lib/asan/asan_allocator2.cc

//===-- asan_allocator2.cc ------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of AddressSanitizer, an address sanity checker.
//
// Implementation of ASan's memory allocator, 2-nd version.
// This variant uses the allocator from sanitizer_common, i.e. the one shared
// with ThreadSanitizer and MemorySanitizer.
//
// Status: under development, not enabled by default yet.
//===----------------------------------------------------------------------===//
#include "asan_allocator.h"
#if ASAN_ALLOCATOR_VERSION == 2

#include "asan_mapping.h"
#include "asan_report.h"
#include "asan_thread.h"
#include "asan_thread_registry.h"
#include "sanitizer/asan_interface.h"
#include "sanitizer_common/sanitizer_allocator.h"
#include "sanitizer_common/sanitizer_internal_defs.h"
#include "sanitizer_common/sanitizer_list.h"
#include "sanitizer_common/sanitizer_stackdepot.h"
#include "sanitizer_common/sanitizer_quarantine.h"

namespace __asan {

struct AsanMapUnmapCallback {
  void OnMap(uptr p, uptr size) const {
    PoisonShadow(p, size, kAsanHeapLeftRedzoneMagic);
    // Statistics.
    AsanStats &thread_stats = asanThreadRegistry().GetCurrentThreadStats();
    thread_stats.mmaps++;
    thread_stats.mmaped += size;
  }
  void OnUnmap(uptr p, uptr size) const {
    PoisonShadow(p, size, 0);
    // We are about to unmap a chunk of user memory.
    // Mark the corresponding shadow memory as not needed.
    // Since asan's mapping is compacting, the shadow chunk may be
    // not page-aligned, so we only flush the page-aligned portion.
    uptr page_size = GetPageSizeCached();
    uptr shadow_beg = RoundUpTo(MemToShadow(p), page_size);
    uptr shadow_end = RoundDownTo(MemToShadow(p + size), page_size);
    FlushUnneededShadowMemory(shadow_beg, shadow_end - shadow_beg);
    // Statistics.
    AsanStats &thread_stats = asanThreadRegistry().GetCurrentThreadStats();
    thread_stats.munmaps++;
    thread_stats.munmaped += size;
  }
};

#if SANITIZER_WORDSIZE == 64
#if defined(__powerpc64__)
const uptr kAllocatorSpace =  0xa0000000000ULL;
#else
const uptr kAllocatorSpace = 0x600000000000ULL;
#endif
const uptr kAllocatorSize  =  0x10000000000ULL;  // 1T.
typedef DefaultSizeClassMap SizeClassMap;
typedef SizeClassAllocator64<kAllocatorSpace, kAllocatorSize, 0 /*metadata*/,
    SizeClassMap, AsanMapUnmapCallback> PrimaryAllocator;
#elif SANITIZER_WORDSIZE == 32
static const u64 kAddressSpaceSize = 1ULL << 32;
typedef CompactSizeClassMap SizeClassMap;
typedef SizeClassAllocator32<0, kAddressSpaceSize, 16,
  SizeClassMap, AsanMapUnmapCallback> PrimaryAllocator;
#endif

typedef SizeClassAllocatorLocalCache<PrimaryAllocator> AllocatorCache;
typedef LargeMmapAllocator<AsanMapUnmapCallback> SecondaryAllocator;
typedef CombinedAllocator<PrimaryAllocator, AllocatorCache,
    SecondaryAllocator> Allocator;

// We can not use THREADLOCAL because it is not supported on some of the
// platforms we care about (OSX 10.6, Android).
// static THREADLOCAL AllocatorCache cache;
AllocatorCache *GetAllocatorCache(AsanThreadLocalMallocStorage *ms) {
  CHECK(ms);
  CHECK_LE(sizeof(AllocatorCache), sizeof(ms->allocator2_cache));
  return reinterpret_cast<AllocatorCache *>(ms->allocator2_cache);
}

static Allocator allocator;

static const uptr kMaxAllowedMallocSize =
  FIRST_32_SECOND_64(3UL << 30, 8UL << 30);

static const uptr kMaxThreadLocalQuarantine =
  FIRST_32_SECOND_64(1 << 18, 1 << 20);

static const uptr kReturnOnZeroMalloc = 2048;  // Zero page is protected.

