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-rw-r--r--js/xpconnect/loader/ScriptPreloader.cpp1375
1 files changed, 1375 insertions, 0 deletions
diff --git a/js/xpconnect/loader/ScriptPreloader.cpp b/js/xpconnect/loader/ScriptPreloader.cpp
new file mode 100644
index 0000000000..fe90dfcf2d
--- /dev/null
+++ b/js/xpconnect/loader/ScriptPreloader.cpp
@@ -0,0 +1,1375 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ScriptPreloader-inl.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Monitor.h"
+
+#include "mozilla/ScriptPreloader.h"
+#include "mozilla/loader/ScriptCacheActors.h"
+
+#include "mozilla/URLPreloader.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Components.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/FileUtils.h"
+#include "mozilla/IOBuffers.h"
+#include "mozilla/Logging.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Services.h"
+#include "mozilla/StaticPrefs_javascript.h"
+#include "mozilla/TaskController.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/Try.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/scache/StartupCache.h"
+
+#include "crc32c.h"
+#include "js/CompileOptions.h" // JS::ReadOnlyCompileOptions
+#include "js/experimental/JSStencil.h" // JS::Stencil, JS::DecodeStencil
+#include "js/experimental/CompileScript.h" // JS::NewFrontendContext, JS::DestroyFrontendContext, JS::SetNativeStackQuota, JS::ThreadStackQuotaForSize
+#include "js/Transcoding.h"
+#include "MainThreadUtils.h"
+#include "nsDebug.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsIFile.h"
+#include "nsIObserverService.h"
+#include "nsJSUtils.h"
+#include "nsMemoryReporterManager.h"
+#include "nsNetUtil.h"
+#include "nsProxyRelease.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+#include "xpcpublic.h"
+
+#define STARTUP_COMPLETE_TOPIC "browser-delayed-startup-finished"
+#define DOC_ELEM_INSERTED_TOPIC "document-element-inserted"
+#define CONTENT_DOCUMENT_LOADED_TOPIC "content-document-loaded"
+#define CACHE_WRITE_TOPIC "browser-idle-startup-tasks-finished"
+#define XPCOM_SHUTDOWN_TOPIC "xpcom-shutdown"
+#define CACHE_INVALIDATE_TOPIC "startupcache-invalidate"
+
+// The maximum time we'll wait for a child process to finish starting up before
+// we send its script data back to the parent.
+constexpr uint32_t CHILD_STARTUP_TIMEOUT_MS = 8000;
+
+namespace mozilla {
+namespace {
+static LazyLogModule gLog("ScriptPreloader");
+
+#define LOG(level, ...) MOZ_LOG(gLog, LogLevel::level, (__VA_ARGS__))
+} // namespace
+
+using mozilla::dom::AutoJSAPI;
+using mozilla::dom::ContentChild;
+using mozilla::dom::ContentParent;
+using namespace mozilla::loader;
+using mozilla::scache::StartupCache;
+
+using namespace JS;
+
+ProcessType ScriptPreloader::sProcessType;
+
+nsresult ScriptPreloader::CollectReports(nsIHandleReportCallback* aHandleReport,
+ nsISupports* aData, bool aAnonymize) {
+ MOZ_COLLECT_REPORT(
+ "explicit/script-preloader/heap/saved-scripts", KIND_HEAP, UNITS_BYTES,
+ SizeOfHashEntries<ScriptStatus::Saved>(mScripts, MallocSizeOf),
+ "Memory used to hold the scripts which have been executed in this "
+ "session, and will be written to the startup script cache file.");
+
+ MOZ_COLLECT_REPORT(
+ "explicit/script-preloader/heap/restored-scripts", KIND_HEAP, UNITS_BYTES,
+ SizeOfHashEntries<ScriptStatus::Restored>(mScripts, MallocSizeOf),
+ "Memory used to hold the scripts which have been restored from the "
+ "startup script cache file, but have not been executed in this session.");
+
+ MOZ_COLLECT_REPORT("explicit/script-preloader/heap/other", KIND_HEAP,
+ UNITS_BYTES, ShallowHeapSizeOfIncludingThis(MallocSizeOf),
+ "Memory used by the script cache service itself.");
+
+ // Since the mem-mapped cache file is mapped into memory, we want to report
+ // it as explicit memory somewhere. But since the child cache is shared
+ // between all processes, we don't want to report it as explicit memory for
+ // all of them. So we report it as explicit only in the parent process, and
+ // non-explicit everywhere else.
+ if (XRE_IsParentProcess()) {
+ MOZ_COLLECT_REPORT("explicit/script-preloader/non-heap/memmapped-cache",
+ KIND_NONHEAP, UNITS_BYTES,
+ mCacheData->nonHeapSizeOfExcludingThis(),
+ "The memory-mapped startup script cache file.");
+ } else {
+ MOZ_COLLECT_REPORT("script-preloader-memmapped-cache", KIND_NONHEAP,
+ UNITS_BYTES, mCacheData->nonHeapSizeOfExcludingThis(),
+ "The memory-mapped startup script cache file.");
+ }
+
+ return NS_OK;
+}
+
+StaticRefPtr<ScriptPreloader> ScriptPreloader::gScriptPreloader;
+StaticRefPtr<ScriptPreloader> ScriptPreloader::gChildScriptPreloader;
+StaticAutoPtr<AutoMemMap> ScriptPreloader::gCacheData;
+StaticAutoPtr<AutoMemMap> ScriptPreloader::gChildCacheData;
+
+ScriptPreloader& ScriptPreloader::GetSingleton() {
+ if (!gScriptPreloader) {
+ if (XRE_IsParentProcess()) {
+ gCacheData = new AutoMemMap();
+ gScriptPreloader = new ScriptPreloader(gCacheData.get());
+ gScriptPreloader->mChildCache = &GetChildSingleton();
+ Unused << gScriptPreloader->InitCache();
+ } else {
+ gScriptPreloader = &GetChildSingleton();
+ }
+ }
+
+ return *gScriptPreloader;
+}
+
+// The child singleton is available in all processes, including the parent, and
+// is used for scripts which are expected to be loaded into child processes
+// (such as process and frame scripts), or scripts that have already been loaded
+// into a child. The child caches are managed as follows:
+//
+// - Every startup, we open the cache file from the last session, move it to a
+// new location, and begin pre-loading the scripts that are stored in it. There
+// is a separate cache file for parent and content processes, but the parent
+// process opens both the parent and content cache files.
+//
+// - Once startup is complete, we write a new cache file for the next session,
+// containing only the scripts that were used during early startup, so we
+// don't waste pre-loading scripts that may not be needed.
+//
+// - For content processes, opening and writing the cache file is handled in the
+// parent process. The first content process of each type sends back the data
+// for scripts that were loaded in early startup, and the parent merges them
+// and writes them to a cache file.
