LXR linux/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
  40static 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
  45static 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
  51static 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
  57static const struct squashfs_decompressor squashfs_zlib_comp_ops = {
  58        NULL, NULL, NULL, NULL, ZLIB_COMPRESSION, "zlib", 0
  59};
  60#endif
  61
  62static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
  63        NULL, NULL, NULL, NULL, 0, "unknown", 0
  64};
  65
  66static 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
  75const 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
  87static 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
 121out:
 122        kfree(actor);
 123        kfree(buffer);
 124        return comp_opts;
 125}
 126
 127
 128void *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}
 142