LXR busybox/util-linux/volume

   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
  25struct squashfs_superblock {
  26        uint32_t        magic;
  27/*
  28        uint32_t        dummy[6];
  29        uint16_t        major;
  30        uint16_t        minor;
  31*/
  32} PACKED;
  33
  34int 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}
  62