package/patch-cmdline/src/patch-cmdline.c

   1 /*
   2  * patch-cmdline.c - patch the kernel command line on rb532
   3  *
   4  * Copyright (C) 2006 Felix Fietkau <nbd@openwrt.org>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version 2
   9  * of the License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  19  *
  20  * $Id:$
  21  */
  22
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <stddef.h>
  26 #include <unistd.h>
  27 #include <fcntl.h>
  28 #include <sys/mman.h>
  29 #include <sys/stat.h>
  30 #include <string.h>
  31
  32 #define SEARCH_SPACE    (16 * 1024)
  33 #define CMDLINE_MAX             512
  34
  35 int main(int argc, char **argv)
  36 {
  37         int fd, found = 0, len, ret = -1;
  38         char *ptr, *p;
  39
  40         if (argc != 3) {
  41                 fprintf(stderr, "Usage: %s <file> <cmdline>\n", argv[0]);
  42                 goto err1;
  43         }
  44         len = strlen(argv[2]);
  45         if (len + 9 > CMDLINE_MAX) {
  46                 fprintf(stderr, "Command line string too long\n");
  47                 goto err1;
  48         }
  49
  50         if (((fd = open(argv[1], O_RDWR)) < 0) ||
  51                 (ptr = (char *) mmap(0, SEARCH_SPACE + CMDLINE_MAX, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)) == (void *) (-1)) {
  52                 fprintf(stderr, "Could not open kernel image");
  53                 goto err2;
  54         }
  55
  56         for (p = ptr; p < (ptr + SEARCH_SPACE); p += 4) {
  57                 if (memcmp(p, "CMDLINE:", 8) == 0) {
  58                         found = 1;
  59                         p += 8;
  60                         break;
  61                 }
  62         }
  63         if (!found) {
  64                 fprintf(stderr, "Command line marker not found!\n");
  65                 goto err3;
  66         }
  67
  68         memset(p, 0, CMDLINE_MAX - 8);
  69         strcpy(p, argv[2]);
  70         msync(p, CMDLINE_MAX, MS_SYNC|MS_INVALIDATE);
  71         ret = 0;
  72
  73 err3:
  74         munmap((void *) ptr, len);
  75 err2:
  76         if (fd > 0)
  77                 close(fd);
  78 err1:
  79         return ret;
  80 }