+//
+// - Currently, content processes only benefit from the cache data written
+// during the *previous* session. Ideally, new content processes should
+// probably use the cache data written during this session if there was no
+// previous cache file, but I'd rather do that as a follow-up.
+ScriptPreloader& ScriptPreloader::GetChildSingleton() {
+ if (!gChildScriptPreloader) {
+ gChildCacheData = new AutoMemMap();
+ gChildScriptPreloader = new ScriptPreloader(gChildCacheData.get());
+ if (XRE_IsParentProcess()) {
+ Unused << gChildScriptPreloader->InitCache(u"scriptCache-child"_ns);
+ }
+ }
+
+ return *gChildScriptPreloader;
+}
+
+/* static */
+void ScriptPreloader::DeleteSingleton() {
+ gScriptPreloader = nullptr;
+ gChildScriptPreloader = nullptr;
+}
+
+/* static */
+void ScriptPreloader::DeleteCacheDataSingleton() {
+ MOZ_ASSERT(!gScriptPreloader);
+ MOZ_ASSERT(!gChildScriptPreloader);
+
+ gCacheData = nullptr;
+ gChildCacheData = nullptr;
+}
+
+void ScriptPreloader::InitContentChild(ContentParent& parent) {
+ auto& cache = GetChildSingleton();
+ cache.mSaveMonitor.AssertOnWritingThread();
+
+ // We want startup script data from the first process of a given type.
+ // That process sends back its script data before it executes any
+ // untrusted code, and then we never accept further script data for that
+ // type of process for the rest of the session.
+ //
+ // The script data from each process type is merged with the data from the
+ // parent process's frame and process scripts, and shared between all
+ // content process types in the next session.
+ //
+ // Note that if the first process of a given type crashes or shuts down
+ // before sending us its script data, we silently ignore it, and data for
+ // that process type is not included in the next session's cache. This
+ // should be a sufficiently rare occurrence that it's not worth trying to
+ // handle specially.
+ auto processType = GetChildProcessType(parent.GetRemoteType());
+ bool wantScriptData = !cache.mInitializedProcesses.contains(processType);
+ cache.mInitializedProcesses += processType;
+
+ auto fd = cache.mCacheData->cloneFileDescriptor();
+ // Don't send original cache data to new processes if the cache has been
+ // invalidated.
+ if (fd.IsValid() && !cache.mCacheInvalidated) {
+ Unused << parent.SendPScriptCacheConstructor(fd, wantScriptData);
+ } else {
+ Unused << parent.SendPScriptCacheConstructor(NS_ERROR_FILE_NOT_FOUND,
+ wantScriptData);
+ }
+}
+
+ProcessType ScriptPreloader::GetChildProcessType(const nsACString& remoteType) {
+ if (remoteType == EXTENSION_REMOTE_TYPE) {
+ return ProcessType::Extension;
+ }
+ if (remoteType == PRIVILEGEDABOUT_REMOTE_TYPE) {
+ return ProcessType::PrivilegedAbout;
+ }
+ return ProcessType::Web;
+}
+
+ScriptPreloader::ScriptPreloader(AutoMemMap* cacheData)
+ : mCacheData(cacheData),
+ mMonitor("[ScriptPreloader.mMonitor]"),
+ mSaveMonitor("[ScriptPreloader.mSaveMonitor]", this) {
+ // We do not set the process type for child processes here because the
+ // remoteType in ContentChild is not ready yet.
+ if (XRE_IsParentProcess()) {
+ sProcessType = ProcessType::Parent;
+ }
+
+ nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+ MOZ_RELEASE_ASSERT(obs);
+
+ if (XRE_IsParentProcess()) {
+ // In the parent process, we want to freeze the script cache as soon
+ // as idle tasks for the first browser window have completed.
+ obs->AddObserver(this, STARTUP_COMPLETE_TOPIC, false);
+ obs->AddObserver(this, CACHE_WRITE_TOPIC, false);
+ }
+
+ obs->AddObserver(this, XPCOM_SHUTDOWN_TOPIC, false);
+ obs->AddObserver(this, CACHE_INVALIDATE_TOPIC, false);
+}
+
+ScriptPreloader::~ScriptPreloader() { Cleanup(); }
+
+void ScriptPreloader::Cleanup() {
+ mScripts.Clear();
+ UnregisterWeakMemoryReporter(this);
+}
+
+void ScriptPreloader::StartCacheWrite() {
+ MOZ_DIAGNOSTIC_ASSERT(!mSaveThread);
+
+ Unused << NS_NewNamedThread("SaveScripts", getter_AddRefs(mSaveThread), this);
+
+ nsCOMPtr<nsIAsyncShutdownClient> barrier = GetShutdownBarrier();
+ barrier->AddBlocker(this, NS_LITERAL_STRING_FROM_CSTRING(__FILE__), __LINE__,
+ u""_ns);
+}
+
+void ScriptPreloader::InvalidateCache() {
+ {
+ mMonitor.AssertNotCurrentThreadOwns();
+ MonitorAutoLock mal(mMonitor);
+
+ // Wait for pending off-thread parses to finish, since they depend on the
+ // memory allocated by our CachedStencil, and can't be canceled
+ // asynchronously.
+ FinishPendingParses(mal);
+
+ // Pending scripts should have been cleared by the above, and the queue
+ // should have been reset.
+ MOZ_ASSERT(mDecodingScripts.isEmpty());
+ MOZ_ASSERT(!mDecodedStencils);
+
+ mScripts.Clear();
+
+ // If we've already finished saving the cache at this point, start a new
+ // delayed save operation. This will write out an empty cache file in place
+ // of any cache file we've already written out this session, which will
+ // prevent us from falling back to the current session's cache file on the
+ // next startup.
+ if (mSaveComplete && !mSaveThread && mChildCache) {
+ mSaveComplete = false;
+
+ StartCacheWrite();
+ }
+ }
+
+ {
+ MonitorSingleWriterAutoLock saveMonitorAutoLock(mSaveMonitor);
+
+ mCacheInvalidated = true;
+ }
+
+ // If we're waiting on a timeout to finish saving, interrupt it and just save
+ // immediately.
+ mSaveMonitor.NotifyAll();
+}
+
+nsresult ScriptPreloader::Observe(nsISupports* subject, const char* topic,
+ const char16_t* data) {
+ nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+ if (!strcmp(topic, STARTUP_COMPLETE_TOPIC)) {
+ obs->RemoveObserver(this, STARTUP_COMPLETE_TOPIC);
+
+ MOZ_ASSERT(XRE_IsParentProcess());
+
+ mStartupFinished = true;
+ URLPreloader::GetSingleton().SetStartupFinished();
+ } else if (!strcmp(topic, CACHE_WRITE_TOPIC)) {
+ obs->RemoveObserver(this, CACHE_WRITE_TOPIC);
+
+ MOZ_ASSERT(mStartupFinished);
+ MOZ_ASSERT(XRE_IsParentProcess());
+
+ if (mChildCache && !mSaveComplete && !mSaveThread) {
+ StartCacheWrite();
+ }
+ } else if (mContentStartupFinishedTopic.Equals(topic)) {
+ // If this is an uninitialized about:blank viewer or a chrome: document
+ // (which should always be an XBL binding document), ignore it. We don't
+ // have to worry about it loading malicious content.
