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 (5.5 kb)" 11//config: default y 12//config: help 13//config: losetup is used to associate or detach a loop device with a regular 14//config: file or block device, and to query the status of a loop device. This 15//config: version does not currently support enabling data encryption. 16 17//applet:IF_LOSETUP(APPLET_NOEXEC(losetup, losetup, BB_DIR_SBIN, BB_SUID_DROP, losetup)) 18 19//kbuild:lib-$(CONFIG_LOSETUP) += losetup.o 20 21//usage:#define losetup_trivial_usage 22//usage: "[-rP] [-o OFS] {-f|LOOPDEV} FILE: associate loop devices\n" 23//usage: " losetup -c LOOPDEV: reread file size\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 -P Scan for partitions" 30//usage: "\n -r Read-only" 31//usage: "\n -f Show/use next free loop device" 32//usage: 33//usage:#define losetup_notes_usage 34//usage: "One argument (losetup /dev/loop1) will display the current association\n" 35//usage: "(if any), or disassociate it (with -d). The display shows the offset\n" 36//usage: "and filename of the file the loop device is currently bound to.\n\n" 37//usage: "Two arguments (losetup /dev/loop1 file.img) create a new association,\n" 38//usage: "with optional partition scanning (creates /dev/loop1p1, /dev/loop1p2\n" 39//usage: "etc. with -P) and with an optional offset (-o 12345). Encryption is\n" 40//usage: "not yet supported. losetup -f will show the first free loop device\n\n" 41 42#include "libbb.h" 43 44/* 1048575 is a max possible minor number in Linux circa 2010 */ 45/* for now use something less extreme */ 46#define MAX_LOOP_NUM 1023 47 48int losetup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; 49int losetup_main(int argc UNUSED_PARAM, char **argv) 50{ 51 unsigned opt; 52 char *opt_o; 53 char dev[LOOP_NAMESIZE]; 54 enum { 55 OPT_c = (1 << 0), 56 OPT_d = (1 << 1), 57 OPT_P = (1 << 2), 58 OPT_o = (1 << 3), 59 OPT_f = (1 << 4), 60 OPT_a = (1 << 5), 61 OPT_r = (1 << 6), 62 }; 63 64 opt = getopt32(argv, "^" "cdPo:far" "\0" "?2:d--Pofar:a--Pofr", &opt_o); 65 argv += optind; 66 67 /* LOOPDEV */ 68 if (!opt && argv[0] && !argv[1]) { 69 char *s; 70 71 s = query_loop(argv[0]); 72 if (!s) 73 bb_simple_perror_msg_and_die(argv[0]); 74 printf("%s: %s\n", argv[0], s); 75 if (ENABLE_FEATURE_CLEAN_UP) 76 free(s); 77 return EXIT_SUCCESS; 78 } 79 80 /* -c LOOPDEV */ 81 if (opt == OPT_c && argv[0]) { 82 int fd = xopen(argv[0], O_RDONLY); 83#ifndef LOOP_SET_CAPACITY 84# define LOOP_SET_CAPACITY 0x4C07 85#endif 86 xioctl(fd, LOOP_SET_CAPACITY, /*ignored:*/0); 87 return EXIT_SUCCESS; 88 } 89 90 /* -d LOOPDEV */ 91 if (opt == OPT_d && argv[0]) { 92 if (del_loop(argv[0])) 93 bb_simple_perror_msg_and_die(argv[0]); 94 return EXIT_SUCCESS; 95 } 96 97 /* -a */ 98 if (opt == OPT_a) { 99 int n; 100 for (n = 0; n < MAX_LOOP_NUM; n++) { 101 char *s; 102 103 sprintf(dev, LOOP_FORMAT, n); 104 s = query_loop(dev); 105 if (s) { 106 printf("%s: %s\n", dev, s); 107 free(s); 108 } 109 } 110 return EXIT_SUCCESS; 111 } 112 113 /* contains -f */ 114 if (opt & OPT_f) { 115 char *s; 116 int n; 117 118 n = get_free_loop(); 119 if (n == -1) 120 bb_simple_error_msg_and_die("no free loop devices"); 121 if (n < 0) /* n == -2: no /dev/loop-control, use legacy method */ 122 n = 0; 123 /* or: n >= 0: the number of next free loopdev, just verify it */ 124 do { 125 if (n > MAX_LOOP_NUM) 126 bb_simple_error_msg_and_die("no free loop devices"); 127 sprintf(dev, LOOP_FORMAT, n++); 128 s = query_loop(dev); 129 free(s); 130 } while (s); 131 /* now: dev is next free "/dev/loopN" */ 132 if ((opt == OPT_f) && !argv[0]) { 133 puts(dev); 134 return EXIT_SUCCESS; 135 } 136 } 137 138 /* [-rP] [-o OFS] {-f|LOOPDEV} FILE */ 139 if (argv[0] && ((opt & OPT_f) || argv[1])) { 140 unsigned long long offset = 0; 141 char *d = dev; 142 143 if (opt & OPT_o) 144 offset = xatoull(opt_o); 145 if (!(opt & OPT_f)) 146 d = *argv++; 147 148 if (argv[0]) { 149 unsigned flags = (opt & OPT_r) ? BB_LO_FLAGS_READ_ONLY : 0; 150 if (opt & OPT_P) { 151 flags |= BB_LO_FLAGS_PARTSCAN; 152 } 153 if (set_loop(&d, argv[0], offset, 0, flags) < 0) 154 bb_simple_perror_msg_and_die(argv[0]); 155 return EXIT_SUCCESS; 156 } 157 } 158 159 /* TODO: util-linux 2.28 shows this when run w/o params: 160 * NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE DIO 161 * /dev/loop0 0 0 1 0 /PATH/TO/FILE 0 162 * 163 * implemented by reading /sys: 164 * 165 * open("/sys/block", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3 166 * newfstatat(3, "loop0/loop/backing_file", {st_mode=S_IFREG|0444, st_size=4096, ...}, 0) = 0 167 * stat("/dev/loop0", {st_mode=S_IFBLK|0660, st_rdev=makedev(7, 0), ...}) = 0 168 * open("/sys/dev/block/7:0/loop/offset", O_RDONLY|O_CLOEXEC) = 5 169 * read(5, "0\n", 4096) = 2 170 * open("/sys/dev/block/7:0/loop/sizelimit", O_RDONLY|O_CLOEXEC) = 5 171 * read(5, "0\n", 4096) = 2 172 * open("/sys/dev/block/7:0/loop/offset", O_RDONLY|O_CLOEXEC) = 5 173 * read(5, "0\n", 4096) = 2 174 * open("/sys/dev/block/7:0/loop/autoclear", O_RDONLY|O_CLOEXEC) = 5 175 * read(5, "1\n", 4096) = 2 176 * open("/sys/dev/block/7:0/ro", O_RDONLY|O_CLOEXEC) = 5 177 * read(5, "0\n", 4096) = 2 178 * open("/sys/dev/block/7:0/loop/backing_file", O_RDONLY|O_CLOEXEC) = 5 179 * read(5, "/PATH/TO/FILE", 4096) = 37 180 * open("/sys/dev/block/7:0/loop/dio", O_RDONLY|O_CLOEXEC) = 5 181 * read(5, "0\n", 4096) = 2 182 */ 183 184 bb_show_usage(); /* does not return */ 185 /*return EXIT_FAILURE;*/ 186} 187