fs/squashfs/decompressor.c

   1 /*
   2  * Squashfs - a compressed read only filesystem for Linux
   3  *
   4  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
   5  * Phillip Lougher <phillip@squashfs.org.uk>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version 2,
  10  * or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  20  *
  21  * decompressor.c
  22  */
  23
  24 #include <linux/types.h>
  25 #include <linux/mutex.h>
  26 #include <linux/slab.h>
  27 #include <linux/buffer_head.h>
  28
  29 #include "squashfs_fs.h"
  30 #include "squashfs_fs_sb.h"
  31 #include "decompressor.h"
  32 #include "squashfs.h"
  33
  34 /*
  35  * This file (and decompressor.h) implements a decompressor framework for
  36  * Squashfs, allowing multiple decompressors to be easily supported
  37  */
  38
  39 static const struct squashfs_decompressor squashfs_lzma_unsupported_comp_ops = {
  40         NULL, NULL, NULL, NULL, LZMA_COMPRESSION, "lzma", 0
  41 };
  42
  43 #ifndef CONFIG_SQUASHFS_LZO
  44 static const struct squashfs_decompressor squashfs_lzo_comp_ops = {
  45         NULL, NULL, NULL, NULL, LZO_COMPRESSION, "lzo", 0
  46 };
  47 #endif
  48
  49 #ifndef CONFIG_SQUASHFS_XZ
  50 static const struct squashfs_decompressor squashfs_xz_comp_ops = {
  51         NULL, NULL, NULL, NULL, XZ_COMPRESSION, "xz", 0
  52 };
  53 #endif
  54
  55 #ifndef CONFIG_SQUASHFS_ZLIB
  56 static const struct squashfs_decompressor squashfs_zlib_comp_ops = {
  57         NULL, NULL, NULL, NULL, ZLIB_COMPRESSION, "zlib", 0
  58 };
  59 #endif
  60
  61 static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
  62         NULL, NULL, NULL, NULL, 0, "unknown", 0
  63 };
  64
  65 static const struct squashfs_decompressor *decompressor[] = {
  66         &squashfs_zlib_comp_ops,
  67         &squashfs_lzo_comp_ops,
  68         &squashfs_xz_comp_ops,
  69         &squashfs_lzma_unsupported_comp_ops,
  70         &squashfs_unknown_comp_ops
  71 };
  72
  73
  74 const struct squashfs_decompressor *squashfs_lookup_decompressor(int id)
  75 {
  76         int i;
  77
  78         for (i = 0; decompressor[i]->id; i++)
  79                 if (id == decompressor[i]->id)
  80                         break;
  81
  82         return decompressor[i];
  83 }
  84
  85
  86 static void *get_comp_opts(struct super_block *sb, unsigned short flags)
  87 {
  88         struct squashfs_sb_info *msblk = sb->s_fs_info;
  89         void *buffer = NULL, *comp_opts;
  90         int length = 0;
  91
  92         /*
  93          * Read decompressor specific options from file system if present
  94          */
  95         if (SQUASHFS_COMP_OPTS(flags)) {
  96                 buffer = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL);
  97                 if (buffer == NULL) {
  98                         comp_opts = ERR_PTR(-ENOMEM);
  99                         goto out;
 100                 }
 101
 102                 length = squashfs_read_data(sb, &buffer,
 103                         sizeof(struct squashfs_super_block), 0, NULL,
 104                                 PAGE_CACHE_SIZE, 1);
 105
 106                 if (length < 0) {
 107                         comp_opts = ERR_PTR(length);
 108                         goto out;
 109                 }
 110         }
 111
 112         comp_opts = squashfs_comp_opts(msblk, buffer, length);
 113
 114 out:
 115         kfree(buffer);
 116         return comp_opts;
 117 }
 118
 119
 120 void *squashfs_decompressor_setup(struct super_block *sb, unsigned short flags)
 121 {
 122         struct squashfs_sb_info *msblk = sb->s_fs_info;
 123         void *stream, *comp_opts = get_comp_opts(sb, flags);
 124
 125         if (IS_ERR(comp_opts))
 126                 return comp_opts;
 127
 128         stream = squashfs_decompressor_create(msblk, comp_opts);
 129         if (IS_ERR(stream))
 130                 kfree(comp_opts);
 131
 132         return stream;
 133 }