release/src/router/busybox/libbb/loop.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Utility routines.
   4  *
   5  * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
   6  * Copyright (C) 2005 by Rob Landley <rob@landley.net>
   7  *
   8  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   9  */
  10 #include "libbb.h"
  11 #include <linux/version.h>
  12
  13 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
  14
  15 /* For 2.6, use the cleaned up header to get the 64 bit API. */
  16 // Commented out per Rob's request
  17 //# include "fix_u32.h" /* some old toolchains need __u64 for linux/loop.h */
  18 # include <linux/loop.h>
  19 typedef struct loop_info64 bb_loop_info;
  20 # define BB_LOOP_SET_STATUS LOOP_SET_STATUS64
  21 # define BB_LOOP_GET_STATUS LOOP_GET_STATUS64
  22
  23 #else
  24
  25 /* For 2.4 and earlier, use the 32 bit API (and don't trust the headers) */
  26 /* Stuff stolen from linux/loop.h for 2.4 and earlier kernels */
  27 # include <linux/posix_types.h>
  28 # define LO_NAME_SIZE        64
  29 # define LO_KEY_SIZE         32
  30 # define LOOP_SET_FD         0x4C00
  31 # define LOOP_CLR_FD         0x4C01
  32 # define BB_LOOP_SET_STATUS  0x4C02
  33 # define BB_LOOP_GET_STATUS  0x4C03
  34 typedef struct {
  35         int                lo_number;
  36         __kernel_dev_t     lo_device;
  37         unsigned long      lo_inode;
  38         __kernel_dev_t     lo_rdevice;
  39         int                lo_offset;
  40         int                lo_encrypt_type;
  41         int                lo_encrypt_key_size;
  42         int                lo_flags;
  43         char               lo_file_name[LO_NAME_SIZE];
  44         unsigned char      lo_encrypt_key[LO_KEY_SIZE];
  45         unsigned long      lo_init[2];
  46         char               reserved[4];
  47 } bb_loop_info;
  48 #endif
  49
  50 char* FAST_FUNC query_loop(const char *device)
  51 {
  52         int fd;
  53         bb_loop_info loopinfo;
  54         char *dev = NULL;
  55
  56         fd = open(device, O_RDONLY);
  57         if (fd >= 0) {
  58                 if (ioctl(fd, BB_LOOP_GET_STATUS, &loopinfo) == 0) {
  59                         dev = xasprintf("%"OFF_FMT"u %s", (off_t) loopinfo.lo_offset,
  60                                         (char *)loopinfo.lo_file_name);
  61                 }
  62                 close(fd);
  63         }
  64
  65         return dev;
  66 }
  67
  68 int FAST_FUNC del_loop(const char *device)
  69 {
  70         int fd, rc;
  71
  72         fd = open(device, O_RDONLY);
  73         if (fd < 0)
  74                 return 1;
  75         rc = ioctl(fd, LOOP_CLR_FD, 0);
  76         close(fd);
  77
  78         return rc;
  79 }
  80
  81 /* Returns 0 if mounted RW, 1 if mounted read-only, <0 for error.
  82    *device is loop device to use, or if *device==NULL finds a loop device to
  83    mount it on and sets *device to a strdup of that loop device name.  This
  84    search will re-use an existing loop device already bound to that
  85    file/offset if it finds one.
  86  */
  87 int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offset, int ro)
  88 {
  89         char dev[LOOP_NAMESIZE];
  90         char *try;
  91         bb_loop_info loopinfo;
  92         struct stat statbuf;
  93         int i, dfd, ffd, mode, rc = -1;
  94
  95         /* Open the file.  Barf if this doesn't work.  */
  96         mode = ro ? O_RDONLY : O_RDWR;
  97  open_ffd:
  98         ffd = open(file, mode);
  99         if (ffd < 0) {
 100                 if (mode != O_RDONLY) {
 101                         mode = O_RDONLY;
 102                         goto open_ffd;
 103                 }
 104                 return -errno;
 105         }
 106
 107         /* Find a loop device.  */
 108         try = *device ? *device : dev;
 109         /* 1048575 (0xfffff) is a max possible minor number in Linux circa 2010 */
 110         for (i = 0; rc && i < 1048576; i++) {
 111                 sprintf(dev, LOOP_FORMAT, i);
 112
 113                 IF_FEATURE_MOUNT_LOOP_CREATE(errno = 0;)
 114                 if (stat(try, &statbuf) != 0 || !S_ISBLK(statbuf.st_mode)) {
 115                         if (ENABLE_FEATURE_MOUNT_LOOP_CREATE
 116                          && errno == ENOENT
 117                          && try == dev
 118                         ) {
 119                                 /* Node doesn't exist, try to create it.  */
 120                                 if (mknod(dev, S_IFBLK|0644, makedev(7, i)) == 0)
 121                                         goto try_to_open;
 122                         }
 123                         /* Ran out of block devices, return failure.  */
 124                         rc = -1;
 125                         break;
 126                 }
 127  try_to_open:
 128                 /* Open the sucker and check its loopiness.  */
 129                 dfd = open(try, mode);
 130                 if (dfd < 0 && errno == EROFS) {
 131                         mode = O_RDONLY;
 132                         dfd = open(try, mode);
 133                 }
 134                 if (dfd < 0) {
 135                         if (errno == ENXIO) {
 136                                 /* Happens if loop module is not loaded */
 137                                 rc = -1;
 138                                 break;
 139                         }
 140                         goto try_again;
 141                 }
 142
 143                 rc = ioctl(dfd, BB_LOOP_GET_STATUS, &loopinfo);
 144
 145                 /* If device is free, claim it.  */
 146                 if (rc && errno == ENXIO) {
 147                         memset(&loopinfo, 0, sizeof(loopinfo));
 148                         safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
 149                         loopinfo.lo_offset = offset;
 150                         /* Associate free loop device with file.  */
 151                         if (ioctl(dfd, LOOP_SET_FD, ffd) == 0) {
 152                                 if (ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo) == 0)
 153                                         rc = 0;
 154                                 else
 155                                         ioctl(dfd, LOOP_CLR_FD, 0);
 156                         }
 157
 158                 /* If this block device already set up right, re-use it.
 159                  * (Yes this is racy, but associating two loop devices with the same
 160                  * file isn't pretty either.  In general, mounting the same file twice
 161                  * without using losetup manually is problematic.)
 162                  */
 163                 } else
 164                 if (strcmp(file, (char *)loopinfo.lo_file_name) != 0
 165                  || offset != loopinfo.lo_offset
 166                 ) {
 167                         rc = -1;
 168                 }
 169                 close(dfd);
 170  try_again:
 171                 if (*device) break;
 172         }
 173         close(ffd);
 174         if (rc == 0) {
 175                 if (!*device)
 176                         *device = xstrdup(dev);
 177                 return (mode == O_RDONLY); /* 1:ro, 0:rw */
 178         }
 179         return rc;
 180 }