ntloader/libnt/cpio.c

/*
 * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * 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 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; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

/**
 * @file
 *
 * CPIO archives
 *
 */

#include <stdint.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "ntloader.h"
#include "cpio.h"

/**
 * Align CPIO length to nearest dword
 *
 * @v len		Length
 * @ret len		Aligned length
 */
static size_t cpio_align (size_t len)
{
    return ((len + 0x03) & ~0x03);
}

/**
 * Parse CPIO field value
 *
 * @v field		ASCII field
 * @ret value		Field value
 */
static unsigned long cpio_value (const char *field)
{
    char buf[9];

    memcpy (buf, field, (sizeof (buf) - 1));
    buf[ sizeof (buf) - 1 ] = '\0';
    return strtoul (buf, NULL, 16);
}

/**
 * Extract files from CPIO archive
 *
 * @v data		CPIO archive
 * @v len		Maximum length of CPIO archive
 * @v file		File handler
 * @ret rc		Return status code
 */
int cpio_extract (void *data, size_t len,
                  int (* file) (const char *name, void *data, size_t len))
{
    const struct cpio_header *cpio;
    const uint32_t *pad;
    const char *file_name;
    void *file_data;
    size_t file_name_len;
    size_t file_len;
    size_t cpio_len;
    int rc;

    while (1)
    {

        /* Skip over any padding */
        while (len >= sizeof (*pad))
        {
            pad = data;
            if (*pad)
                break;
            data += sizeof (*pad);
            len -= sizeof (*pad);
        }

        /* Stop if we have reached the end of the archive */
        if (! len)
            return 0;

        /* Sanity check */
        if (len < sizeof (*cpio))
        {
            DBG ("Truncated CPIO header\n");
            return -1;
        }
        cpio = data;

        /* Check magic */
        if (memcmp (cpio->c_magic, CPIO_MAGIC,
                      sizeof (cpio->c_magic)) != 0)
        {
            DBG ("Bad CPIO magic\n");
            return -1;
        }

        /* Extract file parameters */
        file_name = ((void *) (cpio + 1));
        file_name_len = cpio_value (cpio->c_namesize);
        file_data = (data + cpio_align (sizeof (*cpio) +
                                          file_name_len));
        file_len = cpio_value (cpio->c_filesize);
        cpio_len = (file_data + file_len - data);
        if (cpio_len < len)
            cpio_len = cpio_align (cpio_len);
        if (cpio_len > len)
        {
            DBG ("Truncated CPIO file\n");
            return -1;
        }

        /* If we reach the trailer, we're done */
        if (strcmp (file_name, CPIO_TRAILER) == 0)
            return 0;

        /* Process file */
        if ((rc = file (file_name, file_data, file_len)) != 0)
            return rc;

        /* Move to next file */
        data += cpio_len;
        len -= cpio_len;
    }
}