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#define DEFAULT_LOOP_DEVICE "/dev/block/loop0"
19#define LOOPDEV_MAXLEN 64
20
21struct mount_opts {
22	const char str[16];
23	unsigned long rwmask;
24	unsigned long rwset;
25	unsigned long rwnoset;
26};
27
28struct 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
41static 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	{ "rec",	MS_REC,		MS_REC,		0		},
53	{ "remount",	MS_TYPE,	MS_REMOUNT,	0		},
54	{ "ro",		MS_RDONLY,	MS_RDONLY,	0		},
55	{ "rw",		MS_RDONLY,	0,		MS_RDONLY	},
56	{ "suid",	MS_NOSUID,	0,		MS_NOSUID	},
57	{ "sync",	MS_SYNCHRONOUS,	MS_SYNCHRONOUS,	0		},
58	{ "verbose",	MS_VERBOSE,	MS_VERBOSE,	0		},
59	{ "unbindable",	MS_UNBINDABLE,	MS_UNBINDABLE,	0		},
60	{ "private",	MS_PRIVATE,	MS_PRIVATE,	0		},
61	{ "slave",	MS_SLAVE,	MS_SLAVE,	0		},
62	{ "shared",	MS_SHARED,	MS_SHARED,	0		},
63};
64
65static void add_extra_option(struct extra_opts *extra, char *s)
66{
67	int len = strlen(s);
68	int newlen;
69
70	if (extra->str)
71	       len++;			/* +1 for ',' */
72	newlen = extra->used_size + len;
73
74	if (newlen >= extra->alloc_size) {
75		char *new;
76
77		new = realloc(extra->str, newlen + 1);	/* +1 for NUL */
78		if (!new)
79			return;
80
81		extra->str = new;
82		extra->end = extra->str + extra->used_size;
83		extra->alloc_size = newlen + 1;
84	}
85
86	if (extra->used_size) {
87		*extra->end = ',';
88		extra->end++;
89	}
90	strcpy(extra->end, s);
91	extra->used_size += len;
92
93}
94
95static unsigned long
96parse_mount_options(char *arg, unsigned long rwflag, struct extra_opts *extra, int* loop, char *loopdev)
97{
98	char *s;
99
100    *loop = 0;
101	while ((s = strsep(&arg, ",")) != NULL) {
102		char *opt = s;
103		unsigned int i;
104		int res, no = s[0] == 'n' && s[1] == 'o';
105
106		if (no)
107			s += 2;
108
109        if (strncmp(s, "loop=", 5) == 0) {
110            *loop = 1;
111            strlcpy(loopdev, s + 5, LOOPDEV_MAXLEN);
112            continue;
113        }
114
115        if (strcmp(s, "loop") == 0) {
116            *loop = 1;
117            strlcpy(loopdev, DEFAULT_LOOP_DEVICE, LOOPDEV_MAXLEN);
118            continue;
119        }
120		for (i = 0, res = 1; i < ARRAY_SIZE(options); i++) {
121			res = strcmp(s, options[i].str);
122
123			if (res == 0) {
124				rwflag &= ~options[i].rwmask;
125				if (no)
126					rwflag |= options[i].rwnoset;
127				else
128					rwflag |= options[i].rwset;
129			}
130			if (res <= 0)
131				break;
132		}
133
134		if (res != 0 && s[0])
135			add_extra_option(extra, opt);
136	}
137
138	return rwflag;
139}
140
141/*
142 * Mark the given block device as read-write, using the BLKROSET ioctl.
143 */
144static void fs_set_blk_rw(const char *blockdev)
145{
146    int fd;
147    int OFF = 0;
148
149    fd = open(blockdev, O_RDONLY);
150    if (fd < 0) {
151        // should never happen
152        return;
153    }
154
155    ioctl(fd, BLKROSET, &OFF);
156    close(fd);
157}
158
159static char *progname;
160
161static struct extra_opts extra;
162static unsigned long rwflag;
163
164static int
165do_mount(char *dev, char *dir, char *type, unsigned long rwflag, void *data, int loop,
166         char *loopdev)
167{
168	char *s;
169	int error = 0;
170
171    if (loop) {
172        int file_fd, device_fd;
173        int flags;
174
175        flags = (rwflag & MS_RDONLY) ? O_RDONLY : O_RDWR;
176
177        file_fd = open(dev, flags);
178        if (file_fd < 0) {
179            perror("open backing file failed");
180            return 1;
181        }
182        device_fd = open(loopdev, flags);
183        if (device_fd < 0) {
184            perror("open loop device failed");
185            close(file_fd);
186            return 1;
187        }
188        if (ioctl(device_fd, LOOP_SET_FD, file_fd) < 0) {
189            perror("ioctl LOOP_SET_FD failed");
190            close(file_fd);
191            close(device_fd);
192            return 1;
193        }
194
195        close(file_fd);
196        close(device_fd);
197        dev = loopdev;
198    }
199
200    if ((rwflag & MS_RDONLY) == 0) {
201        fs_set_blk_rw(dev);
202    }
203
204	while ((s = strsep(&type, ",")) != NULL) {
205retry:
206		if (mount(dev, dir, s, rwflag, data) == -1) {
207			error = errno;
208			/*
209			 * If the filesystem is not found, or the
210			 * superblock is invalid, try the next.