+ if (nsCOMPtr<dom::Document> doc = do_QueryInterface(subject)) {
+ nsCOMPtr<nsIURI> uri = doc->GetDocumentURI();
+
+ if ((NS_IsAboutBlank(uri) &&
+ doc->GetReadyStateEnum() == doc->READYSTATE_UNINITIALIZED) ||
+ uri->SchemeIs("chrome")) {
+ return NS_OK;
+ }
+ }
+ FinishContentStartup();
+ } else if (!strcmp(topic, "timer-callback")) {
+ FinishContentStartup();
+ } else if (!strcmp(topic, XPCOM_SHUTDOWN_TOPIC)) {
+ // Wait for any pending parses to finish at this point, to avoid creating
+ // new stencils during destroying the JS runtime.
+ MonitorAutoLock mal(mMonitor);
+ FinishPendingParses(mal);
+ } else if (!strcmp(topic, CACHE_INVALIDATE_TOPIC)) {
+ InvalidateCache();
+ }
+
+ return NS_OK;
+}
+
+void ScriptPreloader::FinishContentStartup() {
+ MOZ_ASSERT(XRE_IsContentProcess());
+
+#ifdef DEBUG
+ if (mContentStartupFinishedTopic.Equals(CONTENT_DOCUMENT_LOADED_TOPIC)) {
+ MOZ_ASSERT(sProcessType == ProcessType::PrivilegedAbout);
+ } else {
+ MOZ_ASSERT(sProcessType != ProcessType::PrivilegedAbout);
+ }
+#endif /* DEBUG */
+
+ nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+ obs->RemoveObserver(this, mContentStartupFinishedTopic.get());
+
+ mSaveTimer = nullptr;
+
+ mStartupFinished = true;
+
+ if (mChildActor) {
+ mChildActor->SendScriptsAndFinalize(mScripts);
+ }
+
+#ifdef XP_WIN
+ // Record the amount of USS at startup. This is Windows-only for now,
+ // we could turn it on for Linux relatively cheaply. On macOS it can have
+ // a perf impact. Only record this for non-privileged processes because
+ // privileged processes record this value at a different time, leading to
+ // a higher value which skews the telemetry.
+ if (sProcessType != ProcessType::PrivilegedAbout) {
+ mozilla::Telemetry::Accumulate(
+ mozilla::Telemetry::MEMORY_UNIQUE_CONTENT_STARTUP,
+ nsMemoryReporterManager::ResidentUnique() / 1024);
+ }
+#endif
+}
+
+bool ScriptPreloader::WillWriteScripts() {
+ return !mDataPrepared && (XRE_IsParentProcess() || mChildActor);
+}
+
+Result<nsCOMPtr<nsIFile>, nsresult> ScriptPreloader::GetCacheFile(
+ const nsAString& suffix) {
+ NS_ENSURE_TRUE(mProfD, Err(NS_ERROR_NOT_INITIALIZED));
+
+ nsCOMPtr<nsIFile> cacheFile;
+ MOZ_TRY(mProfD->Clone(getter_AddRefs(cacheFile)));
+
+ MOZ_TRY(cacheFile->AppendNative("startupCache"_ns));
+ Unused << cacheFile->Create(nsIFile::DIRECTORY_TYPE, 0777);
+
+ MOZ_TRY(cacheFile->Append(mBaseName + suffix));
+
+ return std::move(cacheFile);
+}
+
+static const uint8_t MAGIC[] = "mozXDRcachev003";
+
+Result<Ok, nsresult> ScriptPreloader::OpenCache() {
+ if (StartupCache::GetIgnoreDiskCache()) {
+ return Err(NS_ERROR_ABORT);
+ }
+
+ MOZ_TRY(NS_GetSpecialDirectory("ProfLDS", getter_AddRefs(mProfD)));
+
+ nsCOMPtr<nsIFile> cacheFile;
+ MOZ_TRY_VAR(cacheFile, GetCacheFile(u".bin"_ns));
+
+ bool exists;
+ MOZ_TRY(cacheFile->Exists(&exists));
+ if (exists) {
+ MOZ_TRY(cacheFile->MoveTo(nullptr, mBaseName + u"-current.bin"_ns));
+ } else {
+ MOZ_TRY(cacheFile->SetLeafName(mBaseName + u"-current.bin"_ns));
+ MOZ_TRY(cacheFile->Exists(&exists));
+ if (!exists) {
+ return Err(NS_ERROR_FILE_NOT_FOUND);
+ }
+ }
+
+ MOZ_TRY(mCacheData->init(cacheFile));
+
+ return Ok();
+}
+
+// Opens the script cache file for this session, and initializes the script
+// cache based on its contents. See WriteCache for details of the cache file.
+Result<Ok, nsresult> ScriptPreloader::InitCache(const nsAString& basePath) {
+ mSaveMonitor.AssertOnWritingThread();
+ mCacheInitialized = true;
+ mBaseName = basePath;
+
+ RegisterWeakMemoryReporter(this);
+
+ if (!XRE_IsParentProcess()) {
+ return Ok();
+ }
+
+ // Grab the compilation scope before initializing the URLPreloader, since
+ // it's not safe to run component loader code during its critical section.
+ AutoSafeJSAPI jsapi;
+ JS::RootedObject scope(jsapi.cx(), xpc::CompilationScope());
+
+ // Note: Code on the main thread *must not access Omnijar in any way* until
+ // this AutoBeginReading guard is destroyed.
+ URLPreloader::AutoBeginReading abr;
+
+ MOZ_TRY(OpenCache());
+
+ return InitCacheInternal(scope);
+}
+
+Result<Ok, nsresult> ScriptPreloader::InitCache(
+ const Maybe<ipc::FileDescriptor>& cacheFile, ScriptCacheChild* cacheChild) {
+ mSaveMonitor.AssertOnWritingThread();
+ MOZ_ASSERT(XRE_IsContentProcess());
+
+ mCacheInitialized = true;
+ mChildActor = cacheChild;
+ sProcessType =
+ GetChildProcessType(dom::ContentChild::GetSingleton()->GetRemoteType());
+
+ nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+ MOZ_RELEASE_ASSERT(obs);
+
+ if (sProcessType == ProcessType::PrivilegedAbout) {
+ // Since we control all of the documents loaded in the privileged
+ // content process, we can increase the window of active time for the
+ // ScriptPreloader to include the scripts that are loaded until the
+ // first document finishes loading.
