1 /*
2 * mount.c, by rmk
3 */
4
5 #include <sys/mount.h>
6 #include <sys/stat.h>
7 #include <fcntl.h>
8 #include <errno.h>
9 #include <stdio.h>
10 #include <stdlib.h>
11 #include <string.h>
12 #include <unistd.h>
13
14 #include <linux/loop.h>
15
16 #define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
17
18 // FIXME - only one loop mount is supported at a time
19 #define LOOP_DEVICE "/dev/block/loop0"
20
21 struct mount_opts {
22 const char str[8];
23 unsigned long rwmask;
24 unsigned long rwset;
25 unsigned long rwnoset;
26 };
27
28 struct extra_opts {
29 char *str;
30 char *end;
31 int used_size;
32 int alloc_size;
33 };
34
35 /*
36 * These options define the function of "mount(2)".
37 */
38 #define MS_TYPE (MS_REMOUNT|MS_BIND|MS_MOVE)
39
40
41 static const struct mount_opts options[] = {
42 /* name mask set noset */
43 { "async", MS_SYNCHRONOUS, 0, MS_SYNCHRONOUS },
44 { "atime", MS_NOATIME, 0, MS_NOATIME },
45 { "bind", MS_TYPE, MS_BIND, 0, },
46 { "dev", MS_NODEV, 0, MS_NODEV },
47 { "diratime", MS_NODIRATIME, 0, MS_NODIRATIME },
48 { "dirsync", MS_DIRSYNC, MS_DIRSYNC, 0 },
49 { "exec", MS_NOEXEC, 0, MS_NOEXEC },
50 { "move", MS_TYPE, MS_MOVE, 0 },
51 { "recurse", MS_REC, MS_REC, 0 },
52 { "remount", MS_TYPE, MS_REMOUNT, 0 },
53 { "ro", MS_RDONLY, MS_RDONLY, 0 },
54 { "rw", MS_RDONLY, 0, MS_RDONLY },
55 { "suid", MS_NOSUID, 0, MS_NOSUID },
56 { "sync", MS_SYNCHRONOUS, MS_SYNCHRONOUS, 0 },
57 { "verbose", MS_VERBOSE, MS_VERBOSE, 0 },
58 };
59
add_extra_option(struct extra_opts * extra,char * s)60 static void add_extra_option(struct extra_opts *extra, char *s)
61 {
62 int len = strlen(s);
63 int newlen = extra->used_size + len;
64
65 if (extra->str)
66 len++; /* +1 for ',' */
67
68 if (newlen >= extra->alloc_size) {
69 char *new;
70
71 new = realloc(extra->str, newlen + 1); /* +1 for NUL */
72 if (!new)
73 return;
74
75 extra->str = new;
76 extra->end = extra->str + extra->used_size;
77 extra->alloc_size = newlen;
78 }
79
80 if (extra->used_size) {
81 *extra->end = ',';
82 extra->end++;
83 }
84 strcpy(extra->end, s);
85 extra->used_size += len;
86
87 }
88
89 static unsigned long
parse_mount_options(char * arg,unsigned long rwflag,struct extra_opts * extra,int * loop)90 parse_mount_options(char *arg, unsigned long rwflag, struct extra_opts *extra, int* loop)
91 {
92 char *s;
93
94 *loop = 0;
95 while ((s = strsep(&arg, ",")) != NULL) {
96 char *opt = s;
97 unsigned int i;
98 int res, no = s[0] == 'n' && s[1] == 'o';
99
100 if (no)
101 s += 2;
102
103 if (strcmp(s, "loop") == 0) {
104 *loop = 1;
105 continue;
106 }
107 for (i = 0, res = 1; i < ARRAY_SIZE(options); i++) {
108 res = strcmp(s, options[i].str);
109
110 if (res == 0) {
111 rwflag &= ~options[i].rwmask;
112 if (no)
113 rwflag |= options[i].rwnoset;
114 else
115 rwflag |= options[i].rwset;
116 }
117 if (res <= 0)
118 break;
119 }
120
121 if (res != 0 && s[0])
122 add_extra_option(extra, opt);
123 }
124
125 return rwflag;
126 }
127
128 static char *progname;
129
130 static struct extra_opts extra;
131 static unsigned long rwflag;
132
133 static int
