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/* -*- 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
#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.
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