+ mContentStartupFinishedTopic.AssignLiteral(CONTENT_DOCUMENT_LOADED_TOPIC);
+ } else {
+ // In the child process, we need to freeze the script cache before any
+ // untrusted code has been executed. The insertion of the first DOM
+ // document element may sometimes be earlier than is ideal, but at
+ // least it should always be safe.
+ mContentStartupFinishedTopic.AssignLiteral(DOC_ELEM_INSERTED_TOPIC);
+ }
+ obs->AddObserver(this, mContentStartupFinishedTopic.get(), false);
+
+ RegisterWeakMemoryReporter(this);
+
+ auto cleanup = MakeScopeExit([&] {
+ // If the parent is expecting cache data from us, make sure we send it
+ // before it writes out its cache file. For normal proceses, this isn't
+ // a concern, since they begin loading documents quite early. For the
+ // preloaded process, we may end up waiting a long time (or, indeed,
+ // never loading a document), so we need an additional timeout.
+ if (cacheChild) {
+ NS_NewTimerWithObserver(getter_AddRefs(mSaveTimer), this,
+ CHILD_STARTUP_TIMEOUT_MS,
+ nsITimer::TYPE_ONE_SHOT);
+ }
+ });
+
+ if (cacheFile.isNothing()) {
+ return Ok();
+ }
+
+ MOZ_TRY(mCacheData->init(cacheFile.ref()));
+
+ return InitCacheInternal();
+}
+
+Result<Ok, nsresult> ScriptPreloader::InitCacheInternal(
+ JS::HandleObject scope) {
+ auto size = mCacheData->size();
+
+ uint32_t headerSize;
+ uint32_t crc;
+ if (size < sizeof(MAGIC) + sizeof(headerSize) + sizeof(crc)) {
+ return Err(NS_ERROR_UNEXPECTED);
+ }
+
+ auto data = mCacheData->get<uint8_t>();
+ MOZ_RELEASE_ASSERT(JS::IsTranscodingBytecodeAligned(data.get()));
+
+ auto end = data + size;
+
+ if (memcmp(MAGIC, data.get(), sizeof(MAGIC))) {
+ return Err(NS_ERROR_UNEXPECTED);
+ }
+ data += sizeof(MAGIC);
+
+ headerSize = LittleEndian::readUint32(data.get());
+ data += sizeof(headerSize);
+
+ crc = LittleEndian::readUint32(data.get());
+ data += sizeof(crc);
+
+ if (data + headerSize > end) {
+ return Err(NS_ERROR_UNEXPECTED);
+ }
+
+ if (crc != ComputeCrc32c(~0, data.get(), headerSize)) {
+ return Err(NS_ERROR_UNEXPECTED);
+ }
+
+ {
+ auto cleanup = MakeScopeExit([&]() { mScripts.Clear(); });
+
+ LinkedList<CachedStencil> scripts;
+
+ Range<uint8_t> header(data, data + headerSize);
+ data += headerSize;
+
+ // Reconstruct alignment padding if required.
+ size_t currentOffset = data - mCacheData->get<uint8_t>();
+ data += JS::AlignTranscodingBytecodeOffset(currentOffset) - currentOffset;
+
+ InputBuffer buf(header);
+
+ size_t offset = 0;
+ while (!buf.finished()) {
+ auto script = MakeUnique<CachedStencil>(*this, buf);
+ MOZ_RELEASE_ASSERT(script);
+
+ auto scriptData = data + script->mOffset;
+ if (!JS::IsTranscodingBytecodeAligned(scriptData.get())) {
+ return Err(NS_ERROR_UNEXPECTED);
+ }
+
+ if (scriptData + script->mSize > end) {
+ return Err(NS_ERROR_UNEXPECTED);
+ }
+
+ // Make sure offsets match what we'd expect based on script ordering and
+ // size, as a basic sanity check.
+ if (script->mOffset != offset) {
+ return Err(NS_ERROR_UNEXPECTED);
+ }
+ offset += script->mSize;
+
+ script->mXDRRange.emplace(scriptData, scriptData + script->mSize);
+
+ // Don't pre-decode the script unless it was used in this process type
+ // during the previous session.
+ if (script->mOriginalProcessTypes.contains(CurrentProcessType())) {
+ scripts.insertBack(script.get());
+ } else {
+ script->mReadyToExecute = true;
+ }
+
+ const auto& cachePath = script->mCachePath;
+ mScripts.InsertOrUpdate(cachePath, std::move(script));
+ }
+
+ if (buf.error()) {
+ return Err(NS_ERROR_UNEXPECTED);
+ }
+
+ mDecodingScripts = std::move(scripts);
+ cleanup.release();
+ }
+
+ StartDecodeTask(scope);
+ return Ok();
+}
+
+void ScriptPreloader::PrepareCacheWriteInternal() {
+ MOZ_ASSERT(NS_IsMainThread());
+
+ mMonitor.AssertCurrentThreadOwns();
+
+ auto cleanup = MakeScopeExit([&]() {
+ if (mChildCache) {
+ mChildCache->PrepareCacheWrite();
+ }
+ });
+
+ if (mDataPrepared) {
+ return;
+ }
+
+ AutoSafeJSAPI jsapi;
+ JSAutoRealm ar(jsapi.cx(), xpc::PrivilegedJunkScope());
+ bool found = false;
+ for (auto& script : IterHash(mScripts, Match<ScriptStatus::Saved>())) {
+ // Don't write any scripts that are also in the child cache. They'll be
+ // loaded from the child cache in that case, so there's no need to write
+ // them twice.
+ CachedStencil* childScript =
+ mChildCache ? mChildCache->mScripts.Get(script->mCachePath) : nullptr;
+ if (childScript && !childScript->mProcessTypes.isEmpty()) {
+ childScript->UpdateLoadTime(script->mLoadTime);
+ childScript->mProcessTypes += script->mProcessTypes;
+ script.Remove();
+ continue;
+ }
+
+ if (!(script->mProcessTypes == script->mOriginalProcessTypes)) {
+ // Note: EnumSet doesn't support operator!=, hence the weird form above.
+ found = true;
+ }
+
+ if (!script->mSize && !script->XDREncode(jsapi.cx())) {
+ script.Remove();
+ }
+ }
+
+ if (!found) {
+ mSaveComplete = true;
+ return;
+ }
+
+ mDataPrepared = true;
+}
+
+void ScriptPreloader::PrepareCacheWrite() {
+ MonitorAutoLock mal(mMonitor);
+
+ PrepareCacheWriteInternal();
+}
+
+// Writes out a script cache file for the scripts accessed during early
+// startup in this session. The cache file is a little-endian binary file with
+// the following format:
+//
+// - A uint32 containing the size of the header block.