// Every chunk of memory allocated by this allocator can be in one of 3 states:
// CHUNK_AVAILABLE: the chunk is in the free list and ready to be allocated.
// CHUNK_ALLOCATED: the chunk is allocated and not yet freed.
// CHUNK_QUARANTINE: the chunk was freed and put into quarantine zone.
enum {
  CHUNK_AVAILABLE  = 0,  // 0 is the default value even if we didn't set it.
  CHUNK_ALLOCATED  = 2,
  CHUNK_QUARANTINE = 3
};

// Valid redzone sizes are 16, 32, 64, ... 2048, so we encode them in 3 bits.
// We use adaptive redzones: for larger allocation larger redzones are used.
static u32 RZLog2Size(u32 rz_log) {
  CHECK_LT(rz_log, 8);
  return 16 << rz_log;
}

static u32 RZSize2Log(u32 rz_size) {
  CHECK_GE(rz_size, 16);
  CHECK_LE(rz_size, 2048);
  CHECK(IsPowerOfTwo(rz_size));
  u32 res = __builtin_ctz(rz_size) - 4;
  CHECK_EQ(rz_size, RZLog2Size(res));
  return res;
}

static uptr ComputeRZLog(uptr user_requested_size) {
  u32 rz_log =
    user_requested_size <= 64        - 16   ? 0 :
    user_requested_size <= 128       - 32   ? 1 :
    user_requested_size <= 512       - 64   ? 2 :
    user_requested_size <= 4096      - 128  ? 3 :
    user_requested_size <= (1 << 14) - 256  ? 4 :
    user_requested_size <= (1 << 15) - 512  ? 5 :
    user_requested_size <= (1 << 16) - 1024 ? 6 : 7;
  return Max(rz_log, RZSize2Log(flags()->redzone));
}

// The memory chunk allocated from the underlying allocator looks like this:
// L L L L L L H H U U U U U U R R
//   L -- left redzone words (0 or more bytes)
//   H -- ChunkHeader (16 bytes), which is also a part of the left redzone.
//   U -- user memory.
//   R -- right redzone (0 or more bytes)
// ChunkBase consists of ChunkHeader and other bytes that overlap with user
// memory.

// If a memory chunk is allocated by memalign and we had to increase the
// allocation size to achieve the proper alignment, then we store this magic
// value in the first uptr word of the memory block and store the address of
// ChunkBase in the next uptr.
// M B ? ? ? L L L L L L  H H U U U U U U
//   M -- magic value kMemalignMagic
//   B -- address of ChunkHeader pointing to the first 'H'
static const uptr kMemalignMagic = 0xCC6E96B9;

struct ChunkHeader {
  // 1-st 8 bytes.
  u32 chunk_state       : 8;  // Must be first.
  u32 alloc_tid         : 24;

  u32 free_tid          : 24;
  u32 from_memalign     : 1;
  u32 alloc_type        : 2;
  u32 rz_log            : 3;
  // 2-nd 8 bytes
  // This field is used for small sizes. For large sizes it is equal to
  // SizeClassMap::kMaxSize and the actual size is stored in the
  // SecondaryAllocator's metadata.
  u32 user_requested_size;
  u32 alloc_context_id;
};

struct ChunkBase : ChunkHeader {
  // Header2, intersects with user memory.
  AsanChunk *next;
  u32 free_context_id;
};

static const uptr kChunkHeaderSize = sizeof(ChunkHeader);
static const uptr kChunkHeader2Size = sizeof(ChunkBase) - kChunkHeaderSize;
COMPILER_CHECK(kChunkHeaderSize == 16);
COMPILER_CHECK(kChunkHeader2Size <= 16);

