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 //config:
  12 //config:config FEATURE_VOLUMEID_SQUASHFS
  13 //config:       bool "SquashFS filesystem"
  14 //config:       default y
  15 //config:       depends on VOLUMEID && FEATURE_BLKID_TYPE
  16 //config:       help
  17 //config:         Squashfs is a compressed read-only filesystem for Linux. Squashfs is
  18 //config:         intended for general read-only filesystem use and in constrained block
  19 //config:         device/memory systems (e.g. embedded systems) where low overhead is
  20 //config:         needed.
  21 //config:
  22
  23 #include "volume_id_internal.h"
  24
  25 struct squashfs_superblock {
  26         uint32_t        magic;
  27 /*
  28         uint32_t        dummy[6];
  29         uint16_t        major;
  30         uint16_t        minor;
  31 */
  32 } PACKED;
  33
  34 int FAST_FUNC volume_id_probe_squashfs(struct volume_id *id /*,uint64_t off*/)
  35 {
  36 #define off ((uint64_t)0)
  37         struct squashfs_superblock *sb;
  38
  39         dbg("SquashFS: probing at offset 0x%llx", (unsigned long long) off);
  40         sb = volume_id_get_buffer(id, off, 0x200);
  41         if (!sb)
  42                 return -1;
  43
  44         // Old SquashFS (pre 4.0) can be both big and little endian, so test for both.
  45         // Likewise, it is commonly used in firwmare with some non-standard signatures.
  46 #define pack(a,b,c,d) ( (uint32_t)((a * 256 + b) * 256 + c) * 256 + d )
  47 #define SIG1 pack('s','q','s','h')
  48 #define SIG2 pack('h','s','q','s')
  49 #define SIG3 pack('s','h','s','q')
  50 #define SIG4 pack('q','s','h','s')
  51         if (sb->magic == SIG1
  52          || sb->magic == SIG2
  53          || sb->magic == SIG3
  54          || sb->magic == SIG4
  55         ) {
  56                 IF_FEATURE_BLKID_TYPE(id->type = "squashfs";)
  57                 return 0;
  58         }
  59
  60         return -1;
  61 }