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| 1 // Copyright (c) 2015 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #include "base/metrics/histogram_persistence.h" |
| 6 |
| 7 #include "base/logging.h" |
| 8 #include "base/memory/scoped_ptr.h" |
| 9 #include "base/metrics/histogram.h" |
| 10 #include "base/metrics/histogram_base.h" |
| 11 #include "base/metrics/histogram_samples.h" |
| 12 #include "base/metrics/statistics_recorder.h" |
| 13 #include "base/synchronization/lock.h" |
| 14 |
| 15 namespace base { |
| 16 |
| 17 namespace { |
| 18 |
| 19 // Enumerate possible creation results for reporting. |
| 20 enum CreateHistogramResultType { |
| 21 // Everything was fine. |
| 22 CREATE_HISTOGRAM_SUCCESS = 0, |
| 23 |
| 24 // Pointer to metadata was not valid. |
| 25 CREATE_HISTOGRAM_INVALID_METADATA_POINTER, |
| 26 |
| 27 // Histogram metadata was not valid. |
| 28 CREATE_HISTOGRAM_INVALID_METADATA, |
| 29 |
| 30 // Ranges information was not valid. |
| 31 CREATE_HISTOGRAM_INVALID_RANGES_ARRAY, |
| 32 |
| 33 // Counts information was not valid. |
| 34 CREATE_HISTOGRAM_INVALID_COUNTS_ARRAY, |
| 35 |
| 36 // Could not allocate histogram memory due to corruption. |
| 37 CREATE_HISTOGRAM_ALLOCATOR_CORRUPT, |
| 38 |
| 39 // Could not allocate histogram memory due to lack of space. |
| 40 CREATE_HISTOGRAM_ALLOCATOR_FULL, |
| 41 |
| 42 // Could not allocate histogram memory due to unknown error. |
| 43 CREATE_HISTOGRAM_ALLOCATOR_ERROR, |
| 44 |
| 45 // Always keep this at the end. |
| 46 CREATE_HISTOGRAM_MAX |
| 47 }; |
| 48 |
| 49 // Type identifiers used when storing in persistent memory so they can be |
| 50 // identified during extraction; the first 4 bytes of the SHA1 of the name |
| 51 // is used as a unique integer. A "version number" is added to the base |
| 52 // so that, if the structure of that object changes, stored older versions |
| 53 // will be safely ignored. |
| 54 enum : uint32_t { |
| 55 kTypeIdHistogram = 0xF1645910 + 1, // SHA1(Histogram) v1 |
| 56 kTypeIdRangesArray = 0xBCEA225A + 1, // SHA1(RangesArray) v1 |
| 57 kTypeIdCountsArray = 0x53215530 + 1, // SHA1(CountsArray) v1 |
| 58 }; |
| 59 |
| 60 // This data must be held in persistent memory in order for processes to |
| 61 // locate and use histograms created elsewhere. |
| 62 struct PersistentHistogramData { |
| 63 int histogram_type; |
| 64 int flags; |
| 65 int minimum; |
| 66 int maximum; |
| 67 size_t bucket_count; |
| 68 PersistentMemoryAllocator::Reference ranges_ref; |
| 69 uint32_t ranges_checksum; |
| 70 PersistentMemoryAllocator::Reference counts_ref; |
| 71 HistogramSamples::Metadata samples_metadata; |
| 72 |
| 73 // Space for the histogram name will be added during the actual allocation |
| 74 // request. This must be the last field of the structure. A zero-size array |
| 75 // or a "flexible" array would be preferred but is not (yet) valid C++. |
| 76 char name[1]; |
| 77 }; |
| 78 |
| 79 // The object held here will obviously not be destructed at process exit |
| 80 // but that's okay since PersistentMemoryAllocator objects are explicitly |
| 81 // forbidden from doing anything essential at exit anyway due to the fact |
| 82 // that they depend on data managed elsewhere and which could be destructed |
| 83 // first. |
| 84 PersistentMemoryAllocator* g_allocator = nullptr; |
| 85 |
| 86 // Take an array of range boundaries and create a proper BucketRanges object |
| 87 // which is returned to the caller. A return of nullptr indicates that the |
| 88 // passed boundaries are invalid. |
