shared_memory_mapping.cc 3.5 KB

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798
  1. // Copyright 2018 The Chromium 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. #include "base/memory/shared_memory_mapping.h"
  5. #include <cstdint>
  6. #include <utility>
  7. #include "base/bits.h"
  8. #include "base/logging.h"
  9. #include "base/memory/shared_memory_security_policy.h"
  10. #include "base/memory/shared_memory_tracker.h"
  11. #include "base/system/sys_info.h"
  12. #include "base/unguessable_token.h"
  13. #include "build/build_config.h"
  14. namespace base {
  15. SharedMemoryMapping::SharedMemoryMapping() = default;
  16. SharedMemoryMapping::SharedMemoryMapping(SharedMemoryMapping&& mapping) noexcept
  17. : mapped_span_(std::exchange(mapping.mapped_span_, span<uint8_t>())),
  18. size_(mapping.size_),
  19. guid_(mapping.guid_),
  20. mapper_(mapping.mapper_) {}
  21. SharedMemoryMapping& SharedMemoryMapping::operator=(
  22. SharedMemoryMapping&& mapping) noexcept {
  23. Unmap();
  24. mapped_span_ = std::exchange(mapping.mapped_span_, span<uint8_t>());
  25. size_ = mapping.size_;
  26. guid_ = mapping.guid_;
  27. mapper_ = mapping.mapper_;
  28. return *this;
  29. }
  30. SharedMemoryMapping::~SharedMemoryMapping() {
  31. Unmap();
  32. }
  33. SharedMemoryMapping::SharedMemoryMapping(span<uint8_t> mapped_span,
  34. size_t size,
  35. const UnguessableToken& guid,
  36. SharedMemoryMapper* mapper)
  37. : mapped_span_(mapped_span), size_(size), guid_(guid), mapper_(mapper) {
  38. // Note: except on Windows, `mapped_span_.size() == size_`.
  39. SharedMemoryTracker::GetInstance()->IncrementMemoryUsage(*this);
  40. }
  41. void SharedMemoryMapping::Unmap() {
  42. if (!IsValid())
  43. return;
  44. SharedMemorySecurityPolicy::ReleaseReservationForMapping(size_);
  45. SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);
  46. SharedMemoryMapper* mapper = mapper_;
  47. if (!mapper)
  48. mapper = SharedMemoryMapper::GetDefaultInstance();
  49. // The backing mapper expects offset to be aligned to
  50. // `SysInfo::VMAllocationGranularity()`, so replicate the alignment that was
  51. // done when originally mapping in the region.
  52. uint8_t* aligned_data =
  53. bits::AlignDown(mapped_span_.data(), SysInfo::VMAllocationGranularity());
  54. size_t adjusted_size =
  55. mapped_span_.size() +
  56. static_cast<size_t>(mapped_span_.data() - aligned_data);
  57. span<uint8_t> span_to_unmap = make_span(aligned_data, adjusted_size);
  58. mapper->Unmap(span_to_unmap);
  59. }
  60. ReadOnlySharedMemoryMapping::ReadOnlySharedMemoryMapping() = default;
  61. ReadOnlySharedMemoryMapping::ReadOnlySharedMemoryMapping(
  62. ReadOnlySharedMemoryMapping&&) noexcept = default;
  63. ReadOnlySharedMemoryMapping& ReadOnlySharedMemoryMapping::operator=(
  64. ReadOnlySharedMemoryMapping&&) noexcept = default;
  65. ReadOnlySharedMemoryMapping::ReadOnlySharedMemoryMapping(
  66. span<uint8_t> mapped_span,
  67. size_t size,
  68. const UnguessableToken& guid,
  69. SharedMemoryMapper* mapper)
  70. : SharedMemoryMapping(mapped_span, size, guid, mapper) {}
  71. WritableSharedMemoryMapping::WritableSharedMemoryMapping() = default;
  72. WritableSharedMemoryMapping::WritableSharedMemoryMapping(
  73. WritableSharedMemoryMapping&&) noexcept = default;
  74. WritableSharedMemoryMapping& WritableSharedMemoryMapping::operator=(
  75. WritableSharedMemoryMapping&&) noexcept = default;
  76. WritableSharedMemoryMapping::WritableSharedMemoryMapping(
  77. span<uint8_t> mapped_span,
  78. size_t size,
  79. const UnguessableToken& guid,
  80. SharedMemoryMapper* mapper)
  81. : SharedMemoryMapping(mapped_span, size, guid, mapper) {}
  82. } // namespace base