finddev.c revision f86fa6c7483f6fee33fb128fced4644ec876a1bc 
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 Public
9 * License.
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
34struct dir_list {
35	char	*name;
36	struct dir_list *next;
37};
38
39/*
40 * This function adds an entry to the directory list
41 */
42static void add_to_dirlist(char *name, struct dir_list **list)
43{
44	struct dir_list *dp;
45
46	dp = malloc(sizeof(struct dir_list));
47	if (!dp)
48		return;
49	dp->name = malloc(strlen(name)+1);
50	if (!dp->name) {
51		free(dp);
52		return;
53	}
54	strcpy(dp->name, name);
55	dp->next = *list;
56	*list = dp;
57}
58
59/*
60 * This function frees a directory list
61 */
62static void free_dirlist(struct dir_list **list)
63{
64	struct dir_list *dp, *next;
65
66	for (dp = *list; dp; dp = next) {
67		next = dp->next;
68		free(dp->name);
69		free(dp);
70	}
71	*list = 0;
72}
73
74static int scan_dir(char *dirname, dev_t device, struct dir_list **list,
75		    char **ret_path)
76{
77	DIR	*dir;
78	struct dirent *dp;
79	char	path[1024], *cp;
80	int	dirlen;
81	struct stat st;
82
83	dirlen = strlen(dirname);
84	if ((dir = opendir(dirname)) == NULL)
85		return errno;
86	dp = readdir(dir);
87	while (dp) {
88		if (dirlen + strlen(dp->d_name) + 2 >= sizeof(path))
89			goto skip_to_next;
90		if (dp->d_name[0] == '.' &&
91		    ((dp->d_name[1] == 0) ||
92		     (dp->d_name[1] == '.') && (dp->d_name[2] == 0)))
93			goto skip_to_next;
94		sprintf(path, "%s/%s", dirname, dp->d_name);
95		if (stat(path, &st) < 0)
96			goto skip_to_next;
97		if (S_ISDIR(st.st_mode))
98			add_to_dirlist(path, list);
99		if (S_ISBLK(st.st_mode) && st.st_rdev == device) {
100			cp = malloc(strlen(path)+1);
101			if (!cp)
102				return ENOMEM;
103			strcpy(cp, path);
104			*ret_path = cp;
105			return 0;
106		}
107	skip_to_next:
108		dp = readdir(dir);
109	}
110	closedir(dir);
111	return 0;
112}
113
114/*
115 * This function finds the pathname to a block device with a given
116 * device number.  It returns a pointer to allocated memory to the
117 * pathname on success, and NULL on failure.
118 */
119char *ext2fs_find_block_device(dev_t device)
120{
121	struct dir_list *list = 0, *new_list = 0;
122	struct dir_list *current;
123	char	*ret_path = 0;
124
125	/*
126	 * Add the starting directories to search...
127	 */
128	add_to_dirlist("/devices", &list);
129	add_to_dirlist("/devfs", &list);
130	add_to_dirlist("/dev", &list);
131
132	while (list) {
133		current = list;
134		list = list->next;
135#ifdef DEBUG
136		printf("Scanning directory %s\n", current->name);
137#endif
138		scan_dir(current->name, device, &new_list, &ret_path);
139		free(current->name);
140		free(current);
141		if (ret_path)
142			break;
143		/*
144		 * If we're done checking at this level, descend to
145		 * the next level of subdirectories. (breadth-first)
146		 */
147		if (list == 0) {
148			list = new_list;
149			new_list = 0;
150		}
151	}
152found_it:
153	free_dirlist(&list);
154	free_dirlist(&new_list);
155	return ret_path;
156}
157
158
159#ifdef DEBUG
160int main(int argc, char** argv)
161{
162	char	*devname, *tmp;
163	int	major, minor;
164	dev_t	device;
165	const char *errmsg = "Couldn't parse %s: %s\n";
166
167	if ((argc != 2) && (argc != 3)) {
168		fprintf(stderr, "Usage: %s device_number\n", argv[0]);
169		fprintf(stderr, "\t: %s major minor\n", argv[0]);
170		exit(1);
171	}
172	if (argc == 2) {
173		device = strtoul(argv[1], &tmp, 0);
174		if (*tmp) {
175			fprintf(stderr, errmsg, "device number", argv[1]);
176			exit(1);
177		}
178	} else {
179		major = strtoul(argv[1], &tmp, 0);
180		if (*tmp) {
181			fprintf(stderr, errmsg, "major number", argv[1]);
182			exit(1);
183		}
184		minor = strtoul(argv[2], &tmp, 0);
185		if (*tmp) {
186			fprintf(stderr, errmsg, "minor number", argv[2]);
187			exit(1);
188		}
189		device = makedev(major, minor);
190		printf("Looking for device 0x%04x (%d:%d)\n", device,
191		       major, minor);
192	}
193	devname = ext2fs_find_block_device(device);
194	if (devname) {
195		printf("Found device!  %s\n", devname);
196		free(devname);
197	} else {
198		printf("Couldn't find device.\n");
199	}
200	return 0;
201}
202
203#endif
204