(aLength, aAlignMask);
 939 }
 940
 941 void StartupCacheDebugOutputStream::PutBuffer(char* aBuffer, uint32_t aLength) {
 942   mBinaryStream->PutBuffer(aBuffer, aLength);
 943 }
 944 #endif  // DEBUG
 945
 946 }  // namespace scache
 947 }  // namespace mozilla