1 /* vi: set sw=4 ts=4: */
2 /*
3 * Utility routines.
4 *
5 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
6 * Copyright (C) 2005 by Rob Landley <rob@landley.net>
7 *
8 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
9 */
10 #include "libbb.h"
11 #include <linux/version.h>
12
13 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
14
15 /* For 2.6, use the cleaned up header to get the 64 bit API. */
16 // Commented out per Rob's request
17 //# include "fix_u32.h" /* some old toolchains need __u64 for linux/loop.h */
18 # include <linux/loop.h>
19 typedef struct loop_info64 bb_loop_info;
20 # define BB_LOOP_SET_STATUS LOOP_SET_STATUS64
21 # define BB_LOOP_GET_STATUS LOOP_GET_STATUS64
22
23 #else
24
25 /* For 2.4 and earlier, use the 32 bit API (and don't trust the headers) */
26 /* Stuff stolen from linux/loop.h for 2.4 and earlier kernels */
27 # include <linux/posix_types.h>
28 # define LO_NAME_SIZE 64
29 # define LO_KEY_SIZE 32
30 # define LOOP_SET_FD 0x4C00
31 # define LOOP_CLR_FD 0x4C01
32 # define BB_LOOP_SET_STATUS 0x4C02
33 # define BB_LOOP_GET_STATUS 0x4C03
34 typedef struct {
35 int lo_number;
36 __kernel_dev_t lo_device;
37 unsigned long lo_inode;
38 __kernel_dev_t lo_rdevice;
39 int lo_offset;
40 int lo_encrypt_type;
41 int lo_encrypt_key_size;
42 int lo_flags;
43 char lo_file_name[LO_NAME_SIZE];
44 unsigned char lo_encrypt_key[LO_KEY_SIZE];
45 unsigned long lo_init[2];
46 char reserved[4];
47 } bb_loop_info;
48 #endif
49
query_loop(const char * device)50 char* FAST_FUNC query_loop(const char *device)
51 {
52 int fd;
53 bb_loop_info loopinfo;
54 char *dev = NULL;
55
56 fd = open(device, O_RDONLY);
57 if (fd >= 0) {
58 if (ioctl(fd, BB_LOOP_GET_STATUS, &loopinfo) == 0) {
59 dev = xasprintf("%"OFF_FMT"u %s", (off_t) loopinfo.lo_offset,
60 (char *)loopinfo.lo_file_name);
61 }
62 close(fd);
63 }
64
65 return dev;
66 }
67
del_loop(const char * device)68 int FAST_FUNC del_loop(const char *device)
69 {
70 int fd, rc;
71
72 fd = open(device, O_RDONLY);
73 if (fd < 0)
74 return 1;
75 rc = ioctl(fd, LOOP_CLR_FD, 0);
76 close(fd);
77
78 return rc;
79 }
80
81 /* Obtain an unused loop device number */
get_free_loop(void)82 int FAST_FUNC get_free_loop(void)
83 {
84 int fd;
85 int loopdevno;
86
87 fd = open("/dev/loop-control", O_RDWR | O_CLOEXEC);
88 if (fd == -1)
89 return fd - 1; /* -2: "no /dev/loop-control" */
90
91 #ifndef LOOP_CTL_GET_FREE
92 # define LOOP_CTL_GET_FREE 0x4C82
93 #endif
94 loopdevno = ioctl(fd, LOOP_CTL_GET_FREE);
95 close(fd);
96 return loopdevno; /* can be -1 if error */
97 }
98
99 /* Returns opened fd to the loop device, <0 on error.
100 * *device is loop device to use, or if *device==NULL finds a loop device to
101 * mount it on and sets *device to a strdup of that loop device name.
