tools/patch-image/src/patch-cmdline.c

   1 /*
   2  * patch-cmdline.c - patch the kernel command line
   3  *
   4  * Copyright (C) 2006 Felix Fietkau <nbd@nbd.name>
   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  */
  21
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <stddef.h>
  25 #include <unistd.h>
  26 #include <fcntl.h>
  27 #include <sys/mman.h>
  28 #include <sys/stat.h>
  29 #include <string.h>
  30
  31 #define SEARCH_SPACE    (16 * 1024)
  32 #define CMDLINE_MAX             512
  33
  34 int main(int argc, char **argv)
  35 {
  36         int fd, found = 0, len, ret = -1;
  37         char *ptr, *p;
  38         unsigned int search_space;
  39
  40         if (argc <= 2 || argc > 4) {
  41                 fprintf(stderr, "Usage: %s <file> <cmdline> [size]\n", argv[0]);
  42                 goto err1;
  43         } else if (argc == 3) {
  44                 fprintf(stdout, "search space used is default of 16KB\n");
  45                 search_space = SEARCH_SPACE;
  46         } else {
  47                 search_space = atoi(argv[3]);
  48         }
  49         len = strlen(argv[2]);
  50         if (len + 9 > CMDLINE_MAX) {
  51                 fprintf(stderr, "Command line string too long\n");
  52                 goto err1;
  53         }
  54
  55         if (((fd = open(argv[1], O_RDWR)) < 0) ||
  56                 (ptr = (char *) mmap(0, search_space + CMDLINE_MAX, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)) == (void *) (-1)) {
  57                 fprintf(stderr, "Could not open kernel image");
  58                 goto err2;
  59         }
  60
  61         for (p = ptr; p < (ptr + search_space); p += 4) {
  62                 if (memcmp(p, "CMDLINE:", 8) == 0) {
  63                         found = 1;
  64                         p += 8;
  65                         break;
  66                 }
  67         }
  68         if (!found) {
  69                 fprintf(stderr, "Command line marker not found!\n");
  70                 goto err3;
  71         }
  72
  73         memset(p, 0, CMDLINE_MAX - 8);
  74         strcpy(p, argv[2]);
  75         msync(p, CMDLINE_MAX, MS_SYNC|MS_INVALIDATE);
  76         ret = 0;
  77
  78 err3:
  79         munmap((void *) ptr, len);
  80 err2:
  81         if (fd > 0)
  82                 close(fd);
  83 err1:
  84         return ret;
  85 }