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/*
 * patch-cmdline.c - patch the kernel command line on rb532
 *
 * Copyright (C) 2006 Felix Fietkau <nbd@nbd.name>
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <string.h>

#define SEARCH_SPACE    (16 * 1024)
#define CMDLINE_MAX             512

int main(int argc, char **argv)
{
        int fd, found = 0, len, ret = -1;
        char *ptr, *p;
        unsigned int search_space;

        if (argc <= 2 || argc > 4) {
                fprintf(stderr, "Usage: %s <file> <cmdline> [size]\n", argv[0]);
                goto err1;
        } else if (argc == 3) {
                fprintf(stdout, "search space used is default of 16KB\n");
                search_space = SEARCH_SPACE;
        } else {
                search_space = atoi(argv[3]);
        }
        len = strlen(argv[2]);
        if (len + 9 > CMDLINE_MAX) {
                fprintf(stderr, "Command line string too long\n");
                goto err1;
        }
        
        if (((fd = open(argv[1], O_RDWR)) < 0) ||
                (ptr = (char *) mmap(0, search_space + CMDLINE_MAX, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)) == (void *) (-1)) {
                fprintf(stderr, "Could not open kernel image");
                goto err2;
        }
        
        for (p = ptr; p < (ptr + search_space); p += 4) {
                if (memcmp(p, "CMDLINE:", 8) == 0) {
                        found = 1;
                        p += 8;
                        break;
                }
        }
        if (!found) {
                fprintf(stderr, "Command line marker not found!\n");
                goto err3;
        }

        memset(p, 0, CMDLINE_MAX - 8);
        strcpy(p, argv[2]);
        msync(p, CMDLINE_MAX, MS_SYNC|MS_INVALIDATE);
        ret = 0;

err3:
        munmap((void *) ptr, len);
err2:
        if (fd > 0)
                close(fd);
err1:
        return ret;
}