release/src/router/busybox/util-linux/volume_id/squashfs.c

   1 /*
   2  * volume_id - reads filesystem label and uuid
   3  *
   4  * Copyright (C) 2012 S-G Bergh <sgb@systemasis.org>
   5  *
   6  * Licensed under GPLv2, see file LICENSE in this source tree.
   7  */
   8
   9 //kbuild:lib-$(CONFIG_FEATURE_VOLUMEID_SQUASHFS) += squashfs.o
  10
  11 #include "volume_id_internal.h"
  12
  13 struct squashfs_superblock {
  14         uint32_t        magic;
  15 /*
  16         uint32_t        dummy[6];
  17         uint16_t        major;
  18         uint16_t        minor;
  19 */
  20 } PACKED;
  21
  22 int FAST_FUNC volume_id_probe_squashfs(struct volume_id *id /*,uint64_t off*/)
  23 {
  24 #define off ((uint64_t)0)
  25         struct squashfs_superblock *sb;
  26
  27         dbg("SquashFS: probing at offset 0x%llx", (unsigned long long) off);
  28         sb = volume_id_get_buffer(id, off, 0x200);
  29         if (!sb)
  30                 return -1;
  31
  32         // Old SquashFS (pre 4.0) can be both big and little endian, so test for both.
  33         // Likewise, it is commonly used in firwmare with some non-standard signatures.
  34 #define pack(a,b,c,d) ( (uint32_t)((a * 256 + b) * 256 + c) * 256 + d )
  35 #define SIG1 pack('s','q','s','h')
  36 #define SIG2 pack('h','s','q','s')
  37 #define SIG3 pack('s','h','s','q')
  38 #define SIG4 pack('q','s','h','s')
  39         if (sb->magic == SIG1
  40          || sb->magic == SIG2
  41          || sb->magic == SIG3
  42          || sb->magic == SIG4
  43         ) {
  44                 IF_FEATURE_BLKID_TYPE(id->type = "squashfs";)
  45                 return 0;
  46         }
  47
  48         return -1;
  49 }