+//
+// - A header entry for each file stored in the cache containing:
+// - The URL that the script was originally read from.
+// - Its cache key.
+// - The offset of its XDR data within the XDR data block.
+// - The size of its XDR data in the XDR data block.
+// - A bit field describing which process types the script is used in.
+//
+// - A block of XDR data for the encoded scripts, with each script's data at
+// an offset from the start of the block, as specified above.
+Result<Ok, nsresult> ScriptPreloader::WriteCache() {
+ MOZ_ASSERT(!NS_IsMainThread());
+ mSaveMonitor.AssertCurrentThreadOwns();
+
+ if (!mDataPrepared && !mSaveComplete) {
+ MonitorSingleWriterAutoUnlock mau(mSaveMonitor);
+
+ NS_DispatchAndSpinEventLoopUntilComplete(
+ "ScriptPreloader::PrepareCacheWrite"_ns,
+ GetMainThreadSerialEventTarget(),
+ NewRunnableMethod("ScriptPreloader::PrepareCacheWrite", this,
+ &ScriptPreloader::PrepareCacheWrite));
+ }
+
+ if (mSaveComplete) {
+ // If we don't have anything we need to save, we're done.
+ return Ok();
+ }
+
+ nsCOMPtr<nsIFile> cacheFile;
+ MOZ_TRY_VAR(cacheFile, GetCacheFile(u"-new.bin"_ns));
+
+ bool exists;
+ MOZ_TRY(cacheFile->Exists(&exists));
+ if (exists) {
+ MOZ_TRY(cacheFile->Remove(false));
+ }
+
+ {
+ AutoFDClose raiiFd;
+ MOZ_TRY(cacheFile->OpenNSPRFileDesc(PR_WRONLY | PR_CREATE_FILE, 0644,
+ getter_Transfers(raiiFd)));
+ const auto fd = raiiFd.get();
+
+ // We also need to hold mMonitor while we're touching scripts in
+ // mScripts, or they may be freed before we're done with them.
+ mMonitor.AssertNotCurrentThreadOwns();
+ MonitorAutoLock mal(mMonitor);
+
+ nsTArray<CachedStencil*> scripts;
+ for (auto& script : IterHash(mScripts, Match<ScriptStatus::Saved>())) {
+ scripts.AppendElement(script);
+ }
+
+ // Sort scripts by load time, with async loaded scripts before sync scripts.
+ // Since async scripts are always loaded immediately at startup, it helps to
+ // have them stored contiguously.
+ scripts.Sort(CachedStencil::Comparator());
+
+ OutputBuffer buf;
+ size_t offset = 0;
+ for (auto script : scripts) {
+ script->mOffset = offset;
+ MOZ_DIAGNOSTIC_ASSERT(
+ JS::IsTranscodingBytecodeOffsetAligned(script->mOffset));
+ script->Code(buf);
+
+ offset += script->mSize;
+ MOZ_DIAGNOSTIC_ASSERT(
+ JS::IsTranscodingBytecodeOffsetAligned(script->mSize));
+ }
+
+ uint8_t headerSize[4];
+ LittleEndian::writeUint32(headerSize, buf.cursor());
+
+ uint8_t crc[4];
+ LittleEndian::writeUint32(crc, ComputeCrc32c(~0, buf.Get(), buf.cursor()));
+
+ MOZ_TRY(Write(fd, MAGIC, sizeof(MAGIC)));
+ MOZ_TRY(Write(fd, headerSize, sizeof(headerSize)));
+ MOZ_TRY(Write(fd, crc, sizeof(crc)));
+ MOZ_TRY(Write(fd, buf.Get(), buf.cursor()));
+
+ // Align the start of the scripts section to the transcode alignment.
+ size_t written = sizeof(MAGIC) + sizeof(headerSize) + buf.cursor();
+ size_t padding = JS::AlignTranscodingBytecodeOffset(written) - written;
+ if (padding) {
+ MOZ_TRY(WritePadding(fd, padding));
+ written += padding;
+ }
+
+ for (auto script : scripts) {
+ MOZ_DIAGNOSTIC_ASSERT(JS::IsTranscodingBytecodeOffsetAligned(written));
+ MOZ_TRY(Write(fd, script->Range().begin().get(), script->mSize));
+
+ written += script->mSize;
+ // We can only free the XDR data if the stencil isn't borrowing data from
+ // it.
+ if (script->mStencil && !JS::StencilIsBorrowed(script->mStencil)) {
+ script->FreeData();
+ }
+ }
+ }
+
+ MOZ_TRY(cacheFile->MoveTo(nullptr, mBaseName + u".bin"_ns));
+
+ return Ok();
+}
+
+nsresult ScriptPreloader::GetName(nsACString& aName) {
+ aName.AssignLiteral("ScriptPreloader");
+ return NS_OK;
+}
+
+// Runs in the mSaveThread thread, and writes out the cache file for the next
+// session after a reasonable delay.
+nsresult ScriptPreloader::Run() {
+ MonitorSingleWriterAutoLock mal(mSaveMonitor);
+
+ // Ideally wait about 10 seconds before saving, to avoid unnecessary IO
+ // during early startup. But only if the cache hasn't been invalidated,
+ // since that can trigger a new write during shutdown, and we don't want to
+ // cause shutdown hangs.
+ if (!mCacheInvalidated) {
+ mal.Wait(TimeDuration::FromSeconds(10));
+ }
+
+ auto result = URLPreloader::GetSingleton().WriteCache();
+ Unused << NS_WARN_IF(result.isErr());
+
+ result = WriteCache();
+ Unused << NS_WARN_IF(result.isErr());
+
+ {
+ MonitorSingleWriterAutoLock lock(mChildCache->mSaveMonitor);
+ result = mChildCache->WriteCache();
+ }
+ Unused << NS_WARN_IF(result.isErr());
+
+ NS_DispatchToMainThread(
+ NewRunnableMethod("ScriptPreloader::CacheWriteComplete", this,
+ &ScriptPreloader::CacheWriteComplete),
+ NS_DISPATCH_NORMAL);
+ return NS_OK;
+}
+
+void ScriptPreloader::CacheWriteComplete() {
+ mSaveThread->AsyncShutdown();
+ mSaveThread = nullptr;
+ mSaveComplete = true;
+
+ nsCOMPtr<nsIAsyncShutdownClient> barrier = GetShutdownBarrier();
+ barrier->RemoveBlocker(this);
+}
+
+void ScriptPreloader::NoteStencil(const nsCString& url,
+ const nsCString& cachePath,
+ JS::Stencil* stencil, bool isRunOnce) {
+ if (!Active()) {
+ if (isRunOnce) {
+ if (auto script = mScripts.Get(cachePath)) {
+ script->mIsRunOnce = true;
+ script->MaybeDropStencil();
+ }
+ }
+ return;
+ }
+
+ // Don't bother trying to cache any URLs with cache-busting query
+ // parameters.