struct AsanChunk: ChunkBase {
  uptr Beg() { return reinterpret_cast<uptr>(this) + kChunkHeaderSize; }
  uptr UsedSize() {
    if (user_requested_size != SizeClassMap::kMaxSize)
      return user_requested_size;
    return *reinterpret_cast<uptr *>(allocator.GetMetaData(AllocBeg()));
  }
  void *AllocBeg() {
    if (from_memalign)
      return allocator.GetBlockBegin(reinterpret_cast<void *>(this));
    return reinterpret_cast<void*>(Beg() - RZLog2Size(rz_log));
  }
  // We store the alloc/free stack traces in the chunk itself.
  u32 *AllocStackBeg() {
    return (u32*)(Beg() - RZLog2Size(rz_log));
  }
  uptr AllocStackSize() {
    CHECK_LE(RZLog2Size(rz_log), kChunkHeaderSize);
    return (RZLog2Size(rz_log) - kChunkHeaderSize) / sizeof(u32);
  }
  u32 *FreeStackBeg() {
    return (u32*)(Beg() + kChunkHeader2Size);
  }
  uptr FreeStackSize() {
    if (user_requested_size < kChunkHeader2Size) return 0;
    uptr available = RoundUpTo(user_requested_size, SHADOW_GRANULARITY);
    return (available - kChunkHeader2Size) / sizeof(u32);
  }
};

uptr AsanChunkView::Beg() { return chunk_->Beg(); }
uptr AsanChunkView::End() { return Beg() + UsedSize(); }
uptr AsanChunkView::UsedSize() { return chunk_->UsedSize(); }
uptr AsanChunkView::AllocTid() { return chunk_->alloc_tid; }
uptr AsanChunkView::FreeTid() { return chunk_->free_tid; }

static void GetStackTraceFromId(u32 id, StackTrace *stack) {
  CHECK(id);
  uptr size = 0;
  const uptr *trace = StackDepotGet(id, &size);
  CHECK_LT(size, kStackTraceMax);
  internal_memcpy(stack->trace, trace, sizeof(uptr) * size);
  stack->size = size;
}

void AsanChunkView::GetAllocStack(StackTrace *stack) {
  if (flags()->use_stack_depot)
    GetStackTraceFromId(chunk_->alloc_context_id, stack);
  else
    StackTrace::UncompressStack(stack, chunk_->AllocStackBeg(),
                                chunk_->AllocStackSize());
}

void AsanChunkView::GetFreeStack(StackTrace *stack) {
  if (flags()->use_stack_depot)
    GetStackTraceFromId(chunk_->free_context_id, stack);
  else
    StackTrace::UncompressStack(stack, chunk_->FreeStackBeg(),
                                chunk_->FreeStackSize());
}

struct QuarantineCallback;
typedef Quarantine<QuarantineCallback, AsanChunk> AsanQuarantine;
typedef AsanQuarantine::Cache QuarantineCache;
static AsanQuarantine quarantine(LINKER_INITIALIZED);
static QuarantineCache fallback_quarantine_cache(LINKER_INITIALIZED);
static AllocatorCache fallback_allocator_cache;
static SpinMutex fallback_mutex;

QuarantineCache *GetQuarantineCache(AsanThreadLocalMallocStorage *ms) {
  CHECK(ms);
  CHECK_LE(sizeof(QuarantineCache), sizeof(ms->quarantine_cache));
  return reinterpret_cast<QuarantineCache *>(ms->quarantine_cache);
}

struct QuarantineCallback {
  explicit QuarantineCallback(AllocatorCache *cache)
      : cache_(cache) {
  }

