biossums.c revision 677833bc953b6cb418c701facbdcf4aa18d6c44e
/* biossums.c --- written by Eike W. for the Bochs BIOS */
/* adapted for the LGPL'd VGABIOS by vruppert */
#include <stdlib.h>
#include <stdio.h>
typedef unsigned char byte;
void check( int value, char* message );
#define LEN_BIOS_DATA 0x8000
#define MAX_OFFSET (LEN_BIOS_DATA - 1)
#define BIOS_OFFSET 0x7FFF
long chksum_bios_get_offset( byte* data, long offset );
byte chksum_bios_calc_value( byte* data, long offset );
byte chksum_bios_get_value( byte* data, long offset );
void chksum_bios_set_value( byte* data, long offset, byte value );
#define PMID_LEN 20
#define PMID_CHKSUM 19
long chksum_pmid_get_offset( byte* data, long offset );
byte chksum_pmid_calc_value( byte* data, long offset );
byte chksum_pmid_get_value( byte* data, long offset );
void chksum_pmid_set_value( byte* data, long offset, byte value );
byte bios_data[LEN_BIOS_DATA];
int main( int argc, char* argv[] ) {
FILE* stream;
long offset, tmp_offset;
byte cur_val = 0, new_val = 0;
int hits;
if( argc != 2 ) {
printf( "Error. Need a file-name as an argument.\n" );
exit( EXIT_FAILURE );
}
if(( stream = fopen( argv[1], "rb" )) == NULL ) {
printf( "Error opening %s for reading.\n", argv[1] );
exit( EXIT_FAILURE );
}
if( fread( bios_data, 1, LEN_BIOS_DATA, stream ) >= LEN_BIOS_DATA ) {
printf( "Error reading max. 32767 Bytes from %s.\n", argv[1] );
fclose( stream );
exit( EXIT_FAILURE );
}
fclose( stream );
hits = 0;
offset = 0L;
while( (tmp_offset = chksum_pmid_get_offset( bios_data, offset )) != -1L ) {
offset = tmp_offset;
cur_val = chksum_pmid_get_value( bios_data, offset );
new_val = chksum_pmid_calc_value( bios_data, offset );
printf( "\nPMID entry at: 0x%4lX\n", offset );
printf( "Current checksum: 0x%02X\n", cur_val );
printf( "Calculated checksum: 0x%02X ", new_val );
hits++;
}
if( hits == 1 && cur_val != new_val ) {
printf( "Setting checksum." );
chksum_pmid_set_value( bios_data, offset, new_val );
}
if( hits >= 2 ) {
printf( "Multiple PMID entries! No checksum set." );
}
if( hits ) {
printf( "\n" );
}
offset = 0L;
offset = chksum_bios_get_offset( bios_data, offset );
cur_val = chksum_bios_get_value( bios_data, offset );
new_val = chksum_bios_calc_value( bios_data, offset );
printf( "\nBios checksum at: 0x%4lX\n", offset );
printf( "Current checksum: 0x%02X\n", cur_val );
printf( "Calculated checksum: 0x%02X ", new_val );
if( cur_val != new_val ) {
printf( "Setting checksum." );
chksum_bios_set_value( bios_data, offset, new_val );
}
printf( "\n\n" );
if(( stream = fopen( argv[1], "wb" )) == NULL ) {
printf( "Error opening %s for writing.\n", argv[1] );
exit( EXIT_FAILURE );
}
if( fwrite( bios_data, 1, LEN_BIOS_DATA, stream ) < LEN_BIOS_DATA ) {
printf( "Error writing 32KBytes to %s.\n", argv[1] );
fclose( stream );
exit( EXIT_FAILURE );
}
fclose( stream );
return( EXIT_SUCCESS );
}
void check( int okay, char* message ) {
if( !okay ) {
printf( "\n\nError. %s.\n", message );
exit( EXIT_FAILURE );
}
}
long chksum_bios_get_offset( byte* data, long offset ) {
return( BIOS_OFFSET );
}
byte chksum_bios_calc_value( byte* data, long offset ) {
int i;
byte sum;
sum = 0;
for( i = 0; i < MAX_OFFSET; i++ ) {
sum = sum + *( data + i );
}
sum = -sum; /* iso ensures -s + s == 0 on unsigned types */
return( sum );
}
byte chksum_bios_get_value( byte* data, long offset ) {
return( *( data + BIOS_OFFSET ) );
}
void chksum_bios_set_value( byte* data, long offset, byte value ) {
*( data + BIOS_OFFSET ) = value;
}
byte chksum_pmid_calc_value( byte* data, long offset ) {
int i;
int len;
byte sum;
len = PMID_LEN;
check( offset + len <= MAX_OFFSET, "PMID entry length out of bounds" );
sum = 0;
for( i = 0; i < len; i++ ) {
if( i != PMID_CHKSUM ) {
sum = sum + *( data + offset + i );
}
}
sum = -sum;
return( sum );
}
long chksum_pmid_get_offset( byte* data, long offset ) {
long result = -1L;
while( offset + PMID_LEN < MAX_OFFSET ) {
offset = offset + 1;
if( *( data + offset + 0 ) == 'P' && \
*( data + offset + 1 ) == 'M' && \
*( data + offset + 2 ) == 'I' && \
*( data + offset + 3 ) == 'D' ) {
result = offset;
break;
}
}
return( result );
}
byte chksum_pmid_get_value( byte* data, long offset ) {
check( offset + PMID_CHKSUM <= MAX_OFFSET, "PMID checksum out of bounds" );
return( *( data + offset + PMID_CHKSUM ) );
}
void chksum_pmid_set_value( byte* data, long offset, byte value ) {
check( offset + PMID_CHKSUM <= MAX_OFFSET, "PMID checksum out of bounds" );
*( data + offset + PMID_CHKSUM ) = value;
}