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 #include "page_actor.h"
  34
  35 /*
  36  * This file (and decompressor.h) implements a decompressor framework for
  37  * Squashfs, allowing multiple decompressors to be easily supported
  38  */
  39
  40 static const struct squashfs_decompressor squashfs_lzma_unsupported_comp_ops = {
  41         NULL, NULL, NULL, NULL, LZMA_COMPRESSION, "lzma", 0
  42 };
  43
  44 #ifndef CONFIG_SQUASHFS_LZO
  45 static const struct squashfs_decompressor squashfs_lzo_comp_ops = {
  46         NULL, NULL, NULL, NULL, LZO_COMPRESSION, "lzo", 0
  47 };
  48 #endif
  49
  50 #ifndef CONFIG_SQUASHFS_XZ
  51 static const struct squashfs_decompressor squashfs_xz_comp_ops = {
  52         NULL, NULL, NULL, NULL, XZ_COMPRESSION, "xz", 0
  53 };
  54 #endif
  55
  56 #ifndef CONFIG_SQUASHFS_ZLIB
  57 static const struct squashfs_decompressor squashfs_zlib_comp_ops = {
  58         NULL, NULL, NULL, NULL, ZLIB_COMPRESSION, "zlib", 0
  59 };
  60 #endif
  61
  62 static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
  63         NULL, NULL, NULL, NULL, 0, "unknown", 0
  64 };
  65
  66 static const struct squashfs_decompressor *decompressor[] = {
  67         &squashfs_zlib_comp_ops,
  68         &squashfs_lzo_comp_ops,
  69         &squashfs_xz_comp_ops,
  70         &squashfs_lzma_unsupported_comp_ops,
  71         &squashfs_unknown_comp_ops
  72 };
  73
  74
  75 const struct squashfs_decompressor *squashfs_lookup_decompressor(int id)
  76 {
  77         int i;
  78
  79         for (i = 0; decompressor[i]->id; i++)
  80                 if (id == decompressor[i]->id)
  81                         break;
  82
  83         return decompressor[i];
  84 }
  85
  86
  87 static void *get_comp_opts(struct super_block *sb, unsigned short flags)
  88 {
  89         struct squashfs_sb_info *msblk = sb->s_fs_info;
  90         void *buffer = NULL, *comp_opts;
  91         struct squashfs_page_actor *actor = NULL;
  92         int length = 0;
  93
  94         /*
  95          * Read decompressor specific options from file system if present
  96          */
  97         if (SQUASHFS_COMP_OPTS(flags)) {
  98                 buffer = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL);
  99                 if (buffer == NULL) {
 100                         comp_opts = ERR_PTR(-ENOMEM);
 101                         goto out;
 102                 }
 103
 104                 actor = squashfs_page_actor_init(&buffer, 1, 0);
 105                 if (actor == NULL) {
 106                         comp_opts = ERR_PTR(-ENOMEM);
 107                         goto out;
 108                 }
 109
 110                 length = squashfs_read_data(sb,
 111                         sizeof(struct squashfs_super_block), 0, NULL, actor);
 112
 113                 if (length < 0) {
 114                         comp_opts = ERR_PTR(length);
 115                         goto out;
 116                 }
 117         }
 118
 119         comp_opts = squashfs_comp_opts(msblk, buffer, length);
 120
 121 out:
 122         kfree(actor);
 123         kfree(buffer);
 124         return comp_opts;
 125 }
 126
 127
 128 void *squashfs_decompressor_setup(struct super_block *sb, unsigned short flags)
 129 {
 130         struct squashfs_sb_info *msblk = sb->s_fs_info;
 131         void *stream, *comp_opts = get_comp_opts(sb, flags);
 132
 133         if (IS_ERR(comp_opts))
 134                 return comp_opts;
 135
 136         stream = squashfs_decompressor_create(msblk, comp_opts);
 137         if (IS_ERR(stream))
 138                 kfree(comp_opts);
 139
 140         return stream;
 141 }