mount.c revision 4f6e8d7a00cbeda1e70cc15be9c4af1018bdad53 
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
21struct mount_opts {
22	const char str[8];
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	{ "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
60static 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
89static unsigned long
90parse_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
128static char *progname;
129
130static struct extra_opts extra;
131static unsigned long rwflag;
132
133static int
134do_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
142        // FIXME - only one loop mount supported at a time
143        file_fd = open(dev, O_RDWR);
144        if (file_fd < -1) {
145            perror("open backing file failed");
146            return 1;
147        }
148        device_fd = open(LOOP_DEVICE, O_RDWR);
149        if (device_fd < -1) {
150            perror("open loop device failed");
151            close(file_fd);
152            return 1;
153        }
154        if (ioctl(device_fd, LOOP_SET_FD, file_fd) < 0) {
155            perror("ioctl LOOP_SET_FD failed");
156            close(file_fd);
157            close(device_fd);
158            return 1;
159        }
160
161        close(file_fd);
162        close(device_fd);
163        dev = LOOP_DEVICE;
164    }
165
166	while ((s = strsep(&type, ",")) != NULL) {
167retry:
168		if (mount(dev, dir, s, rwflag, data) == -1) {
169			error = errno;
170			/*
171			 * If the filesystem is not found, or the
172			 * superblock is invalid, try the next.
173			 */
174			if (error == ENODEV || error == EINVAL)
175				continue;
176
177			/*
178			 * If we get EACCESS, and we're trying to
179			 * mount readwrite and this isn't a remount,
180			 * try read only.
181			 */
182			if (error == EACCES &&
183			    (rwflag & (MS_REMOUNT|MS_RDONLY)) == 0) {
184				rwflag |= MS_RDONLY;
185				goto retry;
186			}
187			break;
188		}
189	}
190
191	if (error) {
192		errno = error;
193		perror("mount");
194		return 255;
195	}
196
197	return 0;
198}
199
200static int print_mounts()
201{
202    FILE* f;
203    int length;
204    char buffer[100];
205
206    f = fopen("/proc/mounts", "r");
207    if (!f) {
208        fprintf(stdout, "could not open /proc/mounts\n");
209        return -1;
210    }
211
212    do {
213        length = fread(buffer, 1, 100, f);
214        if (length > 0)
215            fwrite(buffer, 1, length, stdout);
216    } while (length > 0);
217
218    fclose(f);
219    return 0;
220}
221
222int mount_main(int argc, char *argv[])
223{
224	char *type = NULL;
225	int c;
226	int loop;
227
228	progname = argv[0];
229	rwflag = MS_VERBOSE;
230
231	// mount with no arguments is equivalent to "cat /proc/mounts"
232	if (argc == 1) return print_mounts();
233
234	do {
235		c = getopt(argc, argv, "o:rt:w");
236		if (c == EOF)
237			break;
238		switch (c) {
239		case 'o':
240			rwflag = parse_mount_options(optarg, rwflag, &extra, &loop);
241			break;
242		case 'r':
243			rwflag |= MS_RDONLY;
244			break;
245		case 't':
246			type = optarg;
247			break;
248		case 'w':
249			rwflag &= ~MS_RDONLY;
250			break;
251		case '?':
252			fprintf(stderr, "%s: invalid option -%c\n",
253				progname, optopt);
254			exit(1);
255		}
256	} while (1);
257
258	/*
259	 * If remount, bind or move was specified, then we don't
260	 * have a "type" as such.  Use the dummy "none" type.
261	 */
262	if (rwflag & MS_TYPE)
263		type = "none";
264
265	if (optind + 2 != argc || type == NULL) {
266		fprintf(stderr, "Usage: %s [-r] [-w] [-o options] [-t type] "
267			"device directory\n", progname);
268		exit(1);
269	}
270
271	return do_mount(argv[optind], argv[optind + 1], type, rwflag,
272		        extra.str, loop);
273}
274