--- /dev/null
+/* 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" );
+
+
+ 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;
+}
