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: "[-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 46int losetup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; 47int 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 = getopt32(argv, "^" "do:far" "\0" "?2:d--ofar:a--ofr", &opt_o); 61 argv += optind; 62 63 /* LOOPDEV */ 64 if (!opt && argv[0] && !argv[1]) { 65 char *s; 66 67 s = query_loop(argv[0]); 68 if (!s) 69 bb_simple_perror_msg_and_die(argv[0]); 70 printf("%s: %s\n", argv[0], s); 71 if (ENABLE_FEATURE_CLEAN_UP) 72 free(s); 73 return EXIT_SUCCESS; 74 } 75 76 /* -d LOOPDEV */ 77 if (opt == OPT_d && argv[0]) { 78 if (del_loop(argv[0])) 79 bb_simple_perror_msg_and_die(argv[0]); 80 return EXIT_SUCCESS; 81 } 82 83 /* -a */ 84 if (opt == OPT_a) { 85 int n; 86 for (n = 0; n < MAX_LOOP_NUM; n++) { 87 char *s; 88 89 sprintf(dev, LOOP_FORMAT, n); 90 s = query_loop(dev); 91 if (s) { 92 printf("%s: %s\n", dev, s); 93 free(s); 94 } 95 } 96 return EXIT_SUCCESS; 97 } 98 99 /* contains -f */ 100 if (opt & OPT_f) { 101 char *s; 102 int n = 0; 103 104 do { 105 if (n > MAX_LOOP_NUM) 106 bb_error_msg_and_die("no free loop devices"); 107 sprintf(dev, LOOP_FORMAT, n++); 108 s = query_loop(dev); 109 free(s); 110 } while (s); 111 /* now: dev is next free "/dev/loopN" */ 112 if ((opt == OPT_f) && !argv[0]) { 113 puts(dev); 114 return EXIT_SUCCESS; 115 } 116 } 117 118 /* [-r] [-o OFS] {-f|LOOPDEV} FILE */ 119 if (argv[0] && ((opt & OPT_f) || argv[1])) { 120 unsigned long long offset = 0; 121 char *d = dev; 122 123 if (opt & OPT_o) 124 offset = xatoull(opt_o); 125 if (!(opt & OPT_f)) 126 d = *argv++; 127 128 if (argv[0]) { 129 if (set_loop(&d, argv[0], offset, (opt & OPT_r) ? BB_LO_FLAGS_READ_ONLY : 0) < 0) 130 bb_simple_perror_msg_and_die(argv[0]); 131 return EXIT_SUCCESS; 132 } 133 } 134 135 /* TODO: util-linux 2.28 shows this when run w/o params: 136 * NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE DIO 137 * /dev/loop0 0 0 1 0 /PATH/TO/FILE 0 138 * 139 * implemented by reading /sys: 140 * 141 * open("/sys/block", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3 142 * newfstatat(3, "loop0/loop/backing_file", {st_mode=S_IFREG|0444, st_size=4096, ...}, 0) = 0 143 * stat("/dev/loop0", {st_mode=S_IFBLK|0660, st_rdev=makedev(7, 0), ...}) = 0 144 * open("/sys/dev/block/7:0/loop/offset", O_RDONLY|O_CLOEXEC) = 5 145 * read(5, "0\n", 4096) = 2 146 * open("/sys/dev/block/7:0/loop/sizelimit", O_RDONLY|O_CLOEXEC) = 5 147 * read(5, "0\n", 4096) = 2 148 * open("/sys/dev/block/7:0/loop/offset", O_RDONLY|O_CLOEXEC) = 5 149 * read(5, "0\n", 4096) = 2 150 * open("/sys/dev/block/7:0/loop/autoclear", O_RDONLY|O_CLOEXEC) = 5 151 * read(5, "1\n", 4096) = 2 152 * open("/sys/dev/block/7:0/ro", O_RDONLY|O_CLOEXEC) = 5 153 * read(5, "0\n", 4096) = 2 154 * open("/sys/dev/block/7:0/loop/backing_file", O_RDONLY|O_CLOEXEC) = 5 155 * read(5, "/PATH/TO/FILE", 4096) = 37 156 * open("/sys/dev/block/7:0/loop/dio", O_RDONLY|O_CLOEXEC) = 5 157 * read(5, "0\n", 4096) = 2 158 */ 159 160 bb_show_usage(); /* does not return */ 161 /*return EXIT_FAILURE;*/ 162} 163