| 89 BucketRanges* CreateRangesFromData(HistogramBase::Sample* ranges_data, |
| 90 uint32_t ranges_checksum, |
| 91 size_t count) { |
| 92 scoped_ptr<BucketRanges> ranges(new BucketRanges(count)); |
| 93 DCHECK_EQ(count, ranges->size()); |
| 94 for (size_t i = 0; i < count; ++i) { |
| 95 if (i > 0 && ranges_data[i] <= ranges_data[i - 1]) |
| 96 return nullptr; |
| 97 ranges->set_range(i, ranges_data[i]); |
| 98 } |
| 99 |
| 100 ranges->ResetChecksum(); |
| 101 if (ranges->checksum() != ranges_checksum) |
| 102 return nullptr; |
| 103 |
| 104 return ranges.release(); |
| 105 } |
| 106 |
| 107 } // namespace |
| 108 |
| 109 const Feature kPersistentHistogramsFeature{ |
| 110 "PersistentHistograms", FEATURE_DISABLED_BY_DEFAULT |
| 111 }; |
| 112 |
| 113 // Get the histogram in which create results are stored. This is copied almost |
| 114 // exactly from the STATIC_HISTOGRAM_POINTER_BLOCK macro but with added code |
| 115 // to prevent recursion (a likely occurance because the creation of a new |
| 116 // histogram can end up calling this.) |
| 117 HistogramBase* GetCreateHistogramResultHistogram() { |
| 118 static base::subtle::AtomicWord atomic_histogram_pointer = 0; |
| 119 HistogramBase* histogram_pointer( |
| 120 reinterpret_cast<HistogramBase*>( |
| 121 base::subtle::Acquire_Load(&atomic_histogram_pointer))); |
| 122 if (!histogram_pointer) { |
| 123 // It's possible for multiple threads to make it here in parallel but |
| 124 // they'll always return the same result as there is a mutex in the Get. |
| 125 // The purpose of the "initialized" variable is just to ensure that |
| 126 // the same thread doesn't recurse which is also why it doesn't have |
| 127 // to be atomic. |
| 128 static bool initialized = false; |
| 129 if (!initialized) { |
| 130 initialized = true; |
| 131 histogram_pointer = LinearHistogram::FactoryGet( |
| 132 "UMA.CreatePersistentHistogram.Result", |
| 133 1, CREATE_HISTOGRAM_MAX, CREATE_HISTOGRAM_MAX + 1, |
| 134 HistogramBase::kUmaTargetedHistogramFlag); |
| 135 base::subtle::Release_Store( |
| 136 &atomic_histogram_pointer, |
| 137 reinterpret_cast<base::subtle::AtomicWord>(histogram_pointer)); |
| 138 } |
| 139 } |
| 140 return histogram_pointer; |
| 141 } |
| 142 |
| 143 // Record the result of a histogram creation. |
| 144 void RecordCreateHistogramResult(CreateHistogramResultType result) { |
| 145 HistogramBase* result_histogram = GetCreateHistogramResultHistogram(); |
| 146 if (result_histogram) |
| 147 result_histogram->Add(result); |
| 148 } |
| 149 |
| 150 void SetPersistentHistogramMemoryAllocator( |
| 151 PersistentMemoryAllocator* allocator) { |
| 152 // Releasing or changing an allocator is extremely dangerous because it |
| 153 // likely has histograms stored within it. If the backing memory is also |
| 154 // also released, future accesses to those histograms will seg-fault. |
| 155 // It's not a fatal CHECK() because tests do this knowing that all |
| 156 // such persistent histograms have already been forgotten. |
| 157 if (g_allocator) { |
| 158 LOG(WARNING) << "Active PersistentMemoryAllocator has been released." |
| 159 << " Some existing histogram pointers may be invalid."; |
| 160 delete g_allocator; |
| 161 } |
| 162 g_allocator = allocator; |
| 163 } |
| 164 |
| 165 PersistentMemoryAllocator* GetPersistentHistogramMemoryAllocator() { |
| 166 return g_allocator; |
| 167 } |
| 168 |
| 169 PersistentMemoryAllocator* ReleasePersistentHistogramMemoryAllocator() { |
| 170 PersistentMemoryAllocator* allocator = g_allocator; |
