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_LZ4
  45 static const struct squashfs_decompressor squashfs_lz4_comp_ops = {
  46         NULL, NULL, NULL, NULL, LZ4_COMPRESSION, "lz4", 0
  47 };
  48 #endif
  49
  50 #ifndef CONFIG_SQUASHFS_LZO
  51 static const struct squashfs_decompressor squashfs_lzo_comp_ops = {
  52         NULL, NULL, NULL, NULL, LZO_COMPRESSION, "lzo", 0
  53 };
  54 #endif
  55
  56 #ifndef CONFIG_SQUASHFS_XZ
  57 static const struct squashfs_decompressor squashfs_xz_comp_ops = {
  58         NULL, NULL, NULL, NULL, XZ_COMPRESSION, "xz", 0
  59 };
  60 #endif
  61
  62 #ifndef CONFIG_SQUASHFS_ZLIB
  63 static const struct squashfs_decompressor squashfs_zlib_comp_ops = {
  64         NULL, NULL, NULL, NULL, ZLIB_COMPRESSION, "zlib", 0
  65 };
  66 #endif
  67
  68 static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
  69         NULL, NULL, NULL, NULL, 0, "unknown", 0
  70 };
  71
  72 static const struct squashfs_decompressor *decompressor[] = {
  73         &squashfs_zlib_comp_ops,
  74         &squashfs_lz4_comp_ops,
  75         &squashfs_lzo_comp_ops,
  76         &squashfs_xz_comp_ops,
  77         &squashfs_lzma_unsupported_comp_ops,
  78         &squashfs_unknown_comp_ops
  79 };
  80
  81
  82 const struct squashfs_decompressor *squashfs_lookup_decompressor(int id)
  83 {
  84         int i;
  85
  86         for (i = 0; decompressor[i]->id; i++)
  87                 if (id == decompressor[i]->id)
  88                         break;
  89
  90         return decompressor[i];
  91 }
  92
  93
  94 static void *get_comp_opts(struct super_block *sb, unsigned short flags)
  95 {
  96         struct squashfs_sb_info *msblk = sb->s_fs_info;
  97         void *buffer = NULL, *comp_opts;
  98         struct squashfs_page_actor *actor = NULL;
  99         int length = 0;
 100
 101         /*
 102          * Read decompressor specific options from file system if present
 103          */
 104         if (SQUASHFS_COMP_OPTS(flags)) {
 105                 buffer = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL);
 106                 if (buffer == NULL) {
 107                         comp_opts = ERR_PTR(-ENOMEM);
 108                         goto out;
 109                 }
 110
 111                 actor = squashfs_page_actor_init(&buffer, 1, 0);
 112                 if (actor == NULL) {
 113                         comp_opts = ERR_PTR(-ENOMEM);
 114                         goto out;
 115                 }
 116
 117                 length = squashfs_read_data(sb,
 118                         sizeof(struct squashfs_super_block), 0, NULL, actor);
 119
 120                 if (length < 0) {
 121                         comp_opts = ERR_PTR(length);
 122                         goto out;
 123                 }
 124         }
 125
 126         comp_opts = squashfs_comp_opts(msblk, buffer, length);
 127
 128 out:
 129         kfree(actor);
 130         kfree(buffer);
 131         return comp_opts;
 132 }
 133
 134
 135 void *squashfs_decompressor_setup(struct super_block *sb, unsigned short flags)
 136 {
 137         struct squashfs_sb_info *msblk = sb->s_fs_info;
 138         void *stream, *comp_opts = get_comp_opts(sb, flags);
 139
 140         if (IS_ERR(comp_opts))
 141                 return comp_opts;
 142
 143         stream = squashfs_decompressor_create(msblk, comp_opts);
 144         if (IS_ERR(stream))
 145                 kfree(comp_opts);
 146
 147         return stream;
 148 }