path: root/util-linux/losetup.c (plain)
blob: 4424d9cbba1bedf59891d59b0f5752f90a9e2895

1	/* vi: set sw=4 ts=4: */
2	/*
3	* Mini losetup implementation for busybox
4	*
5	* Copyright (C) 2002 Matt Kraai.
6	*
7	* Licensed under GPLv2 or later, see file LICENSE in this source tree.
8	*/
9	//config:config LOSETUP
10	//config: bool "losetup"
11	//config: default y
12	//config: select PLATFORM_LINUX
13	//config: help
14	//config: losetup is used to associate or detach a loop device with a regular
15	//config: file or block device, and to query the status of a loop device. This
16	//config: version does not currently support enabling data encryption.
17
18	//kbuild:lib-$(CONFIG_LOSETUP) += losetup.o
19
20	//applet:IF_LOSETUP(APPLET(losetup, BB_DIR_SBIN, BB_SUID_DROP))
21
22	//usage:#define losetup_trivial_usage
23	//usage: "[-r] [-o OFS] {-f|LOOPDEV} FILE - associate loop devices\n"
24	//usage: " losetup -d LOOPDEV - disassociate\n"
25	//usage: " losetup -a - show status\n"
26	//usage: " losetup -f - show next free loop device"
27	//usage:#define losetup_full_usage "\n\n"
28	//usage: " -o OFS Start OFS bytes into FILE"
29	//usage: "\n -r Read-only"
30	//usage: "\n -f Show/use next free loop device"
31	//usage:
32	//usage:#define losetup_notes_usage
33	//usage: "One argument (losetup /dev/loop1) will display the current association\n"
34	//usage: "(if any), or disassociate it (with -d). The display shows the offset\n"
35	//usage: "and filename of the file the loop device is currently bound to.\n\n"
36	//usage: "Two arguments (losetup /dev/loop1 file.img) create a new association,\n"
37	//usage: "with an optional offset (-o 12345). Encryption is not yet supported.\n"
38	//usage: "losetup -f will show the first loop free loop device\n\n"
39
40	#include "libbb.h"
41
42	/* 1048575 is a max possible minor number in Linux circa 2010 */
43	/* for now use something less extreme */
44	#define MAX_LOOP_NUM 1023
45
46	int losetup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
47	int losetup_main(int argc UNUSED_PARAM, char **argv)
48	{
49	unsigned opt;
50	char *opt_o;
51	char dev[LOOP_NAMESIZE];
52	enum {
53	OPT_d = (1 << 0),
54	OPT_o = (1 << 1),
55	OPT_f = (1 << 2),
56	OPT_a = (1 << 3),
57	OPT_r = (1 << 4), /* must be last */
58	};
59
60	opt_complementary = "?2:d--ofar:a--ofr";
61	opt = getopt32(argv, "do:far", &opt_o);
62	argv += optind;
63
64	/* LOOPDEV */
65	if (!opt && argv[0] && !argv[1]) {
66	char *s;
67
68	s = query_loop(argv[0]);
69	if (!s)
70	bb_simple_perror_msg_and_die(argv[0]);
71	printf("%s: %s\n", argv[0], s);
72	if (ENABLE_FEATURE_CLEAN_UP)
73	free(s);
74	return EXIT_SUCCESS;
75	}
76
77	/* -d LOOPDEV */
78	if (opt == OPT_d && argv[0]) {
79	if (del_loop(argv[0]))
80	bb_simple_perror_msg_and_die(argv[0]);
81	return EXIT_SUCCESS;
82	}
83
84	/* -a */
85	if (opt == OPT_a) {
86	int n;
87	for (n = 0; n < MAX_LOOP_NUM; n++) {
88	char *s;
89
90	sprintf(dev, LOOP_FORMAT, n);
91	s = query_loop(dev);
92	if (s) {
93	printf("%s: %s\n", dev, s);
94	free(s);
95	}
96	}
97	return EXIT_SUCCESS;
98	}
99
100	/* contains -f */
101	if (opt & OPT_f) {
102	char *s;
103	int n = 0;
104
105	do {
106	if (n > MAX_LOOP_NUM)
107	bb_error_msg_and_die("no free loop devices");
108	sprintf(dev, LOOP_FORMAT, n++);
109	s = query_loop(dev);
110	free(s);
111	} while (s);
112	/* now: dev is next free "/dev/loopN" */
113	if ((opt == OPT_f) && !argv[0]) {
114	puts(dev);
115	return EXIT_SUCCESS;
116	}
117	}
118
119	/* [-r] [-o OFS] {-f|LOOPDEV} FILE */
120	if (argv[0] && ((opt & OPT_f) || argv[1])) {
121	unsigned long long offset = 0;
122	char *d = dev;
123
124	if (opt & OPT_o)
125	offset = xatoull(opt_o);
126	if (!(opt & OPT_f))
127	d = *argv++;
128
129	if (argv[0]) {
130	if (set_loop(&d, argv[0], offset, (opt & OPT_r)) < 0)
131	bb_simple_perror_msg_and_die(argv[0]);
132	return EXIT_SUCCESS;
133	}
134	}
135
136	bb_show_usage(); /* does not return */
137	/*return EXIT_FAILURE;*/
138	}
139