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   mTableLock.AssertCurrentThreadOwns();
 272
 273   MOZ_TRY(mCacheData.init(mFile));
 274   auto size = mCacheData.size();
 275   if (CanPrefetchMemory()) {
 276     StartPrefetchMemory();
 277   }
 278
 279   uint32_t headerSize;
 280   if (size < sizeof(MAGIC) + sizeof(headerSize)) {
 281     return Err(NS_ERROR_UNEXPECTED);
 282   }
 283
 284   auto data = mCacheData.get<uint8_t>();
 285   auto end = data + size;
 286
 287   MMAP_FAULT_HANDLER_BEGIN_BUFFER(data.get(), size)
 288
 289   if (memcmp(MAGIC, data.get(), sizeof(MAGIC))) {
 290     return Err(NS_ERROR_UNEXPECTED);
 291   }
 292   data += sizeof(MAGIC);
 293
 294   headerSize = LittleEndian::readUint32(data.get());
 295   data += sizeof(headerSize);
 296
 297   if (headerSize > end - data) {
 298     MOZ_ASSERT(false, "StartupCache file is corrupt.");
 299     return Err(NS_ERROR_UNEXPECTED);
 300   }
 301
 302   Range<uint8_t> header(data, data + headerSize);
 303   data += headerSize;
 304
 305   mCacheEntriesBaseOffset = sizeof(MAGIC) + sizeof(headerSize) + headerSize;
 306   {
 307     if (!mTable.reserve(STARTUP_CACHE_RESERVE_CAPACITY)) {
 308       return Err(NS_ERROR_UNEXPECTED);
 309     }
 310     auto cleanup = MakeScopeExit([&]() {
 311       mTableLock.AssertCurrentThreadOwns();
 312       WaitOnPrefetch();
 313       mTable.clear();
 314       mCacheData.reset();
 315     });
 316     loader::InputBuffer buf(header);
 317
 318     uint32_t currentOffset = 0;
 319     while (!buf.finished()) {
 320       uint32_t offset = 0;
 321       uint32_t compressedSize = 0;
 322       uint32_t uncompressedSize = 0;
 323       nsCString key;
 324       buf.codeUint32(offset);
 325       buf.codeUint32(compressedSize);
 326       buf.codeUint32(uncompressedSize);
 327       buf.codeString(key);
 328
 329       if (offset + compressedSize > end - data) {
 330         MOZ_ASSERT(false, "StartupCache file is corrupt.");
 331         return Err(NS_ERROR_UNEXPECTED);
 332       }
 333
 334       // Make sure offsets match what we'd expect based on script ordering and
 335       // size, as a basic sanity check.
 336       if (offset != currentOffset) {
 337         return Err(NS_ERROR_UNEXPECTED);
 338       }
 339       currentOffset += compressedSize;
 340
 341       // We could use mTable.putNew if we knew the file we're loading weren't
 342       // corrupt. However, we don't know that, so check if the key already
 343       // exists. If it does, we know the file must be corrupt.
 344       decltype(mTable)::AddPtr p = mTable.lookupForAdd(key);
 345       if (p) {
 346         return Err(NS_ERROR_UNEXPECTED);
 347       }
 348
 349       if (!mTable.add(
 350               p, key,
 351               StartupCacheEntry(offset, compressedSize, uncompressedSize))) {
 352         return Err(NS_ERROR_UNEXPECTED);
 353       }
 354     }
 355
 356     if (buf.error()) {
 357       return Err(NS_ERROR_UNEXPECTED);
 358     }
 359
 360     cleanup.release();
 361   }
 362
 363   MMAP_FAULT_HANDLER_CATCH(Err(NS_ERROR_UNEXPECTED))
 364
 365   return Ok();
 366 }
 367
 368 bool StartupCache::HasEntry(const char* id) {
 369   AUTO_PROFILER_LABEL("StartupCache::HasEntry", OTHER);
 370
 371   MOZ_ASSERT(NS_IsMainThread(), "Startup cache only available on main thread");
 372
 373   MutexAutoLock lock(mTableLock);
 374   return mTable.has(nsDependentCString(id));
 375 }
 376
 377 nsresult StartupCache::GetBuffer(const char* id, const char** outbuf,
 378                                  uint32_t* length)
 379     MOZ_NO_THREAD_SAFETY_ANALYSIS {
 380   AUTO_PROFILER_LABEL("StartupCache::GetBuffer", OTHER);