102 */
set_loop(char ** device,const char * file,unsigned long long offset,unsigned long long sizelimit,unsigned flags)103 int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offset,
104 unsigned long long sizelimit, unsigned flags)
105 {
106 char dev[LOOP_NAMESIZE];
107 char *try;
108 bb_loop_info loopinfo;
109 struct stat statbuf;
110 int i, lfd, ffd, mode, rc;
111
112 /* Open the file. Barf if this doesn't work. */
113 mode = (flags & BB_LO_FLAGS_READ_ONLY) ? O_RDONLY : O_RDWR;
114 open_ffd:
115 ffd = open(file, mode);
116 if (ffd < 0) {
117 if (mode != O_RDONLY) {
118 mode = O_RDONLY;
119 goto open_ffd;
120 }
121 return -errno;
122 }
123
124 try = *device;
125 if (!try) {
126 get_free_loopN:
127 i = get_free_loop();
128 if (i == -1) {
129 close(ffd);
130 return -1; /* no free loop devices */
131 }
132 if (i >= 0) {
133 try = xasprintf(LOOP_FORMAT, i);
134 goto open_lfd;
135 }
136 /* i == -2: no /dev/loop-control. Do an old-style search for a free device */
137 try = dev;
138 }
139
140 /* Find a loop device */
141 /* 0xfffff is a max possible minor number in Linux circa 2010 */
142 for (i = 0; i <= 0xfffff; i++) {
143 sprintf(dev, LOOP_FORMAT, i);
144
145 IF_FEATURE_MOUNT_LOOP_CREATE(errno = 0;)
146 if (stat(try, &statbuf) != 0 || !S_ISBLK(statbuf.st_mode)) {
147 if (ENABLE_FEATURE_MOUNT_LOOP_CREATE
148 && errno == ENOENT
149 && try == dev
150 ) {
151 /* Node doesn't exist, try to create it */
152 if (mknod(dev, S_IFBLK|0644, makedev(7, i)) == 0)
153 goto open_lfd;
154 }
155 /* Ran out of block devices, return failure */
156 rc = -1;
157 break;
158 }
159 open_lfd:
160 /* Open the sucker and check its loopiness */
161 lfd = rc = open(try, mode);
162 if (lfd < 0 && errno == EROFS) {
163 mode = O_RDONLY;
164 lfd = rc = open(try, mode);
165 }
166 if (lfd < 0) {
167 if (errno == ENXIO) {
168 /* Happens if loop module is not loaded */
169 /* rc is -1; */
170 break;
171 }
172 goto try_next_loopN;
173 }
174
175 rc = ioctl(lfd, BB_LOOP_GET_STATUS, &loopinfo);
176
177 /* If device is free, try to claim it */
178 if (rc && errno == ENXIO) {
179 /* Associate free loop device with file */
180 if (ioctl(lfd, LOOP_SET_FD, ffd)) {
181 /* Ouch. Are we racing with other mount? */
182 if (!*device /* yes */
183 && try != dev /* tried a _kernel-offered_ loopN? */
184 ) {
185 free(try);
186 close(lfd);
187 //TODO: add "if (--failcount != 0) ..."?
188 goto get_free_loopN;
189 }
190 goto close_and_try_next_loopN;
191 }
192 memset(&loopinfo, 0, sizeof(loopinfo));
193 safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
194 loopinfo.lo_offset = offset;
195 loopinfo.lo_sizelimit = sizelimit;
196 /*
197 * Used by mount to set LO_FLAGS_AUTOCLEAR.
198 * LO_FLAGS_READ_ONLY is not set because RO is controlled by open type of the file.
199 * Note that closing LO_FLAGS_AUTOCLEARed lfd before mount
200 * is wrong (would free the loop device!)
201 */
202 loopinfo.lo_flags = (flags & ~BB_LO_FLAGS_READ_ONLY);
203 rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
204 if (rc != 0 && (loopinfo.lo_flags & BB_LO_FLAGS_AUTOCLEAR)) {
205 /* Old kernel, does not support LO_FLAGS_AUTOCLEAR? */
206 /* (this code path is not tested) */
207 loopinfo.lo_flags -= BB_LO_FLAGS_AUTOCLEAR;
208 rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
209 }
210 if (rc == 0) {
211 /* SUCCESS! */
212 if (try != dev) /* tried a kernel-offered free loopN? */
213 *device = try; /* malloced */
214 if (!*device) /* was looping in search of free "/dev/loopN"? */
215 *device = xstrdup(dev);
216 rc = lfd; /* return this */
217 break;
218 }
219 /* failure, undo LOOP_SET_FD */
220 ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary
221 }
222 /* else: device is not free (rc == 0) or error other than ENXIO */
223 close_and_try_next_loopN:
224 close(lfd);
225 try_next_loopN:
226 rc = -1;
227 if (*device) /* was looking for a particular "/dev/loopN"? */
228 break; /* yes, do not try other names */
229 } /* for() */
230
231 close(ffd);
232 return rc;
233 }
234