1 files changed, 224 insertions, 0 deletions
diff --git a/deps/v8/src/zone/zone.cc b/deps/v8/src/zone/zone.cc
new file mode 100644
index 0000000000..4272e17fd2
--- /dev/null
+++ b/deps/v8/src/zone/zone.cc
@@ -0,0 +1,224 @@
+// Copyright 2012 the V8 project 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 "src/zone/zone.h"
+
+#include <cstring>
+
+#include "src/v8.h"
+
+#ifdef V8_USE_ADDRESS_SANITIZER
+#include <sanitizer/asan_interface.h>
+#endif  // V8_USE_ADDRESS_SANITIZER
+
+namespace v8 {
+namespace internal {
+
+namespace {
+
+#if V8_USE_ADDRESS_SANITIZER
+
+const size_t kASanRedzoneBytes = 24;  // Must be a multiple of 8.
+
+#else
+
+#define ASAN_POISON_MEMORY_REGION(start, size) \
+  do {                                         \
+    USE(start);                                \
+    USE(size);                                 \
+  } while (false)
+
+#define ASAN_UNPOISON_MEMORY_REGION(start, size) \
+  do {                                           \
+    USE(start);                                  \
+    USE(size);                                   \
+  } while (false)
+
+const size_t kASanRedzoneBytes = 0;
+
+#endif  // V8_USE_ADDRESS_SANITIZER
+
+}  // namespace
+
+Zone::Zone(AccountingAllocator* allocator)
+    : allocation_size_(0),
+      segment_bytes_allocated_(0),
+      position_(0),
+      limit_(0),
+      allocator_(allocator),
+      segment_head_(nullptr) {}
+
+Zone::~Zone() {
+  DeleteAll();
+  DeleteKeptSegment();
+
+  DCHECK(segment_bytes_allocated_ == 0);
+}
+
+void* Zone::New(size_t size) {
+  // Round up the requested size to fit the alignment.
+  size = RoundUp(size, kAlignment);
+
+  // If the allocation size is divisible by 8 then we return an 8-byte aligned
+  // address.
+  if (kPointerSize == 4 && kAlignment == 4) {
+    position_ += ((~size) & 4) & (reinterpret_cast<intptr_t>(position_) & 4);
+  } else {
+    DCHECK(kAlignment >= kPointerSize);
+  }
+
+  // Check if the requested size is available without expanding.
+  Address result = position_;
+
+  const size_t size_with_redzone = size + kASanRedzoneBytes;
+  const uintptr_t limit = reinterpret_cast<uintptr_t>(limit_);
+  const uintptr_t position = reinterpret_cast<uintptr_t>(position_);
+  // position_ > limit_ can be true after the alignment correction above.
+  if (limit < position || size_with_redzone > limit - position) {
+    result = NewExpand(size_with_redzone);
+  } else {
+    position_ += size_with_redzone;
+  }
+
+  Address redzone_position = result + size;
+  DCHECK(redzone_position + kASanRedzoneBytes == position_);
+  ASAN_POISON_MEMORY_REGION(redzone_position, kASanRedzoneBytes);
+
+  // Check that the result has the proper alignment and return it.
+  DCHECK(IsAddressAligned(result, kAlignment, 0));
+  allocation_size_ += size;
+  return reinterpret_cast<void*>(result);
+}
+
+void Zone::DeleteAll() {
+  // Find a segment with a suitable size to keep around.
+  Segment* keep = nullptr;
+  // Traverse the chained list of segments, zapping (in debug mode)
+  // and freeing every segment except the one we wish to keep.
+  for (Segment* current = segment_head_; current;) {
+    Segment* next = current->next();
+    if (!keep && current->size() <= kMaximumKeptSegmentSize) {
+      // Unlink the segment we wish to keep from the list.
+      keep = current;
+      keep->set_next(nullptr);
+    } else {
+      size_t size = current->size();
+#ifdef DEBUG
+      // Un-poison first so the zapping doesn't trigger ASan complaints.
+      ASAN_UNPOISON_MEMORY_REGION(current, size);
+#endif
+      current->ZapContents();
+      segment_bytes_allocated_ -= size;
+      allocator_->FreeSegment(current);
+    }
+    current = next;
+  }
+
+  // If we have found a segment we want to keep, we must recompute the
+  // variables 'position' and 'limit' to prepare for future allocate
+  // attempts. Otherwise, we must clear the position and limit to
+  // force a new segment to be allocated on demand.