  void Recycle(AsanChunk *m) {
    CHECK(m->chunk_state == CHUNK_QUARANTINE);
    m->chunk_state = CHUNK_AVAILABLE;
    CHECK_NE(m->alloc_tid, kInvalidTid);
    CHECK_NE(m->free_tid, kInvalidTid);
    PoisonShadow(m->Beg(),
                 RoundUpTo(m->UsedSize(), SHADOW_GRANULARITY),
                 kAsanHeapLeftRedzoneMagic);
    void *p = reinterpret_cast<void *>(m->AllocBeg());
    if (m->from_memalign) {
      uptr *memalign_magic = reinterpret_cast<uptr *>(p);
      CHECK_EQ(memalign_magic[0], kMemalignMagic);
      CHECK_EQ(memalign_magic[1], reinterpret_cast<uptr>(m));
    }

    // Statistics.
    AsanStats &thread_stats = asanThreadRegistry().GetCurrentThreadStats();
    thread_stats.real_frees++;
    thread_stats.really_freed += m->UsedSize();

    allocator.Deallocate(cache_, p);
  }

  void *Allocate(uptr size) {
    return allocator.Allocate(cache_, size, 1, false);
  }

  void Deallocate(void *p) {
    allocator.Deallocate(cache_, p);
  }

  AllocatorCache *cache_;
};

static void Init() {
  static int inited = 0;
  if (inited) return;
  __asan_init();
  inited = true;  // this must happen before any threads are created.
  allocator.Init();
  quarantine.Init((uptr)flags()->quarantine_size, kMaxThreadLocalQuarantine);
}

static void *Allocate(uptr size, uptr alignment, StackTrace *stack,
                      AllocType alloc_type) {
  Init();
  CHECK(stack);
  const uptr min_alignment = SHADOW_GRANULARITY;
  if (alignment < min_alignment)
    alignment = min_alignment;
  if (size == 0) {
    if (alignment <= kReturnOnZeroMalloc)
      return reinterpret_cast<void *>(kReturnOnZeroMalloc);
    else
      return 0;  // 0 bytes with large alignment requested. Just return 0.
  }
  CHECK(IsPowerOfTwo(alignment));
  uptr rz_log = ComputeRZLog(size);
  uptr rz_size = RZLog2Size(rz_log);
  uptr rounded_size = RoundUpTo(size, alignment);
  if (rounded_size < kChunkHeader2Size)
    rounded_size = kChunkHeader2Size;
  uptr needed_size = rounded_size + rz_size;
  if (alignment > min_alignment)
    needed_size += alignment;
  bool using_primary_allocator = true;
  // If we are allocating from the secondary allocator, there will be no
  // automatic right redzone, so add the right redzone manually.
  if (!PrimaryAllocator::CanAllocate(needed_size, alignment)) {
    needed_size += rz_size;
    using_primary_allocator = false;
  }
  CHECK(IsAligned(needed_size, min_alignment));
  if (size > kMaxAllowedMallocSize || needed_size > kMaxAllowedMallocSize) {
    Report("WARNING: AddressSanitizer failed to allocate %p bytes\n",
           (void*)size);
    return 0;
  }

