1 // Copyright (C) 2019 The Android Open Source Project
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 //      http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 
15 #pragma once
16 
17 #include <functional>
18 #include <iostream>
19 #include <string>
20 
21 #include <android-base/macros.h>
22 #include <fstab/fstab.h>
23 #include <libdm/dm.h>
24 #include <libfiemap/image_manager.h>
25 #include <liblp/builder.h>
26 #include <libsnapshot/snapshot.h>
27 #include <update_engine/update_metadata.pb.h>
28 
29 #include <libsnapshot/auto_device.h>
30 #include <libsnapshot/snapshot.h>
31 
32 namespace android {
33 namespace snapshot {
34 
35 // Unit is sectors, this is a 4K chunk.
36 static constexpr uint32_t kSnapshotChunkSize = 8;
37 
38 // A list of devices we created along the way.
39 // - Whenever a device is created that is subject to GC'ed at the end of
40 //   this function, add it to this list.
41 // - If any error has occurred, the list is destroyed, and all these devices
42 //   are cleaned up.
43 // - Upon success, Release() should be called so that the created devices
44 //   are kept.
45 struct AutoDeviceList {
46     ~AutoDeviceList();
47     template <typename T, typename... Args>
EmplaceBackAutoDeviceList48     void EmplaceBack(Args&&... args) {
49         devices_.emplace_back(std::make_unique<T>(std::forward<Args>(args)...));
50     }
51     void Release();
52 
53   private:
54     std::vector<std::unique_ptr<AutoDevice>> devices_;
55 };
56 
57 // Automatically unmap a device upon deletion.
58 struct AutoUnmapDevice : AutoDevice {
59     // On destruct, delete |name| from device mapper.
AutoUnmapDeviceAutoUnmapDevice60     AutoUnmapDevice(android::dm::DeviceMapper* dm, const std::string& name)
61         : AutoDevice(name), dm_(dm) {}
62     AutoUnmapDevice(AutoUnmapDevice&& other) = default;
63     ~AutoUnmapDevice();
64 
65   private:
66     DISALLOW_COPY_AND_ASSIGN(AutoUnmapDevice);
67     android::dm::DeviceMapper* dm_ = nullptr;
68 };
69 
70 // Automatically unmap an image upon deletion.
71 struct AutoUnmapImage : AutoDevice {
72     // On destruct, delete |name| from image manager.
AutoUnmapImageAutoUnmapImage73     AutoUnmapImage(android::fiemap::IImageManager* images, const std::string& name)
74         : AutoDevice(name), images_(images) {}
75     AutoUnmapImage(AutoUnmapImage&& other) = default;
76     ~AutoUnmapImage();
77 
78   private:
79     DISALLOW_COPY_AND_ASSIGN(AutoUnmapImage);
80     android::fiemap::IImageManager* images_ = nullptr;
81 };
82 
83 // Automatically deletes a snapshot. |name| should be the name of the partition, e.g. "system_a".
84 // Client is responsible for maintaining the lifetime of |manager| and |lock|.
85 struct AutoDeleteSnapshot : AutoDevice {
AutoDeleteSnapshotAutoDeleteSnapshot86     AutoDeleteSnapshot(SnapshotManager* manager, SnapshotManager::LockedFile* lock,
87                        const std::string& name)
88         : AutoDevice(name), manager_(manager), lock_(lock) {}
89     AutoDeleteSnapshot(AutoDeleteSnapshot&& other);
90     ~AutoDeleteSnapshot();
91 
92   private:
93     DISALLOW_COPY_AND_ASSIGN(AutoDeleteSnapshot);
94     SnapshotManager* manager_ = nullptr;
95     SnapshotManager::LockedFile* lock_ = nullptr;
96 };
97 
98 struct AutoUnmountDevice : AutoDevice {
99     // Empty object that does nothing.
AutoUnmountDeviceAutoUnmountDevice100     AutoUnmountDevice() : AutoDevice("") {}
101     static std::unique_ptr<AutoUnmountDevice> New(const std::string& path);
102     ~AutoUnmountDevice();
103 
104   private:
AutoUnmountDeviceAutoUnmountDevice105     AutoUnmountDevice(const std::string& path, android::fs_mgr::Fstab&& fstab)
106         : AutoDevice(path), fstab_(std::move(fstab)) {}
107     android::fs_mgr::Fstab fstab_;
108 };
109 
110 // Return a list of partitions in |builder| with the name ending in |suffix|.
111 std::vector<android::fs_mgr::Partition*> ListPartitionsWithSuffix(
112         android::fs_mgr::MetadataBuilder* builder, const std::string& suffix);
113 
114 // Initialize a device before using it as the COW device for a dm-snapshot device.
115 Return InitializeCow(const std::string& device);
116 
117 // "Atomically" write string to file. This is done by a series of actions:
118 // 1. Write to path + ".tmp"
119 // 2. Move temporary file to path using rename()
120 // Note that rename() is an atomic operation. This function may not work properly if there
121 // is an open fd to |path|, because that fd has an old view of the file.
122 bool WriteStringToFileAtomic(const std::string& content, const std::string& path);
123 
124 // Writes current time to a given stream.
125 struct Now {};
126 std::ostream& operator<<(std::ostream& os, const Now&);
127 
128 // Append to |extents|. Merged into the last element if possible.
129 void AppendExtent(google::protobuf::RepeatedPtrField<chromeos_update_engine::Extent>* extents,
130                   uint64_t start_block, uint64_t num_blocks);
131 
132 }  // namespace snapshot
133 }  // namespace android
134