// Copyright (c) 2012 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #include "base/metrics/field_trial.h" #include #include #include "base/base_switches.h" #include "base/build_time.h" #include "base/command_line.h" #include "base/debug/activity_tracker.h" #include "base/logging.h" #include "base/metrics/field_trial_param_associator.h" #include "base/metrics/histogram_macros.h" #include "base/process/memory.h" #include "base/process/process_handle.h" #include "base/process/process_info.h" #include "base/rand_util.h" #include "base/strings/string_number_conversions.h" #include "base/strings/string_split.h" #include "base/strings/string_util.h" #include "base/strings/stringprintf.h" #include "base/strings/utf_string_conversions.h" #include "base/unguessable_token.h" // On POSIX, the fd is shared using the mapping in GlobalDescriptors. #if defined(OS_POSIX) && !defined(OS_NACL) #include "base/posix/global_descriptors.h" #endif namespace base { namespace { // Define a separator character to use when creating a persistent form of an // instance. This is intended for use as a command line argument, passed to a // second process to mimic our state (i.e., provide the same group name). const char kPersistentStringSeparator = '/'; // Currently a slash. // Define a marker character to be used as a prefix to a trial name on the // command line which forces its activation. const char kActivationMarker = '*'; // Use shared memory to communicate field trial (experiment) state. Set to false // for now while the implementation is fleshed out (e.g. data format, single // shared memory segment). See https://codereview.chromium.org/2365273004/ and // crbug.com/653874 // The browser is the only process that has write access to the shared memory. // This is safe from race conditions because MakeIterable is a release operation // and GetNextOfType is an acquire operation, so memory writes before // MakeIterable happen before memory reads after GetNextOfType. #if defined(OS_FUCHSIA) // TODO(752368): Not yet supported on Fuchsia. const bool kUseSharedMemoryForFieldTrials = false; #else const bool kUseSharedMemoryForFieldTrials = true; #endif // Constants for the field trial allocator. const char kAllocatorName[] = "FieldTrialAllocator"; // We allocate 128 KiB to hold all the field trial data. This should be enough, // as most people use 3 - 25 KiB for field trials (as of 11/25/2016). // This also doesn't allocate all 128 KiB at once -- the pages only get mapped // to physical memory when they are touched. If the size of the allocated field // trials does get larger than 128 KiB, then we will drop some field trials in // child processes, leading to an inconsistent view between browser and child // processes and possibly causing crashes (see crbug.com/661617). const size_t kFieldTrialAllocationSize = 128 << 10; // 128 KiB // Writes out string1 and then string2 to pickle. void WriteStringPair(Pickle* pickle, const StringPiece& string1, const StringPiece& string2) { pickle->WriteString(string1); pickle->WriteString(string2); } // Writes out the field trial's contents (via trial_state) to the pickle. The // format of the pickle looks like: // TrialName, GroupName, ParamKey1, ParamValue1, ParamKey2, ParamValue2, ... // If there are no parameters, then it just ends at GroupName. void PickleFieldTrial(const FieldTrial::State& trial_state, Pickle* pickle) { WriteStringPair(pickle, *trial_state.trial_name, *trial_state.group_name); // Get field trial params. std::map params; FieldTrialParamAssociator::GetInstance()->GetFieldTrialParamsWithoutFallback( *trial_state.trial_name, *trial_state.group_name, ¶ms); // Write params to pickle. for (const auto& param : params) WriteStringPair(pickle, param.first, param.second); } // Created a time value based on |year|, |month| and |day_of_month| parameters. Time CreateTimeFromParams(int year, int month, int day_of_month) { DCHECK_GT(year, 1970); DCHECK_GT(month, 0); DCHECK_LT(month, 13); DCHECK_GT(day_of_month, 0); DCHECK_LT(day_of_month, 32); Time::Exploded exploded; exploded.year = year; exploded.month = month; exploded.day_of_week = 0; // Should be unused. exploded.day_of_month = day_of_month; exploded.hour = 0; exploded.minute = 0; exploded.second = 0; exploded.millisecond = 0; Time out_time; if (!Time::FromLocalExploded(exploded, &out_time)) { // TODO(maksims): implement failure handling. // We might just return |out_time|, which is Time(0). NOTIMPLEMENTED(); } return out_time; } // Returns the boundary value for comparing against the FieldTrial's added // groups for a given |divisor| (total probability) and |entropy_value|. FieldTrial::Probability GetGroupBoundaryValue( FieldTrial::Probability divisor, double entropy_value) { // Add a tiny epsilon value to get consistent results when converting floating // points to int. Without it, boundary values have inconsistent results, e.g.: // // static_cast(100 * 0.56) == 56 // static_cast(100 * 0.57) == 56 // static_cast(100 * 0.58) == 57 // static_cast(100 * 0.59) == 59 const double kEpsilon = 1e-8; const FieldTrial::Probability result = static_cast(divisor * entropy_value + kEpsilon); // Ensure that adding the epsilon still results in a value < |divisor|. return std::min(result, divisor - 1); } // Separate type from FieldTrial::State so that it can use StringPieces. struct FieldTrialStringEntry { StringPiece trial_name; StringPiece group_name; bool activated = false; }; // Parses the --force-fieldtrials string |trials_string| into |entries|. // Returns true if the string was parsed correctly. On failure, the |entries| // array may end up being partially filled. bool ParseFieldTrialsString(const std::string& trials_string, std::vector* entries) { const StringPiece trials_string_piece(trials_string); size_t next_item = 0; while (next_item < trials_string.length()) { size_t name_end = trials_string.find(kPersistentStringSeparator, next_item); if (name_end == trials_string.npos || next_item == name_end) return false; size_t group_name_end = trials_string.find(kPersistentStringSeparator, name_end + 1); if (name_end + 1 == group_name_end) return false; if (group_name_end == trials_string.npos) group_name_end = trials_string.length(); FieldTrialStringEntry entry; // Verify if the trial should be activated or not. if (trials_string[next_item] == kActivationMarker) { // Name cannot be only the indicator. if (name_end - next_item == 1) return false; next_item++; entry.activated = true; } entry.trial_name = trials_string_piece.substr(next_item, name_end - next_item); entry.group_name = trials_string_piece.substr(name_end + 1, group_name_end - name_end - 1); next_item = group_name_end + 1; entries->push_back(std::move(entry)); } return true; } void AddFeatureAndFieldTrialFlags(const char* enable_features_switch, const char* disable_features_switch, CommandLine* cmd_line) { std::string enabled_features; std::string disabled_features; FeatureList::GetInstance()->GetFeatureOverrides(&enabled_features, &disabled_features); if (!enabled_features.empty()) cmd_line->AppendSwitchASCII(enable_features_switch, enabled_features); if (!disabled_features.empty()) cmd_line->AppendSwitchASCII(disable_features_switch, disabled_features); std::string field_trial_states; FieldTrialList::AllStatesToString(&field_trial_states, false); if (!field_trial_states.empty()) { cmd_line->AppendSwitchASCII(switches::kForceFieldTrials, field_trial_states); } } void OnOutOfMemory(size_t size) { #if defined(OS_NACL) NOTREACHED(); #else TerminateBecauseOutOfMemory(size); #endif } #if !defined(OS_NACL) // Returns whether the operation succeeded. bool DeserializeGUIDFromStringPieces(base::StringPiece first, base::StringPiece second, base::UnguessableToken* guid) { uint64_t high = 0; uint64_t low = 0; if (!base::StringToUint64(first, &high) || !base::StringToUint64(second, &low)) { return false; } *guid = base::UnguessableToken::Deserialize(high, low); return true; } // Extract a read-only SharedMemoryHandle from an existing |shared_memory| // handle. Note that on Android, this also makes the whole region read-only. SharedMemoryHandle GetSharedMemoryReadOnlyHandle(SharedMemory* shared_memory) { SharedMemoryHandle result = shared_memory->GetReadOnlyHandle(); #if defined(OS_ANDROID) // On Android, turn the region read-only. This prevents any future // writable mapping attempts, but the original one in |shm| survives // and is still usable in the current process. result.SetRegionReadOnly(); #endif // OS_ANDROID return result; } #endif // !OS_NACL } // namespace // statics const int FieldTrial::kNotFinalized = -1; const int FieldTrial::kDefaultGroupNumber = 0; bool FieldTrial::enable_benchmarking_ = false; int FieldTrialList::kNoExpirationYear = 0; //------------------------------------------------------------------------------ // FieldTrial methods and members. FieldTrial::EntropyProvider::~EntropyProvider() = default; FieldTrial::State::State() = default; FieldTrial::State::State(const State& other) = default; FieldTrial::State::~State() = default; bool FieldTrial::FieldTrialEntry::GetTrialAndGroupName( StringPiece* trial_name, StringPiece* group_name) const { PickleIterator iter = GetPickleIterator(); return ReadStringPair(&iter, trial_name, group_name); } bool FieldTrial::FieldTrialEntry::GetParams( std::map* params) const { PickleIterator iter = GetPickleIterator(); StringPiece tmp; // Skip reading trial and group name. if (!ReadStringPair(&iter, &tmp, &tmp)) return false; while (true) { StringPiece key; StringPiece value; if (!ReadStringPair(&iter, &key, &value)) return key.empty(); // Non-empty is bad: got one of a pair. (*params)[key.as_string()] = value.as_string(); } } PickleIterator FieldTrial::FieldTrialEntry::GetPickleIterator() const { const char* src = reinterpret_cast(this) + sizeof(FieldTrialEntry); Pickle pickle(src, pickle_size); return PickleIterator(pickle); } bool FieldTrial::FieldTrialEntry::ReadStringPair( PickleIterator* iter, StringPiece* trial_name, StringPiece* group_name) const { if (!iter->ReadStringPiece(trial_name)) return false; if (!iter->ReadStringPiece(group_name)) return false; return true; } void FieldTrial::Disable() { DCHECK(!group_reported_); enable_field_trial_ = false; // In case we are disabled after initialization, we need to switch // the trial to the default group. if (group_ != kNotFinalized) { // Only reset when not already the default group, because in case we were // forced to the default group, the group number may not be // kDefaultGroupNumber, so we should keep it as is. if (group_name_ != default_group_name_) SetGroupChoice(default_group_name_, kDefaultGroupNumber); } } int FieldTrial::AppendGroup(const std::string& name, Probability group_probability) { // When the group choice was previously forced, we only need to return the // the id of the chosen group, and anything can be returned for the others. if (forced_) { DCHECK(!group_name_.empty()); if (name == group_name_) { // Note that while |group_| may be equal to |kDefaultGroupNumber| on the // forced trial, it will not have the same value as the default group // number returned from the non-forced |FactoryGetFieldTrial()| call, // which takes care to ensure that this does not happen. return group_; } DCHECK_NE(next_group_number_, group_); // We still return different numbers each time, in case some caller need // them to be different. return next_group_number_++; } DCHECK_LE(group_probability, divisor_); DCHECK_GE(group_probability, 0); if (enable_benchmarking_ || !enable_field_trial_) group_probability = 0; accumulated_group_probability_ += group_probability; DCHECK_LE(accumulated_group_probability_, divisor_); if (group_ == kNotFinalized && accumulated_group_probability_ > random_) { // This is the group that crossed the random line, so we do the assignment. SetGroupChoice(name, next_group_number_); } return