// 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/histogram_snapshot_manager.h" #include #include "base/debug/alias.h" #include "base/logging.h" #include "base/memory/raw_ptr.h" #include "base/metrics/histogram_flattener.h" #include "base/metrics/histogram_samples.h" #include "base/metrics/statistics_recorder.h" namespace base { namespace { // A simple object to set an "active" flag and clear it upon destruction. It is // an error if the flag is already set. class MakeActive { public: explicit MakeActive(std::atomic* is_active) : is_active_(is_active) { bool was_active = is_active_->exchange(true, std::memory_order_relaxed); CHECK(!was_active); } MakeActive(const MakeActive&) = delete; MakeActive& operator=(const MakeActive&) = delete; ~MakeActive() { is_active_->store(false, std::memory_order_relaxed); } private: raw_ptr> is_active_; }; } // namespace HistogramSnapshotManager::HistogramSnapshotManager( HistogramFlattener* histogram_flattener) : histogram_flattener_(histogram_flattener) { DCHECK(histogram_flattener_); is_active_.store(false, std::memory_order_relaxed); } HistogramSnapshotManager::~HistogramSnapshotManager() = default; void HistogramSnapshotManager::PrepareDeltas( const std::vector& histograms, HistogramBase::Flags flags_to_set, HistogramBase::Flags required_flags) { for (HistogramBase* const histogram : histograms) { histogram->SetFlags(flags_to_set); if ((histogram->flags() & required_flags) == required_flags) PrepareDelta(histogram); } } void HistogramSnapshotManager::PrepareDelta(HistogramBase* histogram) { PrepareSamples(histogram, histogram->SnapshotDelta()); } void HistogramSnapshotManager::PrepareFinalDelta( const HistogramBase* histogram) { PrepareSamples(histogram, histogram->SnapshotFinalDelta()); } void HistogramSnapshotManager::PrepareSamples( const HistogramBase* histogram, std::unique_ptr samples) { DCHECK(histogram_flattener_); // Ensure that there is no concurrent access going on while accessing the // set of known histograms. The flag will be reset when this object goes // out of scope. MakeActive make_active(&is_active_); // Get information known about this histogram. If it did not previously // exist, one will be created and initialized. SampleInfo* sample_info = &known_histograms_[histogram->name_hash()]; // Crash if we detect that our histograms have been overwritten. This may be // a fair distance from the memory smasher, but we hope to correlate these // crashes with other events, such as plugins, or usage patterns, etc. uint32_t corruption = histogram->FindCorruption(*samples); if (HistogramBase::BUCKET_ORDER_ERROR & corruption) { // Extract fields useful during debug. const BucketRanges* ranges = static_cast(histogram)->bucket_ranges(); uint32_t ranges_checksum = ranges->checksum(); uint32_t ranges_calc_checksum = ranges->CalculateChecksum(); int32_t flags = histogram->flags(); // The checksum should have caught this, so crash separately if it didn't. CHECK_NE(0U, HistogramBase::RANGE_CHECKSUM_ERROR & corruption); CHECK(false); // Crash for the bucket order corruption. // Ensure that compiler keeps around pointers to |histogram| and its // internal |bucket_ranges_| for any minidumps. base::debug::Alias(&ranges_checksum); base::debug::Alias(&ranges_calc_checksum); base::debug::Alias(&flags); } // Checksum corruption might not have caused order corruption. CHECK_EQ(0U, HistogramBase::RANGE_CHECKSUM_ERROR & corruption); // Note, at this point corruption can only be COUNT_HIGH_ERROR or // COUNT_LOW_ERROR and they never arise together, so we don't need to extract // bits from corruption. if (corruption) { DLOG(ERROR) << "Histogram: \"" << histogram->histogram_name() << "\" has data corruption: " << corruption; // Don't record corrupt data to metrics services. const uint32_t old_corruption = sample_info->inconsistencies; if (old_corruption == (corruption | old_corruption)) return; // We've already seen this corruption for this histogram. sample_info->inconsistencies |= corruption; return; } if (samples->TotalCount() > 0) histogram_flattener_->RecordDelta(*histogram, *samples); } } // namespace base