 381
 382   NS_ASSERTION(NS_IsMainThread(),
 383                "Startup cache only available on main thread");
 384
 385   Telemetry::LABELS_STARTUP_CACHE_REQUESTS label =
 386       Telemetry::LABELS_STARTUP_CACHE_REQUESTS::Miss;
 387   auto telemetry =
 388       MakeScopeExit([&label] { Telemetry::AccumulateCategorical(label); });
 389
 390   MutexAutoLock lock(mTableLock);
 391   decltype(mTable)::Ptr p = mTable.lookup(nsDependentCString(id));
 392   if (!p) {
 393     return NS_ERROR_NOT_AVAILABLE;
 394   }
 395
 396   auto& value = p->value();
 397   if (value.mData) {
 398     label = Telemetry::LABELS_STARTUP_CACHE_REQUESTS::HitMemory;
 399   } else {
 400     if (!mCacheData.initialized()) {
 401       return NS_ERROR_NOT_AVAILABLE;
 402     }
 403
 404     size_t totalRead = 0;
 405     size_t totalWritten = 0;
 406     Span<const char> compressed = Span(
 407         mCacheData.get<char>().get() + mCacheEntriesBaseOffset + value.mOffset,
 408         value.mCompressedSize);
 409     value.mData = UniqueFreePtr<char[]>(reinterpret_cast<char*>(
 410         malloc(sizeof(char) * value.mUncompressedSize)));
 411     Span<char> uncompressed = Span(value.mData.get(), value.mUncompressedSize);
 412     MMAP_FAULT_HANDLER_BEGIN_BUFFER(uncompressed.Elements(),
 413                                     uncompressed.Length())
 414     bool finished = false;
 415     while (!finished) {
 416       auto result = mDecompressionContext->Decompress(
 417           uncompressed.From(totalWritten), compressed.From(totalRead));
 418       if (NS_WARN_IF(result.isErr())) {
 419         value.mData = nullptr;
 420         MutexAutoUnlock unlock(mTableLock);
 421         InvalidateCache();
 422         return NS_ERROR_FAILURE;
 423       }
 424       auto decompressionResult = result.unwrap();
 425       totalRead += decompressionResult.mSizeRead;
 426       totalWritten += decompressionResult.mSizeWritten;
 427       finished = decompressionResult.mFinished;
 428     }
 429
 430     MMAP_FAULT_HANDLER_CATCH(NS_ERROR_FAILURE)
 431
 432     label = Telemetry::LABELS_STARTUP_CACHE_REQUESTS::HitDisk;
 433   }
 434
 435   if (!value.mRequested) {
 436     value.mRequested = true;
 437     value.mRequestedOrder = ++mRequestedCount;
 438     MOZ_ASSERT(mRequestedCount <= mTable.count(),
 439                "Somehow we requested more StartupCache items than exist.");
 440     ResetStartupWriteTimerCheckingReadCount();
 441   }
 442
 443   // Track that something holds a reference into mTable, so we know to hold
 444   // onto it in case the cache is invalidated.
 445   mCurTableReferenced = true;
 446   *outbuf = value.mData.get();
 447   *length = value.mUncompressedSize;
 448   return NS_OK;
 449 }
 450
 451 // Makes a copy of the buffer, client retains ownership of inbuf.
 452 nsresult StartupCache::PutBuffer(const char* id, UniqueFreePtr<char[]>&& inbuf,
 453                                  uint32_t len) MOZ_NO_THREAD_SAFETY_ANALYSIS {
 454   NS_ASSERTION(NS_IsMainThread(),
 455                "Startup cache only available on main thread");
 456   if (StartupCache::gShutdownInitiated) {
 457     return NS_ERROR_NOT_AVAILABLE;
 458   }
 459
 460   // Try to gain the table write lock. If the background task to write the
 461   // cache is running, this will fail.
 462   MutexAutoTryLock lock(mTableLock);
 463   if (!lock) {
 464     return NS_ERROR_NOT_AVAILABLE;
 465   }
 466   mTableLock.AssertCurrentThreadOwns();
 467   bool exists = mTable.has(nsDependentCString(id));
 468   if (exists) {
 469     NS_WARNING("Existing entry in StartupCache.");
 470     // Double-caching is undesirable but not an error.