next_group_number_++; } int FieldTrial::group() { FinalizeGroupChoice(); if (trial_registered_) FieldTrialList::NotifyFieldTrialGroupSelection(this); return group_; } const std::string& FieldTrial::group_name() { // Call |group()| to ensure group gets assigned and observers are notified. group(); DCHECK(!group_name_.empty()); return group_name_; } const std::string& FieldTrial::GetGroupNameWithoutActivation() { FinalizeGroupChoice(); return group_name_; } void FieldTrial::SetForced() { // We might have been forced before (e.g., by CreateFieldTrial) and it's // first come first served, e.g., command line switch has precedence. if (forced_) return; // And we must finalize the group choice before we mark ourselves as forced. FinalizeGroupChoice(); forced_ = true; } // static void FieldTrial::EnableBenchmarking() { DCHECK_EQ(0u, FieldTrialList::GetFieldTrialCount()); enable_benchmarking_ = true; } // static FieldTrial* FieldTrial::CreateSimulatedFieldTrial( const std::string& trial_name, Probability total_probability, const std::string& default_group_name, double entropy_value) { return new FieldTrial(trial_name, total_probability, default_group_name, entropy_value); } FieldTrial::FieldTrial(const std::string& trial_name, const Probability total_probability, const std::string& default_group_name, double entropy_value) : trial_name_(trial_name), divisor_(total_probability), default_group_name_(default_group_name), random_(GetGroupBoundaryValue(total_probability, entropy_value)), accumulated_group_probability_(0), next_group_number_(kDefaultGroupNumber + 1), group_(kNotFinalized), enable_field_trial_(true), forced_(false), group_reported_(false), trial_registered_(false), ref_(FieldTrialList::FieldTrialAllocator::kReferenceNull) { DCHECK_GT(total_probability, 0); DCHECK(!trial_name_.empty()); DCHECK(!default_group_name_.empty()) << "Trial " << trial_name << " is missing a default group name."; } FieldTrial::~FieldTrial() = default; void FieldTrial::SetTrialRegistered() { DCHECK_EQ(kNotFinalized, group_); DCHECK(!trial_registered_); trial_registered_ = true; } void FieldTrial::SetGroupChoice(const std::string& group_name, int number) { group_ = number; if (group_name.empty()) StringAppendF(&group_name_, "%d", group_); else group_name_ = group_name; DVLOG(1) << "Field trial: " << trial_name_ << " Group choice:" << group_name_; } void FieldTrial::FinalizeGroupChoice() { FinalizeGroupChoiceImpl(false); } void FieldTrial::FinalizeGroupChoiceImpl(bool is_locked) { if (group_ != kNotFinalized) return; accumulated_group_probability_ = divisor_; // Here it's OK to use |kDefaultGroupNumber| since we can't be forced and not // finalized. DCHECK(!forced_); SetGroupChoice(default_group_name_, kDefaultGroupNumber); // Add the field trial to shared memory. if (kUseSharedMemoryForFieldTrials && trial_registered_) FieldTrialList::OnGroupFinalized(is_locked, this); } bool FieldTrial::GetActiveGroup(ActiveGroup* active_group) const { if (!group_reported_ || !enable_field_trial_) return false; DCHECK_NE(group_, kNotFinalized); active_group->trial_name = trial_name_; active_group->group_name = group_name_; return true; } bool FieldTrial::GetStateWhileLocked(State* field_trial_state, bool include_expired) { if (!include_expired && !enable_field_trial_) return false; FinalizeGroupChoiceImpl(true); field_trial_state->trial_name = &trial_name_; field_trial_state->group_name = &group_name_; field_trial_state->activated = group_reported_; return true; } //------------------------------------------------------------------------------ // FieldTrialList methods and members. // static FieldTrialList* FieldTrialList::global_ = nullptr; // static bool FieldTrialList::used_without_global_ = false; FieldTrialList::Observer::~Observer() = default; FieldTrialList::FieldTrialList( std::unique_ptr entropy_provider) : entropy_provider_(std::move(entropy_provider)), observer_list_(new ObserverListThreadSafe( ObserverListPolicy::EXISTING_ONLY)) { DCHECK(!global_); DCHECK(!used_without_global_); global_ = this; Time two_years_from_build_time = GetBuildTime() + TimeDelta::FromDays(730); Time::Exploded exploded; two_years_from_build_time.LocalExplode(&exploded); kNoExpirationYear = exploded.year; } FieldTrialList::~FieldTrialList() { AutoLock auto_lock(lock_); while (!registered_.empty()) { RegistrationMap::iterator it = registered_.begin(); it->second->Release(); registered_.erase(it->first); } DCHECK_EQ(this, global_); global_ = nullptr; } // static FieldTrial* FieldTrialList::FactoryGetFieldTrial( const std::string& trial_name, FieldTrial::Probability total_probability, const std::string& default_group_name, const int year, const int month, const int day_of_month, FieldTrial::RandomizationType randomization_type, int* default_group_number) { return FactoryGetFieldTrialWithRandomizationSeed( trial_name, total_probability, default_group_name, year, month, day_of_month, randomization_type, 0, default_group_number, nullptr); } // static FieldTrial* FieldTrialList::FactoryGetFieldTrialWithRandomizationSeed( const std::string& trial_name, FieldTrial::Probability total_probability, const std::string& default_group_name, const int year, const int month, const int day_of_month, FieldTrial::RandomizationType randomization_type, uint32_t randomization_seed, int* default_group_number, const FieldTrial::EntropyProvider* override_entropy_provider) { if (default_group_number) *default_group_number = FieldTrial::kDefaultGroupNumber; // Check if the field trial has already been created in some other way. FieldTrial* existing_trial = Find(trial_name); if (existing_trial) { CHECK(existing_trial->forced_); // If the default group name differs between the existing forced trial // and this trial, then use a different value for the default group number. if (default_group_number && default_group_name != existing_trial->default_group_name()) { // If