| 171 g_allocator = nullptr; |
| 172 return allocator; |
| 173 }; |
| 174 |
| 175 HistogramBase* CreatePersistentHistogram( |
| 176 PersistentMemoryAllocator* allocator, |
| 177 PersistentHistogramData* histogram_data_ptr) { |
| 178 if (!histogram_data_ptr) { |
| 179 RecordCreateHistogramResult(CREATE_HISTOGRAM_INVALID_METADATA_POINTER); |
| 180 NOTREACHED(); |
| 181 return nullptr; |
| 182 } |
| 183 |
| 184 // Copy the histogram_data to local storage because anything in persistent |
| 185 // memory cannot be trusted as it could be changed at any moment by a |
| 186 // malicious actor that shares access. The contents of histogram_data are |
| 187 // validated below; the local copy is to ensure that the contents cannot |
| 188 // be externally changed between validation and use. |
| 189 PersistentHistogramData histogram_data = *histogram_data_ptr; |
| 190 |
| 191 HistogramBase::Sample* ranges_data = |
| 192 allocator->GetAsObject<HistogramBase::Sample>(histogram_data.ranges_ref, |
| 193 kTypeIdRangesArray); |
| 194 if (!ranges_data || histogram_data.bucket_count < 2 || |
| 195 histogram_data.bucket_count + 1 > |
| 196 std::numeric_limits<size_t>::max() / sizeof(HistogramBase::Sample) || |
| 197 allocator->GetAllocSize(histogram_data.ranges_ref) < |
| 198 (histogram_data.bucket_count + 1) * sizeof(HistogramBase::Sample)) { |
| 199 RecordCreateHistogramResult(CREATE_HISTOGRAM_INVALID_RANGES_ARRAY); |
| 200 NOTREACHED(); |
| 201 return nullptr; |
| 202 } |
| 203 // To avoid racy destruction at shutdown, the following will be leaked. |
| 204 const BucketRanges* ranges = CreateRangesFromData( |
| 205 ranges_data, |
| 206 histogram_data.ranges_checksum, |
| 207 histogram_data.bucket_count + 1); |
| 208 if (!ranges) { |
| 209 RecordCreateHistogramResult(CREATE_HISTOGRAM_INVALID_RANGES_ARRAY); |
| 210 NOTREACHED(); |
| 211 return nullptr; |
| 212 } |
| 213 ranges = StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges); |
| 214 |
| 215 HistogramBase::AtomicCount* counts_data = |
| 216 allocator->GetAsObject<HistogramBase::AtomicCount>( |
| 217 histogram_data.counts_ref, kTypeIdCountsArray); |
| 218 if (!counts_data || |
| 219 allocator->GetAllocSize(histogram_data.counts_ref) < |
| 220 histogram_data.bucket_count * sizeof(HistogramBase::AtomicCount)) { |
| 221 RecordCreateHistogramResult(CREATE_HISTOGRAM_INVALID_COUNTS_ARRAY); |
| 222 NOTREACHED(); |
| 223 return nullptr; |
| 224 } |
| 225 |
| 226 std::string name(histogram_data_ptr->name); |
| 227 HistogramBase* histogram = nullptr; |
| 228 switch (histogram_data.histogram_type) { |
| 229 case HISTOGRAM: |
| 230 histogram = Histogram::PersistentGet( |
| 231 name, |
| 232 histogram_data.minimum, |
| 233 histogram_data.maximum, |
| 234 ranges, |
| 235 counts_data, |
| 236 histogram_data.bucket_count, |
| 237 &histogram_data_ptr->samples_metadata); |
| 238 break; |
| 239 case LINEAR_HISTOGRAM: |
| 240 histogram = LinearHistogram::PersistentGet( |
| 241 name, |
| 242 histogram_data.minimum, |
| 243 histogram_data.maximum, |
| 244 ranges, |
| 245 counts_data, |
| 246 histogram_data.bucket_count, |
| 247 &histogram_data_ptr->samples_metadata); |
| 248 break; |
| 249 case BOOLEAN_HISTOGRAM: |
| 250 histogram = BooleanHistogram::PersistentGet( |
| 251 name, |
| 252 ranges, |
| 253 counts_data, |
| 254 &histogram_data_ptr->samples_metadata); |
| 255 break; |
| 256 case CUSTOM_HISTOGRAM: |
| 257 histogram = CustomHistogram::PersistentGet( |
| 258 name, |
| 259 ranges, |
| 260 counts_data, |
