1 /* biossums.c --- written by Eike W. for the Bochs BIOS */
2 /* adapted for the LGPL'd VGABIOS by vruppert */
3
4 /* This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this library; If not, see <http://www.gnu.org/licenses/>.
16 */
17 #include <stdlib.h>
18 #include <stdio.h>
19 #include <string.h>
20
21 typedef unsigned char byte;
22
23 void check( int value, char* message );
24
25 #define MAX_BIOS_DATA 0x10000
26
27 long chksum_bios_get_offset( byte* data, long offset );
28 byte chksum_bios_calc_value( byte* data, long offset );
29 byte chksum_bios_get_value( byte* data, long offset );
30 void chksum_bios_set_value( byte* data, long offset, byte value );
31
32 #define PMID_LEN 20
33 #define PMID_CHKSUM 19
34
35 long chksum_pmid_get_offset( byte* data, long offset );
36 byte chksum_pmid_calc_value( byte* data, long offset );
37 byte chksum_pmid_get_value( byte* data, long offset );
38 void chksum_pmid_set_value( byte* data, long offset, byte value );
39
40 #define PCIR_LEN 24
41
42 long chksum_pcir_get_offset( byte* data, long offset );
43
44
45 byte bios_data[MAX_BIOS_DATA];
46 long bios_len;
47
48
main(int argc,char * argv[])49 int main(int argc, char* argv[])
50 {
51 FILE* stream;
52 long offset, tmp_offset, pcir_offset;
53 byte bios_len_byte, cur_val = 0, new_val = 0;
54 int hits, modified;
55
56 if (argc != 2) {
57 printf( "Error. Need a file-name as an argument.\n" );
58 exit( EXIT_FAILURE );
59 }
60
61 if ((stream = fopen(argv[1], "rb")) == NULL) {
62 printf("Error opening %s for reading.\n", argv[1]);
63 exit(EXIT_FAILURE);
64 }
65 memset(bios_data, 0, MAX_BIOS_DATA);
66 bios_len = fread(bios_data, 1, MAX_BIOS_DATA, stream);
67 if (bios_len > MAX_BIOS_DATA) {
68 printf("Error reading max. 65536 Bytes from %s.\n", argv[1]);
69 fclose(stream);
70 exit(EXIT_FAILURE);
71 }
72 fclose(stream);
73 modified = 0;
74 if (bios_len < 0x8000) {
75 bios_len = 0x8000;
76 modified = 1;
77 } else if ((bios_len & 0x1FF) != 0) {
78 bios_len = (bios_len + 0x200) & ~0x1FF;
79 modified = 1;
80 }
81 bios_len_byte = (byte)(bios_len / 512);
82 if (bios_len_byte != bios_data[2]) {
83 if (modified == 0) {
84 bios_len += 0x200;
85 }
86 bios_data[2] = (byte)(bios_len / 512);
87 modified = 1;
88 }
89
90 hits = 0;
91 offset = 0L;
92 while( (tmp_offset = chksum_pmid_get_offset( bios_data, offset )) != -1L ) {
93 offset = tmp_offset;
94 cur_val = chksum_pmid_get_value( bios_data, offset );
95 new_val = chksum_pmid_calc_value( bios_data, offset );
96 printf( "\nPMID entry at: 0x%4lX\n", offset );
97 printf( "Current checksum: 0x%02X\n", cur_val );
98 printf( "Calculated checksum: 0x%02X ", new_val );
99 hits++;
100 }
101 if ((hits == 1) && (cur_val != new_val)) {
102 printf("Setting checksum.");
103 chksum_pmid_set_value( bios_data, offset, new_val );
104 if (modified == 0) {
105 bios_len += 0x200;
106 bios_data[2]++;
107 }
108 modified = 1;
109 }
110 if (hits >= 2) {
111 printf( "Multiple PMID entries! No checksum set." );
112 }
113 if (hits) {
114 printf("\n");
115 }
116
117 offset = 0L;
118 pcir_offset = chksum_pcir_get_offset( bios_data, offset );
119 if (pcir_offset != -1L) {
120 if (bios_data[pcir_offset + 16] != bios_data[2]) {
121 bios_data[pcir_offset + 16] = bios_data[2];
122 if (modified == 0) {
123 bios_len += 0x200;
124 bios_data[2]++;
125 bios_data[pcir_offset + 16]++;
126 }
127 modified = 1;
128 }
129 }
130
131 offset = 0L;
132 do {
133 offset = chksum_bios_get_offset(bios_data, offset);
134 cur_val = chksum_bios_get_value(bios_data, offset);
135 new_val = chksum_bios_calc_value(bios_data, offset);
136 if ((cur_val != new_val) && (modified == 0)) {
137 bios_len += 0x200;
138 bios_data[2]++;
139 if (pcir_offset != -1L) {
140 bios_data[pcir_offset + 16]++;
