xz_wrapper.c

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/*
 * Squashfs - a compressed read only filesystem for Linux
 *
 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
 * Phillip Lougher <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2,
 * or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * xz_wrapper.c
 */


#include <linux/mutex.h>
#include <linux/buffer_head.h>
#include <linux/slab.h>
#include <linux/xz.h>
#include <linux/bitops.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs.h"
#include "decompressor.h"

struct squashfs_xz {
    struct xz_dec *state;
    struct xz_buf buf;
};

struct comp_opts {
    __le32 dictionary_size;
    __le32 flags;
};

static void *squashfs_xz_init(struct squashfs_sb_info *msblk, void *buff,
    int len)
{
    struct comp_opts *comp_opts = buff;
    struct squashfs_xz *stream;
    int dict_size = msblk->block_size;
    int err, n;

    if (comp_opts) {
        /* check compressor options are the expected length */
        if (len < sizeof(*comp_opts)) {
            err = -EIO;
            goto failed;
        }

        dict_size = le32_to_cpu(comp_opts->dictionary_size);

        /* the dictionary size should be 2^n or 2^n+2^(n+1) */
        n = ffs(dict_size) - 1;
        if (dict_size != (1 << n) && dict_size != (1 << n) +
                        (1 << (n + 1))) {
            err = -EIO;
            goto failed;
        }
    }

    dict_size = max_t(int, dict_size, SQUASHFS_METADATA_SIZE);

    stream = kmalloc(sizeof(*stream), GFP_KERNEL);
    if (stream == NULL) {
        err = -ENOMEM;
        goto failed;
    }

    stream->state = xz_dec_init(XZ_PREALLOC, dict_size);
    if (stream->state == NULL) {
        kfree(stream);
        err = -ENOMEM;
        goto failed;
    }

    return stream;

failed:
    ERROR("Failed to initialise xz decompressor\n");
    return ERR_PTR(err);
}


static void squashfs_xz_free(void *strm)
{
    struct squashfs_xz *stream = strm;

    if (stream) {
        xz_dec_end(stream->state);
        kfree(stream);
    }
}


static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void **buffer,
    struct buffer_head **bh, int b, int offset, int length, int srclength,
    int pages)
{
    enum xz_ret xz_err;
    int avail, total = 0, k = 0, page = 0;
    struct squashfs_xz *stream = msblk->stream;

    mutex_lock(&msblk->read_data_mutex);

    xz_dec_reset(stream->state);
    stream->buf.in_pos = 0;
    stream->buf.in_size = 0;
    stream->buf.out_pos = 0;
    stream->buf.out_size = PAGE_CACHE_SIZE;
    stream->buf.out = buffer[page++];

    do {
        if (stream->buf.in_pos == stream->buf.in_size && k < b) {
            avail = min(length, msblk->devblksize - offset);
            length -= avail;
            wait_on_buffer(bh[k]);
            if (!buffer_uptodate(bh[k]))
                goto release_mutex;

            stream->buf.in = bh[k]->b_data + offset;
            stream->buf.in_size = avail;
            stream->buf.in_pos = 0;
            offset = 0;
        }

        if (stream->buf.out_pos == stream->buf.out_size
                            && page < pages) {
            stream->buf.out = buffer[page++];
            stream->buf.out_pos = 0;
            total += PAGE_CACHE_SIZE;
        }

        xz_err = xz_dec_run(stream->state, &stream->buf);

        if (stream->buf.in_pos == stream->buf.in_size && k < b)
            put_bh(bh[k++]);
    } while (xz_err == XZ_OK);

    if (xz_err != XZ_STREAM_END) {
        ERROR("xz_dec_run error, data probably corrupt\n");
        goto release_mutex;
    }

    if (k < b) {
        ERROR("xz_uncompress error, input remaining\n");
        goto release_mutex;
    }

    total += stream->buf.out_pos;
    mutex_unlock(&msblk->read_data_mutex);
    return total;

release_mutex:
    mutex_unlock(&msblk->read_data_mutex);

    for (; k < b; k++)
        put_bh(bh[k]);

    return -EIO;
}

const struct squashfs_decompressor squashfs_xz_comp_ops = {
    .init = squashfs_xz_init,
    .free = squashfs_xz_free,
    .decompress = squashfs_xz_uncompress,
    .id = XZ_COMPRESSION,
    .name = "xz",
    .supported = 1
};