decompress_unlzo.c

Go to the documentation of this file.

/*
 * LZO decompressor for the Linux kernel. Code borrowed from the lzo
 * implementation by Markus Franz Xaver Johannes Oberhumer.
 *
 * Linux kernel adaptation:
 * Copyright (C) 2009
 * Albin Tonnerre, Free Electrons <[email protected]>
 *
 * Original code:
 * Copyright (C) 1996-2005 Markus Franz Xaver Johannes Oberhumer
 * All Rights Reserved.
 *
 * lzop and the LZO library are free software; you can redistribute them
 * and/or modify them under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, 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; see the file COPYING.
 * If not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Markus F.X.J. Oberhumer
 * <[email protected]>
 * http://www.oberhumer.com/opensource/lzop/
 */

#ifdef STATIC
#include "lzo/lzo1x_decompress.c"
#else
#include <linux/decompress/unlzo.h>
#endif

#include <linux/types.h>
#include <linux/lzo.h>
#include <linux/decompress/mm.h>

#include <linux/compiler.h>
#include <asm/unaligned.h>

static const unsigned char lzop_magic[] = {
    0x89, 0x4c, 0x5a, 0x4f, 0x00, 0x0d, 0x0a, 0x1a, 0x0a };

#define LZO_BLOCK_SIZE        (256*1024l)
#define HEADER_HAS_FILTER      0x00000800L
#define HEADER_SIZE_MIN       (9 + 7     + 4 + 8     + 1       + 4)
#define HEADER_SIZE_MAX       (9 + 7 + 1 + 8 + 8 + 4 + 1 + 255 + 4)

STATIC inline int INIT parse_header(u8 *input, int *skip, int in_len)
{
    int l;
    u8 *parse = input;
    u8 *end = input + in_len;
    u8 level = 0;
    u16 version;

    /*
     * Check that there's enough input to possibly have a valid header.
     * Then it is possible to parse several fields until the minimum
     * size may have been used.
     */
    if (in_len < HEADER_SIZE_MIN)
        return 0;

    /* read magic: 9 first bits */
    for (l = 0; l < 9; l++) {
        if (*parse++ != lzop_magic[l])
            return 0;
    }
    /* get version (2bytes), skip library version (2),
     * 'need to be extracted' version (2) and
     * method (1) */
    version = get_unaligned_be16(parse);
    parse += 7;
    if (version >= 0x0940)
        level = *parse++;
    if (get_unaligned_be32(parse) & HEADER_HAS_FILTER)
        parse += 8; /* flags + filter info */
    else
        parse += 4; /* flags */

    /*
     * At least mode, mtime_low, filename length, and checksum must
     * be left to be parsed. If also mtime_high is present, it's OK
     * because the next input buffer check is after reading the
     * filename length.
     */
    if (end - parse < 8 + 1 + 4)
        return 0;

    /* skip mode and mtime_low */
    parse += 8;
    if (version >= 0x0940)
        parse += 4; /* skip mtime_high */

    l = *parse++;
    /* don't care about the file name, and skip checksum */
    if (end - parse < l + 4)
        return 0;
    parse += l + 4;

    *skip = parse - input;
    return 1;
}

STATIC inline int INIT unlzo(u8 *input, int in_len,
                int (*fill) (void *, unsigned int),
                int (*flush) (void *, unsigned int),
                u8 *output, int *posp,
                void (*error) (char *x))
{
    u8 r = 0;
    int skip = 0;
    u32 src_len, dst_len;
    size_t tmp;
    u8 *in_buf, *in_buf_save, *out_buf;
    int ret = -1;

    if (output) {
        out_buf = output;
    } else if (!flush) {
        error("NULL output pointer and no flush function provided");
        goto exit;
    } else {
        out_buf = malloc(LZO_BLOCK_SIZE);
        if (!out_buf) {
            error("Could not allocate output buffer");
            goto exit;
        }
    }

