| 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * Utility routines.
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| 4 | *
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| 5 | * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
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| 6 | * Copyright (C) 2005 by Rob Landley <rob@landley.net>
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| 7 | *
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| 8 | * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
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| 9 | */
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| 10 |
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| 11 | #include "libbb.h"
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| 12 |
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| 13 | /* For 2.6, use the cleaned up header to get the 64 bit API. */
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| 14 | #include <linux/version.h>
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| 15 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
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| 16 | #include <linux/loop.h>
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| 17 | typedef struct loop_info64 bb_loop_info;
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| 18 | #define BB_LOOP_SET_STATUS LOOP_SET_STATUS64
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| 19 | #define BB_LOOP_GET_STATUS LOOP_GET_STATUS64
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| 20 |
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| 21 | /* For 2.4 and earlier, use the 32 bit API (and don't trust the headers) */
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| 22 | #else
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| 23 | /* Stuff stolen from linux/loop.h for 2.4 and earlier kernels*/
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| 24 | #include <linux/posix_types.h>
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| 25 | #define LO_NAME_SIZE 64
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| 26 | #define LO_KEY_SIZE 32
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| 27 | #define LOOP_SET_FD 0x4C00
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| 28 | #define LOOP_CLR_FD 0x4C01
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| 29 | #define BB_LOOP_SET_STATUS 0x4C02
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| 30 | #define BB_LOOP_GET_STATUS 0x4C03
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| 31 | typedef struct {
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| 32 | int lo_number;
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| 33 | __kernel_dev_t lo_device;
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| 34 | unsigned long lo_inode;
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| 35 | __kernel_dev_t lo_rdevice;
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| 36 | int lo_offset;
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| 37 | int lo_encrypt_type;
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| 38 | int lo_encrypt_key_size;
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| 39 | int lo_flags;
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| 40 | char lo_file_name[LO_NAME_SIZE];
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| 41 | unsigned char lo_encrypt_key[LO_KEY_SIZE];
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| 42 | unsigned long lo_init[2];
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| 43 | char reserved[4];
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| 44 | } bb_loop_info;
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| 45 | #endif
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| 46 |
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| 47 | char *query_loop(const char *device)
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| 48 | {
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| 49 | int fd;
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| 50 | bb_loop_info loopinfo;
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| 51 | char *dev = 0;
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| 52 |
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| 53 | fd = open(device, O_RDONLY);
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| 54 | if (fd < 0) return 0;
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| 55 | if (!ioctl(fd, BB_LOOP_GET_STATUS, &loopinfo))
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| 56 | dev = xasprintf("%ld %s", (long) loopinfo.lo_offset,
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| 57 | (char *)loopinfo.lo_file_name);
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| 58 | close(fd);
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| 59 |
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| 60 | return dev;
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| 61 | }
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| 62 |
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| 63 |
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| 64 | int del_loop(const char *device)
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| 65 | {
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| 66 | int fd, rc;
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| 67 |
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| 68 | fd = open(device, O_RDONLY);
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| 69 | if (fd < 0) return 1;
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| 70 | rc = ioctl(fd, LOOP_CLR_FD, 0);
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| 71 | close(fd);
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| 72 |
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| 73 | return rc;
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| 74 | }
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| 75 |
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| 76 | /* Returns 0 if mounted RW, 1 if mounted read-only, <0 for error.
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| 77 | *device is loop device to use, or if *device==NULL finds a loop device to
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| 78 | mount it on and sets *device to a strdup of that loop device name. This
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| 79 | search will re-use an existing loop device already bound to that
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| 80 | file/offset if it finds one.
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| 81 | */
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| 82 | int set_loop(char **device, const char *file, unsigned long long offset)
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| 83 | {
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| 84 | char dev[LOOP_NAMESIZE];
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| 85 | char *try;
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| 86 | bb_loop_info loopinfo;
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| 87 | struct stat statbuf;
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| 88 | int i, dfd, ffd, mode, rc = -1;
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| 89 |
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| 90 | /* Open the file. Barf if this doesn't work. */
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| 91 | mode = O_RDWR;
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| 92 | ffd = open(file, mode);
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| 93 | if (ffd < 0) {
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| 94 | mode = O_RDONLY;
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| 95 | ffd = open(file, mode);
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| 96 | if (ffd < 0)
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| 97 | return -errno;
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| 98 | }
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| 99 |
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| 100 | /* Find a loop device. */
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| 101 | try = *device ? : dev;
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| 102 | for (i = 0; rc; i++) {
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| 103 | sprintf(dev, LOOP_FORMAT, i);
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| 104 |
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| 105 | /* Ran out of block devices, return failure. */
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| 106 | if (stat(try, &statbuf) || !S_ISBLK(statbuf.st_mode)) {
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| 107 | rc = -ENOENT;
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| 108 | break;
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| 109 | }
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| 110 | /* Open the sucker and check its loopiness. */
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| 111 | dfd = open(try, mode);
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| 112 | if (dfd < 0 && errno == EROFS) {
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| 113 | mode = O_RDONLY;
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| 114 | dfd = open(try, mode);
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| 115 | }
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| 116 | if (dfd < 0)
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| 117 | goto try_again;
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| 118 |
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| 119 | rc = ioctl(dfd, BB_LOOP_GET_STATUS, &loopinfo);
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| 120 |
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| 121 | /* If device is free, claim it. */
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| 122 | if (rc && errno == ENXIO) {
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| 123 | memset(&loopinfo, 0, sizeof(loopinfo));
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| 124 | safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
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| 125 | loopinfo.lo_offset = offset;
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| 126 | /* Associate free loop device with file. */
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| 127 | if (!ioctl(dfd, LOOP_SET_FD, ffd)) {
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| 128 | if (!ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo))
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| 129 | rc = 0;
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| 130 | else
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| 131 | ioctl(dfd, LOOP_CLR_FD, 0);
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| 132 | }
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| 133 |
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| 134 | /* If this block device already set up right, re-use it.
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| 135 | (Yes this is racy, but associating two loop devices with the same
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| 136 | file isn't pretty either. In general, mounting the same file twice
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| 137 | without using losetup manually is problematic.)
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| 138 | */
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| 139 | } else if (strcmp(file, (char *)loopinfo.lo_file_name) != 0
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| 140 | || offset != loopinfo.lo_offset) {
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| 141 | rc = -1;
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| 142 | }
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| 143 | close(dfd);
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| 144 | try_again:
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| 145 | if (*device) break;
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| 146 | }
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| 147 | close(ffd);
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| 148 | if (!rc) {
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| 149 | if (!*device)
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| 150 | *device = xstrdup(dev);
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| 151 | return (mode == O_RDONLY); /* 1:ro, 0:rw */
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| 152 | }
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| 153 | return rc;
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| 154 | }
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