the new default group number corresponds to the group that was // chosen for the forced trial (which has been finalized when it was // forced), then set the default group number to that. if (default_group_name == existing_trial->group_name_internal()) { *default_group_number = existing_trial->group_; } else { // Otherwise, use |kNonConflictingGroupNumber| (-2) for the default // group number, so that it does not conflict with the |AppendGroup()| // result for the chosen group. const int kNonConflictingGroupNumber = -2; static_assert( kNonConflictingGroupNumber != FieldTrial::kDefaultGroupNumber, "The 'non-conflicting' group number conflicts"); static_assert(kNonConflictingGroupNumber != FieldTrial::kNotFinalized, "The 'non-conflicting' group number conflicts"); *default_group_number = kNonConflictingGroupNumber; } } return existing_trial; } double entropy_value; if (randomization_type == FieldTrial::ONE_TIME_RANDOMIZED) { // If an override entropy provider is given, use it. const FieldTrial::EntropyProvider* entropy_provider = override_entropy_provider ? override_entropy_provider : GetEntropyProviderForOneTimeRandomization(); CHECK(entropy_provider); entropy_value = entropy_provider->GetEntropyForTrial(trial_name, randomization_seed); } else { DCHECK_EQ(FieldTrial::SESSION_RANDOMIZED, randomization_type); DCHECK_EQ(0U, randomization_seed); entropy_value = RandDouble(); } FieldTrial* field_trial = new FieldTrial(trial_name, total_probability, default_group_name, entropy_value); if (GetBuildTime() > CreateTimeFromParams(year, month, day_of_month)) field_trial->Disable(); FieldTrialList::Register(field_trial); return field_trial; } // static FieldTrial* FieldTrialList::Find(const std::string& trial_name) { if (!global_) return nullptr; AutoLock auto_lock(global_->lock_); return global_->PreLockedFind(trial_name); } // static int FieldTrialList::FindValue(const std::string& trial_name) { FieldTrial* field_trial = Find(trial_name); if (field_trial) return field_trial->group(); return FieldTrial::kNotFinalized; } // static std::string FieldTrialList::FindFullName(const std::string& trial_name) { FieldTrial* field_trial = Find(trial_name); if (field_trial) return field_trial->group_name(); return std::string(); } // static bool FieldTrialList::TrialExists(const std::string& trial_name) { return Find(trial_name) != nullptr; } // static bool FieldTrialList::IsTrialActive(const std::string& trial_name) { FieldTrial* field_trial = Find(trial_name); FieldTrial::ActiveGroup active_group; return field_trial && field_trial->GetActiveGroup(&active_group); } // static void FieldTrialList::StatesToString(std::string* output) { FieldTrial::ActiveGroups active_groups; GetActiveFieldTrialGroups(&active_groups); for (FieldTrial::ActiveGroups::const_iterator it = active_groups.begin(); it != active_groups.end(); ++it) { DCHECK_EQ(std::string::npos, it->trial_name.find(kPersistentStringSeparator)); DCHECK_EQ(std::string::npos, it->group_name.find(kPersistentStringSeparator)); output->append(it->trial_name); output->append(1, kPersistentStringSeparator); output->append(it->group_name); output->append(1, kPersistentStringSeparator); } } // static void FieldTrialList::AllStatesToString(std::string* output, bool include_expired) { if (!global_) return; AutoLock auto_lock(global_->lock_); for (const auto& registered : global_->registered_) { FieldTrial::State trial; if (!registered.second->GetStateWhileLocked(&trial, include_expired)) continue; DCHECK_EQ(std::string::npos, trial.trial_name->find(kPersistentStringSeparator)); DCHECK_EQ(std::string::npos, trial.group_name->find(kPersistentStringSeparator)); if (trial.activated) output->append(1, kActivationMarker); output->append(*trial.trial_name); output->append(1, kPersistentStringSeparator); output->append(*trial.group_name); output->append(1, kPersistentStringSeparator); } } // static std::string FieldTrialList::AllParamsToString(bool include_expired, EscapeDataFunc encode_data_func) { FieldTrialParamAssociator* params_associator = FieldTrialParamAssociator::GetInstance(); std::string output; for (const auto& registered : GetRegisteredTrials()) { FieldTrial::State trial; if (!registered.second->GetStateWhileLocked(&trial, include_expired)) continue; DCHECK_EQ(std::string::npos, trial.trial_name->find(kPersistentStringSeparator)); DCHECK_EQ(std::string::npos, trial.group_name->find(kPersistentStringSeparator)); std::map params; if (params_associator->GetFieldTrialParamsWithoutFallback( *trial.trial_name, *trial.group_name, ¶ms)) { if (params.size() > 0) { // Add comma to seprate from previous entry if it exists. if (!output.empty()) output.append(1, ','); output.append(encode_data_func(*trial.trial_name)); output.append(1, '.'); output.append(encode_data_func(*trial.group_name)); output.append(1, ':'); std::string param_str; for (const auto& param : params) { // Add separator from previous param information if it exists. if (!param_str.empty()) param_str.append(1, kPersistentStringSeparator); param_str.append(encode_data_func(param.first)); param_str.append(1, kPersistentStringSeparator); param_str.append(encode_data_func(param.second)); } output.append(param_str); } } } return output; } // static void FieldTrialList::GetActiveFieldTrialGroups( FieldTrial::ActiveGroups* active_groups) { DCHECK(active_groups->empty()); if (!global_) return; AutoLock auto_lock(global_->lock_); for (RegistrationMap::iterator it = global_->registered_.begin(); it != global_->registered_.end(); ++it) { FieldTrial::ActiveGroup active_group; if (it->second->GetActiveGroup(&active_group)) active_groups->push_back(active_group); } } // static void FieldTrialList::GetActiveFieldTrialGroupsFromString( const std::string& trials_string, FieldTrial::ActiveGroups* active_groups) { std::vector entries; if (!ParseFieldTrialsString(trials_string, &entries)) return; for (const auto& entry : entries) { if (entry.activated) { FieldTrial::ActiveGroup group; group.trial_name = entry.trial_name.as_string(); group.group_name = entry.group_name.as_string(); active_groups->push_back(group); } } } // static void FieldTrialList::GetInitiallyActiveFieldTrials( const base::CommandLine& command_line, FieldTrial::ActiveGroups* active_groups) { DCHECK(global_); DCHECK(global_->create_trials_from_command_line_called_); if (!global_->field_trial_allocator_) { GetActiveFieldTrialGroupsFromString( command_line.GetSwitchValueASCII(switches::kForceFieldTrials), active_groups); return; } FieldTrialAllocator* allocator = global_->field_trial_allocator_.get(); FieldTrialAllocator::Iterator mem_iter(allocator); const FieldTrial::FieldTrialEntry* entry; while ((entry = mem_iter.GetNextOfObject()) != nullptr) { StringPiece trial_name; StringPiece group_name; if (subtle::NoBarrier_Load(&entry->activated) && entry->GetTrialAndGroupName(&trial_name, &group_name)) { FieldTrial::ActiveGroup group; group.trial_name = trial_name.as_string(); group.group_name = group_name.as_string(); active_groups->push_back(group); } } } // static bool FieldTrialList::CreateTrialsFromString( const std::string& trials_string, const std::set& ignored_trial_names) { DCHECK(global_); if (trials_string.empty() || !global_) return true; std::vector entries; if (!ParseFieldTrialsString(trials_string, &entries)) return false; for (const auto& entry : entries) { const std::string trial_name = entry.trial_name.as_string(); const std::string group_name = entry.group_name.as_string(); if (ContainsKey(ignored_trial_names, trial_name)) { // This is to warn that the field trial forced through command-line // input is unforcable. // Use --enable-logging or --enable-logging=stderr to see this warning. LOG(WARNING) << "Field trial: " << trial_name << " cannot be forced."; continue; } FieldTrial* trial = CreateFieldTrial(trial_name, group_name); if (!trial) return false; if (entry.activated) { // Call |group()| to mark the trial as "used" and notify observers, if // any. This is useful to ensure that field trials created in child // processes are properly reported in crash reports. trial->group(); } } return true; } // static void FieldTrialList::CreateTrialsFromCommandLine( const CommandLine& cmd_line, const char* field_trial_handle_switch, int fd_key) { global_->create_trials_from_command_line_called_ = true; #if defined(OS_WIN) || defined(OS_FUCHSIA) if (cmd_line.HasSwitch(field_trial_handle_switch)) { std::string switch_value = cmd_line.GetSwitchValueASCII(field_trial_handle_switch); bool result = CreateTrialsFromSwitchValue(switch_value); UMA_HISTOGRAM_BOOLEAN("ChildProcess.FieldTrials.CreateFromShmemSuccess", result); DCHECK(result); } #elif defined(OS_POSIX) && !defined(OS_NACL) // On POSIX, we check if the handle is valid by seeing if the browser process // sent over the switch (we don't care about the value). Invalid handles // occur in some browser tests which don't initialize the allocator. if (cmd_line.HasSwitch(field_trial_handle_switch)) { std::string switch_value = cmd_line.GetSwitchValueASCII(field_trial_handle_switch); bool result = CreateTrialsFromDescriptor(fd_key, switch_value); UMA_HISTOGRAM_BOOLEAN("ChildProcess.FieldTrials.CreateFromShmemSuccess", result); DCHECK(result); } #endif if (cmd_line.HasSwitch(switches::kForceFieldTrials)) { bool result = FieldTrialList::CreateTrialsFromString( cmd_line.GetSwitchValueASCII(switches::kForceFieldTrials), std::set()); UMA_HISTOGRAM_BOOLEAN("ChildProcess.FieldTrials.CreateFromSwitchSuccess", result); DCHECK(result); } } // static void FieldTrialList::CreateFeaturesFromCommandLine( const base::CommandLine& command_line, const char* enable_features_switch, const char* disable_features_switch, FeatureList* feature_list) { // Fallback to command line if not using shared memory. if (!kUseSharedMemoryForFieldTrials || !global_->field_trial_allocator_.get()) { return feature_list->InitializeFromCommandLine( command_line.GetSwitchValueASCII(enable_features_switch), command_line.GetSwitchValueASCII(disable_features_switch)); } feature_list->InitializeFromSharedMemory( global_->field_trial_allocator_.get()); } #if defined(OS_WIN) // static void FieldTrialList::AppendFieldTrialHandleIfNeeded( HandlesToInheritVector* handles) { if (!global_) return; if (kUseSharedMemoryForFieldTrials) { InstantiateFieldTrialAllocatorIfNeeded(); if (global_->readonly_allocator_handle_.IsValid()) handles->push_back(global_->readonly_allocator_handle_.GetHandle()); } } #elif defined(OS_FUCHSIA) // TODO(fuchsia): Implement shared-memory configuration (crbug.com/752368). #elif defined(OS_POSIX) && !defined(OS_NACL) // static SharedMemoryHandle FieldTrialList::GetFieldTrialHandle() { if (global_ && kUseSharedMemoryForFieldTrials) { InstantiateFieldTrialAllocatorIfNeeded(); // We check for an invalid handle where this gets called. return global_->readonly_allocator_handle_; } return SharedMemoryHandle(); } #endif // static void FieldTrialList::CopyFieldTrialStateToFlags( const char* field_trial_handle_switch, const char* enable_features_switch, const char* disable_features_switch, CommandLine* cmd_line) { // TODO(lawrencewu): Ideally, having the global would be guaranteed. However, // content browser tests currently don't create a FieldTrialList because they // don't run ChromeBrowserMainParts code where it's done for Chrome. // Some tests depend on the enable and disable features flag switch, though, // so we can still add those even though AllStatesToString() will be a no-op. if (!global_) { AddFeatureAndFieldTrialFlags(enable_features_switch, disable_features_switch, cmd_line); return; } // Use shared memory to pass the state if the feature is enabled, otherwise // fallback to passing it via the command line as a string. if (kUseSharedMemoryForFieldTrials) { InstantiateFieldTrialAllocatorIfNeeded(); // If the readonly handle didn't get