    if (input && fill) {
        error("Both input pointer and fill function provided, don't know what to do");
        goto exit_1;
    } else if (input) {
        in_buf = input;
    } else if (!fill) {
        error("NULL input pointer and missing fill function");
        goto exit_1;
    } else {
        in_buf = malloc(lzo1x_worst_compress(LZO_BLOCK_SIZE));
        if (!in_buf) {
            error("Could not allocate input buffer");
            goto exit_1;
        }
    }
    in_buf_save = in_buf;

    if (posp)
        *posp = 0;

    if (fill) {
        /*
         * Start from in_buf + HEADER_SIZE_MAX to make it possible
         * to use memcpy() to copy the unused data to the beginning
         * of the buffer. This way memmove() isn't needed which
         * is missing from pre-boot environments of most archs.
         */
        in_buf += HEADER_SIZE_MAX;
        in_len = fill(in_buf, HEADER_SIZE_MAX);
    }

    if (!parse_header(in_buf, &skip, in_len)) {
        error("invalid header");
        goto exit_2;
    }
    in_buf += skip;
    in_len -= skip;

    if (fill) {
        /* Move the unused data to the beginning of the buffer. */
        memcpy(in_buf_save, in_buf, in_len);
        in_buf = in_buf_save;
    }

    if (posp)
        *posp = skip;

    for (;;) {
        /* read uncompressed block size */
        if (fill && in_len < 4) {
            skip = fill(in_buf + in_len, 4 - in_len);
            if (skip > 0)
                in_len += skip;
        }
        if (in_len < 4) {
            error("file corrupted");
            goto exit_2;
        }
        dst_len = get_unaligned_be32(in_buf);
        in_buf += 4;
        in_len -= 4;

        /* exit if last block */
        if (dst_len == 0) {
            if (posp)
                *posp += 4;
            break;
        }

        if (dst_len > LZO_BLOCK_SIZE) {
            error("dest len longer than block size");
            goto exit_2;
        }

        /* read compressed block size, and skip block checksum info */
        if (fill && in_len < 8) {
            skip = fill(in_buf + in_len, 8 - in_len);
            if (skip > 0)
                in_len += skip;
        }
        if (in_len < 8) {
            error("file corrupted");
            goto exit_2;
        }
        src_len = get_unaligned_be32(in_buf);
        in_buf += 8;
        in_len -= 8;

        if (src_len <= 0 || src_len > dst_len) {
            error("file corrupted");
            goto exit_2;
        }

        /* decompress */
        if (fill && in_len < src_len) {
            skip = fill(in_buf + in_len, src_len - in_len);
            if (skip > 0)
                in_len += skip;
        }
        if (in_len < src_len) {
            error("file corrupted");
            goto exit_2;
        }
        tmp = dst_len;

        /* When the input data is not compressed at all,
         * lzo1x_decompress_safe will fail, so call memcpy()
         * instead */
        if (unlikely(dst_len == src_len))
            memcpy(out_buf, in_buf, src_len);
        else {
            r = lzo1x_decompress_safe((u8 *) in_buf, src_len,
                        out_buf, &tmp);

            if (r != LZO_E_OK || dst_len != tmp) {
                error("Compressed data violation");
                goto exit_2;
            }
        }

        if (flush && flush(out_buf, dst_len) != dst_len)
            goto exit_2;
        if (output)
            out_buf += dst_len;
        if (posp)
            *posp += src_len + 12;

        in_buf += src_len;
        in_len -= src_len;
        if (fill) {
            /*
             * If there happens to still be unused data left in
             * in_buf, move it to the beginning of the buffer.
             * Use a loop to avoid memmove() dependency.
             */
            if (in_len > 0)
                for (skip = 0; skip < in_len; ++skip)
                    in_buf_save[skip] = in_buf[skip];
            in_buf = in_buf_save;
        }
    }

    ret = 0;
exit_2:
    if (!input)
        free(in_buf_save);
exit_1:
    if (!output)
        free(out_buf);
exit:
    return ret;
}

#define decompress unlzo