1 /*
2 * Copyright (C) 2008 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 "sysdeps.h"
18
19 #include <errno.h>
20 #include <fcntl.h>
21 #include <stdio.h>
22 #include <stdlib.h>
23 #include <string.h>
24 #include <sys/mount.h>
25 #include <unistd.h>
26
27 #include "cutils/properties.h"
28
29 #define TRACE_TAG TRACE_ADB
30 #include "adb.h"
31
32
33 static int system_ro = 1;
34 static int vendor_ro = 1;
35
36 /* Returns the device used to mount a directory in /proc/mounts */
find_mount(const char * dir)37 static char *find_mount(const char *dir)
38 {
39 int fd;
40 int res;
41 char *token = NULL;
42 const char delims[] = "\n";
43 char buf[4096];
44
45 fd = unix_open("/proc/mounts", O_RDONLY | O_CLOEXEC);
46 if (fd < 0)
47 return NULL;
48
49 buf[sizeof(buf) - 1] = '\0';
50 adb_read(fd, buf, sizeof(buf) - 1);
51 adb_close(fd);
52
53 token = strtok(buf, delims);
54
55 while (token) {
56 char mount_dev[256];
57 char mount_dir[256];
58 int mount_freq;
59 int mount_passno;
60
61 res = sscanf(token, "%255s %255s %*s %*s %d %d\n",
62 mount_dev, mount_dir, &mount_freq, &mount_passno);
63 mount_dev[255] = 0;
64 mount_dir[255] = 0;
65 if (res == 4 && (strcmp(dir, mount_dir) == 0))
66 return strdup(mount_dev);
67
68 token = strtok(NULL, delims);
69 }
70 return NULL;
71 }
72
hasVendorPartition()73 static int hasVendorPartition()
74 {
75 struct stat info;
76 if (!lstat("/vendor", &info))
77 if ((info.st_mode & S_IFMT) == S_IFDIR)
78 return true;
79 return false;
80 }
81
82 /* Init mounts /system as read only, remount to enable writes. */
remount(const char * dir,int * dir_ro)83 static int remount(const char* dir, int* dir_ro)
84 {
85 char *dev;
86 int fd;
87 int OFF = 0;
88
89 if (dir_ro == 0) {
90 return 0;
91 }
92
93 dev = find_mount(dir);
94
95 if (!dev)
96 return -1;
97
98 fd = unix_open(dev, O_RDONLY | O_CLOEXEC);
99 if (fd < 0)
100 return -1;
101
102 ioctl(fd, BLKROSET, &OFF);
103 adb_close(fd);
104
105 *dir_ro = mount(dev, dir, "none", MS_REMOUNT, NULL);
106
107 free(dev);
108
109 return *dir_ro;
110 }
111
write_string(int fd,const char * str)112 static void write_string(int fd, const char* str)
113 {
114 writex(fd, str, strlen(str));
115 }
116
remount_service(int fd,void * cookie)117 void remount_service(int fd, void *cookie)
118 {
119 char buffer[200];
120 char prop_buf[PROPERTY_VALUE_MAX];
121
122 bool system_verified = false, vendor_verified = false;
123 property_get("partition.system.verified", prop_buf, "0");
124 if (!strcmp(prop_buf, "1")) {
125 system_verified = true;
126 }
127
128 property_get("partition.vendor.verified", prop_buf, "0");
129 if (!strcmp(prop_buf, "1")) {
130 vendor_verified = true;
131 }
132
133 if (system_verified || vendor_verified) {
134 // Allow remount but warn of likely bad effects
135 bool both = system_verified && vendor_verified;
136 snprintf(buffer, sizeof(buffer),
137 "dm_verity is enabled on the %s%s%s partition%s.\n",
138 system_verified ? "system" : "",
139 both ? " and " : "",
140 vendor_verified ? "vendor" : "",
141 both ? "s" : "");
142 write_string(fd, buffer);
143 snprintf(buffer, sizeof(buffer),
144 "Use \"adb disable-verity\" to disable verity.\n"
145 "If you do not, remount may succeed, however, you will still "
146 "not be able to write to these volumes.\n");
147 write_string(fd, buffer);
148 }
149
150 if (remount("/system", &system_ro)) {
151 snprintf(buffer, sizeof(buffer), "remount of system failed: %s\n",strerror(errno));
152 write_string(fd, buffer);
153 }
154
155 if (hasVendorPartition()) {
156 if (remount("/vendor", &vendor_ro)) {
157 snprintf(buffer, sizeof(buffer), "remount of vendor failed: %s\n",strerror(errno));
158 write_string(fd, buffer);
159 }
160 }
161
162 if (!system_ro && (!vendor_ro || !hasVendorPartition()))
163 write_string(fd, "remount succeeded\n");
164 else {
165 write_string(fd, "remount failed\n");
166 }
167
168 adb_close(fd);
169 }
170
171