libsanitizer/sanitizer_common/sanitizer_quarantine.h

   1 //===-- sanitizer_quarantine.h ----------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Memory quarantine for AddressSanitizer and potentially other tools.
  10 // Quarantine caches some specified amount of memory in per-thread caches,
  11 // then evicts to global FIFO queue. When the queue reaches specified threshold,
  12 // oldest memory is recycled.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #ifndef SANITIZER_QUARANTINE_H
  17 #define SANITIZER_QUARANTINE_H
  18
  19 #include "sanitizer_internal_defs.h"
  20 #include "sanitizer_mutex.h"
  21 #include "sanitizer_list.h"
  22
  23 namespace __sanitizer {
  24
  25 template<typename Node> class QuarantineCache;
  26
  27 struct QuarantineBatch {
  28   static const uptr kSize = 1021;
  29   QuarantineBatch *next;
  30   uptr size;
  31   uptr count;
  32   void *batch[kSize];
  33
  34   void init(void *ptr, uptr size) {
  35     count = 1;
  36     batch[0] = ptr;
  37     this->size = size + sizeof(QuarantineBatch);  // Account for the batch size.
  38   }
  39
  40   // The total size of quarantined nodes recorded in this batch.
  41   uptr quarantined_size() const {
  42     return size - sizeof(QuarantineBatch);
  43   }
  44
  45   void push_back(void *ptr, uptr size) {
  46     CHECK_LT(count, kSize);
  47     batch[count++] = ptr;
  48     this->size += size;
  49   }
  50
  51   bool can_merge(const QuarantineBatch* const from) const {
  52     return count + from->count <= kSize;
  53   }
  54
  55   void merge(QuarantineBatch* const from) {
  56     CHECK_LE(count + from->count, kSize);
  57     CHECK_GE(size, sizeof(QuarantineBatch));
  58
  59     for (uptr i = 0; i < from->count; ++i)
  60       batch[count + i] = from->batch[i];
  61     count += from->count;
  62     size += from->quarantined_size();
  63
  64     from->count = 0;
  65     from->size = sizeof(QuarantineBatch);
  66   }
  67 };
  68
  69 COMPILER_CHECK(sizeof(QuarantineBatch) <= (1 << 13));  // 8Kb.
  70
  71 // The callback interface is:
  72 // void Callback::Recycle(Node *ptr);
  73 // void *cb.Allocate(uptr size);
  74 // void cb.Deallocate(void *ptr);
  75 template<typename Callback, typename Node>
  76 class Quarantine {
  77  public:
  78   typedef QuarantineCache<Callback> Cache;
  79
  80   explicit Quarantine(LinkerInitialized)
  81       : cache_(LINKER_INITIALIZED) {
  82   }
  83
  84   void Init(uptr size, uptr cache_size) {
  85     // Thread local quarantine size can be zero only when global quarantine size
  86     // is zero (it allows us to perform just one atomic read per Put() call).
  87     CHECK((size == 0 && cache_size == 0) || cache_size != 0);
  88
  89     atomic_store_relaxed(&max_size_, size);
  90     atomic_store_relaxed(&min_size_, size / 10 * 9);  // 90% of max size.
  91     atomic_store_relaxed(&max_cache_size_, cache_size);
  92
  93     cache_mutex_.Init();
  94     recycle_mutex_.Init();
  95   }
  96
  97   uptr GetSize() const { return atomic_load_relaxed(&max_size_); }
  98   uptr GetCacheSize() const {
  99     return atomic_load_relaxed(&max_cache_size_);
 100   }
 101
 102   void Put(Cache *c, Callback cb, Node *ptr, uptr size) {
 103     uptr cache_size = GetCacheSize();
 104     if (cache_size) {
 105       c->Enqueue(cb, ptr, size);
 106     } else {
 107       // GetCacheSize() == 0 only when GetSize() == 0 (see Init).
 108       cb.Recycle(ptr);
 109     }
 110     // Check cache size anyway to accommodate for runtime cache_size change.
