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/* vi: set sw=4 ts=4: */
/*
* Utility routines.
*
* Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
* Copyright (C) 2005 by Rob Landley <rob@landley.net>
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
#include "libbb.h"
#include <linux/version.h>
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
/* For 2.6, use the cleaned up header to get the 64 bit API. */
// Commented out per Rob's request
//# include "fix_u32.h" /* some old toolchains need __u64 for linux/loop.h */
# include <linux/loop.h>
typedef struct loop_info64 bb_loop_info;
# define BB_LOOP_SET_STATUS LOOP_SET_STATUS64
# define BB_LOOP_GET_STATUS LOOP_GET_STATUS64
#else
/* For 2.4 and earlier, use the 32 bit API (and don't trust the headers) */
/* Stuff stolen from linux/loop.h for 2.4 and earlier kernels */
# include <linux/posix_types.h>
# define LO_NAME_SIZE 64
# define LO_KEY_SIZE 32
# define LOOP_SET_FD 0x4C00
# define LOOP_CLR_FD 0x4C01
# define BB_LOOP_SET_STATUS 0x4C02
# define BB_LOOP_GET_STATUS 0x4C03
typedef struct {
int lo_number;
__kernel_dev_t lo_device;
unsigned long lo_inode;
__kernel_dev_t lo_rdevice;
int lo_offset;
int lo_encrypt_type;
int lo_encrypt_key_size;
int lo_flags;
char lo_file_name[LO_NAME_SIZE];
unsigned char lo_encrypt_key[LO_KEY_SIZE];
unsigned long lo_init[2];
char reserved[4];
} bb_loop_info;
#endif
char* FAST_FUNC query_loop(const char *device)
{
int fd;
bb_loop_info loopinfo;
char *dev = NULL;
fd = open(device, O_RDONLY);
if (fd >= 0) {
if (ioctl(fd, BB_LOOP_GET_STATUS, &loopinfo) == 0) {
dev = xasprintf("%"OFF_FMT"u %s", (off_t) loopinfo.lo_offset,
(char *)loopinfo.lo_file_name);
}
close(fd);
}
return dev;
}
int FAST_FUNC del_loop(const char *device)
{
int fd, rc;
fd = open(device, O_RDONLY);
if (fd < 0)
return 1;
rc = ioctl(fd, LOOP_CLR_FD, 0);
close(fd);
return rc;
}
/* Obtain an unused loop device number */
int FAST_FUNC get_free_loop(void)
{
int fd;
int loopdevno;
fd = open("/dev/loop-control", O_RDWR | O_CLOEXEC);
if (fd == -1)
return fd - 1; /* -2: "no /dev/loop-control" */
#ifndef LOOP_CTL_GET_FREE
# define LOOP_CTL_GET_FREE 0x4C82
#endif
loopdevno = ioctl(fd, LOOP_CTL_GET_FREE);
close(fd);
return loopdevno; /* can be -1 if error */
}
/* Returns opened fd to the loop device, <0 on error.
* *device is loop device to use, or if *device==NULL finds a loop device to
* mount it on and sets *device to a strdup of that loop device name.
*/
int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offset,
unsigned long long sizelimit, unsigned flags)
{
char dev[LOOP_NAMESIZE];
char *try;
bb_loop_info loopinfo;
struct stat statbuf;
int i, lfd, ffd, mode, rc;
/* Open the file. Barf if this doesn't work. */
mode = (flags & BB_LO_FLAGS_READ_ONLY) ? O_RDONLY : O_RDWR;
open_ffd:
ffd = open(file, mode);
if (ffd < 0) {
if (mode != O_RDONLY) {
mode = O_RDONLY;
goto open_ffd;
}
return -errno;
}
try = *device;
if (!try) {
get_free_loopN:
i = get_free_loop();
if (i == -1) {
close(ffd);
return -1; /* no free loop devices */
}
if (i >= 0) {
try = xasprintf(LOOP_FORMAT, i);
goto open_lfd;
}
/* i == -2: no /dev/loop-control. Do an old-style search for a free device */
try = dev;
}
/* Find a loop device */
/* 0xfffff is a max possible minor number in Linux circa 2010 */
for (i = 0; i <= 0xfffff; i++) {
sprintf(dev, LOOP_FORMAT, i);
IF_FEATURE_MOUNT_LOOP_CREATE(errno = 0;)
if (stat(try, &statbuf) != 0 || !S_ISBLK(statbuf.st_mode)) {
if (ENABLE_FEATURE_MOUNT_LOOP_CREATE
&& errno == ENOENT
&& try == dev
) {
/* Node doesn't exist, try to create it */
if (mknod(dev, S_IFBLK|0644, makedev(7, i)) == 0)
goto open_lfd;
}
/* Ran out of block devices, return failure */
rc = -1;
break;
}
open_lfd:
/* Open the sucker and check its loopiness */
lfd = rc = open(try, mode);
if (lfd < 0 && errno == EROFS) {
mode = O_RDONLY;
lfd = rc = open(try, mode);
}
if (lfd < 0) {
if (errno == ENXIO) {
/* Happens if loop module is not loaded */
/* rc is -1; */
break;
}
goto try_next_loopN;
}
rc = ioctl(lfd, BB_LOOP_GET_STATUS, &loopinfo);
/* If device is free, try to claim it */
if (rc && errno == ENXIO) {
/* Associate free loop device with file */
if (ioctl(lfd, LOOP_SET_FD, ffd)) {
/* Ouch. Are we racing with other mount? */
if (!*device /* yes */
&& try != dev /* tried a _kernel-offered_ loopN? */
) {
free(try);
close(lfd);
//TODO: add "if (--failcount != 0) ..."?
goto get_free_loopN;
}
goto close_and_try_next_loopN;
}
memset(&loopinfo, 0, sizeof(loopinfo));
safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
loopinfo.lo_offset = offset;
loopinfo.lo_sizelimit = sizelimit;
/*
* Used by mount to set LO_FLAGS_AUTOCLEAR.
* LO_FLAGS_READ_ONLY is not set because RO is controlled by open type of the file.
* Note that closing LO_FLAGS_AUTOCLEARed lfd before mount
* is wrong (would free the loop device!)
*/
loopinfo.lo_flags = (flags & ~BB_LO_FLAGS_READ_ONLY);
rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
if (rc != 0 && (loopinfo.lo_flags & BB_LO_FLAGS_AUTOCLEAR)) {
/* Old kernel, does not support LO_FLAGS_AUTOCLEAR? */
/* (this code path is not tested) */
loopinfo.lo_flags -= BB_LO_FLAGS_AUTOCLEAR;
rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
}
if (rc == 0) {
/* SUCCESS! */
if (try != dev) /* tried a kernel-offered free loopN? */
*device = try; /* malloced */
if (!*device) /* was looping in search of free "/dev/loopN"? */
*device = xstrdup(dev);
rc = lfd; /* return this */
break;
}
/* failure, undo LOOP_SET_FD */
ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary
}
/* else: device is not free (rc == 0) or error other than ENXIO */
close_and_try_next_loopN:
close(lfd);
try_next_loopN:
rc = -1;
if (*device) /* was looking for a particular "/dev/loopN"? */
break; /* yes, do not try other names */
} /* for() */
close(ffd);
return rc;
}
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