OS_Develop/FreeDOS
OS_Develop/FreeDOS
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

sys: check default content of all magic offset patchsites

Browse Source
This commit is contained in:
E. C. Masloch 2024-02-06 23:19:26 +01:00 committed by Kenneth J Davis
parent 0776645017
commit 55f2a81406
1 changed files with 39 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
sys/sys.c
View File

@ -1579,6 +1579,7 @@ void put_boot(SYSOptions *opts)
/* !!! if boot sector changes then update these locations !!! */
{
/* magic offset: LBA detection */
unsigned offset;
offset = (fs == FAT16) ? 0x178 : 0x17B;
@ -1598,7 +1599,8 @@ void put_boot(SYSOptions *opts)
}
else
{
printf("%s : fat boot sector does not match expected layout\n", pgm);
printf("%s: Internal error: FAT1%c LBA detect unexpected content\n",
pgm, fs == FAT12 ? '2' : '6');
exit(1);
}
}
@ -1653,8 +1655,14 @@ void put_boot(SYSOptions *opts)
*/
if (opts->kernel.stdbs)
{
/* magic offset: loadsegoff_60 */
int defaultload = ((int *)newboot)[0x78/sizeof(int)];
if (defaultload != 0x60 && defaultload != 0x70) {
printf("%s: Internal error: FAT32 load seg unexpected content\n", pgm);
exit(1);
}
((int *)newboot)[0x78/sizeof(int)] = opts->kernel.loadaddr;
bsBiosMovOff = 0x82;
bsBiosMovOff = 0x82; /* magic offset: mov byte [bp + 40h], dl */
}
else /* compatible bs */
{
@ -1693,35 +1701,53 @@ void put_boot(SYSOptions *opts)
*/
if (opts->kernel.stdbs)
{
/* magic offset: loadsegoff_60 */
int defaultload = ((int *)newboot)[0x5C/sizeof(int)];
if (defaultload != 0x60 && defaultload != 0x70) {
printf("%s: Internal error: FAT1%c load seg unexpected content\n",
pgm, fs == FAT12 ? '2' : '6');
exit(1);
}
/* this sets the segment we load the kernel to, default is 0x60:0 */
((int *)newboot)[0x5c/sizeof(int)] = opts->kernel.loadaddr;
bsBiosMovOff = 0x66;
bsBiosMovOff = 0x66; /* magic offset: mov byte [bp + 24h], dl */
}
else
{
int defaultload;
/* load segment hard coded to 0x70 in oem compatible boot sector, */
/* this however changes the offset jumped to default 0x70:0 */
if (fs == FAT12)
if (fs == FAT12) {
/* magic offset: jmp LOADSEG:xxxxh */
defaultload = ((int *)newboot)[0x11c/sizeof(int)];
((int *)newboot)[0x11c/sizeof(int)] = opts->kernel.loadaddr;
else
} else {
/* magic offset: jmp LOADSEG:xxxxh */
defaultload = ((int *)newboot)[0x119/sizeof(int)];
((int *)newboot)[0x119/sizeof(int)] = opts->kernel.loadaddr;
bsBiosMovOff = 0x4F;
}
if (defaultload != 0x0 && defaultload != 0x200) {
printf("%s: Internal error: OEM FAT1%c load ofs unexpected content\n",
pgm, fs == FAT12 ? '2' : '6');
exit(1);
}
bsBiosMovOff = 0x4F; /* magic offset: mov byte [bp + 24h], dl */
}
}
if (opts->ignoreBIOS)
if ( (newboot[bsBiosMovOff]==0x88) && (newboot[bsBiosMovOff+1]==0x56) )
{
if ( (newboot[bsBiosMovOff]==0x88) && (newboot[bsBiosMovOff+1]==0x56) )
if (opts->ignoreBIOS)
{
newboot[bsBiosMovOff] = 0x90; /* NOP */ ++bsBiosMovOff;
newboot[bsBiosMovOff] = 0x90; /* NOP */ ++bsBiosMovOff;
newboot[bsBiosMovOff] = 0x90; /* NOP */ ++bsBiosMovOff;
}
else
{
printf("%s : fat boot sector does not match expected layout\n", pgm);
exit(1);
}
}
else
{
printf("%s: Internal error: Unit save unexpected content\n", pgm);
exit(1);
}
if (opts->verbose) /* display information about filesystem */