+ if (cachePath.FindChar('?') >= 0) {
+ return;
+ }
+
+ // Don't bother caching files that belong to the mochitest harness.
+ constexpr auto mochikitPrefix = "chrome://mochikit/"_ns;
+ if (StringHead(url, mochikitPrefix.Length()) == mochikitPrefix) {
+ return;
+ }
+
+ auto* script =
+ mScripts.GetOrInsertNew(cachePath, *this, url, cachePath, stencil);
+ if (isRunOnce) {
+ script->mIsRunOnce = true;
+ }
+
+ if (!script->MaybeDropStencil() && !script->mStencil) {
+ MOZ_ASSERT(stencil);
+ script->mStencil = stencil;
+ script->mReadyToExecute = true;
+ }
+
+ script->UpdateLoadTime(TimeStamp::Now());
+ script->mProcessTypes += CurrentProcessType();
+}
+
+void ScriptPreloader::NoteStencil(const nsCString& url,
+ const nsCString& cachePath,
+ ProcessType processType,
+ nsTArray<uint8_t>&& xdrData,
+ TimeStamp loadTime) {
+ // After data has been prepared, there's no point in noting further scripts,
+ // since the cache either has already been written, or is about to be
+ // written. Any time prior to the data being prepared, we can safely mutate
+ // mScripts without locking. After that point, the save thread is free to
+ // access it, and we can't alter it without locking.
+ if (mDataPrepared) {
+ return;
+ }
+
+ auto* script =
+ mScripts.GetOrInsertNew(cachePath, *this, url, cachePath, nullptr);
+
+ if (!script->HasRange()) {
+ MOZ_ASSERT(!script->HasArray());
+
+ script->mSize = xdrData.Length();
+ script->mXDRData.construct<nsTArray<uint8_t>>(
+ std::forward<nsTArray<uint8_t>>(xdrData));
+
+ auto& data = script->Array();
+ script->mXDRRange.emplace(data.Elements(), data.Length());
+ }
+
+ if (!script->mSize && !script->mStencil) {
+ // If the content process is sending us an entry for a stencil
+ // which was in the cache at startup, it expects us to already have this
+ // script data, so it doesn't send it.
+ //
+ // However, the cache may have been invalidated at this point (usually
+ // due to the add-on manager installing or uninstalling a legacy
+ // extension during very early startup), which means we may no longer
+ // have an entry for this script. Since that means we have no data to
+ // write to the new cache, and no JSScript to generate it from, we need
+ // to discard this entry.
+ mScripts.Remove(cachePath);
+ return;
+ }
+
+ script->UpdateLoadTime(loadTime);
+ script->mProcessTypes += processType;
+}
+
+/* static */
+void ScriptPreloader::FillCompileOptionsForCachedStencil(
+ JS::CompileOptions& options) {
+ // Users of the cache do not require return values, so inform the JS parser in
+ // order for it to generate simpler bytecode.
+ options.setNoScriptRval(true);
+
+ // The ScriptPreloader trades off having bytecode available but not source
+ // text. This means the JS syntax-only parser is not used. If `toString` is
+ // called on functions in these scripts, the source-hook will fetch it over,
+ // so using `toString` of functions should be avoided in chrome js.
+ options.setSourceIsLazy(true);
+}
+
+/* static */
+void ScriptPreloader::FillDecodeOptionsForCachedStencil(
+ JS::DecodeOptions& options) {
+ // ScriptPreloader's XDR buffer is alive during the Stencil is alive.
+ // The decoded stencil can borrow from it.
+ //
+ // NOTE: The XDR buffer is alive during the entire browser lifetime only
+ // when it's mmapped.
+ options.borrowBuffer = true;
+}
+
+already_AddRefed<JS::Stencil> ScriptPreloader::GetCachedStencil(
+ JSContext* cx, const JS::ReadOnlyDecodeOptions& options,
+ const nsCString& path) {
+ MOZ_RELEASE_ASSERT(
+ !(XRE_IsContentProcess() && !mCacheInitialized),
+ "ScriptPreloader must be initialized before getting cached "
+ "scripts in the content process.");
+
+ // If a script is used by both the parent and the child, it's stored only
+ // in the child cache.
+ if (mChildCache) {
+ RefPtr<JS::Stencil> stencil =
+ mChildCache->GetCachedStencilInternal(cx, options, path);
+ if (stencil) {
+ Telemetry::AccumulateCategorical(
+ Telemetry::LABELS_SCRIPT_PRELOADER_REQUESTS::HitChild);
+ return stencil.forget();
+ }
+ }
+
+ RefPtr<JS::Stencil> stencil = GetCachedStencilInternal(cx, options, path);
+ Telemetry::AccumulateCategorical(
+ stencil ? Telemetry::LABELS_SCRIPT_PRELOADER_REQUESTS::Hit
+ : Telemetry::LABELS_SCRIPT_PRELOADER_REQUESTS::Miss);
+ return stencil.forget();
+}
+
+already_AddRefed<JS::Stencil> ScriptPreloader::GetCachedStencilInternal(
+ JSContext* cx, const JS::ReadOnlyDecodeOptions& options,
+ const nsCString& path) {
+ auto* cachedScript = mScripts.Get(path);
+ if (cachedScript) {
+ return WaitForCachedStencil(cx, options, cachedScript);
+ }
+ return nullptr;
+}
+
+already_AddRefed<JS::Stencil> ScriptPreloader::WaitForCachedStencil(
+ JSContext* cx, const JS::ReadOnlyDecodeOptions& options,
+ CachedStencil* script) {
+ if (!script->mReadyToExecute) {
+ // mReadyToExecute is kept as false only when off-thread decode task was
+ // available (pref is set to true) and the task was successfully created.
+ // See ScriptPreloader::StartDecodeTask methods.
+ MOZ_ASSERT(mDecodedStencils);
+
+ // Check for the finished operations that can contain our target.
+ if (mDecodedStencils->AvailableRead() > 0) {
+ FinishOffThreadDecode();
+ }
+
+ if (!script->mReadyToExecute) {
+ // Our target is not yet decoded.
+
+ // If script is small enough, we'd rather decode on main-thread than wait
+ // for a decode task to complete.
+ if (script->mSize < MAX_MAINTHREAD_DECODE_SIZE) {
+ LOG(Info, "Script is small enough to recompile on main thread\n");
+
+ script->mReadyToExecute = true;
+ Telemetry::ScalarAdd(
+ Telemetry::ScalarID::SCRIPT_PRELOADER_MAINTHREAD_RECOMPILE, 1);
+ } else {
+ LOG(Info, "Must wait for async script load: %s\n", script->mURL.get());
+ auto start = TimeStamp::Now();
+
+ MonitorAutoLock mal(mMonitor);
+
+ // Process finished tasks until our target is found.