  AsanThread *t = asanThreadRegistry().GetCurrent();
  void *allocated;
  if (t) {
    AllocatorCache *cache = GetAllocatorCache(&t->malloc_storage());
    allocated = allocator.Allocate(cache, needed_size, 8, false);
  } else {
    SpinMutexLock l(&fallback_mutex);
    AllocatorCache *cache = &fallback_allocator_cache;
    allocated = allocator.Allocate(cache, needed_size, 8, false);
  }
  uptr alloc_beg = reinterpret_cast<uptr>(allocated);
  // Clear the first allocated word (an old kMemalignMagic may still be there).
  reinterpret_cast<uptr *>(alloc_beg)[0] = 0;
  uptr alloc_end = alloc_beg + needed_size;
  uptr beg_plus_redzone = alloc_beg + rz_size;
  uptr user_beg = beg_plus_redzone;
  if (!IsAligned(user_beg, alignment))
    user_beg = RoundUpTo(user_beg, alignment);
  uptr user_end = user_beg + size;
  CHECK_LE(user_end, alloc_end);
  uptr chunk_beg = user_beg - kChunkHeaderSize;
  AsanChunk *m = reinterpret_cast<AsanChunk *>(chunk_beg);
  m->chunk_state = CHUNK_ALLOCATED;
  m->alloc_type = alloc_type;
  m->rz_log = rz_log;
  u32 alloc_tid = t ? t->tid() : 0;
  m->alloc_tid = alloc_tid;
  CHECK_EQ(alloc_tid, m->alloc_tid);  // Does alloc_tid fit into the bitfield?
  m->free_tid = kInvalidTid;
  m->from_memalign = user_beg != beg_plus_redzone;
  if (m->from_memalign) {
    CHECK_LE(beg_plus_redzone + 2 * sizeof(uptr), user_beg);
    uptr *memalign_magic = reinterpret_cast<uptr *>(alloc_beg);
    memalign_magic[0] = kMemalignMagic;
    memalign_magic[1] = chunk_beg;
  }
  if (using_primary_allocator) {
    CHECK(size);
    m->user_requested_size = size;
    CHECK(allocator.FromPrimary(allocated));
  } else {
    CHECK(!allocator.FromPrimary(allocated));
    m->user_requested_size = SizeClassMap::kMaxSize;
    uptr *meta = reinterpret_cast<uptr *>(allocator.GetMetaData(allocated));
    meta[0] = size;
    meta[1] = chunk_beg;
  }

  if (flags()->use_stack_depot) {
    m->alloc_context_id = StackDepotPut(stack->trace, stack->size);
  } else {
    m->alloc_context_id = 0;
    StackTrace::CompressStack(stack, m->AllocStackBeg(), m->AllocStackSize());
  }

  uptr size_rounded_down_to_granularity = RoundDownTo(size, SHADOW_GRANULARITY);
  // Unpoison the bulk of the memory region.
  if (size_rounded_down_to_granularity)
    PoisonShadow(user_beg, size_rounded_down_to_granularity, 0);
  // Deal with the end of the region if size is not aligned to granularity.
  if (size != size_rounded_down_to_granularity && flags()->poison_heap) {
    u8 *shadow = (u8*)MemToShadow(user_beg + size_rounded_down_to_granularity);
    *shadow = size & (SHADOW_GRANULARITY - 1);
  }

  AsanStats &thread_stats = asanThreadRegistry().GetCurrentThreadStats();
  thread_stats.mallocs++;
  thread_stats.malloced += size;
  thread_stats.malloced_redzones += needed_size - size;
  uptr class_id = Min(kNumberOfSizeClasses, SizeClassMap::ClassID(needed_size));
  thread_stats.malloced_by_size[class_id]++;
  if (needed_size > SizeClassMap::kMaxSize)
    thread_stats.malloc_large++;

  void *res = reinterpret_cast<void *>(user_beg);
  ASAN_MALLOC_HOOK(res, size);
  return res;
}

static void Deallocate(void *ptr, StackTrace *stack, AllocType alloc_type) {
  uptr p = reinterpret_cast<uptr>(ptr);
  if (p == 0 || p == kReturnOnZeroMalloc) return;
  uptr chunk_beg = p - kChunkHeaderSize;
  AsanChunk *m = reinterpret_cast<AsanChunk *>(chunk_beg);

  // Flip the chunk_state atomically to avoid race on double-free.
  u8 old_chunk_state = atomic_exchange((atomic_uint8_t*)m, CHUNK_QUARANTINE,
                                       memory_order_relaxed);

  if (old_chunk_state == CHUNK_QUARANTINE)
    ReportDoubleFree((uptr)ptr, stack);
  else if (old_chunk_state != CHUNK_ALLOCATED)
    ReportFreeNotMalloced((uptr)ptr, stack);
  CHECK(old_chunk_state == CHUNK_ALLOCATED);
  if (m->alloc_type != alloc_type && flags()->alloc_dealloc_mismatch)
    ReportAllocTypeMismatch((uptr)ptr, stack,
                            (AllocType)m->alloc_type, (AllocType)alloc_type);

