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