1 /*
2  * Copyright (C) 2015 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 
18 #include <errno.h>
19 #include <fcntl.h>
20 #include <linux/fs.h>
21 #include <sys/ioctl.h>
22 #include <sys/stat.h>
23 #include <sys/types.h>
24 #include <unistd.h>
25 
26 #include <arpa/inet.h>
27 #include <stdio.h>
28 #include <stdlib.h>
29 #include <string.h>
30 
31 #include <cutils/properties.h>
32 #include <fs_mgr.h>
33 
34 #include "bootinfo.h"
35 
36 using android::fs_mgr::Fstab;
37 using android::fs_mgr::GetEntryForMountPoint;
38 using android::fs_mgr::ReadDefaultFstab;
39 using android::fs_mgr::ReadFstabFromFile;
40 
41 // Open the appropriate fstab file and fallback to /fstab.device if
42 // that's what's being used.
43 static bool open_fstab(Fstab* fstab)
44 {
45   return ReadDefaultFstab(fstab) || ReadFstabFromFile("/fstab.device", fstab);
46 }
47 
48 int boot_info_open_partition(const char *name, uint64_t *out_size, int flags)
49 {
50   char *path;
51   int fd;
52 
53   // We can't use fs_mgr to look up |name| because fstab doesn't list
54   // every slot partition (it uses the slotselect option to mask the
55   // suffix) and |slot| is expected to be of that form, e.g. boot_a.
56   //
57   // We can however assume that there's an entry for the /misc mount
58   // point and use that to get the device file for the misc
59   // partition. From there we'll assume that a by-name scheme is used
60   // so we can just replace the trailing "misc" by the given |name|,
61   // e.g.
62   //
63   //   /dev/block/platform/soc.0/7824900.sdhci/by-name/misc ->
64   //   /dev/block/platform/soc.0/7824900.sdhci/by-name/boot_a
65   //
66   // If needed, it's possible to relax this assumption in the future
67   // by trawling /sys/block looking for the appropriate sibling of
68   // misc and then finding an entry in /dev matching the sysfs entry.
69 
70   Fstab fstab;
71   if (!open_fstab(&fstab)) {
72     return -1;
73   }
74   auto record = GetEntryForMountPoint(&fstab, "/misc");
75   if (record == nullptr) {
76     return -1;
77   }
78   if (strcmp(name, "misc") == 0) {
79     path = strdup(record->blk_device.c_str());
80   } else {
81     size_t trimmed_len, name_len;
82     const char *end_slash = strrchr(record->blk_device.c_str(), '/');
83     if (end_slash == NULL) {
84       return -1;
85     }
86     trimmed_len = end_slash - record->blk_device.c_str() + 1;
87     name_len = strlen(name);
88     path = static_cast<char *>(calloc(trimmed_len + name_len + 1, 1));
89     strncpy(path, record->blk_device.c_str(), trimmed_len);
90     strncpy(path + trimmed_len, name, name_len);
91   }
92 
93   fd = open(path, flags);
94   free(path);
95 
96   // If we successfully opened the device, get size if requested.
97   if (fd != -1 && out_size != NULL) {
98     if (ioctl(fd, BLKGETSIZE64, out_size) != 0) {
99       close(fd);
100       return -1;
101     }
102   }
103 
104   return fd;
105 }
106 
107 // As per struct bootloader_message_ab which is defined in
108 // boot/1.1/default.
109 // struct bootloader_message_ab {
110 //     struct bootloader_message message;
111 //     char slot_suffix[32];
112 //     char update_channel[128];
113 //
114 //     // Round up the entire struct to 4096-byte.
115 //     char reserved[1888];
116 // };
117 //
118 // We can use the 32 bytes in the bootctrl_suffix field provided that they
119 // start with the active slot suffix terminated by NUL. It just so happens
120 // that BrilloBootInfo is laid out this way.
121 #define BOOTINFO_OFFSET 2048
122 
123 bool boot_info_load(BrilloBootInfo *out_info)
124 {
125   int fd;
126 
127   memset(out_info, '\0', sizeof(BrilloBootInfo));
128 
129   fd = boot_info_open_partition("misc", NULL, O_RDONLY);
130   if (fd == -1)
131     return false;
132   if (lseek(fd, BOOTINFO_OFFSET, SEEK_SET) != BOOTINFO_OFFSET) {
133     close(fd);
134     return false;
135   }
136   ssize_t num_read;
137   do {
138     num_read = read(fd, (void*) out_info, sizeof(BrilloBootInfo));
139   } while (num_read == -1 && errno == EINTR);
140   close(fd);
141   if (num_read != sizeof(BrilloBootInfo))
142     return false;
143   return true;
144 }
145 
146 bool boot_info_save(BrilloBootInfo *info)
147 {
148   int fd;
149 
150   fd = boot_info_open_partition("misc", NULL, O_RDWR);
151   if (fd == -1)
152     return false;
153   if (lseek(fd, BOOTINFO_OFFSET, SEEK_SET) != BOOTINFO_OFFSET) {
154     close(fd);
155     return false;
156   }
157   ssize_t num_written;
158   do {
159     num_written = write(fd, (void*) info, sizeof(BrilloBootInfo));
160   } while (num_written == -1 && errno == EINTR);
161   close(fd);
162   if (num_written != sizeof(BrilloBootInfo))
163     return false;
164   return true;
165 }
166 
167 bool boot_info_validate(BrilloBootInfo* info)
168 {
169   if (info->magic[0] != 'B' ||
170       info->magic[1] != 'C' ||
171       info->magic[2] != 'c')
172     return false;
173   if (info->active_slot >= 2)
174     return false;
175   return true;
176 }
177 
178 void boot_info_reset(BrilloBootInfo* info)
179 {
180   memset(info, '\0', sizeof(BrilloBootInfo));
181   info->magic[0] = 'B';
182   info->magic[1] = 'C';
183   info->magic[2] = 'c';
184 }
185