  CHECK_GE(m->alloc_tid, 0);
  if (SANITIZER_WORDSIZE == 64)  // On 32-bits this resides in user area.
    CHECK_EQ(m->free_tid, kInvalidTid);
  AsanThread *t = asanThreadRegistry().GetCurrent();
  m->free_tid = t ? t->tid() : 0;
  if (flags()->use_stack_depot) {
    m->free_context_id = StackDepotPut(stack->trace, stack->size);
  } else {
    m->free_context_id = 0;
    StackTrace::CompressStack(stack, m->FreeStackBeg(), m->FreeStackSize());
  }
  CHECK(m->chunk_state == CHUNK_QUARANTINE);
  // Poison the region.
  PoisonShadow(m->Beg(),
               RoundUpTo(m->UsedSize(), SHADOW_GRANULARITY),
               kAsanHeapFreeMagic);

  AsanStats &thread_stats = asanThreadRegistry().GetCurrentThreadStats();
  thread_stats.frees++;
  thread_stats.freed += m->UsedSize();

  // Push into quarantine.
  if (t) {
    AsanThreadLocalMallocStorage *ms = &t->malloc_storage();
    AllocatorCache *ac = GetAllocatorCache(ms);
    quarantine.Put(GetQuarantineCache(ms), QuarantineCallback(ac),
                   m, m->UsedSize());
  } else {
    SpinMutexLock l(&fallback_mutex);
    AllocatorCache *ac = &fallback_allocator_cache;
    quarantine.Put(&fallback_quarantine_cache, QuarantineCallback(ac),
                   m, m->UsedSize());
  }

  ASAN_FREE_HOOK(ptr);
}

static void *Reallocate(void *old_ptr, uptr new_size, StackTrace *stack) {
  CHECK(old_ptr && new_size);
  uptr p = reinterpret_cast<uptr>(old_ptr);
  uptr chunk_beg = p - kChunkHeaderSize;
  AsanChunk *m = reinterpret_cast<AsanChunk *>(chunk_beg);

  AsanStats &thread_stats = asanThreadRegistry().GetCurrentThreadStats();
  thread_stats.reallocs++;
  thread_stats.realloced += new_size;

  CHECK(m->chunk_state == CHUNK_ALLOCATED);
  uptr old_size = m->UsedSize();
  uptr memcpy_size = Min(new_size, old_size);
  void *new_ptr = Allocate(new_size, 8, stack, FROM_MALLOC);
  if (new_ptr) {
    CHECK(REAL(memcpy) != 0);
    REAL(memcpy)(new_ptr, old_ptr, memcpy_size);
    Deallocate(old_ptr, stack, FROM_MALLOC);
  }
  return new_ptr;
}

static AsanChunk *GetAsanChunkByAddr(uptr p) {
  void *ptr = reinterpret_cast<void *>(p);
  uptr alloc_beg = reinterpret_cast<uptr>(allocator.GetBlockBegin(ptr));
  if (!alloc_beg) return 0;
  uptr *memalign_magic = reinterpret_cast<uptr *>(alloc_beg);
  if (memalign_magic[0] == kMemalignMagic) {
    AsanChunk *m = reinterpret_cast<AsanChunk *>(memalign_magic[1]);
    CHECK(m->from_memalign);
    return m;
  }
  if (!allocator.FromPrimary(ptr)) {
    uptr *meta = reinterpret_cast<uptr *>(
        allocator.GetMetaData(reinterpret_cast<void *>(alloc_beg)));
    AsanChunk *m = reinterpret_cast<AsanChunk *>(meta[1]);
    return m;
  }
  uptr actual_size = allocator.GetActuallyAllocatedSize(ptr);
  CHECK_LE(actual_size, SizeClassMap::kMaxSize);
  // We know the actually allocted size, but we don't know the redzone size.
  // Just try all possible redzone sizes.
  for (u32 rz_log = 0; rz_log < 8; rz_log++) {
    u32 rz_size = RZLog2Size(rz_log);
    uptr max_possible_size = actual_size - rz_size;
    if (ComputeRZLog(max_possible_size) != rz_log)
      continue;
    return reinterpret_cast<AsanChunk *>(
        alloc_beg + rz_size - kChunkHeaderSize);
  }
  return 0;
}