| 261 histogram_data.bucket_count, |
| 262 &histogram_data_ptr->samples_metadata); |
| 263 break; |
| 264 } |
| 265 |
| 266 if (histogram) { |
| 267 DCHECK_EQ(histogram_data.histogram_type, histogram->GetHistogramType()); |
| 268 histogram->SetFlags(histogram_data.flags); |
| 269 } |
| 270 |
| 271 RecordCreateHistogramResult(CREATE_HISTOGRAM_SUCCESS); |
| 272 return histogram; |
| 273 } |
| 274 |
| 275 HistogramBase* GetPersistentHistogram( |
| 276 PersistentMemoryAllocator* allocator, |
| 277 int32_t ref) { |
| 278 // Unfortunately, the above "pickle" methods cannot be used as part of the |
| 279 // persistance because the deserialization methods always create local |
| 280 // count data (these must referenced the persistent counts) and always add |
| 281 // it to the local list of known histograms (these may be simple references |
| 282 // to histograms in other processes). |
| 283 PersistentHistogramData* histogram_data = |
| 284 allocator->GetAsObject<PersistentHistogramData>(ref, kTypeIdHistogram); |
| 285 size_t length = allocator->GetAllocSize(ref); |
| 286 if (!histogram_data || |
| 287 reinterpret_cast<char*>(histogram_data)[length - 1] != '\0') { |
| 288 RecordCreateHistogramResult(CREATE_HISTOGRAM_INVALID_METADATA); |
| 289 NOTREACHED(); |
| 290 return nullptr; |
| 291 } |
| 292 return CreatePersistentHistogram(allocator, histogram_data); |
| 293 } |
| 294 |
| 295 HistogramBase* GetNextPersistentHistogram( |
| 296 PersistentMemoryAllocator* allocator, |
| 297 PersistentMemoryAllocator::Iterator* iter) { |
| 298 PersistentMemoryAllocator::Reference ref; |
| 299 uint32_t type_id; |
| 300 while ((ref = allocator->GetNextIterable(iter, &type_id)) != 0) { |
| 301 if (type_id == kTypeIdHistogram) |
| 302 return GetPersistentHistogram(allocator, ref); |
| 303 } |
| 304 return nullptr; |
| 305 } |
| 306 |
| 307 void FinalizePersistentHistogram(PersistentMemoryAllocator::Reference ref, |
| 308 bool registered) { |
| 309 // If the created persistent histogram was registered then it needs to |
| 310 // be marked as "iterable" in order to be found by other processes. |
| 311 if (registered) |
| 312 GetPersistentHistogramMemoryAllocator()->MakeIterable(ref); |
| 313 // If it wasn't registered then a race condition must have caused |
| 314 // two to be created. The allocator does not support releasing the |
| 315 // acquired memory so just change the type to be empty. |
| 316 else |
| 317 GetPersistentHistogramMemoryAllocator()->SetType(ref, 0); |
| 318 } |
| 319 |
| 320 HistogramBase* AllocatePersistentHistogram( |
| 321 PersistentMemoryAllocator* allocator, |
| 322 HistogramType histogram_type, |
| 323 const std::string& name, |
| 324 int minimum, |
| 325 int maximum, |
| 326 const BucketRanges* bucket_ranges, |
| 327 int32_t flags, |
| 328 PersistentMemoryAllocator::Reference* ref_ptr) { |
| 329 if (!allocator) |
| 330 return nullptr; |
| 331 |
| 332 size_t bucket_count = bucket_ranges->bucket_count(); |
| 333 // An overflow such as this, perhaps as the result of a milicious actor, |
| 334 // could lead to writing beyond the allocation boundary and into other |
| 335 // memory. Just fail the allocation and let the caller deal with it. |
| 336 if (bucket_count > std::numeric_limits<int32_t>::max() / |
| 337 sizeof(HistogramBase::AtomicCount)) { |
| 338 NOTREACHED(); |
| 339 return nullptr; |
| 340 } |
| 341 size_t counts_bytes = bucket_count * sizeof(HistogramBase::AtomicCount); |
| 342 size_t ranges_bytes = (bucket_count + 1) * sizeof(HistogramBase::Sample); |
