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      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 <stdlib.h>
     18 #include <stdio.h>
     19 #include <unistd.h>
     20 #include <string.h>
     21 #include <fcntl.h>
     22 #include <sys/mount.h>
     23 #include <errno.h>
     24 
     25 #include "sysdeps.h"
     26 
     27 #define  TRACE_TAG  TRACE_ADB
     28 #include "adb.h"
     29 
     30 
     31 static int system_ro = 1;
     32 
     33 /* Returns the device used to mount a directory in /proc/mounts */
     34 static char *find_mount(const char *dir)
     35 {
     36     int fd;
     37     int res;
     38     int size;
     39     char *token = NULL;
     40     const char delims[] = "\n";
     41     char buf[4096];
     42 
     43     fd = unix_open("/proc/mounts", O_RDONLY);
     44     if (fd < 0)
     45         return NULL;
     46 
     47     buf[sizeof(buf) - 1] = '\0';
     48     size = adb_read(fd, buf, sizeof(buf) - 1);
     49     adb_close(fd);
     50 
     51     token = strtok(buf, delims);
     52 
     53     while (token) {
     54         char mount_dev[256];
     55         char mount_dir[256];
     56         int mount_freq;
     57         int mount_passno;
     58 
     59         res = sscanf(token, "%255s %255s %*s %*s %d %d\n",
     60                      mount_dev, mount_dir, &mount_freq, &mount_passno);
     61         mount_dev[255] = 0;
     62         mount_dir[255] = 0;
     63         if (res == 4 && (strcmp(dir, mount_dir) == 0))
     64             return strdup(mount_dev);
     65 
     66         token = strtok(NULL, delims);
     67     }
     68     return NULL;
     69 }
     70 
     71 /* Init mounts /system as read only, remount to enable writes. */
     72 static int remount_system()
     73 {
     74     char *dev;
     75     int fd;
     76     int OFF = 0;
     77 
     78     if (system_ro == 0) {
     79         return 0;
     80     }
     81 
     82     dev = find_mount("/system");
     83 
     84     if (!dev)
     85         return -1;
     86 
     87     fd = unix_open(dev, O_RDONLY);
     88     if (fd < 0)
     89         return -1;
     90 
     91     ioctl(fd, BLKROSET, &OFF);
     92     adb_close(fd);
     93 
     94     system_ro = mount(dev, "/system", "none", MS_REMOUNT, NULL);
     95 
     96     free(dev);
     97 
     98     return system_ro;
     99 }
    100 
    101 static void write_string(int fd, const char* str)
    102 {
    103     writex(fd, str, strlen(str));
    104 }
    105 
    106 void remount_service(int fd, void *cookie)
    107 {
    108     int ret = remount_system();
    109 
    110     if (!ret)
    111        write_string(fd, "remount succeeded\n");
    112     else {
    113         char    buffer[200];
    114         snprintf(buffer, sizeof(buffer), "remount failed: %s\n", strerror(errno));
    115         write_string(fd, buffer);
    116     }
    117 
    118     adb_close(fd);
    119 }
    120 
    121