duplicated properly, then fallback to // original behavior. if (!global_->readonly_allocator_handle_.IsValid()) { AddFeatureAndFieldTrialFlags(enable_features_switch, disable_features_switch, cmd_line); return; } global_->field_trial_allocator_->UpdateTrackingHistograms(); std::string switch_value = SerializeSharedMemoryHandleMetadata( global_->readonly_allocator_handle_); cmd_line->AppendSwitchASCII(field_trial_handle_switch, switch_value); // Append --enable-features and --disable-features switches corresponding // to the features enabled on the command-line, so that child and browser // process command lines match and clearly show what has been specified // explicitly by the user. std::string enabled_features; std::string disabled_features; FeatureList::GetInstance()->GetCommandLineFeatureOverrides( &enabled_features, &disabled_features); if (!enabled_features.empty()) cmd_line->AppendSwitchASCII(enable_features_switch, enabled_features); if (!disabled_features.empty()) cmd_line->AppendSwitchASCII(disable_features_switch, disabled_features); return; } AddFeatureAndFieldTrialFlags(enable_features_switch, disable_features_switch, cmd_line); } // static FieldTrial* FieldTrialList::CreateFieldTrial( const std::string& name, const std::string& group_name) { DCHECK(global_); DCHECK_GE(name.size(), 0u); DCHECK_GE(group_name.size(), 0u); if (name.empty() || group_name.empty() || !global_) return nullptr; FieldTrial* field_trial = FieldTrialList::Find(name); if (field_trial) { // In single process mode, or when we force them from the command line, // we may have already created the field trial. if (field_trial->group_name_internal() != group_name) return nullptr; return field_trial; } const int kTotalProbability = 100; field_trial = new FieldTrial(name, kTotalProbability, group_name, 0); FieldTrialList::Register(field_trial); // Force the trial, which will also finalize the group choice. field_trial->SetForced(); return field_trial; } // static bool FieldTrialList::AddObserver(Observer* observer) { if (!global_) return false; global_->observer_list_->AddObserver(observer); return true; } // static void FieldTrialList::RemoveObserver(Observer* observer) { if (!global_) return; global_->observer_list_->RemoveObserver(observer); } // static void FieldTrialList::SetSynchronousObserver(Observer* observer) { DCHECK(!global_->synchronous_observer_); global_->synchronous_observer_ = observer; } // static void FieldTrialList::RemoveSynchronousObserver(Observer* observer) { DCHECK_EQ(global_->synchronous_observer_, observer); global_->synchronous_observer_ = nullptr; } // static void FieldTrialList::OnGroupFinalized(bool is_locked, FieldTrial* field_trial) { if (!global_) return; if (is_locked) { AddToAllocatorWhileLocked(global_->field_trial_allocator_.get(), field_trial); } else { AutoLock auto_lock(global_->lock_); AddToAllocatorWhileLocked(global_->field_trial_allocator_.get(), field_trial); } } // static void FieldTrialList::NotifyFieldTrialGroupSelection(FieldTrial* field_trial) { if (!global_) return; { AutoLock auto_lock(global_->lock_); if (field_trial->group_reported_) return; field_trial->group_reported_ = true; if (!field_trial->enable_field_trial_) return; if (kUseSharedMemoryForFieldTrials) ActivateFieldTrialEntryWhileLocked(field_trial); } // Recording for stability debugging has to be done inline as a task posted // to an observer may not get executed before a crash. base::debug::GlobalActivityTracker* tracker = base::debug::GlobalActivityTracker::Get(); if (tracker) { tracker->RecordFieldTrial(field_trial->trial_name(), field_trial->group_name_internal()); } if (global_->synchronous_observer_) { global_->synchronous_observer_->OnFieldTrialGroupFinalized( field_trial->trial_name(), field_trial->group_name_internal()); } global_->observer_list_->Notify( FROM_HERE, &FieldTrialList::Observer::OnFieldTrialGroupFinalized, field_trial->trial_name(), field_trial->group_name_internal()); } // static size_t FieldTrialList::GetFieldTrialCount() { if (!global_) return 0; AutoLock auto_lock(global_->lock_); return global_->registered_.size(); } // static bool FieldTrialList::GetParamsFromSharedMemory( FieldTrial* field_trial, std::map* params) { DCHECK(global_); // If the field trial allocator is not set up yet, then there are several // cases: // - We are in the browser process and the allocator has not been set up // yet. If we got here, then we couldn't find the params in // FieldTrialParamAssociator, so it's definitely not here. Return false. // - Using shared memory for field trials is not enabled. If we got here, // then there's nothing in shared memory. Return false. // - We are in the child process and the allocator has not been set up yet. // If this is the case, then you are calling this too early. The field trial // allocator should get set up very early in the lifecycle. Try to see if // you can call it after it's been set up. AutoLock auto_lock(global_->lock_); if (!global_->field_trial_allocator_) return false; // If ref_ isn't set, then the field trial data can't be in shared memory. if (!field_trial->ref_) return false; const FieldTrial::FieldTrialEntry* entry = global_->field_trial_allocator_->GetAsObject( field_trial->ref_); size_t allocated_size = global_->field_trial_allocator_->GetAllocSize(field_trial->ref_); size_t actual_size = sizeof(FieldTrial::FieldTrialEntry) + entry->pickle_size; if (allocated_size < actual_size) return false; return entry->GetParams(params); } // static void FieldTrialList::ClearParamsFromSharedMemoryForTesting() { if (!global_) return; AutoLock auto_lock(global_->lock_); if (!global_->field_trial_allocator_) return; // To clear the params, we iterate through every item in the allocator, copy // just the trial and group name into a newly-allocated segment and then clear // the existing item. FieldTrialAllocator* allocator = global_->field_trial_allocator_.get(); FieldTrialAllocator::Iterator