 471     return NS_OK;
 472   }
 473
 474   // putNew returns false on alloc failure - in the very unlikely event we hit
 475   // that and aren't going to crash elsewhere, there's no reason we need to
 476   // crash here.
 477   if (mTable.putNew(nsCString(id), StartupCacheEntry(std::move(inbuf), len,
 478                                                      ++mRequestedCount))) {
 479     return ResetStartupWriteTimer();
 480   }
 481   MOZ_DIAGNOSTIC_ASSERT(mTable.count() < STARTUP_CACHE_MAX_CAPACITY,
 482                         "Too many StartupCache entries.");
 483   return NS_OK;
 484 }
 485
 486 size_t StartupCache::HeapSizeOfIncludingThis(
 487     mozilla::MallocSizeOf aMallocSizeOf) const {
 488   // This function could measure more members, but they haven't been found by
 489   // DMD to be significant.  They can be added later if necessary.
 490
 491   size_t n = aMallocSizeOf(this);
 492
 493   n += mTable.shallowSizeOfExcludingThis(aMallocSizeOf);
 494   for (auto iter = mTable.iter(); !iter.done(); iter.next()) {
 495     if (iter.get().value().mData) {
 496       n += aMallocSizeOf(iter.get().value().mData.get());
 497     }
 498     n += iter.get().key().SizeOfExcludingThisIfUnshared(aMallocSizeOf);
 499   }
 500
 501   return n;
 502 }
 503
 504 /**
 505  * WriteToDisk writes the cache out to disk. Callers of WriteToDisk need to call
 506  * WaitOnWriteComplete to make sure there isn't a write
 507  * happening on another thread.
 508  * We own the mTableLock here.
 509  */
 510 Result<Ok, nsresult> StartupCache::WriteToDisk() {
 511   if (!mDirty || mWrittenOnce) {
 512     return Ok();
 513   }
 514
 515   if (!mFile) {
 516     return Err(NS_ERROR_UNEXPECTED);
 517   }
 518
 519   AutoFDClose fd;
 520   MOZ_TRY(mFile->OpenNSPRFileDesc(PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE,
 521                                   0644, &fd.rwget()));
 522
 523   nsTArray<std::pair<const nsCString*, StartupCacheEntry*>> entries;
 524   for (auto iter = mTable.iter(); !iter.done(); iter.next()) {
 525     if (iter.get().value().mRequested) {
 526       entries.AppendElement(
 527           std::make_pair(&iter.get().key(), &iter.get().value()));
 528     }
 529   }
 530
 531   if (entries.IsEmpty()) {
 532     return Ok();
 533   }
 534
 535   entries.Sort(StartupCacheEntry::Comparator());
 536   loader::OutputBuffer buf;
 537   for (auto& e : entries) {
 538     auto key = e.first;
 539     auto value = e.second;
 540     auto uncompressedSize = value->mUncompressedSize;
 541     // Set the mHeaderOffsetInFile so we can go back and edit the offset.
 542     value->mHeaderOffsetInFile = buf.cursor();
 543     // Write a 0 offset/compressed size as a placeholder until we get the real
 544     // offset after compressing.