141 }
142 modified = 1;
143 } else {
144 printf("\nBios checksum at: 0x%4lX\n", offset);
145 printf("Current checksum: 0x%02X\n", cur_val);
146 printf("Calculated checksum: 0x%02X ", new_val);
147 if (cur_val != new_val) {
148 printf("Setting checksum.");
149 chksum_bios_set_value(bios_data, offset, new_val);
150 cur_val = new_val;
151 modified = 1;
152 }
153 printf( "\n" );
154 }
155 } while (cur_val != new_val);
156
157 if (modified == 1) {
158 if ((stream = fopen( argv[1], "wb")) == NULL) {
159 printf("Error opening %s for writing.\n", argv[1]);
160 exit(EXIT_FAILURE);
161 }
162 if (fwrite(bios_data, 1, bios_len, stream) < bios_len) {
163 printf("Error writing %ld KBytes to %s.\n", bios_len / 1024, argv[1]);
164 fclose(stream);
165 exit(EXIT_FAILURE);
166 }
167 fclose(stream);
168 }
169
170 return (EXIT_SUCCESS);
171 }
172
173
check(int okay,char * message)174 void check( int okay, char* message ) {
175
176 if( !okay ) {
177 printf( "\n\nError. %s.\n", message );
178 exit( EXIT_FAILURE );
179 }
180 }
181
182
chksum_bios_get_offset(byte * data,long offset)183 long chksum_bios_get_offset( byte* data, long offset ) {
184
185 return (bios_len - 1);
186 }
187
188
chksum_bios_calc_value(byte * data,long offset)189 byte chksum_bios_calc_value( byte* data, long offset ) {
190
191 int i;
192 byte sum;
193
194 sum = 0;
195 for( i = 0; i < offset; i++ ) {
196 sum = sum + *( data + i );
197 }
198 sum = -sum; /* iso ensures -s + s == 0 on unsigned types */
199 return( sum );
200 }
201
202
chksum_bios_get_value(byte * data,long offset)203 byte chksum_bios_get_value( byte* data, long offset ) {
204
205 return( *( data + offset ) );
206 }
207
208
chksum_bios_set_value(byte * data,long offset,byte value)209 void chksum_bios_set_value( byte* data, long offset, byte value ) {
210
211 *( data + offset ) = value;
212 }
213
214
chksum_pmid_calc_value(byte * data,long offset)215 byte chksum_pmid_calc_value( byte* data, long offset ) {
216
217 int i;
218 int len;
219 byte sum;
220
221 len = PMID_LEN;
222 check((offset + len) <= (bios_len - 1), "PMID entry length out of bounds" );
223 sum = 0;
224 for( i = 0; i < len; i++ ) {
225 if( i != PMID_CHKSUM ) {
226 sum = sum + *( data + offset + i );
227 }
228 }
229 sum = -sum;
230 return( sum );
231 }
232
233
chksum_pmid_get_offset(byte * data,long offset)234 long chksum_pmid_get_offset( byte* data, long offset ) {
235
236 long result = -1L;
237
238 while ((offset + PMID_LEN) < (bios_len - 1)) {
239 offset = offset + 1;
240 if( *( data + offset + 0 ) == 'P' && \
241 *( data + offset + 1 ) == 'M' && \
242 *( data + offset + 2 ) == 'I' && \
243 *( data + offset + 3 ) == 'D' ) {
244 result = offset;
245 break;
246 }
247 }
248 return( result );
249 }
250
251
chksum_pmid_get_value(byte * data,long offset)252 byte chksum_pmid_get_value( byte* data, long offset ) {
253
254 check((offset + PMID_CHKSUM) <= (bios_len - 1), "PMID checksum out of bounds" );
255 return( *( data + offset + PMID_CHKSUM ) );
256 }
257
258
chksum_pmid_set_value(byte * data,long offset,byte value)259 void chksum_pmid_set_value( byte* data, long offset, byte value ) {
260
261 check((offset + PMID_CHKSUM) <= (bios_len - 1), "PMID checksum out of bounds" );
262 *( data + offset + PMID_CHKSUM ) = value;
263 }
264
265
chksum_pcir_get_offset(byte * data,long offset)266 long chksum_pcir_get_offset( byte* data, long offset ) {
267
268 long result = -1L;
269
270 while ((offset + PCIR_LEN) < (bios_len - 1)) {
271 offset = offset + 1;
272 if( *( data + offset + 0 ) == 'P' && \
273 *( data + offset + 1 ) == 'C' && \
274 *( data + offset + 2 ) == 'I' && \
275 *( data + offset + 3 ) == 'R' ) {
276 result = offset;
277 break;
278 }
279 }
280 return( result );
281 }
282