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abootconf.c

/*
 * abootconf.c
 *
 * This file is part of aboot, the SRM bootloader for Linux/Alpha
 * Copyright (C) 1996 Linus Torvalds, David Mosberger, and Michael Schwingen.
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <sys/fcntl.h>

#include <config.h>


const char * prog_name;

int
main (int argc, char ** argv)
{
      unsigned long sector[512 / sizeof(unsigned long)];
      off_t aboot_pos;
      size_t nbytes;
      long part = -1;
      int disk, i;

      prog_name = argv[0];

      if (argc != 2 && argc != 3) {
            fprintf(stderr, "usage: %s device [partition]\n", prog_name);
            exit(1);
      }

      if (argc > 2) {
          errno = 0;
          part = strtol(argv[2], 0, 10);
          if (errno == ERANGE) {
            fprintf(stderr, "%s: bad partition number %s\n",
                  prog_name, argv[2]);
            exit(1);
          }
      }

      disk = open(argv[1], part < 0 ? O_RDONLY : O_RDWR);
      if (disk < 0) {
            perror(argv[1]);
            exit(1);
      }

      nbytes = read(disk, sector, sizeof(sector));
      if (nbytes != sizeof(sector)) {
            if ((long) nbytes < 0) {
                  perror("read");
            } else {
                  fprintf(stderr, "%s: short read\n", prog_name);
            }
            exit(1);
      }

      aboot_pos = sector[61] * 512;

      if (lseek(disk, aboot_pos, SEEK_SET) != aboot_pos) {
            perror("lseek");
            exit(1);
      }

      nbytes = read(disk, sector, sizeof(sector));
      if (nbytes != sizeof(sector)) {
            if ((long) nbytes < 0) {
                  perror("read");
            } else {
                  fprintf(stderr, "%s: short read\n", prog_name);
            }
            exit(1);
      }

      for (i = 0; i < (int) (sizeof(sector)/sizeof(sector[0])); ++i) {
            if (sector[i] == ABOOT_MAGIC)
                  break;
      }
      if (i >= (int) (sizeof(sector)/sizeof(sector[0]))) {
            fprintf(stderr, "%s: could not find aboot on disk %s\n",
                  prog_name, argv[1]);
            exit(1);
      }

      if (part < 0) {
          printf("aboot.conf partition currently set to %ld\n",
               sector[i + 1]);
          exit(0);
      }

      if (lseek(disk, aboot_pos, SEEK_SET) != aboot_pos) {
            perror("lseek");
            exit(1);
      }

      sector[i + 1] = atoi(argv[2]);

      nbytes = write(disk, sector, sizeof(sector));
      if (nbytes != sizeof(sector)) {
            if ((long) nbytes < 0) {
                  perror("write");
            } else {
                  fprintf(stderr, "%s: short write\n", prog_name);
            }
            exit(1);
      }
      return 0;
}

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