do_mount(char * dev,char * dir,char * type,unsigned long rwflag,void * data,int loop)134 do_mount(char *dev, char *dir, char *type, unsigned long rwflag, void *data, int loop)
135 {
136 char *s;
137 int error = 0;
138
139 if (loop) {
140 int file_fd, device_fd;
141 int flags;
142
143 flags = (rwflag & MS_RDONLY) ? O_RDONLY : O_RDWR;
144
145 // FIXME - only one loop mount supported at a time
146 file_fd = open(dev, flags);
147 if (file_fd < -1) {
148 perror("open backing file failed");
149 return 1;
150 }
151 device_fd = open(LOOP_DEVICE, flags);
152 if (device_fd < -1) {
153 perror("open loop device failed");
154 close(file_fd);
155 return 1;
156 }
157 if (ioctl(device_fd, LOOP_SET_FD, file_fd) < 0) {
158 perror("ioctl LOOP_SET_FD failed");
159 close(file_fd);
160 close(device_fd);
161 return 1;
162 }
163
164 close(file_fd);
165 close(device_fd);
166 dev = LOOP_DEVICE;
167 }
168
169 while ((s = strsep(&type, ",")) != NULL) {
170 retry:
171 if (mount(dev, dir, s, rwflag, data) == -1) {
172 error = errno;
173 /*
174 * If the filesystem is not found, or the
175 * superblock is invalid, try the next.
176 */
177 if (error == ENODEV || error == EINVAL)
178 continue;
179
180 /*
181 * If we get EACCESS, and we're trying to
182 * mount readwrite and this isn't a remount,
183 * try read only.
184 */
185 if (error == EACCES &&
186 (rwflag & (MS_REMOUNT|MS_RDONLY)) == 0) {
187 rwflag |= MS_RDONLY;
188 goto retry;
189 }
190 break;
191 }
192 }
193
194 if (error) {
195 errno = error;
196 perror("mount");
197 return 255;
198 }
199
200 return 0;
201 }
202
print_mounts()203 static int print_mounts()
204 {
205 FILE* f;
206 int length;
207 char buffer[100];
208
209 f = fopen("/proc/mounts", "r");
210 if (!f) {
211 fprintf(stdout, "could not open /proc/mounts\n");
212 return -1;
213 }
214
215 do {
216 length = fread(buffer, 1, 100, f);
217 if (length > 0)
218 fwrite(buffer, 1, length, stdout);
219 } while (length > 0);
220
221 fclose(f);
222 return 0;
223 }
224
mount_main(int argc,char * argv[])225 int mount_main(int argc, char *argv[])
226 {
227 char *type = NULL;
228 int c;
229 int loop = 0;
230
231 progname = argv[0];
232 rwflag = MS_VERBOSE;
233
234 // mount with no arguments is equivalent to "cat /proc/mounts"
235 if (argc == 1) return print_mounts();
236
237 do {
238 c = getopt(argc, argv, "o:rt:w");
239 if (c == EOF)
240 break;
241 switch (c) {
242 case 'o':
243 rwflag = parse_mount_options(optarg, rwflag, &extra, &loop);
244 break;
245 case 'r':
246 rwflag |= MS_RDONLY;
247 break;
248 case 't':
249 type = optarg;
250 break;
251 case 'w':
252 rwflag &= ~MS_RDONLY;
253 break;
254 case '?':
255 fprintf(stderr, "%s: invalid option -%c\n",
256 progname, optopt);
257 exit(1);
258 }
259 } while (1);
260
261 /*
262 * If remount, bind or move was specified, then we don't
263 * have a "type" as such. Use the dummy "none" type.
264 */
265 if (rwflag & MS_TYPE)
266 type = "none";
267
268 if (optind + 2 != argc || type == NULL) {
269 fprintf(stderr, "Usage: %s [-r] [-w] [-o options] [-t type] "
270 "device directory\n", progname);
271 exit(1);
272 }
273
274 return do_mount(argv[optind], argv[optind + 1], type, rwflag,
275 extra.str, loop);
276 }
277