source: rtems/cpukit/libfs/src/imfs/imfs_load_tar.c @ 9ba0e55

/*
 *  COPYRIGHT (c) 1989-2010.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 *
 * $Id$
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

/*
 * This file implements the "mount" procedure for tar-based IMFS
 * extensions.  The TAR is not actually mounted under the IMFS.
 * Directories from the TAR file are created as usual in the IMFS.
 * File entries are created as IMFS_LINEAR_FILE nodes with their nods
 * pointing to addresses in the TAR image.
 */ 

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <string.h>

#include <rtems.h>
#include <rtems/libio_.h>
#include <rtems/imfs.h>
#include <rtems/untar.h>
#include <rtems/tar.h>

/*
 * TAR file format:
 *
 *   Offset   Length   Contents
 *     0    100 bytes  File name ('\0' terminated, 99 maxmum length)
 *   100      8 bytes  File mode (in octal ascii)
 *   108      8 bytes  User ID (in octal ascii)
 *   116      8 bytes  Group ID (in octal ascii)
 *   124     12 bytes  File size (s) (in octal ascii)
 *   136     12 bytes  Modify time (in octal ascii)
 *   148      8 bytes  Header checksum (in octal ascii)
 *   156      1 bytes  Link flag
 *   157    100 bytes  Linkname ('\0' terminated, 99 maxmum length)
 *   257      8 bytes  Magic ("ustar  \0")
 *   265     32 bytes  User name ('\0' terminated, 31 maxmum length)
 *   297     32 bytes  Group name ('\0' terminated, 31 maxmum length)
 *   329      8 bytes  Major device ID (in octal ascii)
 *   337      8 bytes  Minor device ID (in octal ascii)
 *   345    167 bytes  Padding
 *   512   (s+p)bytes  File contents (s+p) := (((s) + 511) & ~511),
 *                     round up to 512 bytes
 *
 *   Checksum:
 *   int i, sum;
 *   char* header = tar_header_pointer;
 *   sum = 0;
 *   for(i = 0; i < 512; i++)
 *       sum += 0xFF & header[i];
 */

#define MAX_NAME_FIELD_SIZE      99

#define MIN(a,b)   ((a)>(b)?(b):(a))

/*
 * rtems_tarfs_load
 *
 * Here we create the mountpoint directory and load the tarfs at
 * that node.  Once the IMFS has been mounted, we work through the
 * tar image and perform as follows:
 *  - For directories, simply call mkdir().  The IMFS creates nodes as
 *    needed.
 *  - For files, we make our own calls to IMFS eval_for_make and
 *    create_node.
 */
int rtems_tarfs_load(
  char *mountpoint,
  uint8_t *tar_image,
  size_t tar_size
)
{
   rtems_filesystem_location_info_t root_loc;
   rtems_filesystem_location_info_t loc;
   const char     *hdr_ptr;
   char            filename[100];
   char            full_filename[256];
   int             hdr_chksum;
   unsigned char   linkflag;
   unsigned long   file_size;
   unsigned long   file_mode;
   int             offset;
   unsigned long   nblocks;
   IMFS_jnode_t    *node;
   int             status;

   status = rtems_filesystem_evaluate_path(mountpoint, strlen(mountpoint),
                                           0, &root_loc, 0);
   if (status != 0)
      return(-1);

   if (root_loc.ops != &IMFS_ops)
      return -1;

   /*
    * Create an IMFS node structure pointing to tar image memory.
    */
   offset = 0;
   while (1) {
      if (offset + 512 > tar_size)
         break;

      /*
       * Read a header.
       */
      hdr_ptr = (char *) &tar_image[offset];
      offset += 512;
      if (strncmp(&hdr_ptr[257], "ustar  ", 7))
         break;

      strncpy(filename, hdr_ptr, MAX_NAME_FIELD_SIZE);
      filename[MAX_NAME_FIELD_SIZE] = '\0';

      linkflag   = hdr_ptr[156];
      file_mode  = _rtems_octal2ulong(&hdr_ptr[100], 8);
      file_size  = _rtems_octal2ulong(&hdr_ptr[124], 12);
      hdr_chksum = _rtems_octal2ulong(&hdr_ptr[148], 8);

      if (_rtems_tar_header_checksum(hdr_ptr) != hdr_chksum)
         break;

      /*
       * Generate an IMFS node depending on the file type.
       * - For directories, just create directories as usual.  IMFS
       *   will take care of the rest.
       * - For files, create a file node with special tarfs properties.
       */
      if (linkflag == DIRTYPE) {
         strcpy(full_filename, mountpoint);
         if (full_filename[strlen(full_filename)-1] != '/')
            strcat(full_filename, "/");
         strcat(full_filename, filename);
         mkdir(full_filename, S_IRWXU | S_IRWXG | S_IRWXO);
      }
      /*
       * Create a LINEAR_FILE node
       *
       * NOTE: Coverity thinks this is a resource leak since a node
       *       is created but never deleted.  The scope of the allocation
       *       is that of a file -- not this method.  Coverity Id 20.
       */
      else if (linkflag == REGTYPE) {
         const char  *name;

         loc = root_loc;
         if (IMFS_evaluate_for_make(filename, &loc, &name) == 0) {
            node = IMFS_create_node(&loc,
                        IMFS_LINEAR_FILE, (char *)name,
                        (file_mode & (S_IRWXU | S_IRWXG | S_IRWXO)) | S_IFREG,
                        NULL);
            node->info.linearfile.size   = file_size;
            node->info.linearfile.direct = &tar_image[offset];
         }

         nblocks = (((file_size) + 511) & ~511) / 512;
         offset += 512 * nblocks;
      }
   }

   return status;
}