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/* vi: set sw=4 ts=4: */
/*
* Mini losetup implementation for busybox
*
* Copyright (C) 2002 Matt Kraai.
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
//config:config LOSETUP
//config: bool "losetup (5.4 kb)"
//config: default y
//config: select PLATFORM_LINUX
//config: help
//config: losetup is used to associate or detach a loop device with a regular
//config: file or block device, and to query the status of a loop device. This
//config: version does not currently support enabling data encryption.
//applet:IF_LOSETUP(APPLET_NOEXEC(losetup, losetup, BB_DIR_SBIN, BB_SUID_DROP, losetup))
//kbuild:lib-$(CONFIG_LOSETUP) += losetup.o
//usage:#define losetup_trivial_usage
//usage: "[-r] [-o OFS] {-f|LOOPDEV} FILE - associate loop devices\n"
//usage: " losetup -d LOOPDEV - disassociate\n"
//usage: " losetup -a - show status\n"
//usage: " losetup -f - show next free loop device"
//usage:#define losetup_full_usage "\n\n"
//usage: " -o OFS Start OFS bytes into FILE"
//usage: "\n -r Read-only"
//usage: "\n -f Show/use next free loop device"
//usage:
//usage:#define losetup_notes_usage
//usage: "One argument (losetup /dev/loop1) will display the current association\n"
//usage: "(if any), or disassociate it (with -d). The display shows the offset\n"
//usage: "and filename of the file the loop device is currently bound to.\n\n"
//usage: "Two arguments (losetup /dev/loop1 file.img) create a new association,\n"
//usage: "with an optional offset (-o 12345). Encryption is not yet supported.\n"
//usage: "losetup -f will show the first loop free loop device\n\n"
#include "libbb.h"
/* 1048575 is a max possible minor number in Linux circa 2010 */
/* for now use something less extreme */
#define MAX_LOOP_NUM 1023
int losetup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int losetup_main(int argc UNUSED_PARAM, char **argv)
{
unsigned opt;
char *opt_o;
char dev[LOOP_NAMESIZE];
enum {
OPT_d = (1 << 0),
OPT_o = (1 << 1),
OPT_f = (1 << 2),
OPT_a = (1 << 3),
OPT_r = (1 << 4), /* must be last */
};
opt = getopt32(argv, "^" "do:far" "\0" "?2:d--ofar:a--ofr", &opt_o);
argv += optind;
/* LOOPDEV */
if (!opt && argv[0] && !argv[1]) {
char *s;
s = query_loop(argv[0]);
if (!s)
bb_simple_perror_msg_and_die(argv[0]);
printf("%s: %s\n", argv[0], s);
if (ENABLE_FEATURE_CLEAN_UP)
free(s);
return EXIT_SUCCESS;
}
/* -d LOOPDEV */
if (opt == OPT_d && argv[0]) {
if (del_loop(argv[0]))
bb_simple_perror_msg_and_die(argv[0]);
return EXIT_SUCCESS;
}
/* -a */
if (opt == OPT_a) {
int n;
for (n = 0; n < MAX_LOOP_NUM; n++) {
char *s;
sprintf(dev, LOOP_FORMAT, n);
s = query_loop(dev);
if (s) {
printf("%s: %s\n", dev, s);
free(s);
}
}
return EXIT_SUCCESS;
}
/* contains -f */
if (opt & OPT_f) {
char *s;
int n = 0;
do {
if (n > MAX_LOOP_NUM)
bb_error_msg_and_die("no free loop devices");
sprintf(dev, LOOP_FORMAT, n++);
s = query_loop(dev);
free(s);
} while (s);
/* now: dev is next free "/dev/loopN" */
if ((opt == OPT_f) && !argv[0]) {
puts(dev);
return EXIT_SUCCESS;
}
}
/* [-r] [-o OFS] {-f|LOOPDEV} FILE */
if (argv[0] && ((opt & OPT_f) || argv[1])) {
unsigned long long offset = 0;
char *d = dev;
if (opt & OPT_o)
offset = xatoull(opt_o);
if (!(opt & OPT_f))
d = *argv++;
if (argv[0]) {
if (set_loop(&d, argv[0], offset, (opt & OPT_r) ? BB_LO_FLAGS_READ_ONLY : 0) < 0)
bb_simple_perror_msg_and_die(argv[0]);
return EXIT_SUCCESS;
}
}
/* TODO: util-linux 2.28 shows this when run w/o params:
* NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE DIO
* /dev/loop0 0 0 1 0 /PATH/TO/FILE 0
*
* implemented by reading /sys:
*
* open("/sys/block", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
* newfstatat(3, "loop0/loop/backing_file", {st_mode=S_IFREG|0444, st_size=4096, ...}, 0) = 0
* stat("/dev/loop0", {st_mode=S_IFBLK|0660, st_rdev=makedev(7, 0), ...}) = 0
* open("/sys/dev/block/7:0/loop/offset", O_RDONLY|O_CLOEXEC) = 5
* read(5, "0\n", 4096) = 2
* open("/sys/dev/block/7:0/loop/sizelimit", O_RDONLY|O_CLOEXEC) = 5
* read(5, "0\n", 4096) = 2
* open("/sys/dev/block/7:0/loop/offset", O_RDONLY|O_CLOEXEC) = 5
* read(5, "0\n", 4096) = 2
* open("/sys/dev/block/7:0/loop/autoclear", O_RDONLY|O_CLOEXEC) = 5
* read(5, "1\n", 4096) = 2
* open("/sys/dev/block/7:0/ro", O_RDONLY|O_CLOEXEC) = 5
* read(5, "0\n", 4096) = 2
* open("/sys/dev/block/7:0/loop/backing_file", O_RDONLY|O_CLOEXEC) = 5
* read(5, "/PATH/TO/FILE", 4096) = 37
* open("/sys/dev/block/7:0/loop/dio", O_RDONLY|O_CLOEXEC) = 5
* read(5, "0\n", 4096) = 2
*/
bb_show_usage(); /* does not return */
/*return EXIT_FAILURE;*/
}
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