tool/mbed/lpc-vector-checksum.c

   1 /***************************************************************************
   2 * https://github.com/dhylands/projects/blob/master/lpc/lpc-vector-checksum/lpc-vector-checksum.c
   3 *
   4 *     Copyright (c) 2012 by Dave Hylands
   5 *           All Rights Reserved
   6 *
   7 *       Permission is granted to any individual or institution to use, copy,
   8 *  modify, or redistribute this file so long as it is not sold for profit,
   9 *  and that this copyright notice is retained.
  10 *
  11 ***************************************************************************
  12 *
  13 *  This program calculates the vector checksum used in LPC17xx binary
  14 *  images.
  15 *
  16 *  Usage:   lpc-vector-checksum file
  17 *
  18 ***************************************************************************/
  19
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <stdint.h>
  23 #include <errno.h>
  24 #include <string.h>
  25
  26 /***************************************************************************/
  27 /**
  28 *   update_vector_checksum
  29 *
  30 *   The algorithim is to write the checksum such that the checksum of the
  31 *   first 8 words is equal to zero.
  32 *
  33 *   The LPC1768 uses little-endian, and this particular routine assumes
  34 *   that it's running on a little-endian architecture.
  35 */
  36 static int update_vector_checksum( const char *filename )
  37 {
  38     uint32_t    sum;
  39     uint32_t    header[8];
  40     FILE       *fs;
  41     int         i;
  42
  43     if (( fs = fopen( filename, "r+b" )) == NULL )
  44     {
  45         fprintf( stderr, "Unable to open '%s' for reading/writing (%d): %s\n",
  46                  filename, errno, strerror( errno ));
  47         return 0;
  48     }
  49
  50     if ( fread( header, sizeof( header ), 1, fs ) != 1 )
  51     {
  52         fprintf( stderr, "Failed to read header from '%s' (perhaps the file is too small?)",
  53                  filename );
  54         fclose( fs );
  55         return 0;
  56     }
  57
  58     sum = 0;
  59     for ( i = 0; i < 7; i++ )
  60     {
  61         sum += header[i];
  62     }
  63     printf( "sum = 0x%08x, value to write = 0x%08x\n", sum, -sum );
  64
  65     /* write back the checksum to location 7
  66      * http://sigalrm.blogspot.jp/2011/10/cortex-m3-exception-vector-checksum.html
  67      */
  68     fseek(fs, 0x1c, SEEK_SET);
  69     sum = -sum;
  70     fwrite(&sum, 4, 1, fs);
  71
  72     fclose( fs );
  73
  74     return 1;
  75 }
  76
  77 /***************************************************************************/
  78 /**
  79 *   main
  80 */
  81 int main( int argc, char **argv )
  82 {
  83     int arg;
  84
  85     if ( argc < 2)
  86     {
  87         fprintf( stderr, "Usage: lpc-vector-checksum file ...\n" );
  88         exit( 1 );
  89     }
  90
  91     for ( arg = 1; arg < argc; arg++ )
  92     {
  93         update_vector_checksum( argv[ arg ]);
  94     }
  95
  96     exit( 0 );
  97     return 0;
  98 }
  99