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: 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//applet:IF_LOSETUP(APPLET_NOEXEC(losetup, losetup, BB_DIR_SBIN, BB_SUID_DROP, losetup)) 19 20//kbuild:lib-$(CONFIG_LOSETUP) += losetup.o 21 22//usage:#define losetup_trivial_usage 23//usage: "[-rP] [-o OFS] {-f|LOOPDEV} FILE: associate loop devices\n" 24//usage: " losetup -c LOOPDEV: reread file size\n" 25//usage: " losetup -d LOOPDEV: disassociate\n" 26//usage: " losetup -a: show status\n" 27//usage: " losetup -f: show next free loop device" 28//usage:#define losetup_full_usage "\n\n" 29//usage: " -o OFS Start OFS bytes into FILE" 30//usage: "\n -P Scan for partitions" 31//usage: "\n -r Read-only" 32//usage: "\n -f Show/use next free loop device" 33//usage: 34//usage:#define losetup_notes_usage 35//usage: "One argument (losetup /dev/loop1) will display the current association\n" 36//usage: "(if any), or disassociate it (with -d). The display shows the offset\n" 37//usage: "and filename of the file the loop device is currently bound to.\n\n" 38//usage: "Two arguments (losetup /dev/loop1 file.img) create a new association,\n" 39//usage: "with optional partition scanning (creates /dev/loop1p1, /dev/loop1p2\n" 40//usage: "etc. with -P) and with an optional offset (-o 12345). Encryption is\n" 41//usage: "not yet supported. losetup -f will show the first free loop device\n\n" 42 43#include "libbb.h" 44 45/* 1048575 is a max possible minor number in Linux circa 2010 */ 46/* for now use something less extreme */ 47#define MAX_LOOP_NUM 1023 48 49int losetup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; 50int losetup_main(int argc UNUSED_PARAM, char **argv) 51{ 52 unsigned opt; 53 char *opt_o; 54 char dev[LOOP_NAMESIZE]; 55 enum { 56 OPT_c = (1 << 0), 57 OPT_d = (1 << 1), 58 OPT_P = (1 << 2), 59 OPT_o = (1 << 3), 60 OPT_f = (1 << 4), 61 OPT_a = (1 << 5), 62 OPT_r = (1 << 6), 63 }; 64 65 opt = getopt32(argv, "^" "cdPo:far" "\0" "?2:d--Pofar:a--Pofr", &opt_o); 66 argv += optind; 67 68 /* LOOPDEV */ 69 if (!opt && argv[0] && !argv[1]) { 70 char *s; 71 72 s = query_loop(argv[0]); 73 if (!s) 74 bb_simple_perror_msg_and_die(argv[0]); 75 printf("%s: %s\n", argv[0], s); 76 if (ENABLE_FEATURE_CLEAN_UP) 77 free(s); 78 return EXIT_SUCCESS; 79 } 80 81 /* -c LOOPDEV */ 82 if (opt == OPT_c && argv[0]) { 83 int fd = xopen(argv[0], O_RDONLY); 84#ifndef LOOP_SET_CAPACITY 85# define LOOP_SET_CAPACITY 0x4C07 86#endif 87 xioctl(fd, LOOP_SET_CAPACITY, /*ignored:*/0); 88 return EXIT_SUCCESS; 89 } 90 91 /* -d LOOPDEV */ 92 if (opt == OPT_d && argv[0]) { 93 if (del_loop(argv[0])) 94 bb_simple_perror_msg_and_die(argv[0]); 95 return EXIT_SUCCESS; 96 } 97 98 /* -a */ 99 if (opt == OPT_a) { 100 int n; 101 for (n = 0; n < MAX_LOOP_NUM; n++) { 102 char *s; 103 104 sprintf(dev, LOOP_FORMAT, n); 105 s = query_loop(dev); 106 if (s) { 107 printf("%s: %s\n", dev, s); 108 free(s); 109 } 110 } 111 return EXIT_SUCCESS; 112 } 113 114 /* contains -f */ 115 if (opt & OPT_f) { 116 char *s; 117 int n; 118 119 n = get_free_loop(); 120 if (n == -1) 121 bb_error_msg_and_die("no free loop devices"); 122 if (n < 0) /* n == -2: no /dev/loop-control, use legacy method */ 123 n = 0; 124 /* or: n >= 0: the number of next free loopdev, just verify it */ 125 do { 126 if (n > MAX_LOOP_NUM) 127 bb_error_msg_and_die("no free loop devices"); 128 sprintf(dev, LOOP_FORMAT, n++); 129 s = query_loop(dev); 130 free(s); 131 } while (s); 132 /* now: dev is next free "/dev/loopN" */ 133 if ((opt == OPT_f) && !argv[0]) { 134 puts(dev); 135 return EXIT_SUCCESS; 136 } 137 } 138 139 /* [-rP] [-o OFS] {-f|LOOPDEV} FILE */ 140 if (argv[0] && ((opt & OPT_f) || argv[1])) { 141 unsigned long long offset = 0; 142 char *d = dev; 143 144 if (opt & OPT_o) 145 offset = xatoull(opt_o); 146 if (!(opt & OPT_f)) 147 d = *argv++; 148 149 if (argv[0]) { 150 unsigned flags = (opt & OPT_r) ? BB_LO_FLAGS_READ_ONLY : 0; 151 if (opt & OPT_P) { 152 flags |= BB_LO_FLAGS_PARTSCAN; 153 } 154 if (set_loop(&d, argv[0], offset, flags) < 0) 155 bb_simple_perror_msg_and_die(argv[0]); 156 return EXIT_SUCCESS; 157 } 158 } 159 160 /* TODO: util-linux 2.28 shows this when run w/o params: 161 * NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE DIO 162 * /dev/loop0 0 0 1 0 /PATH/TO/FILE 0 163 * 164 * implemented by reading /sys: 165 * 166 * open("/sys/block", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3 167 * newfstatat(3, "loop0/loop/backing_file", {st_mode=S_IFREG|0444, st_size=4096, ...}, 0) = 0 168 * stat("/dev/loop0", {st_mode=S_IFBLK|0660, st_rdev=makedev(7, 0), ...}) = 0 169 * open("/sys/dev/block/7:0/loop/offset", O_RDONLY|O_CLOEXEC) = 5 170 * read(5, "0\n", 4096) = 2 171 * open("/sys/dev/block/7:0/loop/sizelimit", O_RDONLY|O_CLOEXEC) = 5 172 * read(5, "0\n", 4096) = 2 173 * open("/sys/dev/block/7:0/loop/offset", O_RDONLY|O_CLOEXEC) = 5 174 * read(5, "0\n", 4096) = 2 175 * open("/sys/dev/block/7:0/loop/autoclear", O_RDONLY|O_CLOEXEC) = 5 176 * read(5, "1\n", 4096) = 2 177 * open("/sys/dev/block/7:0/ro", O_RDONLY|O_CLOEXEC) = 5 178 * read(5, "0\n", 4096) = 2 179 * open("/sys/dev/block/7:0/loop/backing_file", O_RDONLY|O_CLOEXEC) = 5 180 * read(5, "/PATH/TO/FILE", 4096) = 37 181 * open("/sys/dev/block/7:0/loop/dio", O_RDONLY|O_CLOEXEC) = 5 182 * read(5, "0\n", 4096) = 2 183 */ 184 185 bb_show_usage(); /* does not return */ 186 /*return EXIT_FAILURE;*/ 187} 188