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/* vi: set sw=4 ts=4: */
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* Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
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* Copyright (C) 2005 by Rob Landley <rob@landley.net>
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* Licensed under GPLv2 or later, see file LICENSE in this source tree.
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#include <linux/version.h>
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#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
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/* For 2.6, use the cleaned up header to get the 64 bit API. */
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// Commented out per Rob's request
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//# include "fix_u32.h" /* some old toolchains need __u64 for linux/loop.h */
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# include <linux/loop.h>
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typedef struct loop_info64 bb_loop_info;
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# define BB_LOOP_SET_STATUS LOOP_SET_STATUS64
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# define BB_LOOP_GET_STATUS LOOP_GET_STATUS64
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/* For 2.4 and earlier, use the 32 bit API (and don't trust the headers) */
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/* Stuff stolen from linux/loop.h for 2.4 and earlier kernels */
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# include <linux/posix_types.h>
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# define LO_NAME_SIZE 64
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# define LO_KEY_SIZE 32
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# define LOOP_SET_FD 0x4C00
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# define LOOP_CLR_FD 0x4C01
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# define BB_LOOP_SET_STATUS 0x4C02
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# define BB_LOOP_GET_STATUS 0x4C03
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__kernel_dev_t lo_device;
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unsigned long lo_inode;
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__kernel_dev_t lo_rdevice;
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int lo_encrypt_key_size;
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char lo_file_name[LO_NAME_SIZE];
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unsigned char lo_encrypt_key[LO_KEY_SIZE];
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unsigned long lo_init[2];
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char* FAST_FUNC query_loop(const char *device)
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bb_loop_info loopinfo;
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fd = open(device, O_RDONLY);
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if (ioctl(fd, BB_LOOP_GET_STATUS, &loopinfo) == 0) {
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dev = xasprintf("%"OFF_FMT"u %s", (off_t) loopinfo.lo_offset,
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(char *)loopinfo.lo_file_name);
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int FAST_FUNC del_loop(const char *device)
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fd = open(device, O_RDONLY);
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rc = ioctl(fd, LOOP_CLR_FD, 0);
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/* Returns opened fd to the loop device, <0 on error.
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* *device is loop device to use, or if *device==NULL finds a loop device to
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* mount it on and sets *device to a strdup of that loop device name. This
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* search will re-use an existing loop device already bound to that
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* file/offset if it finds one.
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int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offset, unsigned flags)
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char dev[LOOP_NAMESIZE];
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bb_loop_info loopinfo;
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int i, dfd, ffd, mode, rc;
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/* Open the file. Barf if this doesn't work. */
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mode = (flags & BB_LO_FLAGS_READ_ONLY) ? O_RDONLY : O_RDWR;
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ffd = open(file, mode);
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if (mode != O_RDONLY) {
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//TODO: use LOOP_CTL_GET_FREE instead of trying every loopN in sequence? a-la:
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// fd = open("/dev/loop-control", O_RDWR);
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// loopN = ioctl(fd, LOOP_CTL_GET_FREE);
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/* Find a loop device. */
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try = *device ? *device : dev;
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/* 1048575 (0xfffff) is a max possible minor number in Linux circa 2010 */
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for (i = 0; rc && i < 1048576; i++) {
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sprintf(dev, LOOP_FORMAT, i);
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IF_FEATURE_MOUNT_LOOP_CREATE(errno = 0;)
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if (stat(try, &statbuf) != 0 || !S_ISBLK(statbuf.st_mode)) {
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if (ENABLE_FEATURE_MOUNT_LOOP_CREATE
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/* Node doesn't exist, try to create it. */
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if (mknod(dev, S_IFBLK|0644, makedev(7, i)) == 0)
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/* Ran out of block devices, return failure. */
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/* Open the sucker and check its loopiness. */
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dfd = open(try, mode);
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if (dfd < 0 && errno == EROFS) {
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dfd = open(try, mode);
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if (errno == ENXIO) {
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/* Happens if loop module is not loaded */
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rc = ioctl(dfd, BB_LOOP_GET_STATUS, &loopinfo);
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/* If device is free, claim it. */
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if (rc && errno == ENXIO) {
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/* Associate free loop device with file. */
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if (ioctl(dfd, LOOP_SET_FD, ffd) == 0) {
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memset(&loopinfo, 0, sizeof(loopinfo));
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safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
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loopinfo.lo_offset = offset;
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* Used by mount to set LO_FLAGS_AUTOCLEAR.
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* LO_FLAGS_READ_ONLY is not set because RO is controlled by open type of the file.
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* Note that closing LO_FLAGS_AUTOCLEARed dfd before mount
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* is wrong (would free the loop device!)
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loopinfo.lo_flags = (flags & ~BB_LO_FLAGS_READ_ONLY);
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rc = ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo);
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if (rc != 0 && (loopinfo.lo_flags & BB_LO_FLAGS_AUTOCLEAR)) {
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/* Old kernel, does not support LO_FLAGS_AUTOCLEAR? */
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/* (this code path is not tested) */
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loopinfo.lo_flags -= BB_LO_FLAGS_AUTOCLEAR;
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rc = ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo);
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ioctl(dfd, LOOP_CLR_FD, 0);
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*device = xstrdup(dev);