| 343 PersistentMemoryAllocator::Reference ranges_ref = |
| 344 allocator->Allocate(ranges_bytes, kTypeIdRangesArray); |
| 345 PersistentMemoryAllocator::Reference counts_ref = |
| 346 allocator->Allocate(counts_bytes, kTypeIdCountsArray); |
| 347 PersistentMemoryAllocator::Reference histogram_ref = |
| 348 allocator->Allocate(offsetof(PersistentHistogramData, name) + |
| 349 name.length() + 1, kTypeIdHistogram); |
| 350 HistogramBase::Sample* ranges_data = |
| 351 allocator->GetAsObject<HistogramBase::Sample>(ranges_ref, |
| 352 kTypeIdRangesArray); |
| 353 PersistentHistogramData* histogram_data = |
| 354 allocator->GetAsObject<PersistentHistogramData>(histogram_ref, |
| 355 kTypeIdHistogram); |
| 356 |
| 357 // Only continue here if all allocations were successful. If they weren't |
| 358 // there is no way to free the space but that's not really a problem since |
| 359 // the allocations only fail because the space is full and so any future |
| 360 // attempts will also fail. |
| 361 if (counts_ref && ranges_data && histogram_data) { |
| 362 strcpy(histogram_data->name, name.c_str()); |
| 363 for (size_t i = 0; i < bucket_ranges->size(); ++i) |
| 364 ranges_data[i] = bucket_ranges->range(i); |
| 365 |
| 366 histogram_data->histogram_type = histogram_type; |
| 367 histogram_data->flags = flags; |
| 368 histogram_data->minimum = minimum; |
| 369 histogram_data->maximum = maximum; |
| 370 histogram_data->bucket_count = bucket_count; |
| 371 histogram_data->ranges_ref = ranges_ref; |
| 372 histogram_data->ranges_checksum = bucket_ranges->checksum(); |
| 373 histogram_data->counts_ref = counts_ref; |
| 374 |
| 375 // Create the histogram using resources in persistent memory. This ends up |
| 376 // resolving the "ref" values stored in histogram_data instad of just |
| 377 // using what is already known above but avoids duplicating the switch |
| 378 // statement here and serves as a double-check that everything is |
| 379 // correct before commiting the new histogram to persistent space. |
| 380 HistogramBase* histogram = |
| 381 CreatePersistentHistogram(allocator, histogram_data); |
| 382 DCHECK(histogram); |
| 383 if (ref_ptr != nullptr) |
| 384 *ref_ptr = histogram_ref; |
| 385 return histogram; |
| 386 } |
| 387 |
| 388 CreateHistogramResultType result; |
| 389 if (allocator->IsCorrupt()) { |
| 390 result = CREATE_HISTOGRAM_ALLOCATOR_CORRUPT; |
| 391 } else if (allocator->IsFull()) { |
| 392 result = CREATE_HISTOGRAM_ALLOCATOR_FULL; |
| 393 } else { |
| 394 result = CREATE_HISTOGRAM_ALLOCATOR_ERROR; |
| 395 } |
| 396 RecordCreateHistogramResult(result); |
| 397 |
| 398 return nullptr; |
| 399 } |
| 400 |
| 401 void ImportPersistentHistograms() { |
| 402 // Each call resumes from where it last left off so need persistant iterator. |
| 403 // The lock protects against concurrent access to the iterator and is created |
| 404 // dynamically so as to not require destruction during program exit. |
| 405 static PersistentMemoryAllocator::Iterator iter; |
| 406 static base::Lock* lock = new base::Lock(); |
| 407 |
| 408 if (g_allocator) { |
| 409 base::AutoLock auto_lock(*lock); |
| 410 if (iter.is_clear()) |
| 411 g_allocator->CreateIterator(&iter); |
| 412 |
| 413 for (;;) { |
| 414 HistogramBase* histogram = GetNextPersistentHistogram(g_allocator, &iter); |
| 415 if (!histogram) |
| 416 break; |
| 417 StatisticsRecorder::RegisterOrDeleteDuplicate(histogram); |
| 418 } |
| 419 } |
| 420 } |
| 421 |
| 422 } // namespace base |
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