+ while (!script->mReadyToExecute) {
+ if (mDecodedStencils->AvailableRead() > 0) {
+ FinishOffThreadDecode();
+ } else {
+ MOZ_ASSERT(!mDecodingScripts.isEmpty());
+ mWaitingForDecode = true;
+ mal.Wait();
+ mWaitingForDecode = false;
+ }
+ }
+
+ double waitedMS = (TimeStamp::Now() - start).ToMilliseconds();
+ Telemetry::Accumulate(Telemetry::SCRIPT_PRELOADER_WAIT_TIME,
+ int(waitedMS));
+ LOG(Debug, "Waited %fms\n", waitedMS);
+ }
+ }
+ }
+
+ return script->GetStencil(cx, options);
+}
+
+void ScriptPreloader::onDecodedStencilQueued() {
+ mMonitor.AssertNotCurrentThreadOwns();
+ MonitorAutoLock mal(mMonitor);
+
+ if (mWaitingForDecode) {
+ // Wake up the blocked main thread.
+ mal.Notify();
+ }
+
+ // NOTE: Do not perform DoFinishOffThreadDecode for partial data.
+}
+
+void ScriptPreloader::OnDecodeTaskFinished() {
+ mMonitor.AssertNotCurrentThreadOwns();
+ MonitorAutoLock mal(mMonitor);
+
+ if (mWaitingForDecode) {
+ // Wake up the blocked main thread.
+ mal.Notify();
+ } else {
+ // Issue a Runnable to handle all decoded stencils, even if the next
+ // WaitForCachedStencil call has not happened yet.
+ NS_DispatchToMainThread(
+ NewRunnableMethod("ScriptPreloader::DoFinishOffThreadDecode", this,
+ &ScriptPreloader::DoFinishOffThreadDecode));
+ }
+}
+
+void ScriptPreloader::OnDecodeTaskFailed() {
+ // NOTE: nullptr is enqueued to mDecodedStencils, and FinishOffThreadDecode
+ // handles it as failure.
+ OnDecodeTaskFinished();
+}
+
+void ScriptPreloader::FinishPendingParses(MonitorAutoLock& aMal) {
+ mMonitor.AssertCurrentThreadOwns();
+
+ // If off-thread decoding task hasn't been started, nothing to do.
+ // This can happen if the javascript.options.parallel_parsing pref was false,
+ // or the decode task fails to start.
+ if (!mDecodedStencils) {
+ return;
+ }
+
+ // Process any pending decodes that are in flight.
+ while (!mDecodingScripts.isEmpty()) {
+ if (mDecodedStencils->AvailableRead() > 0) {
+ FinishOffThreadDecode();
+ } else {
+ mWaitingForDecode = true;
+ aMal.Wait();
+ mWaitingForDecode = false;
+ }
+ }
+}
+
+void ScriptPreloader::DoFinishOffThreadDecode() {
+ // NOTE: mDecodedStencils could already be reset.
+ if (mDecodedStencils && mDecodedStencils->AvailableRead() > 0) {
+ FinishOffThreadDecode();
+ }
+}
+
+void ScriptPreloader::FinishOffThreadDecode() {
+ MOZ_ASSERT(mDecodedStencils);
+
+ while (mDecodedStencils->AvailableRead() > 0) {
+ RefPtr<JS::Stencil> stencil;
+ DebugOnly<int> reads = mDecodedStencils->Dequeue(&stencil, 1);
+ MOZ_ASSERT(reads == 1);
+
+ if (!stencil) {
+ // DecodeTask failed.
+ // Mark all remaining scripts to be decoded on the main thread.
+ for (CachedStencil* next = mDecodingScripts.getFirst(); next;) {
+ auto* script = next;
+ next = script->getNext();
+
+ script->mReadyToExecute = true;
+ script->remove();
+ }
+
+ break;
+ }
+
+ CachedStencil* script = mDecodingScripts.getFirst();
+ MOZ_ASSERT(script);
+
+ LOG(Debug, "Finished off-thread decode of %s\n", script->mURL.get());
+ script->mStencil = stencil.forget();
+ script->mReadyToExecute = true;
+ script->remove();
+ }
+
+ if (mDecodingScripts.isEmpty()) {
+ mDecodedStencils.reset();
+ }
+}
+
+void ScriptPreloader::StartDecodeTask(JS::HandleObject scope) {
+ auto start = TimeStamp::Now();
+ LOG(Debug, "Off-thread decoding scripts...\n");
+
+ Vector<JS::TranscodeSource> decodingSources;
+
+ size_t size = 0;
+ for (CachedStencil* next = mDecodingScripts.getFirst(); next;) {
+ auto* script = next;
+ next = script->getNext();
+
+ MOZ_ASSERT(script->IsMemMapped());
+
+ // Skip any scripts that we decoded on the main thread rather than
+ // waiting for an off-thread operation to complete.
+ if (script->mReadyToExecute) {
+ script->remove();
+ continue;
+ }
+ if (!decodingSources.emplaceBack(script->Range(), script->mURL.get(), 0)) {
+ break;
+ }
+
+ LOG(Debug, "Beginning off-thread decode of script %s (%u bytes)\n",
+ script->mURL.get(), script->mSize);
+
+ size += script->mSize;
+ }
+
+ MOZ_ASSERT(decodingSources.length() == mDecodingScripts.length());
+
+ if (size == 0 && mDecodingScripts.isEmpty()) {
+ return;
+ }
+
+ AutoSafeJSAPI jsapi;
+ JSContext* cx = jsapi.cx();
+ JSAutoRealm ar(cx, scope ? scope : xpc::CompilationScope());
+
+ JS::CompileOptions options(cx);
+ FillCompileOptionsForCachedStencil(options);
+
+ // All XDR buffers are mmapped and live longer than JS runtime.
+ // The bytecode can be borrowed from the buffer.