 111     if (c->Size() > cache_size)
 112       Drain(c, cb);
 113   }
 114
 115   void NOINLINE Drain(Cache *c, Callback cb) {
 116     {
 117       SpinMutexLock l(&cache_mutex_);
 118       cache_.Transfer(c);
 119     }
 120     if (cache_.Size() > GetSize() && recycle_mutex_.TryLock())
 121       Recycle(atomic_load_relaxed(&min_size_), cb);
 122   }
 123
 124   void NOINLINE DrainAndRecycle(Cache *c, Callback cb) {
 125     {
 126       SpinMutexLock l(&cache_mutex_);
 127       cache_.Transfer(c);
 128     }
 129     recycle_mutex_.Lock();
 130     Recycle(0, cb);
 131   }
 132
 133   void PrintStats() const {
 134     // It assumes that the world is stopped, just as the allocator's PrintStats.
 135     Printf("Quarantine limits: global: %zdMb; thread local: %zdKb\n",
 136            GetSize() >> 20, GetCacheSize() >> 10);
 137     cache_.PrintStats();
 138   }
 139
 140  private:
 141   // Read-only data.
 142   char pad0_[kCacheLineSize];
 143   atomic_uintptr_t max_size_;
 144   atomic_uintptr_t min_size_;
 145   atomic_uintptr_t max_cache_size_;
 146   char pad1_[kCacheLineSize];
 147   StaticSpinMutex cache_mutex_;
 148   StaticSpinMutex recycle_mutex_;
 149   Cache cache_;
 150   char pad2_[kCacheLineSize];
 151
 152   void NOINLINE Recycle(uptr min_size, Callback cb)
 153       SANITIZER_REQUIRES(recycle_mutex_) SANITIZER_RELEASE(recycle_mutex_) {
 154     Cache tmp;
 155     {
 156       SpinMutexLock l(&cache_mutex_);
 157       // Go over the batches and merge partially filled ones to
 158       // save some memory, otherwise batches themselves (since the memory used
 159       // by them is counted against quarantine limit) can overcome the actual
 160       // user's quarantined chunks, which diminishes the purpose of the
 161       // quarantine.
 162       uptr cache_size = cache_.Size();
 163       uptr overhead_size = cache_.OverheadSize();
 164       CHECK_GE(cache_size, overhead_size);
 165       // Do the merge only when overhead exceeds this predefined limit (might
 166       // require some tuning). It saves us merge attempt when the batch list
 167       // quarantine is unlikely to contain batches suitable for merge.
 168       const uptr kOverheadThresholdPercents = 100;
 169       if (cache_size > overhead_size &&
 170           overhead_size * (100 + kOverheadThresholdPercents) >
 171               cache_size * kOverheadThresholdPercents) {
 172         cache_.MergeBatches(&tmp);
 173       }
 174       // Extract enough chunks from the quarantine to get below the max
 175       // quarantine size and leave some leeway for the newly quarantined chunks.
 176       while (cache_.Size() > min_size) {
 177         tmp.EnqueueBatch(cache_.DequeueBatch());
 178       }
 179     }
 180     recycle_mutex_.Unlock();
 181     DoRecycle(&tmp, cb);
 182   }
 183
 184   void NOINLINE DoRecycle(Cache *c, Callback cb) {
 185     while (QuarantineBatch *b = c->DequeueBatch()) {
 186       const uptr kPrefetch = 16;
 187       CHECK(kPrefetch <= ARRAY_SIZE(b->batch));
 188       for (uptr i = 0; i < kPrefetch; i++)
 189         PREFETCH(b->batch[i]);
 190       for (uptr i = 0, count = b->count; i < count; i++) {
 191         if (i + kPrefetch < count)
 192           PREFETCH(b->batch[i + kPrefetch]);
 193         cb.Recycle((Node*)b->batch[i]);
 194       }
 195       cb.Deallocate(b);
 196     }
 197   }
 198 };
 199
 200 // Per-thread cache of memory blocks.
 201 template<typename Callback>
 202 class QuarantineCache {
 203  public:
 204   explicit QuarantineCache(LinkerInitialized) {
 205   }
 206
 207   QuarantineCache()
 208       : size_() {
 209     list_.clear();
 210   }
 211
 212   // Total memory used, including internal accounting.
 213   uptr Size() const {
 214     return atomic_load_relaxed(&size_);
 215   }
 216
 217   // Memory used for internal accounting.
