compiler-rt/lib/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 template<typename Callback, typename Node>
  72 class Quarantine {
  73  public:
  74   typedef QuarantineCache<Callback> Cache;
  75
  76   explicit Quarantine(LinkerInitialized)
  77       : cache_(LINKER_INITIALIZED) {
  78   }
  79
  80   void Init(uptr size, uptr cache_size) {
  81     // Thread local quarantine size can be zero only when global quarantine size
  82     // is zero (it allows us to perform just one atomic read per Put() call).
  83     CHECK((size == 0 && cache_size == 0) || cache_size != 0);
  84
  85     atomic_store_relaxed(&max_size_, size);
  86     atomic_store_relaxed(&min_size_, size / 10 * 9);  // 90% of max size.
  87     atomic_store_relaxed(&max_cache_size_, cache_size);
  88
  89     cache_mutex_.Init();
  90     recycle_mutex_.Init();
  91   }
  92
  93   uptr GetMaxSize() const { return atomic_load_relaxed(&max_size_); }
  94   uptr GetMaxCacheSize() const { return atomic_load_relaxed(&max_cache_size_); }
  95
  96   void Put(Cache *c, Callback cb, Node *ptr, uptr size) {
  97     uptr max_cache_size = GetMaxCacheSize();
  98     if (max_cache_size && size <= GetMaxSize()) {
  99       cb.PreQuarantine(ptr);
 100       c->Enqueue(cb, ptr, size);
 101     } else {
 102       // GetMaxCacheSize() == 0 only when GetMaxSize() == 0 (see Init).
 103       cb.RecyclePassThrough(ptr);
 104     }
 105     // Check cache size anyway to accommodate for runtime cache_size change.
 106     if (c->Size() > max_cache_size)
 107       Drain(c, cb);
 108   }
 109
 110   void NOINLINE Drain(Cache *c, Callback cb) {
 111     {
 112       SpinMutexLock l(&cache_mutex_);
 113       cache_.Transfer(c);
 114     }
 115     if (cache_.Size() > GetMaxSize() && recycle_mutex_.TryLock())
 116       Recycle(atomic_load_relaxed(&min_size_), cb);
 117   }
 118
 119   void NOINLINE DrainAndRecycle(Cache *c, Callback cb) {
 120     {
 121       SpinMutexLock l(&cache_mutex_);
 122       cache_.Transfer(c);
 123     }
 124     recycle_mutex_.Lock();
 125     Recycle(0, cb);
 126   }
 127
 128   void PrintStats() const {
 129     // It assumes that the world is stopped, just as the allocator's PrintStats.
 130     Printf("Quarantine limits: global: %zdMb; thread local: %zdKb\n",
 131            GetMaxSize() >> 20, GetMaxCacheSize() >> 10);
 132     cache_.PrintStats();
 133   }
 134
 135  private:
 136   // Read-only data.
 137   char pad0_[kCacheLineSize];
 138   atomic_uintptr_t max_size_;
 139   atomic_uintptr_t min_size_;
 140   atomic_uintptr_t max_cache_size_;
 141   char pad1_[kCacheLineSize];
 142   StaticSpinMutex cache_mutex_;
 143   StaticSpinMutex recycle_mutex_;
 144   Cache cache_;
 145   char pad2_[kCacheLineSize];
 146
 147   void NOINLINE Recycle(uptr min_size, Callback cb)
 148       SANITIZER_REQUIRES(recycle_mutex_) SANITIZER_RELEASE(recycle_mutex_) {
 149     Cache tmp;
 150     {
 151       SpinMutexLock l(&cache_mutex_);
 152       // Go over the batches and merge partially filled ones to
 153       // save some memory, otherwise batches themselves (since the memory used
 154       // by them is counted against quarantine limit) can overcome the actual
 155       // user's quarantined chunks, which diminishes the purpose of the
 156       // quarantine.
 157       uptr cache_size = cache_.Size();
 158       uptr overhead_size = cache_.OverheadSize();
 159       CHECK_GE(cache_size, overhead_size);
 160       // Do the merge only when overhead exceeds this predefined limit (might
 161       // require some tuning). It saves us merge attempt when the batch list
 162       // quarantine is unlikely to contain batches suitable for merge.
 163       const uptr kOverheadThresholdPercents = 100;
 164       if (cache_size > overhead_size &&
 165           overhead_size * (100 + kOverheadThresholdPercents) >
 166               cache_size * kOverheadThresholdPercents) {
 167         cache_.MergeBatches(&tmp);
 168       }
 169       // Extract enough chunks from the quarantine to get below the max
 170       // quarantine size and leave some leeway for the newly quarantined chunks.