 545     buf.codeUint32(0);
 546     buf.codeUint32(0);
 547     buf.codeUint32(uncompressedSize);
 548     buf.codeString(*key);
 549   }
 550
 551   uint8_t headerSize[4];
 552   LittleEndian::writeUint32(headerSize, buf.cursor());
 553
 554   MOZ_TRY(Write(fd, MAGIC, sizeof(MAGIC)));
 555   MOZ_TRY(Write(fd, headerSize, sizeof(headerSize)));
 556   size_t headerStart = sizeof(MAGIC) + sizeof(headerSize);
 557   size_t dataStart = headerStart + buf.cursor();
 558   MOZ_TRY(Seek(fd, dataStart));
 559
 560   size_t offset = 0;
 561
 562   const size_t chunkSize = 1024 * 16;
 563   LZ4FrameCompressionContext ctx(6,         /* aCompressionLevel */
 564                                  chunkSize, /* aReadBufLen */
 565                                  true,      /* aChecksum */
 566                                  true);     /* aStableSrc */
 567   size_t writeBufLen = ctx.GetRequiredWriteBufferLength();
 568   auto writeBuffer = MakeUnique<char[]>(writeBufLen);
 569   auto writeSpan = Span(writeBuffer.get(), writeBufLen);
 570
 571   for (auto& e : entries) {
 572     auto value = e.second;
 573     value->mOffset = offset;
 574     Span<const char> result;
 575     MOZ_TRY_VAR(result,
 576                 ctx.BeginCompressing(writeSpan).mapErr(MapLZ4ErrorToNsresult));
 577     MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 578     offset += result.Length();
 579
 580     for (size_t i = 0; i < value->mUncompressedSize; i += chunkSize) {
 581       size_t size = std::min(chunkSize, value->mUncompressedSize - i);
 582       char* uncompressed = value->mData.get() + i;
 583       MOZ_TRY_VAR(result, ctx.ContinueCompressing(Span(uncompressed, size))
 584                               .mapErr(MapLZ4ErrorToNsresult));
 585       MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 586       offset += result.Length();
 587     }
 588
 589     MOZ_TRY_VAR(result, ctx.EndCompressing().mapErr(MapLZ4ErrorToNsresult));
 590     MOZ_TRY(Write(fd, result.Elements(), result.Length()));
 591     offset += result.Length();
 592     value->mCompressedSize = offset - value->mOffset;
 593     MOZ_TRY(Seek(fd, dataStart + offset));
 594   }
 595
 596   for (auto& e : entries) {
 597     auto value = e.second;
 598     uint8_t* headerEntry = buf.Get() + value->mHeaderOffsetInFile;
 599     LittleEndian::writeUint32(headerEntry, value->mOffset);
 600     LittleEndian::writeUint32(headerEntry + sizeof(value->mOffset),
 601                               value->mCompressedSize);
 602   }
 603   MOZ_TRY(Seek(fd, headerStart));
 604   MOZ_TRY(Write(fd, buf.Get(), buf.cursor()));
 605
 606   mDirty = false;
 607   mWrittenOnce = true;
 608
 609   return Ok();
 610 }
 611
 612 void StartupCache::InvalidateCache(bool memoryOnly) {
 613   WaitOnPrefetch();
 614   // Ensure we're not writing using mTable...
 615   MutexAutoLock lock(mTableLock);
 616
 617   mWrittenOnce = false;
 618   if (memoryOnly) {
 619     // This should only be called in tests.
 620     auto writeResult = WriteToDisk();
 621     if (NS_WARN_IF(writeResult.isErr())) {
 622       gIgnoreDiskCache = true;
 623       return;
 624     }
 625   }
 626   if (mCurTableReferenced) {
 627     // There should be no way for this assert to fail other than a user manually
 628     // sending startupcache-invalidate messages through the Browser Toolbox. If
 629     // something knowingly invalidates the cache, the event can be counted with
 630     // mAllowedInvalidationsCount.
 631     MOZ_DIAGNOSTIC_ASSERT(
 632         xpc::IsInAutomation() ||
 633             // The allowed invalidations can grow faster than the old tables, so
 634             // guard against incorrect unsigned subtraction.
 635             mAllowedInvalidationsCount > mOldTables.Length() ||
 636             // Now perform the real check.
 637             mOldTables.Length() - mAllowedInvalidationsCount < 10,
 638         "Startup cache invalidated too many times.");
 639     mOldTables.AppendElement(std::move(mTable));
 640     mCurTableReferenced = false;
 641   } else {
 642     mTable.clear();
 643   }
 644   mRequestedCount = 0;
 645   if (!memoryOnly) {
 646     mCacheData.reset();
 647     nsresult rv = mFile->Remove(false);
 648     if (NS_FAILED(rv) && rv != NS_ERROR_FILE_NOT_FOUND) {
 649       gIgnoreDiskCache = true;
 650       return;
 651     }
 652   }
 653   gIgnoreDiskCache = false;
 654   auto result = LoadArchive();
 655   if (NS_WARN_IF(result.isErr())) {
 656     gIgnoreDiskCache = true;
 657   }
 658 }
 659
 660 void StartupCache::CountAllowedInvalidation() { mAllowedInvalidationsCount++; }
 661
 662 void StartupCache::MaybeInitShutdownWrite() {
 663   if (mTimer) {
 664     mTimer->Cancel();
 665   }
 666   gShutdownInitiated = true;
 667
 668   MaybeWriteOffMainThread();
 669 }
 670
 671 void StartupCache::EnsureShutdownWriteComplete() {
 672   MutexAutoLock lock(mTableLock);
 673   // If we've already written or there's nothing to write,
 674   // we don't need to do anything. This is the common case.
