busybox/libbb/loop.c

/* 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 the GPL v2 or later, see the file LICENSE in this tarball.
 */

#include "libbb.h"

/* For 2.6, use the cleaned up header to get the 64 bit API. */
#include <linux/version.h>
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
#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

/* For 2.4 and earlier, use the 32 bit API (and don't trust the headers) */
#else
/* 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 *query_loop(const char *device)
{
	int fd;
	bb_loop_info loopinfo;
	char *dev = 0;

	fd = open(device, O_RDONLY);
	if (fd < 0) return 0;
	if (!ioctl(fd, BB_LOOP_GET_STATUS, &loopinfo))
		dev = xasprintf("%ld %s", (long) loopinfo.lo_offset,
				(char *)loopinfo.lo_file_name);
	close(fd);

	return dev;
}


int 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;
}

/* Returns 0 if mounted RW, 1 if mounted read-only, <0 for 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.  This
   search will re-use an existing loop device already bound to that
   file/offset if it finds one.
 */
int set_loop(char **device, const char *file, unsigned long long offset)
{
	char dev[20], *try;
	bb_loop_info loopinfo;
	struct stat statbuf;
	int i, dfd, ffd, mode, rc=-1;

	/* Open the file.  Barf if this doesn't work.  */
	mode = O_RDWR;
	ffd = open(file, mode);
	if (ffd < 0) {
		mode = O_RDONLY;
		ffd = open(file, mode);
		if (ffd < 0)
			return -errno;
	}

	/* Find a loop device.  */
	try = *device ? : dev;
	for (i=0;rc;i++) {
		sprintf(dev, LOOP_FORMAT, i);

		/* Ran out of block devices, return failure.  */
		if (stat(try, &statbuf) || !S_ISBLK(statbuf.st_mode)) {
			rc=-ENOENT;
			break;
		}
		/* Open the sucker and check its loopiness.  */
		dfd = open(try, mode);
		if (dfd < 0 && errno == EROFS) {
			mode = O_RDONLY;
			dfd = open(try, mode);
		}
		if (dfd < 0) goto try_again;

		rc = ioctl(dfd, BB_LOOP_GET_STATUS, &loopinfo);

		/* If device free, claim it.  */
		if (rc && errno == ENXIO) {
			memset(&loopinfo, 0, sizeof(loopinfo));
			safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
			loopinfo.lo_offset = offset;
			/* Associate free loop device with file.  */
			if (!ioctl(dfd, LOOP_SET_FD, ffd)) {
				if (!ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo)) rc = 0;
				else ioctl(dfd, LOOP_CLR_FD, 0);
			}

