tools/firmware-utils/src/wndr3700.c

   1 /*
   2  * wndr3700.c - partially based on OpenWrt's add_header.c
   3  *
   4  * Copyright (C) 2009 Anael Orlinski  <naouel@naouel.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  * version 2 as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  18  */
  19
  20 /*
  21  * The add_header utility used by various vendors preprends the buf
  22  * image with a header containing a CRC32 value which is generated for the
  23  * model id + reserved space for CRC32 + buf, then replaces the reserved
  24  * area with the actual CRC32. This replacement tool mimics this behavior.
  25  */
  26
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <stddef.h>
  30 #include <unistd.h>
  31 #include <errno.h>
  32 #include <fcntl.h>
  33 #include <sys/mman.h>
  34 #include <string.h>
  35 #include <netinet/in.h>
  36 #include <inttypes.h>
  37
  38 #define BPB 8 /* bits/byte */
  39
  40 static uint32_t crc32[1<<BPB];
  41
  42 static void init_crc32()
  43 {
  44         const uint32_t poly = ntohl(0x2083b8ed);
  45         int n;
  46
  47         for (n = 0; n < 1<<BPB; n++) {
  48                 uint32_t crc = n;
  49                 int bit;
  50
  51                 for (bit = 0; bit < BPB; bit++)
  52                         crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1);
  53                 crc32[n] = crc;
  54         }
  55 }
  56
  57 static uint32_t crc32buf(unsigned char *buf, size_t len)
  58 {
  59         uint32_t crc = 0xFFFFFFFF;
  60
  61         for (; len; len--, buf++)
  62                 crc = crc32[(uint8_t)crc ^ *buf] ^ (crc >> BPB);
  63         return ~crc;
  64 }
  65
  66 struct header {
  67     uint32_t magic;
  68     uint32_t crc;
  69     unsigned char stuff[56];
  70 };
  71
  72 static void usage(const char *) __attribute__ (( __noreturn__ ));
  73
  74 static void usage(const char *mess)
  75 {
  76         fprintf(stderr, "Error: %s\n", mess);
  77         fprintf(stderr, "Usage: wndr3700 input_file output_file\n");
  78         fprintf(stderr, "\n");
  79         exit(1);
  80 }
  81
  82 int main(int argc, char **argv)
  83 {
  84         off_t len;                      // of original buf
  85         off_t buflen;                   // of the output file
  86         int fd;
  87         void *input_file;               // pointer to the input file (mmmapped)
  88         struct header header;
  89         unsigned char *buf;     // pointer to prefix + copy of original buf
  90
  91         // verify parameters
  92
  93         if (argc != 3)
  94                 usage("wrong number of arguments");
  95
  96         // mmap input_file
  97         if ((fd = open(argv[1], O_RDONLY))  < 0
  98         || (len = lseek(fd, 0, SEEK_END)) < 0
  99         || (input_file = mmap(0, len, PROT_READ, MAP_SHARED, fd, 0)) == (void *) (-1)
 100         || close(fd) < 0)
 101         {
 102                 fprintf(stderr, "Error loading file %s: %s\n", argv[1], strerror(errno));
 103                 exit(1);
 104         }
 105
 106         buflen = len;
 107
 108         init_crc32();
 109
 110         // preload header
 111         memcpy(&header, input_file, sizeof(header));
 112
 113         header.magic = htonl(0x33373030); /* 3700 in ascii */
 114         header.crc = 0;
 115
 116         // create a firmware image in memory and copy the input_file to it
 117         buf = malloc(buflen);
 118         memcpy(buf, input_file, len);
 119
 120         // CRC of temporary header
 121         header.crc = htonl(crc32buf((unsigned char*)&header, sizeof(header)));
 122
 123         memcpy(buf, &header, sizeof(header));
 124
 125         // write the buf
 126         if ((fd = open(argv[2], O_CREAT|O_WRONLY|O_TRUNC,0644)) < 0
 127         || write(fd, buf, buflen) != buflen
 128         || close(fd) < 0)
 129         {
 130                 fprintf(stderr, "Error storing file %s: %s\n", argv[2], strerror(errno));
 131                 exit(2);
 132         }
 133
 134         free(buf);
 135
 136         munmap(input_file,len);
 137
 138         return 0;
 139 }