 675   if (mWrittenOnce || (mCacheData.initialized() && !ShouldCompactCache())) {
 676     return;
 677   }
 678   // Otherwise, ensure the write happens. The timer should have been cancelled
 679   // already in MaybeInitShutdownWrite.
 680
 681   // We got the lock. Keep the following in sync with
 682   // MaybeWriteOffMainThread:
 683   WaitOnPrefetch();
 684   mDirty = true;
 685   mCacheData.reset();
 686   // Most of this should be redundant given MaybeWriteOffMainThread should
 687   // have run before now.
 688
 689   auto writeResult = WriteToDisk();
 690   Unused << NS_WARN_IF(writeResult.isErr());
 691   // We've had the lock, and `WriteToDisk()` sets mWrittenOnce and mDirty
 692   // when done, and checks for them when starting, so we don't need to do
 693   // anything else.
 694 }
 695
 696 void StartupCache::IgnoreDiskCache() {
 697   gIgnoreDiskCache = true;
 698   if (gStartupCache) gStartupCache->InvalidateCache();
 699 }
 700
 701 bool StartupCache::GetIgnoreDiskCache() { return gIgnoreDiskCache; }
 702
 703 void StartupCache::WaitOnPrefetch() {
 704   // This can't be called from within ThreadedPrefetch()
 705   MonitorAutoLock lock(mPrefetchComplete);
 706   while (mPrefetchInProgress) {
 707     mPrefetchComplete.Wait();
 708   }
 709 }
 710
 711 void StartupCache::ThreadedPrefetch(uint8_t* aStart, size_t aSize) {
 712   // Always notify of completion, even if MMAP_FAULT_HANDLER_CATCH()
 713   // early-returns.
 714   auto notifyPrefetchComplete = MakeScopeExit([&] {
 715     MonitorAutoLock lock(mPrefetchComplete);
 716     mPrefetchInProgress = false;
 717     mPrefetchComplete.NotifyAll();
 718   });
 719
 720   // PrefetchMemory does madvise/equivalent, but doesn't access the memory
 721   // pointed to by aStart
 722   MMAP_FAULT_HANDLER_BEGIN_BUFFER(aStart, aSize)
 723   PrefetchMemory(aStart, aSize);
 724   MMAP_FAULT_HANDLER_CATCH()
 725 }
 726
 727 // mTableLock must be held
 728 bool StartupCache::ShouldCompactCache() {
 729   // If we've requested less than 4/5 of the startup cache, then we should
 730   // probably compact it down. This can happen quite easily after the first run,
 731   // which seems to request quite a few more things than subsequent runs.
 732   CheckedInt<uint32_t> threshold = CheckedInt<uint32_t>(mTable.count()) * 4 / 5;
 733   MOZ_RELEASE_ASSERT(threshold.isValid(), "Runaway StartupCache size");
 734   return mRequestedCount < threshold.value();
 735 }
 736
 737 /*
 738  * The write-thread is spawned on a timeout(which is reset with every write).
 739  * This can avoid a slow shutdown.
 740  */
 741 void StartupCache::WriteTimeout(nsITimer* aTimer, void* aClosure) {
 742   /*
 743    * It is safe to use the pointer passed in aClosure to reference the
 744    * StartupCache object because the timer's lifetime is tightly coupled to
 745    * the lifetime of the StartupCache object; this timer is canceled in the
 746    * StartupCache destructor, guaranteeing that this function runs if and only
 747    * if the StartupCache object is valid.
 748    */
 749   StartupCache* startupCacheObj = static_cast<StartupCache*>(aClosure);
 750   startupCacheObj->MaybeWriteOffMainThread();
 751 }
 752
 753 /*
 754  * See StartupCache::WriteTimeout above - this is just the non-static body.
 755  */
 756 void StartupCache::MaybeWriteOffMainThread() {
 757   {
 758     MutexAutoLock lock(mTableLock);
 759     if (mWrittenOnce || (mCacheData.initialized() && !ShouldCompactCache())) {
 760       return;
 761     }
 762   }
 763   // Keep this code in sync with EnsureShutdownWriteComplete.
