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         ffd = open(file, mode);
  98         if (ffd < 0) {
  99                 if (mode != O_RDONLY) {
 100                         mode = O_RDONLY;
 101                         ffd = open(file, mode);
 102                 }
 103                 if (ffd < 0)
 104                         return -errno;
 105         }
 106
 107         /* Find a loop device.  */
 108         try = *device ? *device : dev;
 109         /* 1048575 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 = -ENOENT;
 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                         goto try_again;
 136
 137                 rc = ioctl(dfd, BB_LOOP_GET_STATUS, &loopinfo);
 138
 139                 /* If device is free, claim it.  */
 140                 if (rc && errno == ENXIO) {
 141                         memset(&loopinfo, 0, sizeof(loopinfo));
 142                         safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
 143                         loopinfo.lo_offset = offset;
 144                         /* Associate free loop device with file.  */
 145                         if (ioctl(dfd, LOOP_SET_FD, ffd) == 0) {
 146                                 if (ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo) == 0)
 147                                         rc = 0;
 148                                 else
 149                                         ioctl(dfd, LOOP_CLR_FD, 0);
 150                         }
 151
 152                 /* If this block device already set up right, re-use it.
 153                    (Yes this is racy, but associating two loop devices with the same
 154                    file isn't pretty either.  In general, mounting the same file twice
 155                    without using losetup manually is problematic.)
 156                  */
 157                 } else
 158                 if (strcmp(file, (char *)loopinfo.lo_file_name) != 0
 159                  || offset != loopinfo.lo_offset
 160                 ) {
 161                         rc = -1;
 162                 }
 163                 close(dfd);
 164  try_again:
 165                 if (*device) break;
 166         }
 167         close(ffd);
 168         if (rc == 0) {
 169                 if (!*device)
 170                         *device = xstrdup(dev);
 171                 return (mode == O_RDONLY); /* 1:ro, 0:rw */
 172         }
 173         return rc;
 174 }