mem_iter(allocator); // List of refs to eventually be made iterable. We can't make it in the loop, // since it would go on forever. std::vector new_refs; FieldTrial::FieldTrialRef prev_ref; while ((prev_ref = mem_iter.GetNextOfType()) != FieldTrialAllocator::kReferenceNull) { // Get the existing field trial entry in shared memory. const FieldTrial::FieldTrialEntry* prev_entry = allocator->GetAsObject(prev_ref); StringPiece trial_name; StringPiece group_name; if (!prev_entry->GetTrialAndGroupName(&trial_name, &group_name)) continue; // Write a new entry, minus the params. Pickle pickle; pickle.WriteString(trial_name); pickle.WriteString(group_name); size_t total_size = sizeof(FieldTrial::FieldTrialEntry) + pickle.size(); FieldTrial::FieldTrialEntry* new_entry = allocator->New(total_size); subtle::NoBarrier_Store(&new_entry->activated, subtle::NoBarrier_Load(&prev_entry->activated)); new_entry->pickle_size = pickle.size(); // TODO(lawrencewu): Modify base::Pickle to be able to write over a section // in memory, so we can avoid this memcpy. char* dst = reinterpret_cast(new_entry) + sizeof(FieldTrial::FieldTrialEntry); memcpy(dst, pickle.data(), pickle.size()); // Update the ref on the field trial and add it to the list to be made // iterable. FieldTrial::FieldTrialRef new_ref = allocator->GetAsReference(new_entry); FieldTrial* trial = global_->PreLockedFind(trial_name.as_string()); trial->ref_ = new_ref; new_refs.push_back(new_ref); // Mark the existing entry as unused. allocator->ChangeType(prev_ref, 0, FieldTrial::FieldTrialEntry::kPersistentTypeId, /*clear=*/false); } for (const auto& ref : new_refs) { allocator->MakeIterable(ref); } } // static void FieldTrialList::DumpAllFieldTrialsToPersistentAllocator( PersistentMemoryAllocator* allocator) { if (!global_) return; AutoLock auto_lock(global_->lock_); for (const auto& registered : global_->registered_) { AddToAllocatorWhileLocked(allocator, registered.second); } } // static std::vector FieldTrialList::GetAllFieldTrialsFromPersistentAllocator( PersistentMemoryAllocator const& allocator) { std::vector entries; FieldTrialAllocator::Iterator iter(&allocator); const FieldTrial::FieldTrialEntry* entry; while ((entry = iter.GetNextOfObject()) != nullptr) { entries.push_back(entry); } return entries; } // static bool FieldTrialList::IsGlobalSetForTesting() { return global_ != nullptr; } // static std::string FieldTrialList::SerializeSharedMemoryHandleMetadata( const SharedMemoryHandle& shm) { std::stringstream ss; #if defined(OS_WIN) // Tell the child process the name of the inherited HANDLE. uintptr_t uintptr_handle = reinterpret_cast(shm.GetHandle()); ss << uintptr_handle << ","; #elif defined(OS_FUCHSIA) ss << shm.GetHandle() << ","; #elif !defined(OS_POSIX) #error Unsupported OS #endif base::UnguessableToken guid = shm.GetGUID(); ss << guid.GetHighForSerialization() << "," << guid.GetLowForSerialization(); ss << "," << shm.GetSize(); return ss.str(); } #if defined(OS_WIN) || defined(OS_FUCHSIA) // static SharedMemoryHandle FieldTrialList::DeserializeSharedMemoryHandleMetadata( const std::string& switch_value) { std::vector tokens = base::SplitStringPiece( switch_value, ",", base::KEEP_WHITESPACE, base::SPLIT_WANT_ALL); if (tokens.size() != 4) return SharedMemoryHandle(); int field_trial_handle = 0; if (!base::StringToInt(tokens[0], &field_trial_handle)) return SharedMemoryHandle(); #if defined(OS_FUCHSIA) zx_handle_t handle = static_cast(field_trial_handle); #elif defined(OS_WIN) HANDLE handle = reinterpret_cast(field_trial_handle); if (base::IsCurrentProcessElevated()) { // base::LaunchElevatedProcess doesn't have a way to duplicate the handle, // but this process can since by definition it's not sandboxed. base::ProcessId parent_pid = base::GetParentProcessId(GetCurrentProcess()); HANDLE parent_handle = OpenProcess(PROCESS_ALL_ACCESS, FALSE, parent_pid); DuplicateHandle(parent_handle, handle, GetCurrentProcess(), &handle, 0, FALSE, DUPLICATE_SAME_ACCESS); CloseHandle(parent_handle); } #endif // defined(OS_WIN) base::UnguessableToken guid; if (!DeserializeGUIDFromStringPieces(tokens[1], tokens[2], &guid)) return SharedMemoryHandle(); int size; if (!base::StringToInt(tokens[3], &size)) return SharedMemoryHandle(); return SharedMemoryHandle(handle, static_cast(size), guid); } #elif defined(OS_POSIX) && !defined(OS_NACL) // static SharedMemoryHandle FieldTrialList::DeserializeSharedMemoryHandleMetadata( int fd, const std::string& switch_value) { std::vector tokens = base::SplitStringPiece( switch_value, ",", base::KEEP_WHITESPACE, base::SPLIT_WANT_ALL); if (tokens.size() != 3) return SharedMemoryHandle(); base::UnguessableToken guid; if (!DeserializeGUIDFromStringPieces(tokens[0], tokens[1], &guid)) return SharedMemoryHandle(); int size; if (!base::StringToInt(tokens[2], &size)) return SharedMemoryHandle(); return SharedMemoryHandle(FileDescriptor(fd, true), static_cast(size), guid); } #endif #if defined(OS_WIN) || defined(OS_FUCHSIA) // static bool FieldTrialList::CreateTrialsFromSwitchValue( const std::string& switch_value) { SharedMemoryHandle shm = DeserializeSharedMemoryHandleMetadata(switch_value); if (!shm.IsValid()) return false; return FieldTrialList::CreateTrialsFromSharedMemoryHandle(shm); } #elif defined(OS_POSIX) && !defined(OS_NACL) // static bool FieldTrialList::CreateTrialsFromDescriptor( int fd_key, const std::string& switch_value) { if (!kUseSharedMemoryForFieldTrials) return false; if (fd_key == -1) return false; int fd = GlobalDescriptors::GetInstance()->MaybeGet(fd_key); if (fd == -1) return false; SharedMemoryHandle shm = DeserializeSharedMemoryHandleMetadata(fd, switch_value); if (!shm.IsValid()) return false; bool result = FieldTrialList::CreateTrialsFromSharedMemoryHandle(shm); DCHECK(result); return true; } #endif // defined(OS_POSIX) && !defined(OS_NACL) // static bool FieldTrialList::CreateTrialsFromSharedMemoryHandle( SharedMemoryHandle