 171       while (cache_.Size() > min_size) {
 172         tmp.EnqueueBatch(cache_.DequeueBatch());
 173       }
 174     }
 175     recycle_mutex_.Unlock();
 176     DoRecycle(&tmp, cb);
 177   }
 178
 179   void NOINLINE DoRecycle(Cache *c, Callback cb) {
 180     while (QuarantineBatch *b = c->DequeueBatch()) {
 181       const uptr kPrefetch = 16;
 182       CHECK(kPrefetch <= ARRAY_SIZE(b->batch));
 183       for (uptr i = 0; i < kPrefetch; i++)
 184         PREFETCH(b->batch[i]);
 185       for (uptr i = 0, count = b->count; i < count; i++) {
 186         if (i + kPrefetch < count)
 187           PREFETCH(b->batch[i + kPrefetch]);
 188         cb.Recycle((Node*)b->batch[i]);
 189       }
 190       cb.Deallocate(b);
 191     }
 192   }
 193 };
 194
 195 // Per-thread cache of memory blocks.
 196 template<typename Callback>
 197 class QuarantineCache {
 198  public:
 199   explicit QuarantineCache(LinkerInitialized) {
 200   }
 201
 202   QuarantineCache()
 203       : size_() {
 204     list_.clear();
 205   }
 206
 207   // Total memory used, including internal accounting.
 208   uptr Size() const {
 209     return atomic_load_relaxed(&size_);
 210   }
 211
 212   // Memory used for internal accounting.
 213   uptr OverheadSize() const {
 214     return list_.size() * sizeof(QuarantineBatch);
 215   }
 216
 217   void Enqueue(Callback cb, void *ptr, uptr size) {
 218     if (list_.empty() || list_.back()->count == QuarantineBatch::kSize) {
 219       QuarantineBatch *b = (QuarantineBatch *)cb.Allocate(sizeof(*b));
 220       CHECK(b);
 221       b->init(ptr, size);
 222       EnqueueBatch(b);
 223     } else {
 224       list_.back()->push_back(ptr, size);
 225       SizeAdd(size);
 226     }
 227   }
 228
 229   void Transfer(QuarantineCache *from_cache) {
 230     list_.append_back(&from_cache->list_);
 231     SizeAdd(from_cache->Size());
 232
 233     atomic_store_relaxed(&from_cache->size_, 0);
 234   }
 235
 236   void EnqueueBatch(QuarantineBatch *b) {
 237     list_.push_back(b);
 238     SizeAdd(b->size);
 239   }
 240
 241   QuarantineBatch *DequeueBatch() {
 242     if (list_.empty())
 243       return nullptr;
 244     QuarantineBatch *b = list_.front();
 245     list_.pop_front();
 246     SizeSub(b->size);
 247     return b;
 248   }
 249
 250   void MergeBatches(QuarantineCache *to_deallocate) {
 251     uptr extracted_size = 0;
 252     QuarantineBatch *current = list_.front();
 253     while (current && current->next) {
 254       if (current->can_merge(current->next)) {
 255         QuarantineBatch *extracted = current->next;
 256         // Move all the chunks into the current batch.
 257         current->merge(extracted);
 258         CHECK_EQ(extracted->count, 0);
 259         CHECK_EQ(extracted->size, sizeof(QuarantineBatch));
 260         // Remove the next batch from the list and account for its size.
 261         list_.extract(current, extracted);
 262         extracted_size += extracted->size;
 263         // Add it to deallocation list.
 264         to_deallocate->EnqueueBatch(extracted);
 265       } else {
 266         current = current->next;
 267       }
 268     }
 269     SizeSub(extracted_size);
 270   }
 271
 272   void PrintStats() const {
 273     uptr batch_count = 0;
 274     uptr total_overhead_bytes = 0;
 275     uptr total_bytes = 0;
 276     uptr total_quarantine_chunks = 0;
 277     for (List::ConstIterator it = list_.begin(); it != list_.end(); ++it) {
 278       batch_count++;
 279       total_bytes += (*it).size;
 280       total_overhead_bytes += (*it).size - (*it).quarantined_size();
 281       total_quarantine_chunks += (*it).count;
 282     }
 283     uptr quarantine_chunks_capacity = batch_count * QuarantineBatch::kSize;
 284     int chunks_usage_percent = quarantine_chunks_capacity == 0 ?
 285         0 : total_quarantine_chunks * 100 / quarantine_chunks_capacity;
 286     uptr total_quarantined_bytes = total_bytes - total_overhead_bytes;
 287     int memory_overhead_percent = total_quarantined_bytes == 0 ?
 288         0 : total_overhead_bytes * 100 / total_quarantined_bytes;
 289     Printf("Global quarantine stats: batches: %zd; bytes: %zd (user: %zd); "
 290            "chunks: %zd (capacity: %zd); %d%% chunks used; %d%% memory overhead"
 291            "\n",
 292            batch_count, total_bytes, total_quarantined_bytes,
 293            total_quarantine_chunks, quarantine_chunks_capacity,
 294            chunks_usage_percent, memory_overhead_percent);
 295   }
 296
 297  private:
 298   typedef IntrusiveList<QuarantineBatch> List;
 299
 300   List list_;
 301   atomic_uintptr_t size_;
 302
 303   void SizeAdd(uptr add) {
 304     atomic_store_relaxed(&size_, Size() + add);
 305   }
 306   void SizeSub(uptr sub) {
 307     atomic_store_relaxed(&size_, Size() - sub);
 308   }
 309 };
 310
 311 } // namespace __sanitizer
 312
 313 #endif // SANITIZER_QUARANTINE_H