V8 API Reference, 7.2.502.16 (for Deno 0.2.4)
bounded-page-allocator.h
1 // Copyright 2018 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef V8_BASE_BOUNDED_PAGE_ALLOCATOR_H_
6 #define V8_BASE_BOUNDED_PAGE_ALLOCATOR_H_
7 
8 #include "include/v8-platform.h"
9 #include "src/base/platform/mutex.h"
10 #include "src/base/region-allocator.h"
11 
12 namespace v8 {
13 namespace base {
14 
15 // This is a v8::PageAllocator implementation that allocates pages within the
16 // pre-reserved region of virtual space. This class requires the virtual space
17 // to be kept reserved during the lifetime of this object.
18 // The main application of bounded page allocator are
19 // - V8 heap pointer compression which requires the whole V8 heap to be
20 // allocated within a contiguous range of virtual address space,
21 // - executable page allocation, which allows to use PC-relative 32-bit code
22 // displacement on certain 64-bit platforms.
23 // Bounded page allocator uses other page allocator instance for doing actual
24 // page allocations.
25 // The implementation is thread-safe.
26 class V8_BASE_EXPORT BoundedPageAllocator : public v8::PageAllocator {
27  public:
28  typedef uintptr_t Address;
29 
30  BoundedPageAllocator(v8::PageAllocator* page_allocator, Address start,
31  size_t size, size_t allocate_page_size);
32  ~BoundedPageAllocator() override = default;
33 
34  // These functions are not inlined to avoid https://crbug.com/v8/8275.
35  Address begin() const;
36  size_t size() const;
37 
38  // Returns true if given address is in the range controlled by the bounded
39  // page allocator instance.
40  bool contains(Address address) const {
41  return region_allocator_.contains(address);
42  }
43 
44  size_t AllocatePageSize() override { return allocate_page_size_; }
45 
46  size_t CommitPageSize() override { return commit_page_size_; }
47 
48  void SetRandomMmapSeed(int64_t seed) override {
49  page_allocator_->SetRandomMmapSeed(seed);
50  }
51 
52  void* GetRandomMmapAddr() override {
53  return page_allocator_->GetRandomMmapAddr();
54  }
55 
56  void* AllocatePages(void* hint, size_t size, size_t alignment,
57  Permission access) override;
58 
59  // Allocates pages at given address, returns true on success.
60  bool AllocatePagesAt(Address address, size_t size, Permission access);
61 
62  bool FreePages(void* address, size_t size) override;
63 
64  bool ReleasePages(void* address, size_t size, size_t new_size) override;
65 
66  bool SetPermissions(void* address, size_t size, Permission access) override;
67 
68  bool DiscardSystemPages(void* address, size_t size) override;
69 
70  private:
71  v8::base::Mutex mutex_;
72  const size_t allocate_page_size_;
73  const size_t commit_page_size_;
74  v8::PageAllocator* const page_allocator_;
75  v8::base::RegionAllocator region_allocator_;
76 
77  DISALLOW_COPY_AND_ASSIGN(BoundedPageAllocator);
78 };
79 
80 } // namespace base
81 } // namespace v8
82 
83 #endif // V8_BASE_BOUNDED_PAGE_ALLOCATOR_H_
Definition: libplatform.h:13
void SetRandomMmapSeed(int64_t seed) override