1 /*
2 * Copyright (C) 2018 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <errno.h>
18 #include <sys/mman.h>
19 #include <limits>
20
21 #include <cutils/ashmem.h>
22 #include <log/log.h>
23 #include <ui/BufferHubMetadata.h>
24
25 namespace android {
26
27 namespace {
28
29 static const int kAshmemProt = PROT_READ | PROT_WRITE;
30
31 } // namespace
32
33 using BufferHubDefs::kMetadataHeaderSize;
34 using BufferHubDefs::MetadataHeader;
35
36 /* static */
create(size_t userMetadataSize)37 BufferHubMetadata BufferHubMetadata::create(size_t userMetadataSize) {
38 // The size the of metadata buffer is used as the "width" parameter during allocation. Thus it
39 // cannot overflow uint32_t.
40 if (userMetadataSize >= (std::numeric_limits<uint32_t>::max() - kMetadataHeaderSize)) {
41 ALOGE("BufferHubMetadata::Create: metadata size too big: %zu.", userMetadataSize);
42 return {};
43 }
44
45 const size_t metadataSize = userMetadataSize + kMetadataHeaderSize;
46 int fd = ashmem_create_region(/*name=*/"BufferHubMetadata", metadataSize);
47 if (fd < 0) {
48 ALOGE("BufferHubMetadata::Create: failed to create ashmem region.");
49 return {};
50 }
51
52 // Hand over the ownership of the fd to a unique_fd immediately after the successful
53 // return of ashmem_create_region. The ashmemFd is going to own the fd and to prevent fd
54 // leaks during error handling.
55 unique_fd ashmemFd{fd};
56
57 if (ashmem_set_prot_region(ashmemFd.get(), kAshmemProt) != 0) {
58 ALOGE("BufferHubMetadata::Create: failed to set protect region.");
59 return {};
60 }
61
62 return BufferHubMetadata::import(std::move(ashmemFd));
63 }
64
65 /* static */
import(unique_fd ashmemFd)66 BufferHubMetadata BufferHubMetadata::import(unique_fd ashmemFd) {
67 if (!ashmem_valid(ashmemFd.get())) {
68 ALOGE("BufferHubMetadata::Import: invalid ashmem fd.");
69 return {};
70 }
71
72 size_t metadataSize = static_cast<size_t>(ashmem_get_size_region(ashmemFd.get()));
73 size_t userMetadataSize = metadataSize - kMetadataHeaderSize;
74
75 // Note that here the buffer state is mapped from shared memory as an atomic object. The
76 // std::atomic's constructor will not be called so that the original value stored in the memory
77 // region can be preserved.
78 auto metadataHeader = static_cast<MetadataHeader*>(mmap(nullptr, metadataSize, kAshmemProt,
79 MAP_SHARED, ashmemFd.get(),
80 /*offset=*/0));
81 if (metadataHeader == nullptr) {
82 ALOGE("BufferHubMetadata::Import: failed to map region.");
83 return {};
84 }
85
86 return BufferHubMetadata(userMetadataSize, std::move(ashmemFd), metadataHeader);
87 }
88
BufferHubMetadata(size_t userMetadataSize,unique_fd ashmemFd,MetadataHeader * metadataHeader)89 BufferHubMetadata::BufferHubMetadata(size_t userMetadataSize, unique_fd ashmemFd,
90 MetadataHeader* metadataHeader)
91 : mUserMetadataSize(userMetadataSize),
92 mAshmemFd(std::move(ashmemFd)),
93 mMetadataHeader(metadataHeader) {}
94
~BufferHubMetadata()95 BufferHubMetadata::~BufferHubMetadata() {
96 if (mMetadataHeader != nullptr) {
97 int ret = munmap(mMetadataHeader, metadataSize());
98 ALOGE_IF(ret != 0,
99 "BufferHubMetadata::~BufferHubMetadata: failed to unmap ashmem, error=%d.", errno);
100 mMetadataHeader = nullptr;
101 }
102 }
103
104 } // namespace android
105