tools/firmware-utils/src/add_header.c

   1 /*
   2  * add_header.c - partially based on OpenWrt's motorola-bin.c
   3  *
   4  * Copyright (C) 2008 Imre Kaloz  <kaloz@openwrt.org>
   5  *                    Gabor Juhos <juhosg@openwrt.org>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License,
   9  * version 2 as published by the Free Software Foundation.
  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  * The add_header utility used by various vendors preprends the buf
  23  * image with a header containing a CRC32 value which is generated for the
  24  * model id + reserved space for CRC32 + buf, then replaces the reserved
  25  * area with the actual CRC32. This replacement tool mimics this behavior.
  26  */
  27
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30 #include <stddef.h>
  31 #include <unistd.h>
  32 #include <errno.h>
  33 #include <fcntl.h>
  34 #include <sys/mman.h>
  35 #include <string.h>
  36 #include <netinet/in.h>
  37 #include <inttypes.h>
  38
  39 #define BPB 8 /* bits/byte */
  40
  41 static uint32_t crc32[1<<BPB];
  42
  43 static void init_crc32()
  44 {
  45         const uint32_t poly = ntohl(0x2083b8ed);
  46         int n;
  47
  48         for (n = 0; n < 1<<BPB; n++) {
  49                 uint32_t crc = n;
  50                 int bit;
  51
  52                 for (bit = 0; bit < BPB; bit++)
  53                         crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1);
  54                 crc32[n] = crc;
  55         }
  56 }
  57
  58 static uint32_t crc32buf(unsigned char *buf, size_t len)
  59 {
  60         uint32_t crc = 0xFFFFFFFF;
  61
  62         for (; len; len--, buf++)
  63                 crc = crc32[(uint8_t)crc ^ *buf] ^ (crc >> BPB);
  64         return ~crc;
  65 }
  66
  67 struct header {
  68         unsigned char model[16];
  69         uint32_t crc;
  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: add_header model_id 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 != 4)
  94                 usage("wrong number of arguments");
  95
  96         // mmap input_file
  97         if ((fd = open(argv[2], 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[2], strerror(errno));
 103                 exit(1);
 104         }
 105
 106         buflen = len + sizeof(header);
 107
 108         init_crc32();
 109
 110         // copy model name into header
 111         strncpy(header.model, argv[1], sizeof(header.model));
 112         header.crc = 0;
 113
 114         // create a firmware image in memory and copy the input_file to it
 115         buf = malloc(buflen);
 116         memcpy(buf, &header, sizeof(header));
 117         memcpy(&buf[sizeof(header)], input_file, len);
 118
 119         // CRC of temporary header + buf
 120         header.crc = htonl(crc32buf(buf, buflen));
 121
 122         memcpy(buf, &header, sizeof(header));
 123
 124         // write the buf
 125         if ((fd = open(argv[3], O_CREAT|O_WRONLY|O_TRUNC,0644)) < 0
 126         || write(fd, buf, buflen) != buflen
 127         || close(fd) < 0)
 128         {
 129                 fprintf(stderr, "Error storing file %s: %s\n", argv[3], strerror(errno));
 130                 exit(2);
 131         }
 132
 133         free(buf);
 134
 135         munmap(input_file,len);
 136
 137         return 0;
 138 }