finddev.c revision 65f0aab98b20b5994a726ab90d355248bcddfffd 
1/*
2 * finddev.c -- this routine attempts to find a particular device in
3 * 	/dev
4 *
5 * Copyright (C) 2000 Theodore Ts'o.
6 *
7 * %Begin-Header%
8 * This file may be redistributed under the terms of the GNU Library
9 * General Public License, version 2.
10 * %End-Header%
11 */
12
13#include <stdio.h>
14#include <string.h>
15#if HAVE_UNISTD_H
16#include <unistd.h>
17#endif
18#include <stdlib.h>
19#include <string.h>
20#if HAVE_SYS_TYPES_H
21#include <sys/types.h>
22#endif
23#if HAVE_SYS_STAT_H
24#include <sys/stat.h>
25#endif
26#include <dirent.h>
27#if HAVE_ERRNO_H
28#include <errno.h>
29#endif
30#if HAVE_SYS_MKDEV_H
31#include <sys/mkdev.h>
32#endif
33
34#include "ext2_fs.h"
35#include "ext2fs.h"
36
37struct dir_list {
38	char	*name;
39	struct dir_list *next;
40};
41
42/*
43 * This function adds an entry to the directory list
44 */
45static void add_to_dirlist(const char *name, struct dir_list **list)
46{
47	struct dir_list *dp;
48
49	dp = malloc(sizeof(struct dir_list));
50	if (!dp)
51		return;
52	dp->name = malloc(strlen(name)+1);
53	if (!dp->name) {
54		free(dp);
55		return;
56	}
57	strcpy(dp->name, name);
58	dp->next = *list;
59	*list = dp;
60}
61
62/*
63 * This function frees a directory list
64 */
65static void free_dirlist(struct dir_list **list)
66{
67	struct dir_list *dp, *next;
68
69	for (dp = *list; dp; dp = next) {
70		next = dp->next;
71		free(dp->name);
72		free(dp);
73	}
74	*list = 0;
75}
76
77static int scan_dir(char *dirname, dev_t device, struct dir_list **list,
78		    char **ret_path)
79{
80	DIR	*dir;
81	struct dirent *dp;
82	char	path[1024], *cp;
83	int	dirlen;
84	struct stat st;
85
86	dirlen = strlen(dirname);
87	if ((dir = opendir(dirname)) == NULL)
88		return errno;
89	dp = readdir(dir);
90	while (dp) {
91		if (dirlen + strlen(dp->d_name) + 2 >= sizeof(path))
92			goto skip_to_next;
93		if (dp->d_name[0] == '.' &&
94		    ((dp->d_name[1] == 0) ||
95		     ((dp->d_name[1] == '.') && (dp->d_name[2] == 0))))
96			goto skip_to_next;
97		sprintf(path, "%s/%s", dirname, dp->d_name);
98		if (stat(path, &st) < 0)
99			goto skip_to_next;
100		if (S_ISDIR(st.st_mode))
101			add_to_dirlist(path, list);
102		if (S_ISBLK(st.st_mode) && st.st_rdev == device) {
103			cp = malloc(strlen(path)+1);
104			if (!cp) {
105				closedir(dir);
106				return ENOMEM;
107			}
108			strcpy(cp, path);
109			*ret_path = cp;
110			goto success;
111		}
112	skip_to_next:
113		dp = readdir(dir);
114	}
115success:
116	closedir(dir);
117	return 0;
118}
119
120/*
121 * This function finds the pathname to a block device with a given
122 * device number.  It returns a pointer to allocated memory to the
123 * pathname on success, and NULL on failure.
124 */
125char *ext2fs_find_block_device(dev_t device)
126{
127	struct dir_list *list = 0, *new_list = 0;
128	struct dir_list *current;
129	char	*ret_path = 0;
130
131	/*
132	 * Add the starting directories to search...
133	 */
134	add_to_dirlist("/devices", &list);
135	add_to_dirlist("/devfs", &list);
136	add_to_dirlist("/dev", &list);
137
138	while (list) {
139		current = list;
140		list = list->next;
141#ifdef DEBUG
142		printf("Scanning directory %s\n", current->name);
143#endif
144		scan_dir(current->name, device, &new_list, &ret_path);
145		free(current->name);
146		free(current);
147		if (ret_path)
148			break;
149		/*
150		 * If we're done checking at this level, descend to
151		 * the next level of subdirectories. (breadth-first)
152		 */
153		if (list == 0) {
154			list = new_list;
155			new_list = 0;
156		}
157	}
158	free_dirlist(&list);
159	free_dirlist(&new_list);
160	return ret_path;
161}
162
163
164#ifdef DEBUG
165int main(int argc, char** argv)
166{
167	char	*devname, *tmp;
168	int	major, minor;
169	dev_t	device;
170	const char *errmsg = "Couldn't parse %s: %s\n";
171
172	if ((argc != 2) && (argc != 3)) {
173		fprintf(stderr, "Usage: %s device_number\n", argv[0]);
174		fprintf(stderr, "\t: %s major minor\n", argv[0]);
175		exit(1);
176	}
177	if (argc == 2) {
178		device = strtoul(argv[1], &tmp, 0);
179		if (*tmp) {
180			fprintf(stderr, errmsg, "device number", argv[1]);
181			exit(1);
182		}
183	} else {
184		major = strtoul(argv[1], &tmp, 0);
185		if (*tmp) {
186			fprintf(stderr, errmsg, "major number", argv[1]);
187			exit(1);
188		}
189		minor = strtoul(argv[2], &tmp, 0);
190		if (*tmp) {
191			fprintf(stderr, errmsg, "minor number", argv[2]);
192			exit(1);
193		}
194		device = makedev(major, minor);
195		printf("Looking for device 0x%04x (%d:%d)\n", device,
196		       major, minor);
197	}
198	devname = ext2fs_find_block_device(device);
199	if (devname) {
200		printf("Found device!  %s\n", devname);
201		free(devname);
202	} else {
203		printf("Couldn't find device.\n");
204	}
205	return 0;
206}
207
208#endif
209