Home | History | Annotate | Download | only in adb 
      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 #define TRACE_TAG ADB
     18 
     19 #include "sysdeps.h"
     20 
     21 #include <errno.h>
     22 #include <fcntl.h>
     23 #include <mntent.h>
     24 #include <stdio.h>
     25 #include <stdlib.h>
     26 #include <string.h>
     27 #include <sys/mount.h>
     28 #include <unistd.h>
     29 
     30 #include <string>
     31 
     32 #include "adb.h"
     33 #include "adb_io.h"
     34 #include "adb_utils.h"
     35 #include "cutils/properties.h"
     36 #include "fs_mgr.h"
     37 
     38 // Returns the device used to mount a directory in /proc/mounts.
     39 static std::string find_proc_mount(const char* dir) {
     40     std::unique_ptr<FILE, int(*)(FILE*)> fp(setmntent("/proc/mounts", "r"), endmntent);
     41     if (!fp) {
     42         return "";
     43     }
     44 
     45     mntent* e;
     46     while ((e = getmntent(fp.get())) != nullptr) {
     47         if (strcmp(dir, e->mnt_dir) == 0) {
     48             return e->mnt_fsname;
     49         }
     50     }
     51     return "";
     52 }
     53 
     54 // Returns the device used to mount a directory in the fstab.
     55 static std::string find_fstab_mount(const char* dir) {
     56     char propbuf[PROPERTY_VALUE_MAX];
     57 
     58     property_get("ro.hardware", propbuf, "");
     59     std::string fstab_filename = std::string("/fstab.") + propbuf;
     60     struct fstab* fstab = fs_mgr_read_fstab(fstab_filename.c_str());
     61     struct fstab_rec* rec = fs_mgr_get_entry_for_mount_point(fstab, dir);
     62     std::string dev = rec ? std::string(rec->blk_device) : "";
     63     fs_mgr_free_fstab(fstab);
     64     return dev;
     65 }
     66 
     67 // The proc entry for / is full of lies, so check fstab instead.
     68 // /proc/mounts lists rootfs and /dev/root, neither of which is what we want.
     69 static std::string find_mount(const char* dir) {
     70     if (strcmp(dir, "/") == 0) {
     71        return find_fstab_mount(dir);
     72     } else {
     73        return find_proc_mount(dir);
     74     }
     75 }
     76 
     77 bool make_block_device_writable(const std::string& dev) {
     78     int fd = unix_open(dev.c_str(), O_RDONLY | O_CLOEXEC);
     79     if (fd == -1) {
     80         return false;
     81     }
     82 
     83     int OFF = 0;
     84     bool result = (ioctl(fd, BLKROSET, &OFF) != -1);
     85     unix_close(fd);
     86     return result;
     87 }
     88 
     89 static bool remount_partition(int fd, const char* dir) {
     90     if (!directory_exists(dir)) {
     91         return true;
     92     }
     93     std::string dev = find_mount(dir);
     94     if (dev.empty()) {
     95         return true;
     96     }
     97     if (!make_block_device_writable(dev)) {
     98         WriteFdFmt(fd, "remount of %s failed; couldn't make block device %s writable: %s\n",
     99                    dir, dev.c_str(), strerror(errno));
    100         return false;
    101     }
    102     if (mount(dev.c_str(), dir, "none", MS_REMOUNT, nullptr) == -1) {
    103         WriteFdFmt(fd, "remount of %s failed: %s\n", dir, strerror(errno));
    104         return false;
    105     }
    106     return true;
    107 }
    108 
    109 void remount_service(int fd, void* cookie) {
    110     if (getuid() != 0) {
    111         WriteFdExactly(fd, "Not running as root. Try \"adb root\" first.\n");
    112         adb_close(fd);
    113         return;
    114     }
    115 
    116     char prop_buf[PROPERTY_VALUE_MAX];
    117     property_get("partition.system.verified", prop_buf, "");
    118     bool system_verified = (strlen(prop_buf) > 0);
    119 
    120     property_get("partition.vendor.verified", prop_buf, "");
    121     bool vendor_verified = (strlen(prop_buf) > 0);
    122 
    123     if (system_verified || vendor_verified) {
    124         // Allow remount but warn of likely bad effects
    125         bool both = system_verified && vendor_verified;
    126         WriteFdFmt(fd,
    127                    "dm_verity is enabled on the %s%s%s partition%s.\n",
    128                    system_verified ? "system" : "",
    129                    both ? " and " : "",
    130                    vendor_verified ? "vendor" : "",
    131                    both ? "s" : "");
    132         WriteFdExactly(fd,
    133                        "Use \"adb disable-verity\" to disable verity.\n"
    134                        "If you do not, remount may succeed, however, you will still "
    135                        "not be able to write to these volumes.\n");
    136     }
    137 
    138     bool success = true;
    139     property_get("ro.build.system_root_image", prop_buf, "");
    140     bool system_root = !strcmp(prop_buf, "true");
    141     if (system_root) {
    142         success &= remount_partition(fd, "/");
    143     } else {
    144         success &= remount_partition(fd, "/system");
    145     }
    146     success &= remount_partition(fd, "/vendor");
    147     success &= remount_partition(fd, "/oem");
    148 
    149     WriteFdExactly(fd, success ? "remount succeeded\n" : "remount failed\n");
    150 
    151     adb_close(fd);
    152 }
    153