1 // Copyright 2018 The Chromium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifdef UNSAFE_BUFFERS_BUILD
6 // TODO(crbug.com/40284755): Remove this and spanify to fix the errors.
7 #pragma allow_unsafe_buffers
8 #endif
9
10 #include "base/memory/shared_memory_mapping.h"
11
12 #include <cstdint>
13 #include <utility>
14
15 #include "base/bits.h"
16 #include "base/logging.h"
17 #include "base/memory/shared_memory_security_policy.h"
18 #include "base/memory/shared_memory_tracker.h"
19 #include "base/system/sys_info.h"
20 #include "base/unguessable_token.h"
21 #include "build/build_config.h"
22
23 namespace base {
24
25 SharedMemoryMapping::SharedMemoryMapping() = default;
26
SharedMemoryMapping(SharedMemoryMapping && mapping)27 SharedMemoryMapping::SharedMemoryMapping(SharedMemoryMapping&& mapping) noexcept
28 : mapped_span_(std::exchange(mapping.mapped_span_, span<uint8_t>())),
29 size_(mapping.size_),
30 guid_(mapping.guid_),
31 mapper_(mapping.mapper_) {}
32
operator =(SharedMemoryMapping && mapping)33 SharedMemoryMapping& SharedMemoryMapping::operator=(
34 SharedMemoryMapping&& mapping) noexcept {
35 Unmap();
36 mapped_span_ = std::exchange(mapping.mapped_span_, span<uint8_t>());
37 size_ = mapping.size_;
38 guid_ = mapping.guid_;
39 mapper_ = mapping.mapper_;
40 return *this;
41 }
42
~SharedMemoryMapping()43 SharedMemoryMapping::~SharedMemoryMapping() {
44 Unmap();
45 }
46
SharedMemoryMapping(span<uint8_t> mapped_span,size_t size,const UnguessableToken & guid,SharedMemoryMapper * mapper)47 SharedMemoryMapping::SharedMemoryMapping(span<uint8_t> mapped_span,
48 size_t size,
49 const UnguessableToken& guid,
50 SharedMemoryMapper* mapper)
51 : mapped_span_(mapped_span), size_(size), guid_(guid), mapper_(mapper) {
52 CHECK_LE(size_, mapped_span_.size());
53 // Note: except on Windows, `mapped_span_.size() == size_`.
54 SharedMemoryTracker::GetInstance()->IncrementMemoryUsage(*this);
55 }
56
Unmap()57 void SharedMemoryMapping::Unmap() {
58 if (!IsValid())
59 return;
60
61 SharedMemorySecurityPolicy::ReleaseReservationForMapping(size_);
62 SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);
63
64 SharedMemoryMapper* mapper = mapper_;
65 if (!mapper)
66 mapper = SharedMemoryMapper::GetDefaultInstance();
67
68 // The backing mapper expects offset to be aligned to
69 // `SysInfo::VMAllocationGranularity()`, so replicate the alignment that was
70 // done when originally mapping in the region.
71 uint8_t* aligned_data =
72 bits::AlignDown(mapped_span_.data(), SysInfo::VMAllocationGranularity());
73 size_t adjusted_size =
74 mapped_span_.size() +
75 static_cast<size_t>(mapped_span_.data() - aligned_data);
76 mapper->Unmap(span(aligned_data, adjusted_size));
77 }
78
79 ReadOnlySharedMemoryMapping::ReadOnlySharedMemoryMapping() = default;
80 ReadOnlySharedMemoryMapping::ReadOnlySharedMemoryMapping(
81 ReadOnlySharedMemoryMapping&&) noexcept = default;
82 ReadOnlySharedMemoryMapping& ReadOnlySharedMemoryMapping::operator=(
83 ReadOnlySharedMemoryMapping&&) noexcept = default;
ReadOnlySharedMemoryMapping(span<uint8_t> mapped_span,size_t size,const UnguessableToken & guid,SharedMemoryMapper * mapper)84 ReadOnlySharedMemoryMapping::ReadOnlySharedMemoryMapping(
85 span<uint8_t> mapped_span,
86 size_t size,
87 const UnguessableToken& guid,
88 SharedMemoryMapper* mapper)
89 : SharedMemoryMapping(mapped_span, size, guid, mapper) {}
90
91 WritableSharedMemoryMapping::WritableSharedMemoryMapping() = default;
92 WritableSharedMemoryMapping::WritableSharedMemoryMapping(
93 WritableSharedMemoryMapping&&) noexcept = default;
94 WritableSharedMemoryMapping& WritableSharedMemoryMapping::operator=(
95 WritableSharedMemoryMapping&&) noexcept = default;
WritableSharedMemoryMapping(span<uint8_t> mapped_span,size_t size,const UnguessableToken & guid,SharedMemoryMapper * mapper)96 WritableSharedMemoryMapping::WritableSharedMemoryMapping(
97 span<uint8_t> mapped_span,
98 size_t size,
99 const UnguessableToken& guid,
100 SharedMemoryMapper* mapper)
101 : SharedMemoryMapping(mapped_span, size, guid, mapper) {}
102
103 } // namespace base
104