static uptr AllocationSize(uptr p) {
  AsanChunk *m = GetAsanChunkByAddr(p);
  if (!m) return 0;
  if (m->chunk_state != CHUNK_ALLOCATED) return 0;
  if (m->Beg() != p) return 0;
  return m->UsedSize();
}

// We have an address between two chunks, and we want to report just one.
AsanChunk *ChooseChunk(uptr addr,
                       AsanChunk *left_chunk, AsanChunk *right_chunk) {
  // Prefer an allocated chunk over freed chunk and freed chunk
  // over available chunk.
  if (left_chunk->chunk_state != right_chunk->chunk_state) {
    if (left_chunk->chunk_state == CHUNK_ALLOCATED)
      return left_chunk;
    if (right_chunk->chunk_state == CHUNK_ALLOCATED)
      return right_chunk;
    if (left_chunk->chunk_state == CHUNK_QUARANTINE)
      return left_chunk;
    if (right_chunk->chunk_state == CHUNK_QUARANTINE)
      return right_chunk;
  }
  // Same chunk_state: choose based on offset.
  uptr l_offset = 0, r_offset = 0;
  CHECK(AsanChunkView(left_chunk).AddrIsAtRight(addr, 1, &l_offset));
  CHECK(AsanChunkView(right_chunk).AddrIsAtLeft(addr, 1, &r_offset));
  if (l_offset < r_offset)
    return left_chunk;
  return right_chunk;
}

AsanChunkView FindHeapChunkByAddress(uptr addr) {
  AsanChunk *m1 = GetAsanChunkByAddr(addr);
  if (!m1) return AsanChunkView(m1);
  uptr offset = 0;
  if (AsanChunkView(m1).AddrIsAtLeft(addr, 1, &offset)) {
    // The address is in the chunk's left redzone, so maybe it is actually
    // a right buffer overflow from the other chunk to the left.
    // Search a bit to the left to see if there is another chunk.
    AsanChunk *m2 = 0;
    for (uptr l = 1; l < GetPageSizeCached(); l++) {
      m2 = GetAsanChunkByAddr(addr - l);
      if (m2 == m1) continue;  // Still the same chunk.
      break;
    }
    if (m2 && AsanChunkView(m2).AddrIsAtRight(addr, 1, &offset))
      m1 = ChooseChunk(addr, m2, m1);
  }
  return AsanChunkView(m1);
}

void AsanThreadLocalMallocStorage::CommitBack() {
  AllocatorCache *ac = GetAllocatorCache(this);
  quarantine.Drain(GetQuarantineCache(this), QuarantineCallback(ac));
  allocator.SwallowCache(GetAllocatorCache(this));
}

void PrintInternalAllocatorStats() {
  allocator.PrintStats();
}

SANITIZER_INTERFACE_ATTRIBUTE
void *asan_memalign(uptr alignment, uptr size, StackTrace *stack,
                    AllocType alloc_type) {
  return Allocate(size, alignment, stack, alloc_type);
}

SANITIZER_INTERFACE_ATTRIBUTE
void asan_free(void *ptr, StackTrace *stack, AllocType alloc_type) {
  Deallocate(ptr, stack, alloc_type);
}

