remount_service.c revision 4f6e8d7a00cbeda1e70cc15be9c4af1018bdad53 
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
31static int system_ro = 1;
32
33/* Returns the mount number of the requested partition from /proc/mtd */
34static int find_mount(const char *findme)
35{
36    int fd;
37    int res;
38    int size;
39    char *token = NULL;
40    const char delims[] = "\n";
41    char buf[1024];
42
43    fd = unix_open("/proc/mtd", O_RDONLY);
44    if (fd < 0)
45        return -errno;
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 mtdname[16];
55        int mtdnum, mtdsize, mtderasesize;
56
57        res = sscanf(token, "mtd%d: %x %x %15s",
58                     &mtdnum, &mtdsize, &mtderasesize, mtdname);
59
60        if (res == 4 && !strcmp(mtdname, findme))
61            return mtdnum;
62
63        token = strtok(NULL, delims);
64    }
65    return -1;
66}
67
68/* Init mounts /system as read only, remount to enable writes. */
69static int remount_system()
70{
71    int num;
72    char source[64];
73    if (system_ro == 0) {
74        return 0;
75    }
76    if ((num = find_mount("\"system\"")) < 0)
77        return -1;
78
79    snprintf(source, sizeof source, "/dev/block/mtdblock%d", num);
80    system_ro = mount(source, "/system", "yaffs2", MS_REMOUNT, NULL);
81    return system_ro;
82}
83
84static void write_string(int fd, const char* str)
85{
86    writex(fd, str, strlen(str));
87}
88
89void remount_service(int fd, void *cookie)
90{
91    int ret = remount_system();
92
93    if (!ret)
94       write_string(fd, "remount succeeded\n");
95    else {
96        char    buffer[200];
97        snprintf(buffer, sizeof(buffer), "remount failed: %s\n", strerror(errno));
98        write_string(fd, buffer);
99    }
100
101    adb_close(fd);
102}
103
104