		/* If this block device already set up right, re-use it.
		   (Yes this is racy, but associating two loop devices with the same
		   file isn't pretty either.  In general, mounting the same file twice
		   without using losetup manually is problematic.)
		 */
		} else if (strcmp(file,(char *)loopinfo.lo_file_name)
		|| offset != loopinfo.lo_offset) {
			rc = -1;
		}
		close(dfd);
try_again:
		if (*device) break;
	}
	close(ffd);
	if (!rc) {
		if (!*device) *device = xstrdup(dev);
		return mode==O_RDONLY ? 1 : 0;
	}
	return rc;
}
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 the GPL v2 or later, see the file LICENSE in this tarball.
9	*/
10
11	#include "libbb.h"
12
13	/* For 2.6, use the cleaned up header to get the 64 bit API. */
14	#include <linux/version.h>
15	#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
16	#include <linux/loop.h>
17	typedef struct loop_info64 bb_loop_info;
18	#define BB_LOOP_SET_STATUS LOOP_SET_STATUS64
19	#define BB_LOOP_GET_STATUS LOOP_GET_STATUS64
20
21	/* For 2.4 and earlier, use the 32 bit API (and don't trust the headers) */
22	#else
23	/* Stuff stolen from linux/loop.h for 2.4 and earlier kernels*/
24	#include <linux/posix_types.h>
25	#define LO_NAME_SIZE 64
26	#define LO_KEY_SIZE 32
27	#define LOOP_SET_FD 0x4C00
28	#define LOOP_CLR_FD 0x4C01
29	#define BB_LOOP_SET_STATUS 0x4C02
30	#define BB_LOOP_GET_STATUS 0x4C03
31	typedef struct {
32	int lo_number;
33	__kernel_dev_t lo_device;
34	unsigned long lo_inode;
35	__kernel_dev_t lo_rdevice;
36	int lo_offset;
37	int lo_encrypt_type;
38	int lo_encrypt_key_size;
39	int lo_flags;
40	char lo_file_name[LO_NAME_SIZE];
41	unsigned char lo_encrypt_key[LO_KEY_SIZE];
42	unsigned long lo_init[2];
43	char reserved[4];
44	} bb_loop_info;
45	#endif
46
47	char query_loop(const char device)
48	{
49	int fd;
50	bb_loop_info loopinfo;
51	char *dev = 0;
52
53	fd = open(device, O_RDONLY);
54	if (fd < 0) return 0;
55	if (!ioctl(fd, BB_LOOP_GET_STATUS, &loopinfo))
56	dev = xasprintf("%ld %s", (long) loopinfo.lo_offset,
57	(char *)loopinfo.lo_file_name);
58	close(fd);
59
60	return dev;
61	}
62
63
64	int del_loop(const char *device)
65	{
66	int fd, rc;
67
68	fd = open(device, O_RDONLY);
69	if (fd < 0) return 1;
70	rc = ioctl(fd, LOOP_CLR_FD, 0);
71	close(fd);
72
73	return rc;
74	}
75
76	/* Returns 0 if mounted RW, 1 if mounted read-only, <0 for error.
77	device is loop device to use, or if device==NULL finds a loop device to
78	mount it on and sets *device to a strdup of that loop device name. This
79	search will re-use an existing loop device already bound to that
80	file/offset if it finds one.
81	*/
82	int set_loop(char *device, const char file, unsigned long long offset)
83	{
84	char dev[20], *try;
85	bb_loop_info loopinfo;
86	struct stat statbuf;
87	int i, dfd, ffd, mode, rc=-1;
88
89	/* Open the file. Barf if this doesn't work. */
90	mode = O_RDWR;
91	ffd = open(file, mode);
92	if (ffd < 0) {
93	mode = O_RDONLY;
94	ffd = open(file, mode);
95	if (ffd < 0)
96	return -errno;
97	}
98
99	/* Find a loop device. */
100	try = *device ? : dev;
101	for (i=0;rc;i++) {
102	sprintf(dev, LOOP_FORMAT, i);
103
104	/* Ran out of block devices, return failure. */
105	if (stat(try, &statbuf) \|\| !S_ISBLK(statbuf.st_mode)) {
106	rc=-ENOENT;
107	break;
108	}
109	/* Open the sucker and check its loopiness. */
110	dfd = open(try, mode);
111	if (dfd < 0 && errno == EROFS) {
112	mode = O_RDONLY;
113	dfd = open(try, mode);
114	}
115	if (dfd < 0) goto try_again;
116
117	rc = ioctl(dfd, BB_LOOP_GET_STATUS, &loopinfo);
118
119	/* If device free, claim it. */
120	if (rc && errno == ENXIO) {
121	memset(&loopinfo, 0, sizeof(loopinfo));
122	safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
123	loopinfo.lo_offset = offset;
124	/* Associate free loop device with file. */
125	if (!ioctl(dfd, LOOP_SET_FD, ffd)) {
126	if (!ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo)) rc = 0;
127	else ioctl(dfd, LOOP_CLR_FD, 0);
128	}
129
130	/* If this block device already set up right, re-use it.
131	(Yes this is racy, but associating two loop devices with the same
132	file isn't pretty either. In general, mounting the same file twice
133	without using losetup manually is problematic.)
134	*/
135	} else if (strcmp(file,(char *)loopinfo.lo_file_name)
136	\|\| offset != loopinfo.lo_offset) {
137	rc = -1;
138	}
139	close(dfd);
140	try_again:
141	if (*device) break;
142	}
143	close(ffd);
144	if (!rc) {
145	if (!device) device = xstrdup(dev);
146	return mode==O_RDONLY ? 1 : 0;
147	}
148	return rc;
149	}