busybox/util-linux/losetup.c

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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 (5.5 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: "[-rP] [-o OFS] {-f|LOOPDEV} FILE: associate loop devices\n"
//usage: " losetup -c LOOPDEV: reread file size\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 -P Scan for partitions"
//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 optional partition scanning (creates /dev/loop1p1, /dev/loop1p2\n"
//usage: "etc. with -P) and with an optional offset (-o 12345). Encryption is\n"
//usage: "not yet supported. losetup -f will show the first 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_c = (1 << 0),
OPT_d = (1 << 1),
OPT_P = (1 << 2),
OPT_o = (1 << 3),
OPT_f = (1 << 4),
OPT_a = (1 << 5),
OPT_r = (1 << 6),
};
opt = getopt32(argv, "^" "cdPo:far" "\0" "?2:d--Pofar:a--Pofr", &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;
}
/* -c LOOPDEV */
if (opt == OPT_c && argv[0]) {
int fd = xopen(argv[0], O_RDONLY);
#ifndef LOOP_SET_CAPACITY
# define LOOP_SET_CAPACITY 0x4C07
#endif
xioctl(fd, LOOP_SET_CAPACITY, /*ignored:*/0);
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;
n = get_free_loop();
if (n == -1)
libbb: reduce the overhead of single parameter bb_error_msg() calls Back in 2007, commit 0c97c9d43707 ("'simple' error message functions by Loic Grenie") introduced bb_simple_perror_msg() to allow for a lower overhead call to bb_perror_msg() when only a string was being printed with no parameters. This saves space for some CPU architectures because it avoids the overhead of a call to a variadic function. However there has never been a simple version of bb_error_msg(), and since 2007 many new calls to bb_perror_msg() have been added that only take a single parameter and so could have been using bb_simple_perror_message(). This changeset introduces 'simple' versions of bb_info_msg(), bb_error_msg(), bb_error_msg_and_die(), bb_herror_msg() and bb_herror_msg_and_die(), and replaces all calls that only take a single parameter, or use something like ("%s", arg), with calls to the corresponding 'simple' version. Since it is likely that single parameter calls to the variadic functions may be accidentally reintroduced in the future a new debugging config option WARN_SIMPLE_MSG has been introduced. This uses some macro magic which will cause any such calls to generate a warning, but this is turned off by default to avoid use of the unpleasant macros in normal circumstances. This is a large changeset due to the number of calls that have been replaced. The only files that contain changes other than simple substitution of function calls are libbb.h, libbb/herror_msg.c, libbb/verror_msg.c and libbb/xfuncs_printf.c. In miscutils/devfsd.c, networking/udhcp/common.h and util-linux/mdev.c additonal macros have been added for logging so that single parameter and multiple parameter logging variants exist. The amount of space saved varies considerably by architecture, and was found to be as follows (for 'defconfig' using GCC 7.4): Arm: -92 bytes MIPS: -52 bytes PPC: -1836 bytes x86_64: -938 bytes Note that for the MIPS architecture only an exception had to be made disabling the 'simple' calls for 'udhcp' (in networking/udhcp/common.h) because it made these files larger on MIPS. Signed-off-by: James Byrne <james.byrne@origamienergy.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2019-07-02 15:05:03 +05:30
bb_simple_error_msg_and_die("no free loop devices");
if (n < 0) /* n == -2: no /dev/loop-control, use legacy method */
n = 0;
/* or: n >= 0: the number of next free loopdev, just verify it */
do {
if (n > MAX_LOOP_NUM)
libbb: reduce the overhead of single parameter bb_error_msg() calls Back in 2007, commit 0c97c9d43707 ("'simple' error message functions by Loic Grenie") introduced bb_simple_perror_msg() to allow for a lower overhead call to bb_perror_msg() when only a string was being printed with no parameters. This saves space for some CPU architectures because it avoids the overhead of a call to a variadic function. However there has never been a simple version of bb_error_msg(), and since 2007 many new calls to bb_perror_msg() have been added that only take a single parameter and so could have been using bb_simple_perror_message(). This changeset introduces 'simple' versions of bb_info_msg(), bb_error_msg(), bb_error_msg_and_die(), bb_herror_msg() and bb_herror_msg_and_die(), and replaces all calls that only take a single parameter, or use something like ("%s", arg), with calls to the corresponding 'simple' version. Since it is likely that single parameter calls to the variadic functions may be accidentally reintroduced in the future a new debugging config option WARN_SIMPLE_MSG has been introduced. This uses some macro magic which will cause any such calls to generate a warning, but this is turned off by default to avoid use of the unpleasant macros in normal circumstances. This is a large changeset due to the number of calls that have been replaced. The only files that contain changes other than simple substitution of function calls are libbb.h, libbb/herror_msg.c, libbb/verror_msg.c and libbb/xfuncs_printf.c. In miscutils/devfsd.c, networking/udhcp/common.h and util-linux/mdev.c additonal macros have been added for logging so that single parameter and multiple parameter logging variants exist. The amount of space saved varies considerably by architecture, and was found to be as follows (for 'defconfig' using GCC 7.4): Arm: -92 bytes MIPS: -52 bytes PPC: -1836 bytes x86_64: -938 bytes Note that for the MIPS architecture only an exception had to be made disabling the 'simple' calls for 'udhcp' (in networking/udhcp/common.h) because it made these files larger on MIPS. Signed-off-by: James Byrne <james.byrne@origamienergy.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2019-07-02 15:05:03 +05:30
bb_simple_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;
}
}
/* [-rP] [-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]) {
unsigned flags = (opt & OPT_r) ? BB_LO_FLAGS_READ_ONLY : 0;
if (opt & OPT_P) {
flags |= BB_LO_FLAGS_PARTSCAN;
}
if (set_loop(&d, argv[0], offset, flags) < 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;*/
}