+ options.borrowBuffer = true;
+ options.usePinnedBytecode = true;
+
+ JS::DecodeOptions decodeOptions(options);
+
+ size_t decodingSourcesLength = decodingSources.length();
+
+ if (!StaticPrefs::javascript_options_parallel_parsing() ||
+ !StartDecodeTask(decodeOptions, std::move(decodingSources))) {
+ LOG(Info, "Can't decode %lu bytes of scripts off-thread",
+ (unsigned long)size);
+ for (auto* script : mDecodingScripts) {
+ script->mReadyToExecute = true;
+ }
+ return;
+ }
+
+ LOG(Debug, "Initialized decoding of %u scripts (%u bytes) in %fms\n",
+ (unsigned)decodingSourcesLength, (unsigned)size,
+ (TimeStamp::Now() - start).ToMilliseconds());
+}
+
+bool ScriptPreloader::StartDecodeTask(
+ const JS::ReadOnlyDecodeOptions& decodeOptions,
+ Vector<JS::TranscodeSource>&& decodingSources) {
+ mDecodedStencils.emplace(decodingSources.length());
+ MOZ_ASSERT(mDecodedStencils);
+
+ nsCOMPtr<nsIRunnable> task =
+ new DecodeTask(this, decodeOptions, std::move(decodingSources));
+
+ nsresult rv = NS_DispatchBackgroundTask(task.forget());
+
+ return NS_SUCCEEDED(rv);
+}
+
+NS_IMETHODIMP ScriptPreloader::DecodeTask::Run() {
+ auto failure = [&]() {
+ RefPtr<JS::Stencil> stencil;
+ DebugOnly<int> writes = mPreloader->mDecodedStencils->Enqueue(stencil);
+ MOZ_ASSERT(writes == 1);
+ mPreloader->OnDecodeTaskFailed();
+ };
+
+ JS::FrontendContext* fc = JS::NewFrontendContext();
+ if (!fc) {
+ failure();
+ return NS_OK;
+ }
+
+ auto cleanup = MakeScopeExit([&]() { JS::DestroyFrontendContext(fc); });
+
+ size_t stackSize = TaskController::GetThreadStackSize();
+ JS::SetNativeStackQuota(fc, JS::ThreadStackQuotaForSize(stackSize));
+
+ size_t remaining = mDecodingSources.length();
+ for (auto& source : mDecodingSources) {
+ RefPtr<JS::Stencil> stencil;
+ auto result = JS::DecodeStencil(fc, mDecodeOptions, source.range,
+ getter_AddRefs(stencil));
+ if (result != JS::TranscodeResult::Ok) {
+ failure();
+ return NS_OK;
+ }
+
+ DebugOnly<int> writes = mPreloader->mDecodedStencils->Enqueue(stencil);
+ MOZ_ASSERT(writes == 1);
+
+ remaining--;
+ if (remaining) {
+ mPreloader->onDecodedStencilQueued();
+ }
+ }
+
+ mPreloader->OnDecodeTaskFinished();
+ return NS_OK;
+}
+
+ScriptPreloader::CachedStencil::CachedStencil(ScriptPreloader& cache,
+ InputBuffer& buf)
+ : mCache(cache) {
+ Code(buf);
+
+ // Swap the mProcessTypes and mOriginalProcessTypes values, since we want to
+ // start with an empty set of processes loaded into for this session, and
+ // compare against last session's values later.
+ mOriginalProcessTypes = mProcessTypes;
+ mProcessTypes = {};
+}
+
+bool ScriptPreloader::CachedStencil::XDREncode(JSContext* cx) {
+ auto cleanup = MakeScopeExit([&]() { MaybeDropStencil(); });
+
+ mXDRData.construct<JS::TranscodeBuffer>();
+
+ JS::TranscodeResult code = JS::EncodeStencil(cx, mStencil, Buffer());
+ if (code == JS::TranscodeResult::Ok) {
+ mXDRRange.emplace(Buffer().begin(), Buffer().length());
+ mSize = Range().length();
+ return true;
+ }
+ mXDRData.destroy();
+ JS_ClearPendingException(cx);
+ return false;
+}
+
+already_AddRefed<JS::Stencil> ScriptPreloader::CachedStencil::GetStencil(
+ JSContext* cx, const JS::ReadOnlyDecodeOptions& options) {
+ MOZ_ASSERT(mReadyToExecute);
+ if (mStencil) {
+ return do_AddRef(mStencil);
+ }
+
+ if (!HasRange()) {
+ // We've already executed the script, and thrown it away. But it wasn't
+ // in the cache at startup, so we don't have any data to decode. Give
+ // up.
+ return nullptr;
+ }
+
+ // If we have no script at this point, the script was too small to decode
+ // off-thread, or it was needed before the off-thread compilation was
+ // finished, and is small enough to decode on the main thread rather than
+ // wait for the off-thread decoding to finish. In either case, we decode
+ // it synchronously the first time it's needed.
+
+ auto start = TimeStamp::Now();
+ LOG(Info, "Decoding stencil %s on main thread...\n", mURL.get());
+
+ RefPtr<JS::Stencil> stencil;
+ if (JS::DecodeStencil(cx, options, Range(), getter_AddRefs(stencil)) ==
+ JS::TranscodeResult::Ok) {
+ // Lock the monitor here to avoid data races on mScript
+ // from other threads like the cache writing thread.
+ //
+ // It is possible that we could end up decoding the same
+ // script twice, because DecodeScript isn't being guarded
+ // by the monitor; however, to encourage off-thread decode
+ // to proceed for other scripts we don't hold the monitor
+ // while doing main thread decode, merely while updating
+ // mScript.
+ mCache.mMonitor.AssertNotCurrentThreadOwns();
+ MonitorAutoLock mal(mCache.mMonitor);
+
+ mStencil = stencil.forget();
+
+ if (mCache.mSaveComplete) {
+ // We can only free XDR data if the stencil isn't borrowing data out of
+ // it.
+ if (!JS::StencilIsBorrowed(mStencil)) {
+ FreeData();
+ }
+ }
+ }
+
+ LOG(Debug, "Finished decoding in %fms",
+ (TimeStamp::Now() - start).ToMilliseconds());
+
+ return do_AddRef(mStencil);
+}
+
+// nsIAsyncShutdownBlocker
+
+nsresult ScriptPreloader::GetName(nsAString& aName) {
+ aName.AssignLiteral(u"ScriptPreloader: Saving bytecode cache");
+ return NS_OK;
+}
+
+nsresult ScriptPreloader::GetState(nsIPropertyBag** aState) {
+ *aState = nullptr;
+ return NS_OK;
+}
+
+nsresult ScriptPreloader::BlockShutdown(
+ nsIAsyncShutdownClient* aBarrierClient) {
+ // If we're waiting on a timeout to finish saving, interrupt it and just save
+ // immediately.
+ mSaveMonitor.NotifyAll();
+ return NS_OK;
+}
+
+already_AddRefed<nsIAsyncShutdownClient> ScriptPreloader::GetShutdownBarrier() {
+ nsCOMPtr<nsIAsyncShutdownService> svc = components::AsyncShutdown::Service();
+ MOZ_RELEASE_ASSERT(svc);
+
+ nsCOMPtr<nsIAsyncShutdownClient> barrier;
+ Unused << svc->GetXpcomWillShutdown(getter_AddRefs(barrier));
+ MOZ_RELEASE_ASSERT(barrier);
+
+ return barrier.forget();
+}
+
+NS_IMPL_ISUPPORTS(ScriptPreloader, nsIObserver, nsIRunnable, nsIMemoryReporter,
+ nsINamed, nsIAsyncShutdownBlocker)
+
+#undef LOG
+
+} // namespace mozilla