211			 */
212			if (error == ENODEV || error == EINVAL)
213				continue;
214
215			/*
216			 * If we get EACCESS, and we're trying to
217			 * mount readwrite and this isn't a remount,
218			 * try read only.
219			 */
220			if (error == EACCES &&
221			    (rwflag & (MS_REMOUNT|MS_RDONLY)) == 0) {
222				rwflag |= MS_RDONLY;
223				goto retry;
224			}
225			break;
226		}
227	}
228
229	if (error) {
230		errno = error;
231		perror("mount");
232		return 255;
233	}
234
235	return 0;
236}
237
238static int print_mounts()
239{
240    FILE* f;
241    int length;
242    char buffer[100];
243
244    f = fopen("/proc/mounts", "r");
245    if (!f) {
246        fprintf(stdout, "could not open /proc/mounts\n");
247        return -1;
248    }
249
250    do {
251        length = fread(buffer, 1, 100, f);
252        if (length > 0)
253            fwrite(buffer, 1, length, stdout);
254    } while (length > 0);
255
256    fclose(f);
257    return 0;
258}
259
260static int get_mounts_dev_dir(const char *arg, char **dev, char **dir)
261{
262	FILE *f;
263	char mount_dev[256];
264	char mount_dir[256];
265	char mount_type[256];
266	char mount_opts[256];
267	int mount_freq;
268	int mount_passno;
269	int match;
270
271	f = fopen("/proc/mounts", "r");
272	if (!f) {
273		fprintf(stdout, "could not open /proc/mounts\n");
274		return -1;
275	}
276
277	do {
278		match = fscanf(f, "%255s %255s %255s %255s %d %d\n",
279					   mount_dev, mount_dir, mount_type,
280					   mount_opts, &mount_freq, &mount_passno);
281		mount_dev[255] = 0;
282		mount_dir[255] = 0;
283		mount_type[255] = 0;
284		mount_opts[255] = 0;
285		if (match == 6 &&
286			(strcmp(arg, mount_dev) == 0 ||
287			 strcmp(arg, mount_dir) == 0)) {
288			*dev = strdup(mount_dev);
289			*dir = strdup(mount_dir);
290			fclose(f);
291			return 0;
292		}
293	} while (match != EOF);
294
295	fclose(f);
296	return -1;
297}
298
299int mount_main(int argc, char *argv[])
300{
301	char *type = NULL;
302	char *dev = NULL;
303	char *dir = NULL;
304	int c;
305	int loop = 0;
306	char loopdev[LOOPDEV_MAXLEN];
307
308	progname = argv[0];
309	rwflag = MS_VERBOSE;
310
311	// mount with no arguments is equivalent to "cat /proc/mounts"
312	if (argc == 1) return print_mounts();
313
314	do {
315		c = getopt(argc, argv, "o:rt:w");
316		if (c == EOF)
317			break;
318		switch (c) {
319		case 'o':
320			rwflag = parse_mount_options(optarg, rwflag, &extra, &loop, loopdev);
321			break;
322		case 'r':
323			rwflag |= MS_RDONLY;
324			break;
325		case 't':
326			type = optarg;
327			break;
328		case 'w':
329			rwflag &= ~MS_RDONLY;
330			break;
331		case '?':
332			fprintf(stderr, "%s: invalid option -%c\n",
333				progname, optopt);
334			exit(1);
335		}
336	} while (1);
337
338	/*
339	 * If remount, bind or move was specified, then we don't
340	 * have a "type" as such.  Use the dummy "none" type.
341	 */
342	if (rwflag & MS_TYPE)
343		type = "none";
344
345	if (optind + 2 == argc) {
346		dev = argv[optind];
347		dir = argv[optind + 1];
348	} else if (optind + 1 == argc && rwflag & MS_REMOUNT) {
349		get_mounts_dev_dir(argv[optind], &dev, &dir);
350	}
351
352	if (dev == NULL || dir == NULL || type == NULL) {
353		fprintf(stderr, "Usage: %s [-r] [-w] [-o options] [-t type] "
354			"device directory\n", progname);
355		exit(1);
356	}
357
358	return do_mount(dev, dir, type, rwflag, extra.str, loop, loopdev);
359	/* We leak dev and dir in some cases, but we're about to exit */
360}
361