 764   WaitOnPrefetch();
 765   {
 766     MutexAutoLock lock(mTableLock);
 767     mDirty = true;
 768     mCacheData.reset();
 769   }
 770
 771   RefPtr<StartupCache> self = this;
 772   nsCOMPtr<nsIRunnable> runnable =
 773       NS_NewRunnableFunction("StartupCache::Write", [self]() mutable {
 774         MutexAutoLock lock(self->mTableLock);
 775         auto result = self->WriteToDisk();
 776         Unused << NS_WARN_IF(result.isErr());
 777       });
 778   NS_DispatchBackgroundTask(runnable.forget(), NS_DISPATCH_EVENT_MAY_BLOCK);
 779 }
 780
 781 // We don't want to refcount StartupCache, so we'll just
 782 // hold a ref to this and pass it to observerService instead.
 783 NS_IMPL_ISUPPORTS(StartupCacheListener, nsIObserver)
 784
 785 nsresult StartupCacheListener::Observe(nsISupports* subject, const char* topic,
 786                                        const char16_t* data) {
 787   StartupCache* sc = StartupCache::GetSingleton();
 788   if (!sc) return NS_OK;
 789
 790   if (strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
 791     // Do not leave the thread running past xpcom shutdown
 792     sc->WaitOnPrefetch();
 793     StartupCache::gShutdownInitiated = true;
 794     // Note that we don't do anything special for the background write
 795     // task; we expect the threadpool to finish running any tasks already
 796     // posted to it prior to shutdown. FastShutdown will call
 797     // EnsureShutdownWriteComplete() to ensure any pending writes happen
 798     // in that case.
 799   } else if (strcmp(topic, "startupcache-invalidate") == 0) {
 800     sc->InvalidateCache(data && nsCRT::strcmp(data, u"memoryOnly") == 0);
 801   } else if (strcmp(topic, "intl:app-locales-changed") == 0) {
 802     // Live language switching invalidates the startup cache due to the history
 803     // sidebar retaining localized strings in its internal SQL query. This
 804     // should be a relatively rare event, but a user could do it an arbitrary
 805     // number of times.
 806     sc->CountAllowedInvalidation();
 807   }
 808   return NS_OK;
 809 }
 810
 811 nsresult StartupCache::GetDebugObjectOutputStream(
 812     nsIObjectOutputStream* aStream, nsIObjectOutputStream** aOutStream) {
 813   NS_ENSURE_ARG_POINTER(aStream);
 814 #ifdef DEBUG
 815   auto* stream = new StartupCacheDebugOutputStream(aStream, &mWriteObjectMap);
 816   NS_ADDREF(*aOutStream = stream);
 817 #else
 818   NS_ADDREF(*aOutStream = aStream);
 819 #endif
 820
 821   return NS_OK;
 822 }
 823
 824 nsresult StartupCache::ResetStartupWriteTimerCheckingReadCount() {
 825   nsresult rv = NS_OK;
 826   if (!mTimer)
 827     mTimer = NS_NewTimer();
 828   else
 829     rv = mTimer->Cancel();
 830   NS_ENSURE_SUCCESS(rv, rv);
 831   // Wait for the specified timeout, then write out the cache.
 832   mTimer->InitWithNamedFuncCallback(
 833       StartupCache::WriteTimeout, this, STARTUP_CACHE_WRITE_TIMEOUT * 1000,
 834       nsITimer::TYPE_ONE_SHOT, "StartupCache::WriteTimeout");
 835   return NS_OK;
 836 }
 837
 838 // For test code only
 839 nsresult StartupCache::ResetStartupWriteTimerAndLock() {
 840   MutexAutoLock lock(mTableLock);
 841   return ResetStartupWriteTimer();
 842 }
 843
 844 nsresult StartupCache::ResetStartupWriteTimer() {
 845   mDirty = true;
 846   nsresult rv = NS_OK;
 847   if (!mTimer)
 848     mTimer = NS_NewTimer();
 849   else
 850     rv = mTimer->Cancel();
 851   NS_ENSURE_SUCCESS(rv, rv);
 852   // Wait for the specified timeout, then write out the cache.
