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