1 files changed, 160 insertions, 0 deletions
diff --git a/deps/v8/src/isolate-allocator.cc b/deps/v8/src/isolate-allocator.cc
new file mode 100644
index 0000000000..939fc1e5fc
--- /dev/null
+++ b/deps/v8/src/isolate-allocator.cc
@@ -0,0 +1,160 @@
+// Copyright 2018 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/isolate-allocator.h"
+#include "src/base/bounded-page-allocator.h"
+#include "src/isolate.h"
+#include "src/ptr-compr.h"
+#include "src/utils.h"
+
+namespace v8 {
+namespace internal {
+
+IsolateAllocator::IsolateAllocator(IsolateAllocationMode mode) {
+#if V8_TARGET_ARCH_64_BIT
+  if (mode == IsolateAllocationMode::kInV8Heap) {
+    Address heap_base = InitReservation();
+    CommitPagesForIsolate(heap_base);
+    return;
+  }
+#endif  // V8_TARGET_ARCH_64_BIT
+
+  // Allocate Isolate in C++ heap.
+  CHECK_EQ(mode, IsolateAllocationMode::kInCppHeap);
+  page_allocator_ = GetPlatformPageAllocator();
+  isolate_memory_ = ::operator new(sizeof(Isolate));
+  DCHECK(!reservation_.IsReserved());
+}
+
+IsolateAllocator::~IsolateAllocator() {
+  if (reservation_.IsReserved()) {
+    // The actual memory will be freed when the |reservation_| will die.
+    return;
+  }
+
+  // The memory was allocated in C++ heap.
+  ::operator delete(isolate_memory_);
+}
+
+#if V8_TARGET_ARCH_64_BIT
+Address IsolateAllocator::InitReservation() {
+  v8::PageAllocator* platform_page_allocator = GetPlatformPageAllocator();
+
+  // Reserve a 4Gb region so that the middle is 4Gb aligned.
+  // The VirtualMemory API does not support such an constraint so we have to
+  // implement it manually here.
+  size_t reservation_size = kPtrComprHeapReservationSize;
+  size_t base_alignment = kPtrComprIsolateRootAlignment;
+
+  const int kMaxAttempts = 3;
+  for (int attempt = 0; attempt < kMaxAttempts; ++attempt) {
+    Address hint = RoundDown(reinterpret_cast<Address>(
+                                 platform_page_allocator->GetRandomMmapAddr()),
+                             base_alignment) +
+                   kPtrComprIsolateRootBias;
+
+    // Within this reservation there will be a sub-region with proper alignment.
+    VirtualMemory padded_reservation(platform_page_allocator,
+                                     reservation_size * 2,
+                                     reinterpret_cast<void*>(hint));
+    if (!padded_reservation.IsReserved()) break;
+
+    // Find such a sub-region inside the reservation that it's middle is
+    // |base_alignment|-aligned.
+    Address address =
+        RoundUp(padded_reservation.address() + kPtrComprIsolateRootBias,
+                base_alignment) -
+        kPtrComprIsolateRootBias;
+    CHECK(padded_reservation.InVM(address, reservation_size));
+
+    // Now free the padded reservation and immediately try to reserve an exact
+    // region at aligned address. We have to do this dancing because the
+    // reservation address requirement is more complex than just a certain
+    // alignment and not all operating systems support freeing parts of reserved
+    // address space regions.
+    padded_reservation.Free();
+
+    VirtualMemory reservation(platform_page_allocator, reservation_size,
+                              reinterpret_cast<void*>(address));
+    if (!reservation.IsReserved()) break;
+
+    // The reservation could still be somewhere else but we can accept it
+    // if the reservation has the required alignment.
+    Address aligned_address =
+        RoundUp(reservation.address() + kPtrComprIsolateRootBias,
+                base_alignment) -
+        kPtrComprIsolateRootBias;
+
+    if (reservation.address() == aligned_address) {
+      reservation_ = std::move(reservation);
+      break;
+    }
+  }
+  if (!reservation_.IsReserved()) {
+    V8::FatalProcessOutOfMemory(nullptr,
+                                "Failed to reserve memory for new V8 Isolate");
+  }
+
+  CHECK_EQ(reservation_.size(), reservation_size);
+
+  Address heap_base = reservation_.address() + kPtrComprIsolateRootBias;
+  CHECK(IsAligned(heap_base, base_alignment));
+
+  return heap_base;
+}
+
+void IsolateAllocator::CommitPagesForIsolate(Address heap_base) {
+  v8::PageAllocator* platform_page_allocator = GetPlatformPageAllocator();
+
+  // Simplify BoundedPageAllocator's life by configuring it to use same page
+  // size as the Heap will use (MemoryChunk::kPageSize).
+  size_t page_size = RoundUp(size_t{1} << kPageSizeBits,
+                             platform_page_allocator->AllocatePageSize());
+
+  page_allocator_instance_ = base::make_unique<base::BoundedPageAllocator>(
+      platform_page_allocator, reservation_.address(), reservation_.size(),
+      page_size);
+  page_allocator_ = page_allocator_instance_.get();
+
+  Address isolate_address = heap_base - Isolate::isolate_root_bias();
+  Address isolate_end = isolate_address + sizeof(Isolate);
+
+  // Inform the bounded page allocator about reserved pages.
+  {
+    Address reserved_region_address = RoundDown(isolate_address, page_size);
+    size_t reserved_region_size =
+        RoundUp(isolate_end, page_size) - reserved_region_address;
+
+    CHECK(page_allocator_instance_->AllocatePagesAt(
+        reserved_region_address, reserved_region_size,
+        PageAllocator::Permission::kNoAccess));
+  }
+
+  // Commit pages where the Isolate will be stored.
+  {
+    size_t commit_page_size = platform_page_allocator->CommitPageSize();
+    Address committed_region_address =
+        RoundDown(isolate_address, commit_page_size);
+    size_t committed_region_size =
+        RoundUp(isolate_end, commit_page_size) - committed_region_address;
+
+    // We are using |reservation_| directly here because |page_allocator_| has
+    // bigger commit page size than we actually need.
+    CHECK(reservation_.SetPermissions(committed_region_address,
+                                      committed_region_size,
+                                      PageAllocator::kReadWrite));
+
+    if (Heap::ShouldZapGarbage()) {
+      for (Address address = committed_region_address;
+           address < committed_region_size; address += kSystemPointerSize) {
+        Memory<Address>(address) = static_cast<Address>(kZapValue);
+      }
+    }
+  }
+  isolate_memory_ = reinterpret_cast<void*>(isolate_address);
+}
+#endif  // V8_TARGET_ARCH_64_BIT
+
+}  // namespace internal
+}  // namespace v8