diff options
Diffstat (limited to 'bootblocks/sysboot.s')
| -rw-r--r-- | bootblocks/sysboot.s | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/bootblocks/sysboot.s b/bootblocks/sysboot.s new file mode 100644 index 0000000..496b7a5 --- /dev/null +++ b/bootblocks/sysboot.s @@ -0,0 +1,77 @@ + +! The master boot sector will have setup a stack, +! this is normally at 0:7c00 down. +! DS, SS, CS and ES will all have value 0 so the execution address is 0:7c00 +! On entry the register SI will be pointer to the partition entry that +! this sector was loaded from, DL is the drive. + +! Also if it's a standard Master boot DH will be the head, CX will be the +! sector and cylinder, BX=7C00, AX=1, DI=7DFE, BP=SI. There's a reasonable +! chance that this isn't true though. + +! The Master boot itself will have been loaded and run at $07c00 +! The BIOS must have setup a stack because interrupts are enabled +! Little else can be assumed because DOS doesn`t assume anything either + +sysboot_start: +j codestart + +.blkb sysboot_start+3-* +public dosfs_stat +dosfs_stat: +.blkb 8 ! System ID +.word 0 ! Sector size +.byte 0 ! Cluster size +.word 0 ! Res-sector +.byte 0 ! FAT count +.word 0 ! Root dir entries +.word 0 ! Sector count (=0 if large FS) +.byte 0 ! Media code +.word 0 ! FAT length +.word 0 ! Sect/Track +.word 0 ! Heads +.long 0 ! Hidden sectors +! Here down is DOS 4+ +.long 0 ! Large FS sector count +.byte 0 ! Phys drive +.byte 0 ! Reserved +.byte 0 ! DOS 4 +.long 0 ! Serial number +.blkb 11 ! Disk Label (DOS 4+) +.blkb 8 ! FAT type + +.blkb sysboot_start+0x3E-* +public codestart +codestart: + hlt + +! Partition table +public partition_1 +public partition_2 +public partition_3 +public partition_4 + +.blkb sysboot_start+0x1BE-* +partition_1: +.byte 0,0,0,0,0,0,0,0 ! IN,SH,SS,ST,OS,EH,ES,ET +.long 0 ! Linear position (0 based) +.long 0 ! Linear length +.blkb sysboot_start+0x1CE-* +partition_2: +.byte 0,0,0,0,0,0,0,0 ! IN,SH,SS,ST,OS,EH,ES,ET +.long 0 ! Linear position (0 based) +.long 0 ! Linear length +.blkb sysboot_start+0x1DE-* +partition_3: +.byte 0,0,0,0,0,0,0,0 ! IN,SH,SS,ST,OS,EH,ES,ET +.long 0 ! Linear position (0 based) +.long 0 ! Linear length +.blkb sysboot_start+0x1EE-* +partition_4: +.byte 0,0,0,0,0,0,0,0 ! IN,SH,SS,ST,OS,EH,ES,ET +.long 0 ! Linear position (0 based) +.long 0 ! Linear length + +.blkb sysboot_start+0x1FE-* +.word 0xAA55 + |