 853   mTimer->InitWithNamedFuncCallback(
 854       StartupCache::WriteTimeout, this, STARTUP_CACHE_WRITE_TIMEOUT * 1000,
 855       nsITimer::TYPE_ONE_SHOT, "StartupCache::WriteTimeout");
 856   return NS_OK;
 857 }
 858
 859 // Used only in tests:
 860 bool StartupCache::StartupWriteComplete() {
 861   // Need to have written to disk and not added new things since;
 862   MutexAutoLock lock(mTableLock);
 863   return !mDirty && mWrittenOnce;
 864 }
 865
 866 // StartupCacheDebugOutputStream implementation
 867 #ifdef DEBUG
 868 NS_IMPL_ISUPPORTS(StartupCacheDebugOutputStream, nsIObjectOutputStream,
 869                   nsIBinaryOutputStream, nsIOutputStream)
 870
 871 bool StartupCacheDebugOutputStream::CheckReferences(nsISupports* aObject) {
 872   nsresult rv;
 873
 874   nsCOMPtr<nsIClassInfo> classInfo = do_QueryInterface(aObject);
 875   if (!classInfo) {
 876     NS_ERROR("aObject must implement nsIClassInfo");
 877     return false;
 878   }
 879
 880   uint32_t flags;
 881   rv = classInfo->GetFlags(&flags);
 882   NS_ENSURE_SUCCESS(rv, false);
 883   if (flags & nsIClassInfo::SINGLETON) return true;
 884
 885   bool inserted = mObjectMap->EnsureInserted(aObject);
 886   if (!inserted) {
 887     NS_ERROR(
 888         "non-singleton aObject is referenced multiple times in this"
 889         "serialization, we don't support that.");
 890   }
 891
 892   return inserted;
 893 }
 894
 895 // nsIObjectOutputStream implementation
 896 nsresult StartupCacheDebugOutputStream::WriteObject(nsISupports* aObject,
 897                                                     bool aIsStrongRef) {
 898   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 899
 900   NS_ASSERTION(rootObject.get() == aObject,
 901                "bad call to WriteObject -- call WriteCompoundObject!");
 902   bool check = CheckReferences(aObject);
 903   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 904   return mBinaryStream->WriteObject(aObject, aIsStrongRef);
 905 }
 906
 907 nsresult StartupCacheDebugOutputStream::WriteSingleRefObject(
 908     nsISupports* aObject) {
 909   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 910
 911   NS_ASSERTION(rootObject.get() == aObject,
 912                "bad call to WriteSingleRefObject -- call WriteCompoundObject!");
 913   bool check = CheckReferences(aObject);
 914   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 915   return mBinaryStream->WriteSingleRefObject(aObject);
 916 }
 917
 918 nsresult StartupCacheDebugOutputStream::WriteCompoundObject(
 919     nsISupports* aObject, const nsIID& aIID, bool aIsStrongRef) {
 920   nsCOMPtr<nsISupports> rootObject(do_QueryInterface(aObject));
 921
 922   nsCOMPtr<nsISupports> roundtrip;
 923   rootObject->QueryInterface(aIID, getter_AddRefs(roundtrip));
 924   NS_ASSERTION(roundtrip.get() == aObject,
 925                "bad aggregation or multiple inheritance detected by call to "
 926                "WriteCompoundObject!");
 927
 928   bool check = CheckReferences(aObject);
 929   NS_ENSURE_TRUE(check, NS_ERROR_FAILURE);
 930   return mBinaryStream->WriteCompoundObject(aObject, aIID, aIsStrongRef);
 931 }
 932
 933 nsresult StartupCacheDebugOutputStream::WriteID(nsID const& aID) {
 934   return mBinaryStream->WriteID(aID);
 935 }
 936
 937 char* StartupCacheDebugOutputStream::GetBuffer(uint32_t aLength,
 938                                                uint32_t aAlignMask) {
 939   return mBinaryStream->GetBuffer(aLength, aAlignMask);
 940 }
 941
 942 void StartupCacheDebugOutputStream::PutBuffer(char* aBuffer, uint32_t aLength) {
 943   mBinaryStream->PutBuffer(aBuffer, aLength);
 944 }
 945 #endif  // DEBUG
 946
 947 }  // namespace scache
 948 }  // namespace mozilla