1 /*
2 * devno.c - find a particular device by its device number (major/minor)
3 *
4 * Copyright (C) 2000, 2001, 2003 Theodore Ts'o
5 * Copyright (C) 2001 Andreas Dilger
6 *
7 * %Begin-Header%
8 * This file may be redistributed under the terms of the
9 * GNU Lesser General Public 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
34 #include "blkidP.h"
35
36 struct dir_list {
37 char *name;
38 struct dir_list *next;
39 };
40
blkid_strndup(const char * s,int length)41 char *blkid_strndup(const char *s, int length)
42 {
43 char *ret;
44
45 if (!s)
46 return NULL;
47
48 if (!length)
49 length = strlen(s);
50
51 ret = malloc(length + 1);
52 if (ret) {
53 strncpy(ret, s, length);
54 ret[length] = '\0';
55 }
56 return ret;
57 }
58
blkid_strdup(const char * s)59 char *blkid_strdup(const char *s)
60 {
61 return blkid_strndup(s, 0);
62 }
63
64 /*
65 * This function adds an entry to the directory list
66 */
add_to_dirlist(const char * name,struct dir_list ** list)67 static void add_to_dirlist(const char *name, struct dir_list **list)
68 {
69 struct dir_list *dp;
70
71 dp = malloc(sizeof(struct dir_list));
72 if (!dp)
73 return;
74 dp->name = blkid_strdup(name);
75 if (!dp->name) {
76 free(dp);
77 return;
78 }
79 dp->next = *list;
80 *list = dp;
81 }
82
83 /*
84 * This function frees a directory list
85 */
free_dirlist(struct dir_list ** list)86 static void free_dirlist(struct dir_list **list)
87 {
88 struct dir_list *dp, *next;
89
90 for (dp = *list; dp; dp = next) {
91 next = dp->next;
92 free(dp->name);
93 free(dp);
94 }
95 *list = NULL;
96 }
97
scan_dir(char * dirname,dev_t devno,struct dir_list ** list,char ** devname)98 static void scan_dir(char *dirname, dev_t devno, struct dir_list **list,
99 char **devname)
100 {
101 DIR *dir;
102 struct dirent *dp;
103 char path[1024];
104 int dirlen;
105 struct stat st;
106
107 if ((dir = opendir(dirname)) == NULL)
108 return;
109 dirlen = strlen(dirname) + 2;
110 while ((dp = readdir(dir)) != 0) {
111 if (dirlen + strlen(dp->d_name) >= sizeof(path))
112 continue;
113
114 if (dp->d_name[0] == '.' &&
115 ((dp->d_name[1] == 0) ||
116 ((dp->d_name[1] == '.') && (dp->d_name[2] == 0))))
117 continue;
118
119 sprintf(path, "%s/%s", dirname, dp->d_name);
120 if (stat(path, &st) < 0)
121 continue;
122
123 if (S_ISBLK(st.st_mode) && st.st_rdev == devno) {
124 *devname = blkid_strdup(path);
125 DBG(DEBUG_DEVNO,
126 printf("found 0x%llx at %s (%p)\n", (long long)devno,
127 path, *devname));
128 break;
129 }
130 if (S_ISDIR(st.st_mode) && !lstat(path, &st) &&
131 S_ISDIR(st.st_mode))
132 add_to_dirlist(path, list);
133 }
134 closedir(dir);
135 return;
136 }
137
138 /* Directories where we will try to search for device numbers */
139 const char *blkid_devdirs[] = { "/devices", "/devfs", "/dev", NULL };
140
141 /*
142 * This function finds the pathname to a block device with a given
143 * device number. It returns a pointer to allocated memory to the
144 * pathname on success, and NULL on failure.
145 */
blkid_devno_to_devname(dev_t devno)146 char *blkid_devno_to_devname(dev_t devno)
147 {
148 struct dir_list *list = NULL, *new_list = NULL;
149 char *devname = NULL;
150 const char **dir;
151
152 /*
153 * Add the starting directories to search in reverse order of
154 * importance, since we are using a stack...
155 */
156 for (dir = blkid_devdirs; *dir; dir++)
157 add_to_dirlist(*dir, &list);
158
159 while (list) {
160 struct dir_list *current = list;
161
162 list = list->next;
163 DBG(DEBUG_DEVNO, printf("directory %s\n", current->name));
164 scan_dir(current->name, devno, &new_list, &devname);
165 free(current->name);
166 free(current);
167 if (devname)
168 break;
169 /*
170 * If we're done checking at this level, descend to
171 * the next level of subdirectories. (breadth-first)
172 */
173 if (list == NULL) {
174 list = new_list;
175 new_list = NULL;
176 }
177 }
178 free_dirlist(&list);
179 free_dirlist(&new_list);
180
181 if (!devname) {
182 DBG(DEBUG_DEVNO,
183 printf("blkid: couldn't find devno 0x%04lx\n",
184 (unsigned long) devno));
185 } else {
186 DBG(DEBUG_DEVNO,
187 printf("found devno 0x%04llx as %s\n", (long long)devno, devname));
188 }
189
190
191 return devname;
192 }
193
194 #ifdef TEST_PROGRAM
main(int argc,char ** argv)195 int main(int argc, char** argv)
196 {
197 char *devname, *tmp;
198 int major, minor;
199 dev_t devno;
200 const char *errmsg = "Couldn't parse %s: %s\n";
201
202 blkid_debug_mask = DEBUG_ALL;
203 if ((argc != 2) && (argc != 3)) {
204 fprintf(stderr, "Usage:\t%s device_number\n\t%s major minor\n"
205 "Resolve a device number to a device name\n",
206 argv[0], argv[0]);
207 exit(1);
208 }
209 if (argc == 2) {
210 devno = strtoul(argv[1], &tmp, 0);
211 if (*tmp) {
212 fprintf(stderr, errmsg, "device number", argv[1]);
213 exit(1);
214 }
215 } else {
216 major = strtoul(argv[1], &tmp, 0);
217 if (*tmp) {
218 fprintf(stderr, errmsg, "major number", argv[1]);
219 exit(1);
220 }
221 minor = strtoul(argv[2], &tmp, 0);
222 if (*tmp) {
223 fprintf(stderr, errmsg, "minor number", argv[2]);
224 exit(1);
225 }
226 devno = makedev(major, minor);
227 }
228 printf("Looking for device 0x%04llx\n", (long long)devno);
229 devname = blkid_devno_to_devname(devno);
230 if (devname)
231 free(devname);
232 return 0;
233 }
234 #endif
235