Fat.cpp revision bf04185c88161f13118b9975cdff7967d49a4fa0 
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 <stdio.h>
18#include <fcntl.h>
19#include <unistd.h>
20#include <errno.h>
21#include <string.h>
22#include <dirent.h>
23#include <errno.h>
24#include <fcntl.h>
25
26#include <sys/types.h>
27#include <sys/stat.h>
28#include <sys/types.h>
29#include <sys/mman.h>
30#include <sys/mount.h>
31
32#include <linux/kdev_t.h>
33
34#define LOG_TAG "Vold"
35
36#include <cutils/log.h>
37#include <cutils/properties.h>
38
39#include "Fat.h"
40
41static char FSCK_MSDOS_PATH[] = "/system/bin/fsck_msdos";
42static char MKDOSFS_PATH[] = "/system/bin/newfs_msdos";
43extern "C" int logwrap(int argc, const char **argv, int background);
44extern "C" int mount(const char *, const char *, const char *, unsigned long, const void *);
45
46int Fat::check(const char *fsPath) {
47    bool rw = true;
48    if (access(FSCK_MSDOS_PATH, X_OK)) {
49        LOGW("Skipping fs checks\n");
50        return 0;
51    }
52
53    int pass = 1;
54    int rc = 0;
55    do {
56        const char *args[5];
57        args[0] = FSCK_MSDOS_PATH;
58        args[1] = "-p";
59        args[2] = "-f";
60        args[3] = fsPath;
61        args[4] = NULL;
62
63        rc = logwrap(4, args, 1);
64
65        switch(rc) {
66        case 0:
67            LOGI("Filesystem check completed OK");
68            return 0;
69
70        case 2:
71            LOGE("Filesystem check failed (not a FAT filesystem)");
72            errno = ENODATA;
73            return -1;
74
75        case 4:
76            if (pass++ <= 3) {
77                LOGW("Filesystem modified - rechecking (pass %d)",
78                        pass);
79                continue;
80            }
81            LOGE("Failing check after too many rechecks");
82            errno = EIO;
83            return -1;
84
85        default:
86            LOGE("Filesystem check failed (unknown exit code %d)", rc);
87            errno = EIO;
88            return -1;
89        }
90    } while (0);
91
92    return 0;
93}
94
95int Fat::doMount(const char *fsPath, const char *mountPoint) {
96    int rc;
97    unsigned long flags;
98
99    flags = MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_DIRSYNC;
100
101    /*
102     * Note: This is a temporary hack. If the sampling profiler is enabled,
103     * we make the SD card world-writable so any process can write snapshots.
104     *
105     * TODO: Remove this code once we have a drop box in system_server.
106     */
107    char value[PROPERTY_VALUE_MAX];
108    property_get("persist.sampling_profiler", value, "");
109    if (value[0] == '1') {
110        LOGW("The SD card is world-writable because the"
111            " 'persist.sampling_profiler' system property is set to '1'.");
112        rc = mount(fsPath, mountPoint, (const char *) "vfat", (unsigned long) flags,
113                (const void *) "utf8,uid=1000,gid=1015,fmask=000,dmask=000,shortname=mixed");
114    } else {
115        /*
116         * The mount masks restrict access so that:
117         * 1. The 'system' user cannot access the SD card at all -
118         *    (protects system_server from grabbing file references)
119         * 2. Group users can RWX
120         * 3. Others can only RX
121         */
122        rc = mount(fsPath, mountPoint, "vfat", flags,
123                "utf8,uid=1000,gid=1015,fmask=702,dmask=702,shortname=mixed");
124    }
125
126    if (rc && errno == EROFS) {
127        LOGE("%s appears to be a read only filesystem - retrying mount RO", fsPath);
128        flags |= MS_RDONLY;
129        rc = mount(fsPath, mountPoint, "vfat", flags,
130                   "utf8,uid=1000,gid=1015,fmask=702,dmask=702,shortname=mixed");
131    }
132
133    if (rc == 0) {
134        char *lost_path;
135        asprintf(&lost_path, "%s/LOST.DIR", mountPoint);
136        if (access(lost_path, F_OK)) {
137            /*
138             * Create a LOST.DIR in the root so we have somewhere to put
139             * lost cluster chains (fsck_msdos doesn't currently do this)
140             */
141            if (mkdir(lost_path, 0755)) {
142                LOGE("Unable to create LOST.DIR (%s)", strerror(errno));
143            }
144        }
145        free(lost_path);
146    }
147
148    return rc;
149}
150
151int Fat::format(const char *fsPath) {
152    unsigned int nr_sec;
153    int fd;
154
155    if ((fd = open(fsPath, O_RDWR)) < 0) {
156        LOGE("Error opening disk file (%s)", strerror(errno));
157        return -1;
158    }
159
160    if (ioctl(fd, BLKGETSIZE, &nr_sec)) {
161        LOGE("Unable to get device size (%s)", strerror(errno));
162        close(fd);
163        return -1;
164    }
165    close(fd);
166
167    const char *args[7];
168    int rc;
169    args[0] = MKDOSFS_PATH;
170    args[1] = "-F";
171    if ((nr_sec * 512) <= ((unsigned int) (1024*1024*1024) * 2))
172            args[2] = "16";
173    else
174            args[2] = "32";
175
176    args[3] = "-O";
177    args[4] = "android";
178    args[5] = fsPath;
179    args[6] = NULL;
180    rc = logwrap(7, args, 1);
181
182    if (rc == 0) {
183        LOGI("Filesystem formatted OK");
184        return 0;
185    } else {
186        LOGE("Format failed (unknown exit code %d)", rc);
187        errno = EIO;
188        return -1;
189    }
190    return 0;
191}
192