shm_handle) { // shm gets deleted when it gets out of scope, but that's OK because we need // it only for the duration of this method. std::unique_ptr shm(new SharedMemory(shm_handle, true)); if (!shm.get()->Map(kFieldTrialAllocationSize)) OnOutOfMemory(kFieldTrialAllocationSize); return FieldTrialList::CreateTrialsFromSharedMemory(std::move(shm)); } // static bool FieldTrialList::CreateTrialsFromSharedMemory( std::unique_ptr shm) { global_->field_trial_allocator_.reset( new FieldTrialAllocator(std::move(shm), 0, kAllocatorName, true)); FieldTrialAllocator* shalloc = global_->field_trial_allocator_.get(); FieldTrialAllocator::Iterator mem_iter(shalloc); const FieldTrial::FieldTrialEntry* entry; while ((entry = mem_iter.GetNextOfObject()) != nullptr) { StringPiece trial_name; StringPiece group_name; if (!entry->GetTrialAndGroupName(&trial_name, &group_name)) return false; // TODO(lawrencewu): Convert the API for CreateFieldTrial to take // StringPieces. FieldTrial* trial = CreateFieldTrial(trial_name.as_string(), group_name.as_string()); trial->ref_ = mem_iter.GetAsReference(entry); if (subtle::NoBarrier_Load(&entry->activated)) { // Call |group()| to mark the trial as "used" and notify observers, if // any. This is useful to ensure that field trials created in child // processes are properly reported in crash reports. trial->group(); } } return true; } // static void FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded() { if (!global_) return; AutoLock auto_lock(global_->lock_); // Create the allocator if not already created and add all existing trials. if (global_->field_trial_allocator_ != nullptr) return; SharedMemoryCreateOptions options; options.size = kFieldTrialAllocationSize; options.share_read_only = true; #if defined(OS_MACOSX) && !defined(OS_IOS) options.type = SharedMemoryHandle::POSIX; #endif std::unique_ptr shm(new SharedMemory()); if (!shm->Create(options)) OnOutOfMemory(kFieldTrialAllocationSize); if (!shm->Map(kFieldTrialAllocationSize)) OnOutOfMemory(kFieldTrialAllocationSize); global_->field_trial_allocator_.reset( new FieldTrialAllocator(std::move(shm), 0, kAllocatorName, false)); global_->field_trial_allocator_->CreateTrackingHistograms(kAllocatorName); // Add all existing field trials. for (const auto& registered : global_->registered_) { AddToAllocatorWhileLocked(global_->field_trial_allocator_.get(), registered.second); } // Add all existing features. FeatureList::GetInstance()->AddFeaturesToAllocator( global_->field_trial_allocator_.get()); #if !defined(OS_NACL) global_->readonly_allocator_handle_ = GetSharedMemoryReadOnlyHandle( global_->field_trial_allocator_->shared_memory()); #endif } // static void FieldTrialList::AddToAllocatorWhileLocked( PersistentMemoryAllocator* allocator, FieldTrial* field_trial) { // Don't do anything if the allocator hasn't been instantiated yet. if (allocator == nullptr) return; // Or if the allocator is read only, which means we are in a child process and // shouldn't be writing to it. if (allocator->IsReadonly()) return; FieldTrial::State trial_state; if (!field_trial->GetStateWhileLocked(&trial_state, false)) return; // Or if we've already added it. We must check after GetState since it can // also add to the allocator. if (field_trial->ref_) return; Pickle pickle; PickleFieldTrial(trial_state, &pickle); size_t total_size = sizeof(FieldTrial::FieldTrialEntry) + pickle.size(); FieldTrial::FieldTrialRef ref = allocator->Allocate( total_size, FieldTrial::FieldTrialEntry::kPersistentTypeId); if (ref == FieldTrialAllocator::kReferenceNull) { NOTREACHED(); return; } FieldTrial::FieldTrialEntry* entry = allocator->GetAsObject(ref); subtle::NoBarrier_Store(&entry->activated, trial_state.activated); entry->pickle_size = pickle.size(); // TODO(lawrencewu): Modify base::Pickle to be able to write over a section in // memory, so we can avoid this memcpy. char* dst = reinterpret_cast(entry) + sizeof(FieldTrial::FieldTrialEntry); memcpy(dst, pickle.data(), pickle.size()); allocator->MakeIterable(ref); field_trial->ref_ = ref; } // static void FieldTrialList::ActivateFieldTrialEntryWhileLocked( FieldTrial* field_trial) { FieldTrialAllocator* allocator = global_->field_trial_allocator_.get(); // Check if we're in the child process and return early if so. if (!allocator || allocator->IsReadonly()) return; FieldTrial::FieldTrialRef ref = field_trial->ref_; if (ref == FieldTrialAllocator::kReferenceNull) { // It's fine to do this even if the allocator hasn't been instantiated // yet -- it'll just return early. AddToAllocatorWhileLocked(allocator, field_trial); } else { // It's also okay to do this even though the callee doesn't have a lock -- // the only thing that happens on a stale read here is a slight performance // hit from the child re-synchronizing activation state. FieldTrial::FieldTrialEntry* entry = allocator->GetAsObject(ref); subtle::NoBarrier_Store(&entry->activated, 1); } } // static const FieldTrial::EntropyProvider* FieldTrialList::GetEntropyProviderForOneTimeRandomization() { if (!global_) { used_without_global_ = true; return nullptr; } return global_->entropy_provider_.get(); } FieldTrial* FieldTrialList::PreLockedFind(const std::string& name) { RegistrationMap::iterator it = registered_.find(name); if (registered_.end() == it) return nullptr; return it->second; } // static void FieldTrialList::Register(FieldTrial* trial) { if (!global_) { used_without_global_ = true; return; } AutoLock auto_lock(global_->lock_); CHECK(!global_->PreLockedFind(trial->trial_name())) << trial->trial_name(); trial->AddRef(); trial->SetTrialRegistered(); global_->registered_[trial->trial_name()] = trial; } // static FieldTrialList::RegistrationMap FieldTrialList::GetRegisteredTrials() { RegistrationMap output; if (global_) { AutoLock auto_lock(global_->lock_); output = global_->registered_; } return output; } } // namespace base