 218   uptr OverheadSize() const {
 219     return list_.size() * sizeof(QuarantineBatch);
 220   }
 221
 222   void Enqueue(Callback cb, void *ptr, uptr size) {
 223     if (list_.empty() || list_.back()->count == QuarantineBatch::kSize) {
 224       QuarantineBatch *b = (QuarantineBatch *)cb.Allocate(sizeof(*b));
 225       CHECK(b);
 226       b->init(ptr, size);
 227       EnqueueBatch(b);
 228     } else {
 229       list_.back()->push_back(ptr, size);
 230       SizeAdd(size);
 231     }
 232   }
 233
 234   void Transfer(QuarantineCache *from_cache) {
 235     list_.append_back(&from_cache->list_);
 236     SizeAdd(from_cache->Size());
 237
 238     atomic_store_relaxed(&from_cache->size_, 0);
 239   }
 240
 241   void EnqueueBatch(QuarantineBatch *b) {
 242     list_.push_back(b);
 243     SizeAdd(b->size);
 244   }
 245
 246   QuarantineBatch *DequeueBatch() {
 247     if (list_.empty())
 248       return nullptr;
 249     QuarantineBatch *b = list_.front();
 250     list_.pop_front();
 251     SizeSub(b->size);
 252     return b;
 253   }
 254
 255   void MergeBatches(QuarantineCache *to_deallocate) {
 256     uptr extracted_size = 0;
 257     QuarantineBatch *current = list_.front();
 258     while (current && current->next) {
 259       if (current->can_merge(current->next)) {
 260         QuarantineBatch *extracted = current->next;
 261         // Move all the chunks into the current batch.
 262         current->merge(extracted);
 263         CHECK_EQ(extracted->count, 0);
 264         CHECK_EQ(extracted->size, sizeof(QuarantineBatch));
 265         // Remove the next batch from the list and account for its size.
 266         list_.extract(current, extracted);
 267         extracted_size += extracted->size;
 268         // Add it to deallocation list.
 269         to_deallocate->EnqueueBatch(extracted);
 270       } else {
 271         current = current->next;
 272       }
 273     }
 274     SizeSub(extracted_size);
 275   }
 276
 277   void PrintStats() const {
 278     uptr batch_count = 0;
 279     uptr total_overhead_bytes = 0;
 280     uptr total_bytes = 0;
 281     uptr total_quarantine_chunks = 0;
 282     for (List::ConstIterator it = list_.begin(); it != list_.end(); ++it) {
 283       batch_count++;
 284       total_bytes += (*it).size;
 285       total_overhead_bytes += (*it).size - (*it).quarantined_size();
 286       total_quarantine_chunks += (*it).count;
 287     }
 288     uptr quarantine_chunks_capacity = batch_count * QuarantineBatch::kSize;
 289     int chunks_usage_percent = quarantine_chunks_capacity == 0 ?
 290         0 : total_quarantine_chunks * 100 / quarantine_chunks_capacity;
 291     uptr total_quarantined_bytes = total_bytes - total_overhead_bytes;
 292     int memory_overhead_percent = total_quarantined_bytes == 0 ?
 293         0 : total_overhead_bytes * 100 / total_quarantined_bytes;
 294     Printf("Global quarantine stats: batches: %zd; bytes: %zd (user: %zd); "
 295            "chunks: %zd (capacity: %zd); %d%% chunks used; %d%% memory overhead"
 296            "\n",
 297            batch_count, total_bytes, total_quarantined_bytes,
 298            total_quarantine_chunks, quarantine_chunks_capacity,
 299            chunks_usage_percent, memory_overhead_percent);
 300   }
 301
 302  private:
 303   typedef IntrusiveList<QuarantineBatch> List;
 304
 305   List list_;
 306   atomic_uintptr_t size_;
 307
 308   void SizeAdd(uptr add) {
 309     atomic_store_relaxed(&size_, Size() + add);
 310   }
 311   void SizeSub(uptr sub) {
 312     atomic_store_relaxed(&size_, Size() - sub);
 313   }
 314 };
 315
 316 } // namespace __sanitizer
 317
 318 #endif // SANITIZER_QUARANTINE_H