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 "update_engine/payload_consumer/mount_history.h"
18 
19 #include <inttypes.h>
20 
21 #include <string>
22 #include <vector>
23 
24 #include <base/logging.h>
25 #include <base/time/time.h>
26 
27 #include "update_engine/common/utils.h"
28 
29 namespace chromeos_update_engine {
30 void LogMountHistory(const FileDescriptorPtr blockdevice_fd) {
31   static constexpr ssize_t kBlockSize = 4096;
32 
33   if (blockdevice_fd == nullptr) {
34     return;
35   }
36 
37   brillo::Blob block0_buffer(kBlockSize);
38   ssize_t bytes_read;
39 
40   if (!utils::ReadAll(
41           blockdevice_fd, block0_buffer.data(), kBlockSize, 0, &bytes_read)) {
42     LOG(WARNING) << "PReadAll failed";
43     return;
44   }
45 
46   if (bytes_read != kBlockSize) {
47     LOG(WARNING) << "Could not read an entire block";
48     return;
49   }
50 
51   // https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout
52   // Super block starts from block 0, offset 0x400
53   //   0x2C: len32 Mount time
54   //   0x30: len32 Write time
55   //   0x34: len16 Number of mounts since the last fsck
56   //   0x38: len16 Magic signature 0xEF53
57   //   0x40: len32 Time of last check
58   //   0x108: len32 When the filesystem was created
59 
60   time_t mount_time =
61       *reinterpret_cast<uint32_t*>(&block0_buffer[0x400 + 0x2C]);
62   time_t write_time =
63       *reinterpret_cast<uint32_t*>(&block0_buffer[0x400 + 0x30]);
64   uint16_t mount_count =
65       *reinterpret_cast<uint16_t*>(&block0_buffer[0x400 + 0x34]);
66   uint16_t magic = *reinterpret_cast<uint16_t*>(&block0_buffer[0x400 + 0x38]);
67   time_t check_time =
68       *reinterpret_cast<uint32_t*>(&block0_buffer[0x400 + 0x40]);
69   time_t created_time =
70       *reinterpret_cast<uint32_t*>(&block0_buffer[0x400 + 0x108]);
71 
72   if (magic == 0xEF53) {
73     // Timestamps can be updated by fsck without updating mount count,
74     // log if any timestamp differ
75     if (! (write_time == created_time && check_time == created_time)) {
76       LOG(WARNING) << "Device have been modified after being created. "
77                    << "Filesystem created on "
78                    << base::Time::FromTimeT(created_time) << ", "
79                    << "last written on "
80                    << base::Time::FromTimeT(write_time) << ", "
81                    << "last checked on "
82                    << base::Time::FromTimeT(check_time) << ".";
83     }
84     if (mount_count > 0) {
85       LOG(WARNING) << "Device was remounted R/W " << mount_count << " times. "
86                    << "Last remount happened on "
87                    << base::Time::FromTimeT(mount_time) << ".";
88     }
89   }
90 }
91 }  // namespace chromeos_update_engine
92