+  if (keep) {
+    Address start = keep->start();
+    position_ = RoundUp(start, kAlignment);
+    limit_ = keep->end();
+    // Un-poison so we can re-use the segment later.
+    ASAN_UNPOISON_MEMORY_REGION(start, keep->capacity());
+    keep->ZapContents();
+  } else {
+    position_ = limit_ = 0;
+  }
+
+  allocation_size_ = 0;
+  // Update the head segment to be the kept segment (if any).
+  segment_head_ = keep;
+}
+
+void Zone::DeleteKeptSegment() {
+  DCHECK(segment_head_ == nullptr || segment_head_->next() == nullptr);
+  if (segment_head_ != nullptr) {
+    size_t size = segment_head_->size();
+#ifdef DEBUG
+    // Un-poison first so the zapping doesn't trigger ASan complaints.
+    ASAN_UNPOISON_MEMORY_REGION(segment_head_, size);
+#endif
+    segment_head_->ZapContents();
+    segment_bytes_allocated_ -= size;
+    allocator_->FreeSegment(segment_head_);
+    segment_head_ = nullptr;
+  }
+
+  DCHECK(segment_bytes_allocated_ == 0);
+}
+
+// Creates a new segment, sets it size, and pushes it to the front
+// of the segment chain. Returns the new segment.
+Segment* Zone::NewSegment(size_t size) {
+  Segment* result = allocator_->AllocateSegment(size);
+  segment_bytes_allocated_ += size;
+  if (result != nullptr) {
+    result->Initialize(segment_head_, size, this);
+    segment_head_ = result;
+  }
+  return result;
+}
+
+Address Zone::NewExpand(size_t size) {
+  // Make sure the requested size is already properly aligned and that
+  // there isn't enough room in the Zone to satisfy the request.
+  DCHECK_EQ(size, RoundDown(size, kAlignment));
+  DCHECK(limit_ < position_ ||
+         reinterpret_cast<uintptr_t>(limit_) -
+                 reinterpret_cast<uintptr_t>(position_) <
+             size);
+
+  // Compute the new segment size. We use a 'high water mark'
+  // strategy, where we increase the segment size every time we expand
+  // except that we employ a maximum segment size when we delete. This
+  // is to avoid excessive malloc() and free() overhead.
+  Segment* head = segment_head_;
+  const size_t old_size = (head == nullptr) ? 0 : head->size();
+  static const size_t kSegmentOverhead = sizeof(Segment) + kAlignment;
+  const size_t new_size_no_overhead = size + (old_size << 1);
+  size_t new_size = kSegmentOverhead + new_size_no_overhead;
+  const size_t min_new_size = kSegmentOverhead + size;
+  // Guard against integer overflow.
+  if (new_size_no_overhead < size || new_size < kSegmentOverhead) {
+    V8::FatalProcessOutOfMemory("Zone");
+    return nullptr;
+  }
+  if (new_size < kMinimumSegmentSize) {
+    new_size = kMinimumSegmentSize;
+  } else if (new_size > kMaximumSegmentSize) {
+    // Limit the size of new segments to avoid growing the segment size
+    // exponentially, thus putting pressure on contiguous virtual address space.
+    // All the while making sure to allocate a segment large enough to hold the
+    // requested size.
+    new_size = Max(min_new_size, kMaximumSegmentSize);
+  }
+  if (new_size > INT_MAX) {
+    V8::FatalProcessOutOfMemory("Zone");
+    return nullptr;
+  }
+  Segment* segment = NewSegment(new_size);
+  if (segment == nullptr) {
+    V8::FatalProcessOutOfMemory("Zone");
+    return nullptr;
+  }
+
+  // Recompute 'top' and 'limit' based on the new segment.
+  Address result = RoundUp(segment->start(), kAlignment);
+  position_ = result + size;
+  // Check for address overflow.
+  // (Should not happen since the segment is guaranteed to accomodate
+  // size bytes + header and alignment padding)
+  DCHECK(reinterpret_cast<uintptr_t>(position_) >=
+         reinterpret_cast<uintptr_t>(result));
+  limit_ = segment->end();
+  DCHECK(position_ <= limit_);
+  return result;
+}
+
+}  // namespace internal
+}  // namespace v8