SANITIZER_INTERFACE_ATTRIBUTE
void *asan_malloc(uptr size, StackTrace *stack) {
  return Allocate(size, 8, stack, FROM_MALLOC);
}

void *asan_calloc(uptr nmemb, uptr size, StackTrace *stack) {
  void *ptr = Allocate(nmemb * size, 8, stack, FROM_MALLOC);
  if (ptr)
    REAL(memset)(ptr, 0, nmemb * size);
  return ptr;
}

void *asan_realloc(void *p, uptr size, StackTrace *stack) {
  if (p == 0)
    return Allocate(size, 8, stack, FROM_MALLOC);
  if (size == 0) {
    Deallocate(p, stack, FROM_MALLOC);
    return 0;
  }
  return Reallocate(p, size, stack);
}

void *asan_valloc(uptr size, StackTrace *stack) {
  return Allocate(size, GetPageSizeCached(), stack, FROM_MALLOC);
}

void *asan_pvalloc(uptr size, StackTrace *stack) {
  uptr PageSize = GetPageSizeCached();
  size = RoundUpTo(size, PageSize);
  if (size == 0) {
    // pvalloc(0) should allocate one page.
    size = PageSize;
  }
  return Allocate(size, PageSize, stack, FROM_MALLOC);
}

int asan_posix_memalign(void **memptr, uptr alignment, uptr size,
                        StackTrace *stack) {
  void *ptr = Allocate(size, alignment, stack, FROM_MALLOC);
  CHECK(IsAligned((uptr)ptr, alignment));
  *memptr = ptr;
  return 0;
}

uptr asan_malloc_usable_size(void *ptr, StackTrace *stack) {
  CHECK(stack);
  if (ptr == 0) return 0;
  uptr usable_size = AllocationSize(reinterpret_cast<uptr>(ptr));
  if (flags()->check_malloc_usable_size && (usable_size == 0))
    ReportMallocUsableSizeNotOwned((uptr)ptr, stack);
  return usable_size;
}

uptr asan_mz_size(const void *ptr) {
  UNIMPLEMENTED();
  return 0;
}

void asan_mz_force_lock() {
  UNIMPLEMENTED();
}

void asan_mz_force_unlock() {
  UNIMPLEMENTED();
}

}  // namespace __asan

// ---------------------- Interface ---------------- {{{1
using namespace __asan;  // NOLINT

// ASan allocator doesn't reserve extra bytes, so normally we would
// just return "size". We don't want to expose our redzone sizes, etc here.
uptr __asan_get_estimated_allocated_size(uptr size) {
  return size;
}

bool __asan_get_ownership(const void *p) {
  uptr ptr = reinterpret_cast<uptr>(p);
  return (ptr == kReturnOnZeroMalloc) || (AllocationSize(ptr) > 0);
}

uptr __asan_get_allocated_size(const void *p) {
  if (p == 0) return 0;
  uptr ptr = reinterpret_cast<uptr>(p);
  uptr allocated_size = AllocationSize(ptr);
  // Die if p is not malloced or if it is already freed.
  if (allocated_size == 0 && ptr != kReturnOnZeroMalloc) {
    GET_STACK_TRACE_FATAL_HERE;
    ReportAsanGetAllocatedSizeNotOwned(ptr, &stack);
  }
  return allocated_size;
}

#if !SANITIZER_SUPPORTS_WEAK_HOOKS
// Provide default (no-op) implementation of malloc hooks.
extern "C" {
SANITIZER_WEAK_ATTRIBUTE SANITIZER_INTERFACE_ATTRIBUTE
void __asan_malloc_hook(void *ptr, uptr size) {
  (void)ptr;
  (void)size;
}
SANITIZER_WEAK_ATTRIBUTE SANITIZER_INTERFACE_ATTRIBUTE
void __asan_free_hook(void *ptr) {
  (void)ptr;
}
}  // extern "C"
#endif


#endif  // ASAN_ALLOCATOR_VERSION